Sorption studies of Cd and Cu on Brazilian alluvial soils

Estudo de sorção de Cd and Cu em solos aluviais Brasileiros

Abstract

The Local Production Arrangement, located in the Pernambuco’s Agreste state, has been significantly developing the region's economy. Despite its importance, industrial activity has caused relevant environmental concerns regarding the disposal of textile effluents, especially from industrial laundries. This waste is made up of many chemicals, and among them are various types of heavy metals. The evaluation of the sorption behavior of contaminant transport mechanisms such as heavy metals is essential to assess the risk of contamination of alluvial aquifers. This study evaluated the sorption of heavy metals (Cu and Cd) in an alluvial sediment deposit in the Capibaribe River. Kinetics and isotherm experiments allowed the analyses of Cu and Cd sorption. Kinetics sorption showed an equilibrium tendency after 16 h for Cu and 18 h for Cd and was better described by a pseudo-second order model. The isotherm data were adjusted to the Linear, Freundlich and Langmuir models. Both linear and Freundlich models satisfactorily described sorption isotherms for the two pollutants. The metals in the study represent a risk of contamination of the groundwater of alluvial aquifers, mainly due to physicochemical attributes of the soil, such as high sand content (85%), low MO (2.1 g kg-1) and alkaline pH (8.2). The environmental conditions decrease absorption and facilitate metal mobility, greatly increasing the environmental risks inherent in pollutant leaching. Cu showed a higher affinity with the soil studied in all assays performed compared with the results of the tests for Cd.

Keywords:
heavy metals; isotherm; kinetics

Resumo

O Arranjo Produtivo Local localizado no Agreste de Pernambuco vem desenvolvendo significativamente a economia da região. Apesar da sua importância, a atividade industrial traz preocupações ambientais relevantes no que diz respeito à eliminação de efluentes têxteis, principalmente das lavanderias industriais. Esses resíduos são compostos por diversos produtos químicos e, entre eles, vários tipos de metais pesados. A avaliação do comportamento de sorção de mecanismos de transporte de contaminantes como metais pesados é essencial para avaliar o risco de contaminação de aquíferos aluviais. Este estudo avaliou a sorção de metais pesados (Cu e Cd) em um depósito de sedimento aluvial no rio Capibaribe. Experimentos cinéticos e isotérmicos permitiram as análises de sorção de Cu e Cd. A cinética de sorção mostrou uma tendência de equilíbrio após 16h para Cu e 18h para Cd e foi melhor descrita por um modelo de pseudo-segunda ordem. Os dados de isoterma foram ajustados aos modelos Linear, Freundlich e Langmuir. Os modelos linear e de Freundlich descreveram satisfatoriamente as isotermas de sorção para os dois poluentes. Os metais em estudo representam risco de contaminação das águas subterrâneas de aquíferos aluviais, principalmente devido aos atributos físico-químicos do solo, como alto teor de areia (85%), baixa MO (2,1 g kg-1) e pH alcalino (8,2 ) As condições ambientais diminuem a absorção e facilitam a mobilidade do metal, aumentando muito os riscos ambientais inerentes à lixiviação de poluentes. O Cu apresentou maior afinidade com o solo estudado em todos os ensaios realizados em comparação com os resultados dos ensaios para o Cd.

Palavras-chave:
cinética; isoterma; metais pesados

1. INTRODUCTION

Recently, heavy metal (HM) environmental contamination has become critical on a global scale. The deposition of HM in the soil has caused considerable concern about its environmental impacts and human health, especially regarding the consumption of contaminated water resources (Cerqueira et al., 2011; Shokr et al., 2016). Nowadays, the increasing pollution of water resources has been a major environmental problem. Potentially toxic metals may enter the environment from many sources, including metal enrichment, mining, automotive emissions, industrial emissions, fertilizers, pesticides, industrial effluent dyes, wastewater irrigation, and sewage sludge (Lu and Gibb, 2008; Tahervand and Jalali, 2017; Kanbar and Kaouk, 2019; Rechberger et al., 2019).

Part of the northeast region of Brazil stands out as the second largest textile-manufacturing hub in the country (Alexandre et al., 2020). Pernambuco’s Agreste (Brazil) has an important local production arrangement of clothing factories, conferring over 1200 production units in more than 10 municipalities (Sebrae, 2013). This region has also historically suffered from prolonged droughts and low rainwater storage capacity (Montenegro and Ragab, 2012). Thus, one of the main alternatives for water supply is the exploitation of intermittent dry-bed alluvial aquifers (Usman et al., 2015). Besides being a source of water supply, alluvial aquifers are also used for the indiscriminate disposal of wastewater without treatment by industrial laundries and dry cleaners. This can create a considerable environmental problem, as the release of textile effluents is pointed to be one of the main ways of heavy metal entry such as Cd and Cu into the environment. (Ali et al., 2009; Shehzadi et al., 2014).

Regarding the toxicity in human health, Cd and Cu are among the most problematic HMs, making it important to study the fate of these HMs in fundamental alluvial formations for the preservation of water resources and public health. The consumption of water contaminated with Cu can lead to problems such as liver cirrhosis, kidney damage and intoxication. Cd poisoning can lead to kidney failure and chronic anemia (NRC, 2000; Genchi et al., 2020). The World Health Organization (WHO) has recommended a maximum acceptable Cu concentration of 0.05 mg L-1 and Cd of 0.005 mg L-1 in drinking water. However, a small dose from them may have negative effects (Abdellaoui et al., 2019).

The fate of HMs in the environment is related to their mobility in soil. Mobilization or leaching potential, in turn, occurs as a function of the complex interactions (for example sorption and desorption) between HMs and the environmental matrix. These interactions depend on the chemical state of the metal and the physicochemical properties of the soil, such as pH, redox potential, soil colloids, mineralogy, cation exchange capacity, ionic strength, particle size, and organic matter content (Du et al., 2018; Shaheen et al., 2018; Fariña et al., 2018; Kanbar and Kaouk, 2019).

The use of sorption isotherm to describe sorption phenomena is essential for the correlation between its parameters and the physicochemical attributes of the soil (Covelo et al., 2007). Generally, HM sorption can minimize mobility in soil, but with the saturation of sorption sites, it can decrease the binding energy, facilitating mobility and increasing the risk of contamination (Cerqueira et al., 2011). The soil-water partition coefficient (KD) represents the mobility of solute; this parameter represents the distribution of the chemical between the liquid phase and the solid surface, being a reference parameter in sorption, becoming a prerequisite important for risk assessment of water-table contamination (Pavlovic et al., 2018).

This work therefore evaluates the mobility of the heavy metals Cu and Cd in an alluvial deposit typical of the High Capibaribe, in Pernambuco’s Agreste. This work also assessed the sorption dynamics of these pollutants using kinetic and isotherm sorption experiments.

