Enhanced solubility of foliar fertilizer via spray dryer: Process analysis and productivity optimization by response surface methodology

Incremento da solubilidade de fertilizante foliar em spray dryer: Análise do processo e otimização da produtividade pela metodologia de superfície de resposta

ABSTRACT

Foliar fertilization is a highly efficient technique of applying needed plant nutrients. During pulverization in the field, the incompatibility between fertilizer and pesticides can cause clogging of the spray nozzles. So, this work aims to improve the solubility of foliar fertilizers to facilitate its application. The effect of airflow, inlet gas temperature, and feed solution flow rate over yield, productivity, solubility, and final moisture were evaluated. The powder solubility was improved because of the capillary effect caused by greater porosity, roughness, and particle agglomeration. The maximum productivity of 0.336 kg/h was obtained at 175 ºC, with a liquid feed of 0.82 L/h and an airflow rate of 1.95 m³/min.

Index terms:
Atomization; application of fertilizers; experimental design

RESUMO

A fertilização foliar é uma técnica altamente eficiente de aplicação de nutrientes necessários às plantas. Durante sua pulverização nas culturas, a a imcompatibilidade entre fertilizantes e e pesticidas pode causar o entupimento do spray devido à precispitação. Neste contexto, este trabalho teve como objetivo desenvolver um fertilizante foliar altamente dispersível para facilitar sua aplicação. Foi avaliado o efeito da vazão de ar, temperatura e vazão de alimentação da solução sobre o rendimento e produção de pó, sua solubilidade e umidade final. A solubilidade do pó foi aumentada devido a efeitos de capilaridade causados pela alta porosidade, rugosidade e aglomeração das partículas. Uma produtividade máxima de 0.336 kg/h f oi obtida a 175 ºC, com vazão de alimentação de 0.82 L/h e vazão de ar de 1.95 m³/min.

Termos para indexação:
Atomização; aplicação de fertilizantes; planejamento experimental

INTRODUCTION

The population growth demands higher food productivity, but at the same time diseases, pests and minerals deficiency can adversely impact the agricultural food production (Serri; Souri; Rezapanah 2021; Ebrahimi et al., 2021). So, the application of chemical fertilizers has an inevitable role in cropping systems and food production (Zargar Shooshtari et al., 2020). On the other hand, soil application of fertilizers always result in limited use efficiency (Souri; Hatamian, 2018), and other techniques such as foliar fertilization can be quite attractive regarding higher efficiency and better environmental protection issues (Noroozlo; Souri; Delshad, 2019; Mohammadipour; Souri, 2019). In this context, the importance of using fertilizers with high-performance rises (Fageria; Morais; Santos, 2010.)

During field application, foliar fertilizers are usually mixed with pesticides and pulverized on the crops (Zandonadi et al., 2019). However, incompatibility between these two components leads to decreased fertilizer solubility, causing clogging of the spray nozzles. Thus, increasing fertilizer solubility in water could dramatically facilitate its application and the plant nutrients absorption (Chien; Prochnow; Cantarella, 2009).

Furthermore, in foliar fertilization, droplet size and fertilizer solubility must be carefully controlled as they affect not necessarily the crop yield, but increases the protein content of the plant, if applied during maturation or flowering.

Solubility, defined as the tendency of a substance to mix uniformly with another, is related to the concentration of nutrients and can be considered essential for the fertilizer quality (Alcarde; Guidolin; Lopes, 1998). The high solubility brings advantages such as the application of smaller volumes of solution, with a consequent cost reduction for the consumer, and also the prevention of problems with clogging of nozzles and equipment (Ali et al., 2019). In foliar fertilization, the application of nutrients being carried out in aqueous solution, their high solubility allows penetration into the plant cell, enabling the execution of their biological functions (Alexander; Hunsche, 2016).

An improvement goal of foliar fertilizer production is to alter formulation to enhance the powder dispersibility, in order to decrease the solubility time and increase the application efficiency (Knowles, 1998). The main micro-granulation techniques comprises spray dryer, lyophilization, and fluidized bed dryer (Mujumdar, 2014). The spray dryer has been used in the chemical industry for many years, for the production of dry drinks, such as instant milk (Jaskulski et al., 2017) and fruit puilp (Catelam; Trindade; Romero, 2011); oil encapsulation (Cano-Higuita; Vélez; Telis, 2015); curcumin (Nogami et al., 2021); polymers (Chen; Zheng; Shen, 2013); blackberry pomace (Santos; Paraíso; Madrona, 2020), yacon extract (Brites et al., 2016); drugs (Mirankó et al., 2021) and a wide variety of inorganic compounds including mineral fertilizers (Nasri et al., 2015; Messa; Souza; Faez, 2020; Chow; Sun; Hockey 2004).

