Assessment of sulfamethoxazole adsorption capacity on Pirangi clay from the State of Sergipe, Brazil, modified by heating and addition of organic cation

Rezende, J. C. T. de; Ramos, V. H. S.; Silva, A. S.; Santos, C. P.; Oliveira, H. A.; Jesus, E. de

doi:10.1590/0366-69132019653762774

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Articles • Cerâmica 65 (376) • Oct-Dec 2019 • https://doi.org/10.1590/0366-69132019653762774 copy

Assessment of sulfamethoxazole adsorption capacity on Pirangi clay from the State of Sergipe, Brazil, modified by heating and addition of organic cation

Avaliação da capacidade de adsorção de sulfametoxazol em argila Pirangi do estado de Sergipe, Brasil, modificada por aquecimento e adição de cátion orgânico

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

Sulfamethoxazole (SMX) is a widely-used antibiotic in human and veterinary medicine for treating diseases and infections and is often detected in the surface water ecosystem. Thus, this study evaluated the capacity of removing SMX from aqueous systems using Pirangi clay (PIR) from the state of Sergipe (Brazil). Pirangi clay samples were treated at 100, 400 and 600 °C and modified with hexadecyltrimethylammonium (HDTMA) cationic surfactant. The modification process used was based on the layered organization of the mineral clay, allowing the intercalation of cationic surfactant, giving a hydrophobic character to the clay. The Pirangi clay treated at 100 °C and modified with HDTMA (org-PIR-100) showed adsorption capacity of 27.3 mg.g^-1 with 90% removal of the SMX in 100 min and pH 6, following the pseudo-second-order model and Langmuir isotherm. Different characterization methods were employed to characterize the clays, such as XRF, FTIR, XRD, thermogravimetric analyzes (TG/DTG) and BET method, confirming that the surfactant molecules were incorporated on the clay surface and that org-PIR-100 showed potential for use in water treatment plant filters.

Keywords:
Pirangi clay; organoclay; adsorption; sulfamethoxazole

Table I SMX removal percentage (R%) of clays in study.

Sample	Nomenclature	R%
In natura clay	PIR	0%
Thermally-treated clays	PIR-100	0%
	PIR-400	0%
	PIR-600	0%
Organophilic clays	org-PIR	34.5%
	org-PIR-100	89.2%
	org-PIR-400	11.2%
	org-PIR-600	0%

Table II Chemical composition, organic matter (OM) content and loss on ignition (LOI) of clays (%).

Sample	PIR	PIR-100	org-PIR-100
SiO₂	63.43	63.31	67.03
Al₂O₃	19.03	19.25	14.43
Fe₂O₃	6.12	5.96	4.24
Na₂O	3.79	4.13	5.27
CaO	2.82	2.73	2.83
MgO	1.82	1.87	0.94
K₂O	1.76	1.72	1.80
TiO₂	0.79	0.72	0.46
BaO	0.12	0.13	0.11
MnO	0.07	0.07	0.06
SrO	0.06	0.06	0.06
ZrO₂	0.06	0.05	-
Cr₂O₃	0.03	-	-
Cl	0.10	-	-
Br	-	-	2.77
LOI	6.65	5.71	16.94
OM	5.48	3.91	16.52

Table III Textural characteristics of clays.

Clay	SBET (m².g^-1)	TPV (cm³.g^-1)	MPD (nm)
PIR	30.38	0.0393	5.17
PIR-100	30.30	0.0398	5.25
org-PIR-100	2.09	0.0071	13.51

Table IV Kinetic parameters of SMX adsorption on org-PIR-100.

Model	Q_e,exp (mg.g^-1)	Q_e,calc (mg.g^-1)	k₁ (min^-1)	k₂ (g.mg^-1.min^-1)	r²
Pseudo-first order	4.48±0.01	4.32±0.07	0.46±0.05	-	0.884
Pseudo-second order	4.48±0.01	4.50±0.02	-	0.181±0.007	0.994

Table V Equilibrium parameters for the adsorption of SMX in org-PIR-100.

Temperature (°C)	Langmuir				Freundlich
Temperature (°C)	Q_max (mg.g^-1)	b (L.mg^-1)	R_L	r²	K_f ([L.g^-1]^1/n)	1/n	r²
15	27.4±1.7	0.29 ±0.05	0.055	0.983	7.3±1.3	0.43±0.08	0.903
25	27.3±1.3	0.35±0.05	0.045	0.990	7.6±0.8	0.45±0.05	0.963
35	23.2±1.7	0.58±0.17	0.028	0.963	8.9±0.7	0.34±0.04	0.971
45	23.4±1.6	0.33±0.07	0.048	0.975	7.0±1.0	0.38±0.06	0.928

Table VI Thermodynamic variables for the SMX adsorption in org-PIR-100 (Co=50 mg.L-1, V=50 mL, m=0.1 g).

Temperature (K)	ΔG° (kJ.mol^-1)	K_C (L/g)
288.15	-2.287	2.546
298.15	-2.002	2.200
308.15	-1.717	2.170
318.15	-1.431	1.610

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