2. MATERIALS AND METHODS

2.1. Study area

The soil used in this research belongs to the most superficial layer of an alluvial sediment deposit of the Capibaribe Basin. The collection site of the study is located in the macrozone of Alto Capibaribe, in the division between the Pernambuco municipalities of Santa Cruz do Capibaribe and Brejo da Madre de Deus (Figure 1), with the geographic coordinates 7º56’57,6” S e 36º17’57,2” W. The Capibaribe riverbed at the collection site is dry during dry seasons.

In contrast, the alluvial aquifer is widely exploited as a source of groundwater resources. The region has an average rainfall of 600 mm/year and a potential evapotranspiration of 1900 mm/year. The climatic conditions are semiarid and the native vegetation cover is Caatinga (Braga et al., 2015). Geologically the study area is located over the Borborema Province with crystalline rocky features and fissural domain hydrogeology (Beltrão et al., 2005).

Figure 1.
Study area sites.

2.2. Soil Physical-Chemical Characteristics

The physicochemical attributes of the soil are presented in Table 1. The Zero Charge Point (ZPC) was obtained by Alexandre et al. (2020) and others presented in the Table 1 were determined by Rabelo et al. (2021).

Table 1.
Physicochemical attributes of the soil.

Sand	Silt	Clay	Soil classif.	SS	pH in water		ZPC		BS		CEC	OM	OC	V2
%			m2 g-1				cmolc dm-3					g g-1		%
82	11	7	Loamy sand	3.75	8.26		5.02		7		7.4	2.17	1.26	94
Oxides
Mn	Fe	Ni	Zn	Pb	Sr	Ti		Mg		Al		Si	K	Ca	V
mg.kg-1
231	13897	9	25	32	409	2356		7112		64760		384913	28185	7367	66
±	±	±	±	±	±	±		±		±		±	±	±	±
29	445	4.9	7	12	6	93		981		1852		11468	633	927	12

• SS: Specific Surface; ZPC: Zero Charge Point; BS: Sum of Bases; CEC: Cation Exchange Capacity; OM: organic matter; OC: organic carbon; V²: Base saturation, calculated as the ratio between effective CEC and total CEC.

The studied soil is 82% sand and 11% clay, respectively. Despite the low percentage of clay (7%) and OM (2.17 g kg^-1), the soil presented average values of cation exchange capacity (7.0 cmol_c dm^-1). Soil CEC values indicate average cation retention (Kalubi et al., 2017). The soil presents pH in water (8.26) greater than ZPC (5.02). The ZPC represents the pH value of the environment when the matrix shows zero surface charge. The low OM, clay and moderately alkaline pH values (8.26) favor the low sorption of cations increasing the risk of groundwater contamination.

2.3. Sorption Kinetics

The sorption kinetics assay consisted of stirring mixtures between the soil and the solutions with the studied solutes. In each flask (amber type), 5 g of soil and 50 mL of the contaminant solution (soil:solution ratio of 1:10 m/v) were added (Elbana et al., 2018). This solution was prepared with a CaCl₂ (purity ≥ 99%) support electrolyte at a concentration of 0.01 mol L-1, aiming to avoid the precipitation of metals in the solutions. The concentration for Cd (Cadmium Nitrate - Cd(NO₃)₂.4H₂O) was 60 mg L-1 (Linhares et al., 2009) and for the Cu (Copper Nitrate - Cu(NO₃)₂.3H₂O) was 100 mg L-1 (Linhares et al., 2010; Xing et al., 2018). Other studies with a similar theme also used heavy metals in the form of nitrate (Yang et al., 2017).

The flasks were stirred on a shaker test table at 200 rpm, as per Freitas et al. (2017), at the following time intervals: 0 h (solutions were manually shaken to ensure the interaction between sediment and solution), 1 h, 2 h, 4 h, 8 h, 10 h, 12 h, 16 h, 24 h, 36 h and 48 h. To read Cu and Cd concentration in the samples, the Agilent Atomic Absorption Spectrometry (AAS) apparatus was used, following the manufacturer's recommendations for wavelength and calibration curve (Agilent, 2017). In order to ensure the accuracy of the results, three parallel experiments were conducted for each stirring time.

Two kinetic models were used to adjust the experimental data, the pseudo-first order models and the pseudo-second order model (Ho e Mckay, 1999). The pseudo-first order model assumes that the sorption rate is directly proportional to the difference between equilibrium concentration and solid-phase concentration over time (Equation 1), whereas the pseudo-second order model assumes that the adsorption indices are proportional to the square of this difference (Equation 2). This difference is called the driving force of adsorption (Febrianto et al., 2009).

The integrated pseudo-first order model is represented by applying the limits t=0 to t=t and S_t=0 to S_t=S_t, by Equation 2 (Ho and Mckay, 1999; Yaneva and Koumanova, 2006):

$\frac{{dS}_t}{dt}=k_1\left(S_{e1}-S_t\right)$ (1)

$log\left(S_{e1}-S_t\right)=log{S}_{e1}-\frac{k_1}{\mathrm{2,303}}t$ (2)

Where in, S_e1 and S_t represent the equilibrium sorption capacities in time, represented by t, for the first-order model and k₁ is the constant first-order sorption rate.

For the pseudo-second order model, applying the same limits for integration, we have the Equations 3 and 4 (Ho and Mckay, 1999; Yaneva and Koumanova, 2006):

$\frac{{dS}_t}{dt}=k_2{\left(S_{e2}-S_t\right)}^2$ (3)

$\frac{1}{S_{e2}-S_t}=\frac{1}{S_{e2}}+k_{2}t$ (4)

Where in, S_e2 and S_t represent the equilibrium sorption capacities in time, represented by t and k₂ is the constant second-order sorption rate.

After adjusting for these two models, a statistical analysis was performed to determine which of these models best fit the data. This analysis was based on four statistical criteria: Mean Square Error (MSE), Deviation Ratio (DR), Modeling Efficiency (ME), and Residual Mass Coefficient (RMC). Besides these, the determination factor (R²) will also be analyzed. The equations of these parameters are shown below (Equations 5, 6, 7 and 8):

$MSE={\left(\frac{{\sum }_{i=1}^N{(T_i-M_i)}^2}{N}\right)}^{\frac{1}{2}}\bullet \frac{100}{M}$ (5)

$DR=\frac{{\sum }_{i=1}^N(M_i-\stackrel{-}{M})²}{{\sum }_{i=1}^N(T_i-M)²}$ (6)

$ME=\frac{{\sum }_{i=1}^N(M_i-\stackrel{-}{M})²-{\sum }_{i=1}^N{\left(T_i-M_i\right)}^2}{{\sum }_{i=1}^N{\left(M_i-M\right)}^2}$ (7)

$RMC=\frac{{\sum }_{i=1}^N{M}_i-{\sum }_{i=1}^N{T}_i}{{\sum }_{i=1}^N{M}_i}$ (8)

Where in, T_i is the values calculated by the model, M_i is the experimental values, M is the average of the experimental values and N is the number of determinations.