The spray dryer has a wide application on an industrial scale, since it stands out in comparison to the others in terms of process cost and the quality of the final product, while also having the ability to improve the efficiency of the fertilizer, increasing its solubility and decreasing the negative effects associated with overdose (Al-Zahrani, 1999).

The spray drying technique can alter the powder morphology in order to improve or decrease powder solubility. Nasri et al. (2015) studied a purification of phosphate fertilizer and produced a high soluble powder using spray drying. However, Messa, Souza and Faez (2020) used spray drying to develop a chitosan-based fertilizer to prolong the potassium nitrate release in soil, with a released controlled by pH. Therefore, it is essential to study the operational conditions of drying on the particle structure and its effects on solubility, especially when it comes to a multi-nutient fertilizer (Yermiyahu et al., 2017).

Thus, the aim of this work was to alter the composition of a commertial foliar fertilizer and improve its dispersibility by the spray dryer technique. The experimental design technique was used to evaluate the effect of inlet gas temperature, the airflow rate, and the feed solution flow rate over powder yield, productivity, solubility, and final moisture. A Central Composite Design (CCD) was performed and the responses were evaluated using the response surface methodology (RSM). After that, a constrained optimization problem was formulated and solved to find an experimental condition that maximizes productivity, with a powder moisture up to 5%. After that, the experimental validation of optimal condition was performed and analyzed.

MATERIAL AND METHODS

In order to find the optimal conditions for the powder foliar fertilizer production using the spray drying process, some sequential steps were performed, as shown in Figure 1.

Figure 1:
Steps used in this investigation.

Formulation of powder foliar fertilizer (PFF)

In order to improve the foliar fertilizer solubility along with pesticides, some additives were mixed with the commercial foliar fertilizer (CFF), which have low solubility.

A compatibility test was carried out, mixing both CFF and PFF with the 4 main pesticides used for the soybean crops. After that, the mixture was monitored at each hour, to evaluate the precipitate formation. After that, a larger scale test evaluated both formulations (CFF and PFF) on a soybean crop field.

The new formulation of powder foliar fertilizer (PFF) used in this work comprises 25% Mn, 4% Zn, 1% Cu, 0.5% Bo, and 16% S (%wt), and some additives used to improve the solubility and compatibility with the main pesticides used in soybean crops. So, the PFF was reprocessed by the spray drying technique, in order to change powder structure and to increase solubility.

Drying procedure and experimental design

The experiments were performed using an MSDi-1.0 mini spray dryer (Labmaq of Brazil). The system comprises pumping and heating control systems; a spray chamber with two-fluid nozzles (diameter of 1 mm); a high-efficiency cyclone separator to collect the dried particles. All tests used an atomization pressure of 6.0 bar and an atomization gas flow of 45 L.min^-1. About 100 mL of an aqueous solution of PFF were fed in the spray-drying, at a concentration of 0.5 kg/L. Then, this solution was evaporated to dryness to give the spray-dried powder foliar fertilizer (SD-PFF). The dried powder, collected at the underflow chamber of the cyclone separator, was weighed to give the granulation yield.

A three-factor CCD was performed and the Response Surface Technique (Espinosa; Garzón; Medina, 2017; Batista Júnior et al., 2021) was used to evaluate the effect of inlet gas temperature (T_in=102 to 165 °C); the feed solution flowrate (Q_in=0.2 to 0.8 L/h); as airflow rate (Q_air=1.25 to 1.95 m³/min) on the following responses: product yield, mass productivity, solubility, and final moisture. The entire set of experimental data was comprehensively analyzed using multiple regression. The significance of regression parameters was analyzed using the Student’s t-test, with a P-level α=0.10 (Guimarães et al., 2015). The Equation 1, 2 and Equation 3 represent the coding factor of inlet gas temperature (T_in); the feed solution flow rate (Q_in) and airflow rate (Q_air), respectively.

$$x_1=\frac{T_{in}-140}{25}$$ (1)

$$x_2=\frac{Q_{in}-0.5}{0.2}$$ (2)

$$x_3=\frac{Q_{air}-1.6}{0.23}$$ (3)

PFF yield and productivity

The powder yield (η) was calculated as the ratio of the amount of powder collected after drying (m) to the initial amount of solids in the feed solution (m0), according to Equation 4; while the productivity (P [kg/h]) was obtained by Equation 5.

$\eta =\frac{m}{m_0}.100$ (4)

$$P=\frac{m_0.\eta .Q_{in}}{0.1}$$ (5)

Fertilizer characterization

The moisture analysis of SD-PFF followed a Brazilian procedure for fertilizer. Samples with 1 g were weighed and placed in an oven at 65 °C, until constant weight. The moisture was measured in triplicate and expressed on a wet basis.