The DR describes the dispersion ratio of the values calculated by the theoretical model, and it tends to one. In the absence of systematic deviations between the theoretical and experimental values, the RMC tends to zero. It indicates whether the model tends to overestimate or underestimate, with negative or positive RMC values, respectively. The MSE indicates the deviation degree between the experimental determinations and the values calculated by the theoretical model. Its expected value tends to zero. The ME indicates whether the theoretical model provides a better estimation of the experimental determinations than the mean value of these determinations, and its value tends to one (Rabelo et al., 2021).

2.4. Sorption Isotherms

The concentrations chosen for this part of the study were: 0; 10; 20; 40; 60; 80; 100; 120 mg L-1 for the Cu (Copper Nitrate - Cu(NO₃)₂.3H₂O) and 0; 10; 20; 30; 40; 50; 60; 80 mg L-1 for the Cd (Cadmium Nitrate - Cd(NO₃)₂.4H₂O). The sediment-solution ratio was 1:10, i.e., 5 g of sediment and 50 mL and was prepared in triplicate to ensure accuracy of the results.

The solutions were transferred through a graduated burette pellet to 50 mL amber glasses sealed with black phenolic screw caps with a PTFE-faced rubber liner. The samples were shaken at 200 rpm on a shaker table for 24 h, which corresponds to the equilibration time established by sorption kinetics for the two pollutants. After stirring, 1 mL aliquots of the supernatant were collected in triplicate for each of the three parallel experiments of the sediment sample. In order to read Cu and Cd concentration in the samples, the Agilent Atomic Absorption Spectrometry (AAS) apparatus was used, following the manufacturer's recommendations for wavelength and calibration curve (Agilent, 2017).

Readings were also taken by atomic absorption spectrometry. Thus, it was possible to determine the concentration sorbed by the soil through Equation 9 below.

$S=\left(C_o-C_e\right)FD$ (9)

Where in, S is the concentration sorbed by the soil, C 𝑜 is the initial concentration of the contaminant placed in contact with the soil, 𝐶 𝑒 is the concentration of the contaminant after equilibrium and FD is the soil-solution ratio.

After this step, the values of the sorbed concentrations were adjusted by the Freundlich and Langmuir linear model, using the computer software SigmaPlot Version 11.

Langmuir's model is based on the hypothesis that the interaction forces between the adsorbed molecules are negligible and that each void site can be occupied by only one molecule. Freundlich's model considers heterogeneous solid and exponential distribution to characterize the various types of adsorption sites, in which one has different adsorptive energies (Xiang et al., 2018). The expressions of these models are represented in Equations 10, 11 and 12 below.

$\mathrm{L}\mathrm{i}\mathrm{n}\mathrm{e}\mathrm{a}\mathrm{r}:S=K_D{C}_e$ (10)

$\mathrm{L}\mathrm{a}\mathrm{n}\mathrm{g}\mathrm{m}\mathrm{u}\mathrm{i}\mathrm{r}:S=\frac{K_L{q}_m{C}_e}{1+K_L{C}_e}$ (11)

$\mathrm{F}\mathrm{r}\mathrm{e}\mathrm{u}\mathrm{n}\mathrm{d}\mathrm{l}\mathrm{i}\mathrm{c}\mathrm{h}:S=K_F{C}_e^{1/n}$ (12)

Where in, S is the amount of metal adsorbed in mg.kg^-1 from the soil, K_D is the soil-solution partition coefficient, C_e is the concentration of metal in the equilibrium solution in mg L-1, q_m is the maximum adsorption capacity in mg kg-1, K_L is the constant related to the binding energy in mg L-1 from the metal in the soil, K_F is the Freundlich adsorption coefficient in mg kg-1 and n is a dimensionless parameter (indicates the affinity of the soil for the solute) (Sodré et al., 2001; Linhares et al., 2010).

3. RESULTS AND DISCUSSION

3.1. Sorption Kinetics

At all stages of testing, the pH of the solutions was kept between 5.0 and 6.0. The sorption kinetics of Cu and Cd, as well as the respective adjusted curves of the pseudo-first order and pseudo-second order models, are represented in Figure 2. The parameters concerning the adjustments of pseudo-first order and pseudo-second order models are displayed in Table 2.

Figure 2.
The sorption kinetics for the Cu (A) and Cd (B).

Table 2.
Equilibrium sorption capacity values and Statistical Parameters for pseudo-first and pseudo-second orders fitted models.

	Model	Se (mg kg-1)	k1 (h-1) k2 (kg kg-1h-1)	R2	MSE	DR	ME	RMC
Cu	Pseudo-first order	86.56	0.738	0.970	6.319	0.836	0.977	0.014
	Pseudo-second order	86.96	0.008	0.996	10.837	1.124	0.934	-0.013
Cd	Pseudo-first order	10.92	0.233	0.991	3.299	1.099	0.991	-0.002
	Pseudo-second order	14.99	0.049	0.999	9.061	0.844	0.935	-0.003

The sorption equilibrium time was determined by sorption kinetics assays. This time was approximately 16 h for Cu and 18 h for Cd. In the first case, the value adsorbed by the soil was of the order of 83 mg kg-1 and 14 mg kg-1 in the second case. Regarding the equilibrium time, the results are in accordance with those presented by Mellis and Rodella (2008), in a study that included an adsorption of metals Cu and Cd in an untreated Latosol treated with sewage sludge, in which the authors concluded that the stirring time of 24 h is the most appropriate time to obtain the real adsorption of the metal for both cases. Other studies also used this value (Mattos et al., 2016; Fangjie et al., 2017). These results indicate that Cu has a greater potential to be absorbed, that is, less mobility than Cd. Cu, on the other hand, has a high capacity to interact chemically with the organic and mineral components of the soil (Linhares et al., 2010). Several studies confirm a higher sorption of Cu metal than Cd metal in different soils by the method of Batch and column study (Fonseca et al., 2011; Mouni et al., 2017; Kim and Hyun, 2017; Elbana et al., 2018; Lin and Xu, 2020). The aspects related to the interactions of both metals with the soil are better understood from the isothermal study.

From the statistical data shown in Table 2, the two models showed good adjustments to the experimental data for both pollutants. R² values for all cases were close to the unit, with the pseudo-second order model being higher. The values of the MSE parameters indicate a better fit of the model when they tend to zero, this trend was observed for the pseudo-first order model for both pollutants. Yet the values of ME and DR indicate better adjustment when they tend to be close to unity; considering the ME, this trend was observed for both pollutants. Considering the DR, for copper the best model was the second order, for Cd the best model was first order. Analyzing the RMC results, the pseudo-second order model overestimated in both pollutants and the pseudo-first order model overestimated only in the case of Cd.

The values of the equilibrium sorption capacities reaffirm the higher affinity of Cu sorption with the studied soil type, since for the two adjusted models the values of S_e1 and S_e2 were higher. The difference in soil sorption capacity between Cu and Cd is explained by the presence of organic matter in the study soil layer. Cerqueira et al. (2011) evaluated, in a study with different soils, that organic matter is the main component of the soil that retains Cu. Elbana et al. (2018) also demonstrated, in a study with varied soils, that Cu is more strongly retained by factors such as CEC and organic matter compared to Cd.

Bogusz et al. (2019), in a study to evaluate the effect of biochar on soil adsorption capacity, confirmed that the pseudo-second order model best describes the kinetic behavior of these contaminants, obtaining a coefficient of determination of 1.000 for Cu and of 0.998 for Cd. Other studies also report a good fit of the pseudo-second order model to the experimental data of metal adsorption kinetics in soils (Mishra et al., 2017; Umeh et al., 2021). Hence, on the basis of better fitting of experimental data in the pseudo-second order kinetic model, the main adsorption mechanism is probably a chemisorption reaction that may be the rate-limiting step (Kumar et al., 2010; Mishra et al., 2017; Abdus-salam and Adekola, 2018).

Thus, the time chosen for the isotherm agitation was 24 hours.

3.2. Sorption Isotherms

In Figure 3 are displayed the Cu and Cd sorption isotherms and their adjustments for the linear, Freundlich and Langmuir models. The parameter values found in the adjustments made are shown in Table 3.

Figure 3.
Adjustments for the Linear Model, of Langmuir and Freundlich for Cu (A) and Cd (B) sorption isotherms.

Table 3.
Sorption parameters adjusted for sorption isotherms.

Model	Parameters	Cu	Cd
Linear	KD (L kg-1)	0.8593	0.7674
	R2	0.988	0.932
Freundlich	KF (kg-1 mg1-1/n L1/n)	1.45	1.356
	R2	0.991	0.987
Langmuir	KL (L mg-1)	0.0027	0.0236
	R2	0.987	0.979

The data of Table 3 infers that the linear isotherm adjustment was satisfactory for Cu (R² = 0.9882), but it was not satisfactory for Cd (R² = 0.9321). The values of K_D were 0.8593 L kg-1 for Cu and 0.7674 L kg-1 for Cd. The Langmuir model presented a good adjustment (R² = 0.987 for Cu and R² = 0.979 for Cd) and the values of KL were close to zero (K_L = 0.0027 L mg-1 for Cu and K_L = 0.0236 L mg-1 for Cd). Bogusz et al. (2019) performed adjustments according to the Langmuir and Freundlich models for Cu and Cd isotherms and observed, for the Langmuir model, K_L = 0.0103 L mg-1 (R² = 0.977) for Cu and K_L = 0.0036 L mg-1 (R² = 0.564) for Cd. Finally, Freundlich model best adjusts the experimental data for both Cu (R² = 0.991) and Cd (R² = 0.987). By the distribution of the experimental points obtained for the two cases (Figure 3), it is noted that there was no equilibrium of the sorption sites, only a trend in the highest concentration points, especially in the Cd isotherm.

The absence of a level in the isotherms indicates, for the analyzed concentration range, that the saturation of the surface has not been reached (Linhares et al., 2008). It is important to highlight that, even with the satisfactory performance of the Freundlich and Langmuir models to describe the experimental isotherms (R²>0.95), both models suffered considerable deviations to higher concentrations, especially in Cd isotherms.

By the distribution of the experimental points obtained for the two cases, it is noted that there was no equilibrium of the sorption sites, only a trend in the highest concentration points, especially in the Cd isotherm. This fact indicates that isotherms are adjusted in the Freundlich model better, as this model considers that sorption sites have not yet been fully depleted. This result is in accord with the results found by Pierangeli et al. (2009) for Cd. It may also be said that Freundlich's model adjusts better for Cu than Cd data.

Waleeittikul et al. (2019), in the investigation of the effect of salinity levels in the Cd sorption in sandy loam soils, observed that, for all salinity levels, the sorption was well explained by the Freundlich isotherm. Similarly, this isothermal model fit the adsorption characteristics for Zn, Cd, Cu and Pb, alone or as a mixture, in different soils classified as loam, clay, silty clay and clay (Mouni et al., 2017). From the validation of this model to describe the sorption isotherms of both metals in the soil, considerations can be made. First, the Freundlich isotherm is a function of two parameters, K_F and exponent 1/n. K_F is positively related to the metal sorption capacity of soils (Elbana et al., 2018; Lin and Xu, 2020). The values found for the parameter were 1.45 kg-1 mg-1−1/n L1/n and 1.356 kg-1 mg-1-1/n L1/n, respectively for Cu and Cd, and indicate that Cu has a higher retention potential in this soil than Cd. The values obtained for n were 1.135 for Cu and 1.253 for Cd. The value obtained for Cu is closer to the unit, indicating an approximation for a linear-type isotherm.

The data of Table 3, is inferred that the Langmuir model graphically presented a good adjustment (R² = 0.987 for Cu and R² = 0.979 for Cd). The values of K_L were close to zero (K_L = 0.0027 L mg-1 for Cu and K_L = 0.0236 L mg-1 for Cd). Values of the same order of magnitude were also found by Linhares et al. (2008), that found a value of 0.0053 L mg-1. Values close to zero indicate that the model does not apply to the measured data or has no physical significance. The adsorption behavior of the tested systems does not follow the assumption on which Langmuir's approach is based (Kiurski et al., 2011). Other papers also found values of the same order of magnitude for the Langmuir model adjustments (Kiurski et al., 2012; Amosa et al., 2016; Potgieter et al., 2018).

Bogusz et al. (2019) performed adjustments according to the Langmuir and Freundlich models for Cu and Cd isotherms. Observing the Langmuir values, the authors obtained a K_L = 0.01 L mg-1 for Cu and K_L = 0.0036 L mg-1 for Cd, which indicates that the binding energy between sandy soils and these metals is low, that is, sorption is not difficult to reverse.

The analysis of soil characteristics to understand the aspects involved in the adsorption process is of fundamental importance. For example, Lin and Xu (2020) observed that loam with high OC and CEC exhibited strong sorption for Cd and Zn. Gonçalves et al. (2013), in a study of Cu adsorption in a Brazilian clay soil, point out that the high content of clay, organic matter and CEC in this soil were factors that favored the adsorption process. Elbana et al. (2018) found that soils with high organic matter and soils with high CEC and pH exhibited strong sorption for Pb, Cu, Cd, Zn and Ni, while sandy soils with low CEC showed the lowest sorption for all metals analyzed. Regarding organic content, Defo et al. (2016) found a strong influence of organic matter in the retention of Pb and Cd in soils in a tropical urban watershed. Considering characteristics such as low clay content (7%), low OM (2.17 gg-1) and median CEC value (7.4 cmolc.dm-3), it is possible to infer that the analyzed soil does not present favorable conditions for a considerable retention of both metals in the soil, being indicative of high mobility and low retention.

Mishra et al. (2017), studying Cu sorption isotherms, found, for a red soil with CEC conditions similar to the soil sample of this work, a value of K_F equal to 1.71 L mg-1, which resembles the value found of 1.45 kg-1 mg1-1/n L1/n for adjusting the Freundlich model.