The solubility time was defined as the time needed to solubilize the fertilizer dosage recommend for the soybean crop, about 0.02 kg of fertilizer/(L of water). So, an amount of 1 g fertilizer was added to 50 mL of water, under agitation at 720 rpm (Brasil, 2016). The time needed to obtain a translucent solution was recorded. This test was made in triplicate, for each SD-PFF sample according to the CCD and also for the PFF.

The fertilizer composition was evaluated before and after the spray-drying process. The fertilizer nutrient content was obtained according to standard methods for quality control of agricultural inputs (Brasil 2016; 2017). The acidity was analyzed using a pH meter that has a temperature-compensation electrode. Morphological characterization was performed by Scanning electron microscopy (SEM), carried using a DSM 960A microscope (Carl Zeiss), at 10 kV. The structure identifications were made using X-ray powder diffraction (XRD) (PANalytical model Empyren) using Cu Kα radiation.

Optimization and validation of spray drying operational conditions

An optimization problem was formulated to determine maximum productivity, in order to produce a SD-PFF, with moisture up to 5%. For that, it was used the equations obtained by statistical analyzes of the productivity (P(x)) and moisture (M(x)). The objective function (O.F.) was defined in order to maximize productivity as a function of inlet gas temperature (x ₁), the feed solution flow rate (x ₂) and the airflow rate (x ₃). The search domain was limited to the experimental range ​​studied, through inequalities constraints. The optimization problem can be defined by Equation 6. The problem was solved by the fmincon function in Matlab, by the Sequential Quadratic Programming (SQP) optimization method (Gonçalves; Sanfelice; Santos, 2020).

$$\{\begin{array}{l}\text{Min: O}\text{.F}\text{. = -P}(x)\\ \text{Constraints: M}(x)-5\le 0\\ -1.525\le x_1^{},x_2^{},x_3^{}\le 1.525\end{array}$$ (6)

RESULTS AND DISCUSSION

Formulation of powder foliar fertilizer (PFF)

Figure 2 shows the compatibility tests results of PFF and CFF with pesticides, over time (0, 3 and 6 h). The numbers 1 to 4 correspond to the different pesticides tested with, while the letters (a) and (b) refer to PFF and CFF, respectively. It can be seen that the new formulation showed no precipitation, while the CFF was incompatible with pesticides 1 and 4, whose precipitate can be observed since 3 h of time-out, becoming more pronounced over time. This indicates that the additives were able to reduce the fertilizer incompatibility with common pesticides, facilitating its application on crops usually done by aerial topdressing.

Figure 2:
Compatibility test between PFF (a) and CFF (b) fertilizers with 4 different pesticides (1 to 4), over time (t=0, 3 and 6 h).

A large-scale test, performed to verify the application influence of PFF on a soybean crop field, showed that the PFF formulation had a great application performance, maintaining its quality when compared with the commercial product. The farmer also reported an excellent PFF solubility when mixed with pesticides.

The spray drying results

The powder properties produced by spray drying are function operational conditions. For this reason, the aim of this work was to investigate the effect of factors (T, Q_in and Q_air) on yield, moisture and solubility of SD-PFF.

Table 1 shows the CCD design in original and coded variables, along with the main responses investigated: granulation yield and productivity, solubility time, and moisture. All responses were evaluated individually. A second-order model was estimated by multiple regression and its coefficients were evaluated according to an analysis of variance (ANOVA), that excluded the non-significant factors from the model.

Table 1:
Central Composite Design: factors and main responses.

Test	Factors			Responses
	Tin [ºC] (x 1)	Qin [L/h] (x 2)	Qair [m³/min] (x 3)	η [%]	P [kg/h]	t [s]	M [%]
1	115.00 (-1.00)	0.30 (-1.00)	1.37 (-1.00)	82.00	0.12	13.00	6.80
2	115.00 (-1.00)	0.30 (-1.00)	1.83 (+1.00)	78.00	0.12	13.00	5.47
3	115.00 (-1.00)	0.70 (+1.00)	1.37 (-1.00)	67.00	0.23	16.00	11.02
4	115.00 (-1.00)	0.70 (+1.00)	1.83 (+1.00)	68.00	0.24	12.00	7.64
5	165.00 (+1.00)	0.30 (-1.00)	1.37 (-1.00)	80.00	0.12	18.00	3.32
6	165.00 (+1.00)	0.30 (-1.00)	1.83 (+1.00)	78.00	0.12	13.00	1.40
7	165.00 (+1.00)	0.70 (+1.00)	1.37 (-1.00)	68.00	0.24	24.00	3.80
8	165.00 (+1.00)	0.70 (+1.00)	1.83 (+1.00)	76.00	0.27	28.00	3.37
9	101.90 ( -1.53)	0.50 ( 0.00)	1.60 ( 0.00)	71.00	0.18	20.00	8.89
10	178.10 (+1.53)	0.50 ( 0.00)	1.60 ( 0.00)	74.00	0.18	31.00	3.52
11	140.00 ( 0.00)	0.20 (-1.53)	1.60 ( 0.00)	72.00	0.07	12.00	9.96
12	140.00 ( 0.00)	0.80 (+1.53)	1.60 ( 0.00)	74.00	0.30	14.00	5.54
13	140.00 ( 0.00)	0.50 ( 0.00)	1.25 (-1.53)	76.00	0.19	12.00	6.33
14	140.00 ( 0.00)	0.50 ( 0.00)	1.95 (+1.53)	79.00	0.20	14.00	3.41
15	140.00 ( 0.00)	0.50 ( 0.00)	1.60 ( 0.00)	76.00	0.19	13.00	4.16
16	140.00 ( 0.00)	0.50 ( 0.00)	1.60 ( 0.00)	76.00	0.19	12.00	3.51
17	140.00 ( 0.00)	0.50 ( 0.00)	1.60 ( 0.00)	78.00	0.20	12.00	3.54
18	140.00 ( 0.00)	0.50 ( 0.00)	1.60 ( 0.00)	76.00	0.19	11.00	4.28
19	140.00 ( 0.00)	0.50 ( 0.00)	1.60 ( 0.00)	77.00	0.19	12.00	3.73
20	140.00 ( 0.00)	0.50 ( 0.00)	1.60 ( 0.00)	78.00	0.20	11.00	3.94

Powder yield and productivity

According Table 1, the effective powder recovery was between 67% and 82%, which is elevated when compared to other spray dryer results: 22.5-73.2% for chicken meat powder (Kurozawa et al., 2009); 42.3-70.1% for aquasolv lignin (Gil-Chávez et al., 2020); 20.5-70.4% for ginger oleoresin powder (Ahad et al., 2021) and 24.9-76.7% for agave juice (Chávez-Rodríguez et al., 2014).

Figure 3 shows the response surface of powder yield (η) as a function of different factors studied., obtained from the Equation (7) (R²=0.932). The highest yields were obtained at intermediate temperature (T_in=140 °C), associated with lower levels of both feed flow (Q_in= 0.2 L/h) and drying airflow (Q_air = 1.25 m³/min).

$$\eta [\%]=75.932+1.276x_1-5.161x_2+1.091x_3-2.389x_1^2+1.736x_1{x}_2+2.367x_2{x}_3$$ (7)

Figure 3:
Powder yield response surface as a function of: (a) x ₁ (temperature) and x ₂ (liquid feed flow rate); (b)x ₂ (liquid feed flow rate) and x ₃ (air flow rate).

The Equation 7 indicates that yield is highly influenced by Q_in (x₂), once high Q _in levels can improve the amount of powder stuck to the dryer wall, which reduces the yield. According to Maury et al. (2005), larger spray droplets are formed when the liquid feed flow rate is increased, at a constant atomizing airflow rate. This can result in larger particles with higher moisture, which can favor the particle wall adhesion, decreasing the powder yield. The negative influence of Q_in could also be due to slow mass and heat transfer in this condition. These results agree weel with those reported by Tonon, Freitas and Hubinger (2011) and Ahad et al. (2021).

However, high levels of liquid feed flow rate associated with both high temperature and airflow rate can increase the yield, due to the interaction between these factors.

Besides the interaction, both linear and quadratic terms of inlet gas temperature (x ₁) also significantly affected the powder yield. Low drying temperatures usually promote the powder deposits inside the drying chamber leading to smaller powder yield. This occurs when a too-wet droplet/particle collides with the wall, causing a wet deposit that reduces the powder yield. With the increase of temperature, a progressively drier product is obtained and the extent of particle wall deposition decline, until reaches a maximum yield of around 140 °C. However, due to the quadratic effect of temperature, the yield decays again for the highest temperatures. This occurs probably because the temperature on the inside wall of the spray-dryer became close to the ‘sticky point’, causing higher inter-particulate cohesion that decreased the particle drag (Maury et al., 2005). The powder yield is also improved linearly by the higher airflow rate, which promotes higher mass and heat transfer coefficients.