Oliveira et al. (2010), performing the linear adjustment for the Cd sorption isotherms, for a soil-like Eutroferric Red Nitosol of content such as studied in this paper (79% of sand) and with a CEC of 3.43, obtained values close to those shown in Table 3 (K_D = 0.4304 L kg-1 and R² = 0.8566). This difference may be explained by the high soil CEC studied in this work, which is a critical intervening factor for Cd adsorption, where Cerqueira et al. (2011) showed that the correlation between these parameters is 0.833, greater than the correlation with the particle-size content, which is 0.732.

Regarding the influence of the pH of the solution, Umeh et al. (2021) observed that the level of Cd2+ removal increases with increase in pH. Rezaei et al. (2021) observed that soils with higher pH values showed greater Cd sorption capacity than acidic soils. Lin and Xu (2020) observed that sandy loam with high pH exhibited strong sorption for Cu. According to Yang et al. (2017), at higher pH more specific adsorption with strong selectivity and irreversibility may occur. Under acidic conditions, electrostatic repulsion occurs on the bonding location of the adsorbent site (Umeh et al. (2021) and, with the increase in pH, there is a decrease by competition between hydrogen and metal ions for the surface sites (Abdus-salam and Adekola, 2018). Additionally, for higher pH values more negatively charged surface becomes available (Abdus-salam and Adekola, 2018), a condition that favors the exchange of cationic compounds (Nomanbhay and Palanisamy, 2005), such as Cu and Cd. In this study, the pH value is moderately high (8.26) and higher than the ZPC (5.02), a condition for the occurrence of the negative surface load of the soil (Bachratá et al., 2013), being, therefore, a configuration that benefits the retention of the metals in the analyzed soil.

From the adjustments of the Freundlich and Langmuir models, it may be inferred that most models adjusted the experimental data for both Cu and Cd. All adjustments suffered considerable deviations to higher concentrations, especially in Cd isotherms.

4. CONCLUSION

This work evaluated the mobility of heavy metals Cu and Cd in an alluvial soil of the Capibaribe River, in northeastern Brazil. The study consisted of kinetic tests, with adjustments to the pseudo-first and pseudo-second order model, and sorption isotherms, with adjustments to the Linear, Freundlich and Langmuir models.

Although both models describe the sorption kinetics satisfactorily, the Cu and Cd sorption kinetics were best described by a pseudo-second order model, which indicates a slow sorption for the analyzed soil. On the other hand, both linear and Freundlich models satisfactorily described sorption isotherms for the two pollutants. The Langmuir model presented Kl values close to zero, having no physical significance.

It is noted by the distribution of the experimental points of sorption isotherms, that there was no equilibrium of the sorption sites, only a trend in the highest concentration points, especially in the Cd isotherm, i.e, the saturation of the surface has not been reached.

The results indicated that Cu has more affinity with this type of soil. This fact represents that Cu was more retained by the soil, while Cd is more mobile.

5. ACKNOWLEDGMENTS

This work was carried out with the support of the project "Transfer of Water and Mixtures of Reactive Pollutants in Anthropized Soils" (CNPq process No. 436875/2018-7) and of the Foundation for the Support of Science and Technology of the State of Pernambuco (FACEPE process IBPG-1889-3.01/16), and by project “National Observatory of Water and Carbon Dynamics in the Caatinga Biome ONDACBC (CNPq process N° 465764/2014-2; CAPES process N° 88887.136369/2017-00; FACEPE process APQ-0498-3.07/17).