The productivity (P [kg/h]) was calculated by Equation 5 and can be also expressed as a function of the factors by Equation 8, used as the objective function in the optimization.

$$P=\text{0}\text{.1924+0}\text{.0032}{x}_1^{}-\text{0}\text{.0055}{x}_1^2\text{+0}\text{.0665}{x}_2^{}-\text{0}\text{.0043}{x}_2^2\text{+0}\text{.0027}{x}_3^{}+\text{0}\text{.0001}{x}_3^2\text{+0}\text{.0043}{x}_1^{}{x}_2^{}\text{0}\text{.0034}{x}_1^{}{x}_3^{}\text{+0}\text{.0051}{x}_2^{}{x}_3^{}$$ (8)

Solubility time

Fertilizer solubility time was measured by a color pattern during product dispersion in water under agitation. At first, the solution was cloudy, as depicted in Figure 4a. So, the vortex formed allows the identification of the solubility time at which the solution becomes translucent (Figure 4b).

Figure 4:
Identification of solubility time: (a) initial powder dispersion; (b) complete powder solubilization.

The standard powder, before drying, presented a solubility time of 112 seconds. Table 1 shows solubility time for PFF between 11 and 31 s, which corresponds to a reduction up to 90.2% when compared to the original powder. Similar behavior was found by Gong et al. (2008), who verified that the humidity of bayberry powder increased from the wetting time of 120 s to 15 s after spray dryer agglomeration.

Figure 5 reports the factors that influence the solubility time, also expressed by Equation 9 (R²=0.923). The temperature was the main factor that influenced the fertilizer solubility. The faster solubility occurred at an intermediate temperature (T=140 °C), associated with the lower level of the feed flow (Q_in= 0.2 L/h).

$$t[s]=12.018+7.237x_1+4.119x_2+10.892x_1^2+4.750x_1{x}_2$$ (9)

Figure 5:
Response surface of time solubility (t [s]) as function of x ₁ (temperature) and x ₂ (liquid flow rate).

This experimental condition of shorter solubilization time also approaches the condition where there are higher powder yields. The airflow rate had not statistically influenced the solubility time.

Moisture content

Brazilian legislation does not establish maximum moisture for powder foliar fertilizers, only for organomineral fertilizers via soil, with a maximum allowed moisture up 30% (Brazil, 2009). However, lower moisture powders are less susceptible to warping effects during storage, improving stability and avoiding agglomeration (Ahad et al., 2021).

The final moisture of SD-PFF was between 3.4 and 11% (wb), according to Table 1. The statistical analysis revealed that all studied factors affect the powder moisture, mostly the temperature, according to Equation 10 (R²=0.967).

$M[\%]=4.153-4.563x_1+2.787x_2-1.820x_3+2.044x_1^2+0.895x_3^2-1.243x_1{x}_2$ (10)

Figure 6 displays the moisture response surface as a function of temperature (x ₁) and feed rate (x₂), for x ₃=0, where drying was favored at high temperatures and low feed rates.

Figure 6:
Powder moisture (M,%wb) response surface as function of the independent variables x ₁ (temperature) and x ₂ (liquid flow rate).

Higher temperatures lead to higher heat transfer coefficients and, consequently, greater water evaporation. Low liquid feed rates had less amount of water to be evaporated. It provides a longer contact time between the powder and air, which improves the heat transfer and leads to smaller powder moisture. This behaviour of temperature over the powder moisture was also reported by others materials, such as raisin juice concentrate (Papadakis; Gardeli; Tzia, 2007); açai pulp (Tonon; Freitas; Hubinger, 2011) and chicken meat powder (Kurozawa et al., 2009).

Regarding the PFF produced in this work, the particles with less than 5% did not present any tendency of agglomeration during storage. So, a constrain was added to the optimization problem, in order to find an experimental condition that maximizes productivity but ensures powder moisture up to 5%.

Optimization and experimental validation

The SQP algorithm converged with 12 iterations. The optimal conditions that maximize SD-PFF productivity by spray drying process were x₁= 1.398; x₂= 1.565 and x₃= 1.565. This condition corresponds to a hot air temperature of 175 °C, a liquid flow rate of 0.82 L/h and an airflow rate of 1.95 m³/min. The predicted yield and productivity under these optimal conditions were 76% and 0.3148 kg/h, respectively.

A new experiment was performed in this optimal condition, in order to confirm this optimization. The powder yield obtained was about 82%, with a maximum productivity of 0.336 kg/h, a number higher than the predicted values. The powder presented a 1.75% of moisture and a solubility time of 29 s. Therefore, the SD-PFF produced at the optimal conditions achieved the expectations to obtain a highly soluble powder with an elevated yield and productivity, with low moisture content.

Composition and structural analysis

Table 2 shows the powder nutrient content and acidity of SD-PFF obtained at the optimal condition and compares it with the Brazilian tolerance limits. We can note that there was no nutrient loss after the spray-drying process. The PFF presented a pH of 3.1, within the pH range established by the industry (2.8 to 3.8).

Table 2:
Composition and acidity of PFF obtained at optimal conditions.

Nutrient	Guarantee (%)	Tolerance limits (%)	SD-PFF nutrient content (%)
S	16.5	14.98 - 24.75	19.42
B	0.50	0.38 - 1.50	0.58
Cu	1.00	0.75 - 3.00	0.92
Mn	25.0	23.12 - 37.50	24.01
Zn	4.00	3.19 - 8.00	4.39
Acidity	-	2.80 - 3.80	3.10

A Scanning Electron Microscope analysis (SEM) was performed to verify the particle structure, which could directly influence the solubility. Figure 7 compares the particles structures of PFF (a) and SD-PFF (b). The PFF particles presented non-porous, with irregular shapes, rough surfaces and a heterogeneous size (Figure 7a).

Figure 7:
Particle morphology: (a) Micrographs of PFF showing non porous particles with irregular shape, rough surfaces and a heterogeneous size; (b) Micrographs of SD-PFF in the optimal condition, showing samples with hollow spherical particles, porous, clusters due particle aggregation and some blow-holes, different magnifcations.

Figure 7b suggests that the optimal experimental condition using spray drying technique favors a formation of hollow spherical particles, with particle aggregation and some blow-holes. This agglomeration could be a result of a random particle collision in the atomizer cloud, seen as particles of different diameters have different deceleration paths, or due to the adhesion, a solid link between the particles (Westergaard, 2004).

According to Gong et al. (2008), agglomeration can greatly improve the powder reconstituted properties and reduce the wetting time, once it facilitates the water penetration in the space between the agglomerates, besides increasing the capillary-driven water flow into the agglomerate pores. The presenc of some blow-holes could be due to the permeable nature of the particle (Anandharamakrishnan; Ishwarya, 2015), since this was a significant amount of visible pores on the particle shell. So, the high particle porosity could also improve the SD-PFF solubility (Tonon; Freitas; Hubinger, 2011).

We believe that the increase in solubility is only due to changes in the morphology of the fertilizer, with a consequent increase in its surface area, and that the spray drier process does not have enough energy to cause chemical changes in the mixture. To corroborate this, Figure 8 shows the X-ray powder pattern of the mixture before (PFF) and after the spray drier process (SD-PFF).

Figure 8:
X-ray diffraction patterns of the powder before (PFF) and after the spray drier process (SD-PFF).

The samples contained a series of reflections that can be observed at different 2θ values which shows that the fertilizer exhibits well-developed crystalization. Unfortunately, we are unable to identify the phases present in the mixture because it is a commercial fertilizer whose composition is protected by intellectual property laws. We can note that the difractograms are quite similar which save as above the spray drier process does not chemically change the fertilizer.

CONCLUSIONS

The powder solubility was highly satisfactory, with a 90.2% of solubility time reduction. The fertilizer morphology showed a greater porosity and roughness, as observed by SEM images. Optimum productivity of 0.336 kg/h was obtained at T_in =175 ºC; Q_in=0.82 L/h; Q_air=1.95 m³/min, showing a powder yield of 82%; final moisture of 1.75% (wb) and solubility time of 29 s. So, the spray drying technique was able to improve the powder solubility, which can favor the marketing of this product.

AUTHOR CONTRIBUTION

Conceptual Idea: Alberto, L.; Santos, K.G.; Okura, M.H.; Methodology design: Alberto, L.; Santos, K.G.; Da Luz, M.S.; Okura, M.H.; Data collection: Alberto, L.; Data analysis and interpretation: Alberto, L.; Da Luz, M.S.; Santos, K.G.; Okura, M.H.; and Writing and editing: Alberto, L.; Da Luz, M.S.; Santos, K.G.; Okura, M.H.

ACKNOWLEDGEMENTS

The authors wish to thanks the Professional Master’s Programme in Thecnological Innovation of UFTM, the UbyFol Company, Capes and the financial support by CNPq (Universal 433958/2018-9).