6. REFERENCES

• ABDELLAOUI, Y.; OLGUÍN, M. T.; ABATAL, M.; ALI, B.; MÉNDEZ, S. E. D.; SANTIAGO, A. A. Comparison of the divalent heavy metals (Pb, Cu and Cd) adsorption behavior by montmorillonite-KSF and their calcium- and sodium-forms. Superlatices and Microstructures, v. 127, p. 165-175, 2019. https://doi.org/10.1016/j.spmi.2017.11.061
  » https://doi.org/10.1016/j.spmi.2017.11.061
• ABDUS-SALAM, N.; ADEKOLA, S. K. Adsorption studies of zinc(II) on magnetite, baobab (Adansonia digitata) and magnetite-baobab composite. Applied Water Science, v. 8, n. 8, p. 1-11, 2018. http://dx.doi.org/10.1007/s13201-018-0867-7
  » http://dx.doi.org/10.1007/s13201-018-0867-7
• AGILENT. Flame atomic absorption spectrometry - Analytical Methods. Agilent Technologies, 2017. 40. ed. Available at: Available at: https://www.agilent.com/cs/library/usermanuals/Public/0009.pdf Access: Nov. 12, 2018.
  » https://www.agilent.com/cs/library/usermanuals/Public/0009.pdf
• ALEXANDRE, J. I. S.; SANTOS NETO, S. M.; COUTINHO, A. P.; MELO, T. A. T.; GONÇALVES, E. A. P.; GONDIM, M. V. S. et al. Sorption of the Direct Black 22 dye in alluvial soil. Revista Ambiente & Agua, v. 15, n. 4, p. 1-13, 2020. http://dx.doi.org/10.4136/ambi-agua.2483
  » http://dx.doi.org/10.4136/ambi-agua.2483
• ALI, N.; HAMEED, A.; AHMED, S. Physicochemical characterization and bioremediation perspective of textile effluent, dyes and metals by indigenous Bacteria. Journal of Hazardous Material, v. 164, p. 322-328, 2009.
• AMOSA, M. K.; JAML, M. S.; ALKHATIB, M. F. R.; TAJARI, T.; JIMAT, D. N.; OWOLABL, R. U. Turbidity and suspended solids removal from high-strength wastewater using high surface área adsorbent: Mechanistic pathway and statistical analysis. Cogent Engineering, v. 3, p. 1-18, 2016. https://doi.org/10.1080/23311916.2016.1162384
  » https://doi.org/10.1080/23311916.2016.1162384
• BACHRATÁ, M.; ŠUŇOVSKÁ, A.; HORNÍK, M.; PIPÍŠKA, M.; AUGUSTÍN, J. Sorption of Synthetic Dyes Onto River Sediments: a laboratory study. Nova Biotechnologica et Chimica, v. 12, n. 1, p. 12-29, 2013. http://dx.doi.org/10.2478/nbec-2013-0002
  » http://dx.doi.org/10.2478/nbec-2013-0002
• BELTRÃO, B. A.; MASCARENHAS, J. de C.; MIRANDA, J. L. F. de; SOUZA JUNIOR, L. C. de; GALVÃO, M. J. da T. G.; PEREIRA, S. N. (Orgs.). Projeto cadastro de fontes de abastecimento por água subterrânea: estado de Pernambuco: diagnóstico do município de Santa Cruz do Capibaribe. Recife: CPRM, 2005. 21 p.
• BRAGA, R. A. P.; FARIAS, C. R. de O.; SILVA, S. R. da; CAVALCANTI, E. R. Gestão e educação socioambiental na Bacia do Capibaribe. Recife: Clã, 2015. 140 p.
• BOGUSZ, A.; OLESZCZUK, P.; DOBROWOLSKI, R. Adsorption and desorption of heavy metals by the sewage sludge and biochar-amended soil. Environmental Geochemical Health, v.41, p. 1663-1674, 2019. https://doi.org/10.1007/s10653-017-0036-1
  » https://doi.org/10.1007/s10653-017-0036-1
• CERQUEIRA, B.; COVELO, E. F.; ANDRADE, L.; VEJA, F. A. The influence of soil properties on the individual and competitive sorption and desorption of Cu and Cd. Geoderma, v. 162, p. 20-26, 2011. https://doi.org/10.1016/j.geoderma.2010.08.013
  » https://doi.org/10.1016/j.geoderma.2010.08.013
• COVELO, E. F.; VEGA, F. A.; ANDRADE, M. L. Heavy metal sorption and desorption capacity of soils containing endogenous contaminants. Journal of Hazardous Materials, v. 142, p. 419-430, 2007. https://doi.org/10.1016/j.jhazmat.2006.09.047
  » https://doi.org/10.1016/j.jhazmat.2006.09.047
• DEFO, C.; YERIMA, B. P. K.; BEMMO, N. Investigating soils retention ratios and modelling geochemical factors affecting heavy metals retention in soils in a tropical urban watershed. Environment, Development and Sustainability, v. 19, n. 5, p. 1649-1671, 2016. http://dx.doi.org/10.1007/s10668-016-9819-2
  » http://dx.doi.org/10.1007/s10668-016-9819-2
• DU, H.; HUANG, Q.; PEACOCK, C. L.; TIE, B.; LEI, M.; LIU, X.; WEI, X. Competitive binding of Cd, Ni and Cu on goethite organo-mineral composites made with soil bacteria. Environmental Pollution, v. 243, p. 444-452, 2018. https://doi.org/10.1016/j.envpol.2018.08.087
  » https://doi.org/10.1016/j.envpol.2018.08.087
• ELBANA, T. A.; SELIM, H. M.; AKRAMI, N.; NEWMAN, A.; SHAHEEN, S. M.; RINKLEBE, J. Freundlich sorption parameters for cadmium, copper, nickel, lead, and zinc for different soils: influence of kinetics. Geoderma, v. 324, p. 80-88, 2018. http://dx.doi.org/10.1016/j.geoderma.2018.03.019
  » http://dx.doi.org/10.1016/j.geoderma.2018.03.019
• FARIÑA, A. O.; PEACOCK, C. L.; FIOL, S.; ANTELO, J.; CARVIN, B. A universal adsorption behaviour for Cu uptake by iron (hydr)oxide organo-material composites. Chemical Geology, v. 479, p. 22-35, 2018. https://doi.org/10.1016/j.chemgeo.2017.12.022
  » https://doi.org/10.1016/j.chemgeo.2017.12.022
• FANGJIE, Q.; YAN, Y.; LAMB, D.; NAIDU, R.; BOLAN, N. S.; LIU, Y.; OK, Y. S.; DONNE, S. W.; SEMPLE, K. T. Thermal stability of biochar and its effects on Cadmium sorption capacity. Bioresource Technology, v. 246, p. 48-56, 2017. https://doi.org/10.1016/j.biortech.2017.07.033
  » https://doi.org/10.1016/j.biortech.2017.07.033
• FEBRIANTO, J.; KOSASIH, A. N.; SUNARSO, J.; JU, Y.; INDRASWATI, N.; ISMADJI, S. Equilibrium and kinetic studies in adsorption of heavy metals using biosorbent: A summary of recent studies. Journal of Hazardous Materials, v. 162, p. 616-645, 2009. https://doi.org/10.1016/j.jhazmat.2008.06.042
  » https://doi.org/10.1016/j.jhazmat.2008.06.042
• FONSECA, B.; FIGUEIREDO, H.; RODRIGUES, J.; QUEIROZ, A.; TAVARES, T. Mobility of Cr, Pb, Cd, Cu and Zn in a loamy sand soil: A comparative study. Geoderma, v. 164, p. 232 - 237, 2011.
• FREITAS, E. D.; CARMOS, A. C. R.; ALMEIDA NETO, A. F.; VIEIRA, M. G. A. Binary adsorption of silver and copper on Verde-lodo bentonite: Kinetic and equilibrium study. Applied Clay Science, v. 137, p. 69-76, 2017. https://doi.org/10.1016/j.clay.2016.12.016
  » https://doi.org/10.1016/j.clay.2016.12.016
• GENCHI, G.; SINICROPI, M. S.; LAURIA, G.; CAROCCI, A.; CATALANO, A. The effects of cadmium toxicity. International Journal of Environmental Research and Public Health, v. 17, p. 1-24, 2020. https://doi.org/10.3390/ijerph17113782
  » https://doi.org/10.3390/ijerph17113782
• GONÇALVES, M. S.; BETTIN, J. P.; SILVA JUNIOR, L. C. S.; SAMPAIO, S. C.; BOSCO, T. C. Adequação dos modelos de Langmuir e Freundlich na adsorção de cobre em solo argiloso do sul do Brasil. Holos, v. 4, n. 29, p. 37-44, 2013.
• HO, Y. S.; MCKAY, G. Pseudo-second-order model for sorption processes. Process Biochemistry, v. 34, p. 451-465, 1999. https://doi.org/10.1016/S0032-9592(98)00112-5
  » https://doi.org/10.1016/S0032-9592(98)00112-5
• KALUBI, K. N.; MEHES-SMITH, M.; SPIERS, G.; OMRI, A. Variation in whole DNA methylation in red maple (Acer rubrum) populations from a mining region: association with metal contamination and cation exchange capacity (cec) in podzolic soils. Ecotoxicology, v. 26, n. 3, p. 405-414, 2017. http://dx.doi.org/10.1007/s10646-017-1773-8
  » http://dx.doi.org/10.1007/s10646-017-1773-8
• KANBAR, H. J.; KAOUK, M. Mineral and chemical changes of sediments after Cu sorption and then desorption induced by synthetic root exudate. Chemosphere, v. 236, p. 2-9, 2019. https://doi.org/10.1016/j.chemosphere.2019.124393
  » https://doi.org/10.1016/j.chemosphere.2019.124393
• KIM, J.; HYUN, S. Soil attenuation of the seepage potential of metallic elements (Cu, Zn, As(V), Cd, and Pb) at abandoned mine sites: a batch equilibrium sorption and seepage column study. Journal of Hazardous Materials, v. 339, p. 292-300, 2017. http://dx.doi.org/10.1016/j.jhazmat.2017.05.054
  » http://dx.doi.org/10.1016/j.jhazmat.2017.05.054
• KIURSKI, J.; ADAMOVIC, S; KRSTIC, J.; OROS, I.; MILORADOV, M. V. Adsorption efficiency of low-cost materials in the removal of Zn(II) ions from printing developer. Acta Technica Corviniensis - Bulletin of Engineering, v. 4, p. 61 - 66, 2011.
• KIURSKI, J.; ADAMOVIC, S.; OROS, I.; KRSTIC, J.; KOVACEVIC, I. Adsorption feasibility in the Cr(total) ions removal from waste printing developer. Global NEST Journal, v. 14, n. 1, p. 18-23, 2012. https://doi.org/10.30955/gnj.000810
  » https://doi.org/10.30955/gnj.000810
• KUMAR, P. S.; RAMAKRISHNAN, K.; KIRUPHA, S. D.; SIVANESAN, S. Thermodynamic and kinetic studies of cadmium adsorption from aqueous solution onto rice husk. Brazilian Journal of Chemical Engineering, v. 27, n. 2, p. 347-355, 2010. http://dx.doi.org/10.1590/s0104-66322010000200013
  » http://dx.doi.org/10.1590/s0104-66322010000200013
• LINHARES, L. A.; EGREJA FILHO, F. B.; IANHEZ, R.; SANTOS, E. A. Aplicação dos modelos de Langmuir e Freundlich na adsorção de cadmio e chumbo em diferentes classes de solos brasileiros. Revista Tecnológica, v. 17, p. 49-60, 2008. https://doi.org/10.4025/revtecnol.v17i1.5274
  » https://doi.org/10.4025/revtecnol.v17i1.5274
• LINHARES, L. A.; EGREJA FILHO, F. B.; OLIVEIRA, C. V.; BELLIS, V. M. Adsorção de cadmio e chumbo em solos tropicais altamente intemperizados. Pesquisa Agropecuária Brasileira, v. 44, n. 3, p. 291-299, 2009.
• LINHARES, L. A.; EGREJA FILHO, F. B.; BELLIS, V. M.; SANTOS, E. A.; IANHEZ, R. Utilização dos modelos de Langmuir e de Freundlich na adsorção de cobre e zinco em solos Brasileiros. Acta Agronômica, v. 59, n. 3, p. 303-315, 2010.
• LIN, Q.; XU, S. Co-transport of heavy metals in layered saturated soil: characteristics and simulation. Environmental Pollution, v. 261, p. 1-9, 2020. http://dx.doi.org/10.1016/j.envpol.2020.114072
  » http://dx.doi.org/10.1016/j.envpol.2020.114072
• LU, S.; GIBB, S. W. Copper removal from wastewater using spent-grain as biosorbent. Bioresource Technology, v. 99, n. 6, p. 1509-1517, 2008. https://doi.org/10.1016/j.biortech.2007.04.024
  » https://doi.org/10.1016/j.biortech.2007.04.024
• MATTOS, A. G.; SOBRINHO DO AMARAL, N. M. B.; LIMA, E. S. A.; GUEDES, J. N.; SOUSA, F. F. Sorção de Cd e Pb nos solos da região do Médio Rio Paraíba - RJ, Brasil. Revista Ciência Agronômica, v. 47, n. 1, p. 1-12, 2016. https://doi.org/10.5935/1806-6690.20160001
  » https://doi.org/10.5935/1806-6690.20160001
• MELLIS, E. V.; RODELLA, A. A. Influência do tempo de agitação na adsorção de Cd, Cu, Ni e Zn em latossolo tratado com lodo de esgoto. Bragantia, v. 67, n. 4, p. 977 - 982, 2008. https://doi.org/10.1590/S0006-87052008000400021
  » https://doi.org/10.1590/S0006-87052008000400021
• MISHRA, S. R.; CHANDRA, R.; JIPSI, K. A.; SAVARIYA, D. B. Kinetics and isotherm studies for the adsorption of metal ions on to two soil types. Environmental Technology & Innovation, v. 7, p. 87-10, 2017. https://doi.org/10.1016/j.eti.2016.12.006
  » https://doi.org/10.1016/j.eti.2016.12.006
• MONTENEGRO, S.; RAGAB, R. Impact of possible climate and land use changes in the semi arid regions: A case study from North Eastern Brazil. Journal of Hydrology, v. 434, p. 55-68, 2012. https://doi.org/10.1016/j.jhydrol.2012.02.036
• MOUNI, L.; BELKHIRI, L.; BOUZAZA, A.; BOLLINGER, J. Interactions between Cd, Cu, Pb, and Zn and four different mine soils. Arabian Journal Of Geosciences, v. 10, n. 4, p. 1-9, 2017. http://dx.doi.org/10.1007/s12517-017-2864-9
  » http://dx.doi.org/10.1007/s12517-017-2864-9
• NOMANBHAY, S. M.; PALANISAMY, K. Removal of heavy metal from industrial wastewater using chitosan coated oil palm shell charcoal. Electronic Journal of Biotechnology, v. 8, n. 1, p. 258-264, 2005. http://dx.doi.org/10.2225/vol8-issue1-fulltext-7
  » http://dx.doi.org/10.2225/vol8-issue1-fulltext-7
• NRC. Health effects of excess copper. In: NRC. Copper in drinking water. Washington: National Academies Press, 2000. p. 78-113.
• OLIVEIRA, L. F. C.; LEMKE-DE-CASTRO, M. L.; RODRIGUES, C.; BORGES, J. D. Isotermas de sorção de metais pesados em solos do cerrado de Goiás. Revista Brasileira de Engenharia Agrícola e Ambiental, v. 14, n. 7, p. 776-782, 2010. https://doi.org/10.1590/S1415-43662010000700014
  » https://doi.org/10.1590/S1415-43662010000700014
• PIERANGELI, M. A. P.; NÓBREGA, J. C. A.; LIMA, J. M.; GUILHERME, L. R. G.; ARANTES, S. A. C. M. Sorção de cádmio e chumbo em latossolo vermelho distrófico sob efeito de calcário e fosfato. Revista Brasileira de Ciências Agrárias, v. 4, n. 1, p. 42-47, 2009.