REFERENCES

• AHAD, T. et al. Optimization of process parameters for spray drying of ginger oleoresin powder using response surface methodology. Journal of Food Processing and Preservation, 45:e15190, 2021.
• ALCARDE, J.; GUIDOLIN, J.; LOPES, A. Fertilizers and the efficiency of fertilization. 3th ed. São Paulo: 1998. 43p.
• ALEXANDER, A.; HUNSCHE, M. Influence of formulation on the cuticular penetration and on spray deposit properties of manganese and zinc foliar fertilizers. Agronomy, 6(3):39, 2016.
• ALI, A. B. et al. Nozzles clogging as limiting factor in pressurize irrigation systems. Agricultural Research and Technology, 20(5):556146, 2019.
• AL-ZAHRANI, S. M. Controlled-release of fertilizers: Modelling and simulation. International Journal of Engineering Science, 37(10):1299-1307, 1999.
• ANANDHARAMAKRISHNAN, C.; ISHWARYA, S. P. Spray drying techniques for food ingredient encapsulation. 1 st Ed, JohnWiley & Sons Ltd: 2015. 312p.
• BATISTA JÚNIOR, R. et al. Response surface methodology applied to spent coffee residue pyrolysis: Effect of temperature and heating rate on product yield and product characterization. Biomass Conversion and Biorefinery, 1-14, 2021.
• BRASIL. MAPA - Ministério da Agricultura, Pecuária e Abastecimento. Instrução Normativa Nº 46, de 22 de novembro de 20162016. Avaliable in: < Avaliable in: https://www.in.gov.br/materia/-/asset_publisher/Kujrw0TZC2Mb/content/id/21295271/do1-2016-12-07-instrucao-normativa-n-46-de-22-de-novembro-de-2016-21295017 >. Access in: May, 7, 2022.
  » https://www.in.gov.br/materia/-/asset_publisher/Kujrw0TZC2Mb/content/id/21295271/do1-2016-12-07-instrucao-normativa-n-46-de-22-de-novembro-de-2016-21295017
• BRASIL. MAPA- Ministério da Agricultura, Pecuária e Abastecimento. Manual de métodos analíticos oficiais para fertilizantes e corretivos. Brasília: MAPA; 2017. 240p.
• BRASIL. MAPA- Ministério da Agricultura, Pecuária e Abastecimento. Instrução Normativa MAPA No. 25. Off Gaz Bras 2009. 2009. Available in: <Available in: https://www.diariodasleis.com.br/tabelas/211809.pdf >. Access in: May, 7, 2022.
  » https://www.diariodasleis.com.br/tabelas/211809.pdf
• BRITES, M. L. et al. Characterization of powder from the permeate of yacon extract by ultrafiltration and dehydrated by spray drying. Ciência e Agrotecnologia; 40(5):585-595, 2016.
• CANO-HIGUITA, D. M.; HAV, V.; TELIS, V. R. N. Microencapsulation of turmeric oleoresin in binary and ternary blends of Arabic gum, maltodextrin and modified starch. Ciência e Agrotecnologia , 39(2):173-182, 2015.
• CATELAM, K. T.; TRINDADE, C. S. F.; ROMERO, J. T. Water adsorption isotherms and isosteric sorption heat of spray-dried and freeze-dried dehydrated passion fruit pulp with additives and skimmed milk. Ciência e Agrotecnologia ; 35(6):1196-1203, 2011.
• CHÁVEZ-RODRÍGUEZ, A. et al. Optimization of Agave tequilana weber var. Azul juice spray drying process. Journal of Chemistry, ID 915941, 2014.
• CHEN, X.; ZHENG, B.; SHEN, J. Morphologies of polymer grains during spray drying. Drying Technology, 31(4):433-338, 2013.
• CHIEN, S. H.; PROCHNOW, L. I.; CANTARELLA, H. Recent developments of fertilizer production and use to improve nutrient efficiency and minimize environmental impacts. Advances in Agronomy , 102:267-322, 2009.
• CHOW, L. C.; SUN, L.; HOCKEY, B. Properties of nanostructured hydroxyapatite prepared by a spray drying technique. Journal of Research of the National Institute of Standards and Technology, 109(6):543-551, 2004.
• EBRAHIMI, M. et al. Biochar and vermicompost improve growth and physiological traits of eggplant (Solanum melongena L.) under deficit irrigation. Chemical and Biological Technologies in Agriculture, 8:19, 2021.
• ESPINOSA, W. E.; GARZÓN, L. C. A.; MEDINA, O. J. Microwave-assisted extraction in dry fruit of andean species Vaccinium meridionale: Experimental conditions on the recovery of total polyphenols. Ciência e Agrotecnologia , 41(6):701-712, 2017.
• FAGERIA, N. K.; MORAIS, O. P.; SANTOS A. B. Nitrogen use efficiency in upland rice genotypes. Journal of Plant Nutrition, 33(11):1696-1711, 2010.
• GIL-CHÁVEZ, J. et al. Optimization of the spray-drying process for developing aquasolv lignin particles using response surface methodology. Advanced Powder Technology, 31(6):2348-2356, 2020.