• PAVLOVIC, D.; PAVLOVIC, M.; CAKMAK, D.; KOSTIC, O.; JARIC, S.; SAKAN, S.; DORDEVIC, D.; MITROVIC, M.; GRZETC, I.; PAVLOVIC, P. Fractionation, mobility, and contamination assessment of potentially toxic metals in urban soils in four industrial Serbian cities. Environmental contamination and Toxicology, v. 75, p. 335-350, 2018. https://doi.org/10.1007/s00244-018-0518-x
  » https://doi.org/10.1007/s00244-018-0518-x
• POTGIETER, J. H.; PEARSON, S.; PARDESI, C. Kinetic and thermodynamic parameters for the adsorption of methylene blue using fly ash under batch, column, and heap leaching configurations. Coal Combustion and Gasification Products, v. 3, p. 23-33, 2018. https://doi.org/10.4177/CCGP-D-17-00011.1
  » https://doi.org/10.4177/CCGP-D-17-00011.1
• RABELO, A. E. C. G. C.; SANTOS NETO, S. M.; COUTINHO, A. P.; ANTONINO, A. C. D. Sorption of sulfadiazine and water flow modeling in an alluvial deposit of a dry riverbed in the Brazilian semiarid. Journal of Contaminant Hydrology, 2021. https://doi.org/10.1016/j.jconhyd.2021.103818
  » https://doi.org/10.1016/j.jconhyd.2021.103818
• RECHBERGER, M. V.; KLOSS, S.; WANG, S.; LEHMANN, J.; RENNHOFER, H.; OTTNER, F.; WRIESSNIG, K.; DAUDIN, G.; LICHTENEGGER, H.; SOJA, G.; ZEHETNER, F.. Enhanced Cu e Cd sorption after soil aging of woodchip-derived biochar: What were the driving factors? Chemosphere, v. 216, p. 463-471, 2019. https://doi.org/10.1016/j.chemosphere.2018.10.094
  » https://doi.org/10.1016/j.chemosphere.2018.10.094
• REZAEI, M. J.; FARAHBAKHSH, M.; SHAHBAZI, K.; MARZI, M. Study of cadmium distribution coefficient in acidic and calcareous soils of Iran: comparison between low and high concentrations. Environmental Technology & Innovation, v. 22, p. 1-11, 2021. http://dx.doi.org/10.1016/j.eti.2021.101516
  » http://dx.doi.org/10.1016/j.eti.2021.101516
• SEBRAE. Estudo econômico do Arranjo Produtivo Local de Confecções do Agreste Pernambucano, 2012. Recife, 2013. 151 p.
• SHAHEEN, S. M.; TSADILAS, C. D.; NIAZI, N. K.; HSEU, Z.; OK, Y. S.; SELIM, M.; RINKLEBE, J. Impact of biosolid application rates on competitive sorption and distribution coefficients of Cd, Cu, Ni, Pb, and Zn in an Alfisoil and an Entisol. Process safety and Environmental Protection, v. 115, p. 38-48, 2018. https://doi.org/10.1016/j.psep.2017.10.013
  » https://doi.org/10.1016/j.psep.2017.10.013
• SHEHZADI, M.; AFZAL, M.; KHAN, M. U.; ISLAM, E.; MOBIN, A.; ANWAR, S.; KHAN, Q. M. Enhanced degradation of textile effluent in constructed wetland system using Typha domingensis and textile effluent-degrading endophytic bacteria. Water Research, v. 58, p. 152 -159, 2014. https://doi.org/10.1016/j.watres.2014.03.064
  » https://doi.org/10.1016/j.watres.2014.03.064
• SHOKR, M. S.; EL BAROUDY, A. A.; FULLEN, M A.; EL-BESHBESHY, T. R.; ALI, R. R.; ELHALIM, A. et al. Mapping of heavy metal contamination in alluvial soils of the middle Nile Delta of Egypt. Journal of Environmental Engineering and Landscape Management, v. 24, n. 3, p. 218-231, 2016. https://doi.org/10.3846/16486897.2016.1184152
  » https://doi.org/10.3846/16486897.2016.1184152
• SODRÉ, F. F.; LENZI, E.; COSTA, A. C. S. Utilização de modelos físico-químicos de adsorção no estudo do comportamento do cobre em solos argilosos. Química Nova, v. 24, n. 3, p. 324-330, 2001. https://doi.org/10.1590/S0100-40422001000300008
  » https://doi.org/10.1590/S0100-40422001000300008
• TAHERVAND, S.; JALALI, M. Sorption and desorption of potentially toxic metals (Cd, Cu, Ni and Zn) by soil amended with bentonite, calcite and zeolite as a function of pH. Journal of Geochemical Exploration, v. 181, p. 148-159, 2017. https://doi.org/10.1016/j.gexplo.2017.07.005
  » https://doi.org/10.1016/j.gexplo.2017.07.005
• UMEH, T. C.; NDUKA, J. K.; AKPOMIE, K. G. Kinetics and isotherm modeling of Pb(II) and Cd(II) sequestration from polluted water onto tropical ultisol obtained from Enugu Nigeria. Applied Water Science, v. 11, n. 4, p. 1-8, 2021. http://dx.doi.org/10.1007/s13201-021-01402-8
  » http://dx.doi.org/10.1007/s13201-021-01402-8
• USMAN, M.; LIEDL, R.; AWAN, U. K. Spatio-temporal estimation of consumptive water use for assessment of irrigation system performance and management of water resources in irrigated Indus Basin, Pakistan. Journal of Hydrology, v. 525, p.26-41, 2015. https://doi.org/10.1016/j.jhydrol.2015.03.031
  » https://doi.org/10.1016/j.jhydrol.2015.03.031
• WALEEITTIKUL, A.; CHOTPANTARAT, S.; ONG, S. K. Impacts of salinity level and flood irrigation on Cd mobility through a Cd-contaminated soil, Thailand: experimental and modeling techniques. Journal of Soils and Sediments, v. 19, n. 5, p. 2357-2373, 2019. http://dx.doi.org/10.1007/s11368-018-2207-9
  » http://dx.doi.org/10.1007/s11368-018-2207-9
• XIANG, L.; XIAO, T.; MO, C.; ZHAO, H.; LI, Y.; LI, H.; CAI, Q.; ZHOU, D.; WONG, M. Sorption kinetics, isotherms, and mechanism of aniline aerofloat to agricultural soils with various physicochemical properties. Ecotoxicology and Environmental Safety, v. 154, p. 84-91, 2018. https://doi.org/10.1016/j.ecoenv.2018.01.032
  » https://doi.org/10.1016/j.ecoenv.2018.01.032
• XING, Q.; WANG, Y.; CHAI, L., TANG, C.; HUANG, X.; WANG, W.; YOU, W. Adsorption of copper ions on porous ceramsite prepared by diatomite and tungsten residue. Transactions of Nonferrous Metals Society of China, v. 28, n. 5, p. 1053-1060, 2018. https://doi.org/10.1016/S1003-6326(18)64731-4
• YANEVA, Z.; KOUMANOVA, B. Comparative modelling of mono- and dinitrophenols sorption on yellow bentonite from aqueous solutions. Journal of Colloid and Interface Science, v. 293, n. 2, p. 303-311, 2006. https://doi.org/10.1016/j.jcis.2005.06.069
  » https://doi.org/10.1016/j.jcis.2005.06.069
• YANG, Z.; LIANG, J.; TANG, L.; ZENG, G.; YU, M.; LI, X.; LI, X.; QIAN, Y.; WU, H.; LUO, Y. Sorption-desorption behaviors of heavy metals by biochar-compost amendment with different ratios in contaminated wetland soil. Journal of Soils and Sediments, v. 18, n. 4, p. 1530-1539, 2017. http://dx.doi.org/10.1007/s11368-017-1856-4
  » http://dx.doi.org/10.1007/s11368-017-1856-4

Publication Dates

• Publication in this collection
  20 Aug 2021
• Date of issue
  2021

History

• Received
  04 Mar 2021
• Accepted
  21 June 2021