• GONÇALVES, S. A.; SANFELICE, R. C.; SANTOS, K. G. Multi-response optimization of the stabilization/solidification process of industrial hazardous waste. Research, Society and Development, 9(4):e144942997, 2020.
• GONG, Z. et al. Spray drying and agglomeration of instant bayberry powder. Drying Technology , 26(1):116-121, 2008.
• GUIMARÃES, T. F. et al. A multivariate approach applied to quality on particle engineering of spray-dried mannitol. Advanced Powder Technology , 26(4):1094-1101, 2015.
• JASKULSKI, M. et al. Predictive CFD modeling of whey protein denaturation in skim milk spray drying powder production. Advanced Powder Technology , 28(12):3140-3147, 2017.
• KNOWLES, D. A. Chemistry and technology of agrochemical formulations. chemistry and technology of agrochemical formulations. Springer Netherlands, 1998. 440p.
• KUROZAWA, L.E. et al. Influence of spray drying conditions on physicochemical properties of chicken meat powder. Drying Technology , 27(11):1248-1257, 2009.
• MAURY, M. et al. Effects of process variables on the powder yield of spray-dried trehalose on a laboratory spray-dryer. European Journal of Pharmaceutics and Biopharmaceutics, 59(3):565-573, 2005.
• MESSA, L. L.; SOUZA, C. F.; FAEZ, R. Spray-dried potassium nitrate-containing chitosan/montmorillonite microparticles as potential enhanced efficiency fertilizer. Polymer Testing, 81:106196, 2020.
• MIRANKÓ, M. et al. Nanostructured micronized solid dispersion of crystalline-amorphous metronidazole embedded in amorphous polymer matrix prepared by nano spray drying. Advanced Powder Technology , 32(7):2621-2633, 2021.
• MOHAMMADIPOUR, N.; SOURI, M. K. Beneficial effects of glycine on growth and leaf nutrient concentrations of coriander (Coriandrum sativum) plants. Journal of Plant Nutrition , 42(14):1637-1644, 2019.
• MUJUMDAR, A. S. Handbook of industrial drying. 4th Edition. Fourth Edition. CRC Press. 2014. 1348p.
• NASRI, K. et al. Spray-dried monocalcium phosphate monohydrate for soluble phosphate fertilizer. Industrial and Engineering Chemistry Research, 54(33):8043-8047, 2015.
• NOGAMI, S. et al. Stabilizing effect of the cyclodextrins additive to spray-dried particles of curcumin/polyvinylpyrrolidone on the supersaturated state of curcumin. Advanced Powder Technology , 32(5):1750-56, 2021.
• NOROOZLO, Y. A.; SOURI, M. K.; DELSHAD, M. Effects of foliar application of glycine and glutamine amino acids on growth and quality of sweet basil. Advances in Horticultural Science, 33(4):495-501, 2019.
• PAPADAKIS, S. E.; GARDELI, C.; TZIA, C. Spray drying of raisin juice concentrate. Drying Technology , 24(2):173-180, 2007.
• SANTOS, S. S.; PARAÍSO, C. M.; MADRONA, G. S. Blackberry pomace microspheres: An approach on anthocyanin degradation. Ciência e Agrotecnologia 44:e014420, 2020.
• SERRI, F.; SOURI, M. K.; REZAPANAH, M. Growth, biochemical quality and antioxidant capacity of coriander leaves under organic and inorganic fertilization programs. Chemical and Biological Technologies in Agriculture , 8:33, 2021.
• SOURI, M. K.; HATAMIAN, M. Aminochelates in plant nutrition: A review. Journal of Plant Nutrition , 42(1):67-78, 2018.
• TONON, R. V.; FREITAS, S. S.; HUBINGER, M. D. Spray drying of açai (Euterpe Oleraceae Mart.) juice: Effect of inlet air temperature and type of carrier agent. Journal of Food Processing and Preservation, 35(5):691-700, 2011.
• WESTERGAARD, V. Milk powder technology: Evaporation and spray drying. 5th ed. Edited by Niro A/S. 2004. 337p.
• YERMIYAHU, U. et al. Polyhalite as a multi nutrient fertilizer - potassium, magnesium, calcium and sulfate. Israel Journal of Plant Sciences, 64(3-4):145-157, 2017.
• ZANDONADI, C. et al. Tank mixture of pesticides and foliar fertilizers for triozoida limbata control in guava trees (Psidium guajava L.). Revista Ceres, 66(4):297-306, 2019.
• ZARGAR SHOOSHTARI, F. et al. Glycine mitigates fertilizer requirements of agricultural crops: Case study with cucumber as a high fertilizer demanding crop. Chemical and Biological Technologies in Agriculture , 7:19, 2020.

Publication Dates

• Publication in this collection
  05 Aug 2022
• Date of issue
  2022

History

• Received
  08 Feb 2022
• Accepted
  01 June 2022