Removal of Pb<sup>2+</sup> and Zn<sup>2+</sup> using modified Chocolate B clay: a study using statistical analysis, equilibrium isotherms, and adsorption kinetics

Mota, J. D.; Cunha, R. S. S.; Rodrigues, M. G. F.

doi:10.1590/0366-69132021673843072

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Articles • Cerâmica 67 (384) • Oct-Dec 2021 • https://doi.org/10.1590/0366-69132021673843072 copy

Removal of Pb²⁺ and Zn²⁺ using modified Chocolate B clay: a study using statistical analysis, equilibrium isotherms, and adsorption kinetics

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

In this work, natural and thermally modified Chocolate B clays were used for batch adsorption of Pb²⁺ and Zn²⁺ from an aqueous solution. The materials were characterized by X-ray diffraction, X-ray fluorescence spectroscopy, nitrogen adsorption, and cation exchange capacity. The tests were performed in a finite bath following a 2² factorial design, with the variables: pH and initial concentrations of metal. Results revealed that the thermal treatment caused alterations on the Chocolate B clay structure and decreased the specific surface area. Affinities between Pb²⁺ or Zn²⁺ and Chocolate B clay were found with adsorption capacities up to 3.36 and 3.72 mg.g^-1, respectively. The maximum adsorption capacities were 6.79 mg.g^-1 for Pb²⁺ and 3.35 mg.g^-1 for Zn²⁺ using thermally activated clay. The Langmuir and Freundlich models were used for the adsorption equilibrium analysis, and the Langmuir model provided the best fit for sorption isotherms. The adsorption kinetics was evaluated by two models: pseudo-first-order and pseudo-second-order. The pseudo-first-order kinetic model represented well the mechanism of interaction involved during Pb²⁺ adsorption into the pores of the clay. However, the two models represented well the mechanism of interaction of Zn²⁺ adsorption into the pores of the clay.

Keywords:
Chocolate B clay; thermal activation; lead; zinc; sorption; isotherm; kinetics

Chocolate B clay	SiO₂	Al₂O₃	Fe₂O₃	CaO	MgO	Impurities
Natural	69.4	14.9	9.1	2.0	1.7	2.9
Thermally activated	68.2	13.8	8.9	1.9	1.8	2.7

Chocolate B clay	S_BET (m².g^-1)	V_micropores (cm³.g^-1)	V_mesopores (cm³.g^-1)
Natural	82	0.0124	0.0559
Thermally activated 500 °C	59	0.0097	0.0387

Test	Variables		q_eq (mg/g) - natural		q_eq (mg/g) - thermally activated
Test	C_i (mg/L)	pH	Pb²⁺	Zn²⁺	Pb²⁺	Zn²⁺
1	10	3	0.44	0.60	0.52	0.39
2	50	3	3.33	2.83	4.19	1.69
3	10	5	0.49	0.73	0.85	0.71
4	50	5	3.36	3.72	6.79	3.35
5	30	4	2.07	2.07	3.22	1.82
6	30	4	2.05	2.01	3.29	1.72
7	30	4	2.06	2.04	3.08	1.87

Source	df	Natural Chocolate B clay						Thermally activated Chocolate B clay
		q_eq - Pb²⁺			q_eq - Zn²⁺			q_eq - Pb²⁺			q_eq - Zn²⁺
		R²=100.00%; R² _adj=99.99%			R²=99.98%; R² _adj=99.93%			R²=99.91%; R² _adj=99.74%			R²=99.79%; R² _adj=99.36%
		Sum of squares	Mean square	p-value	Sum of squares	Mean square	p-value	Sum of squares	Mean square	p-value	Sum of squares	Mean square	p-value
Main effects	2	8.29	4.14	0.000	7.07	3.54	0.000	25.23	12.61	0.001	4.86	2.43	0.004
Interaction	1	0.00	0.00	0.000	0.14	0.14	0.006	1.29	1.29	0.009	0.45	0.45	0.013
Curvature	1	0.04	0.04	0.002	0.01	0.01	0.093	0.02	0.02	0.313	0.12	0.12	0.044
Pure error	2	0.00	0.00	-	0.002	0.002	-	0.02	0.01	-	0.01	0.01	-
Total	6	8.33	-	-	7.23	-	-	26.56	-	-	5.44	-	-

Metal	Langmuir parameters			Freundlich parameters
Metal	q_m (mg.g^-1)	KL (_L.mg^-1)	R²	K_F (g.L^-1)	n	R²
Pb²⁺	19.85	0.0352	0.989	1.376	1.729	0.975
Zn²⁺	12.64	0.0181	0.994	0.466	1.524	0.967

Metal	Pseudo-first order			Pseudo-second order
Metal	q_eq (mg.g^-1)	K₁ (min^-1)	R²	q_eq (mg.g^-1)	K₂ (g.mg^-1.min^-1)	R²
Pb²⁺	5.83	0.537	0.704	6.21	0.128	0.593
Zn²⁺	4.00	1.826	0.999	4.02	6.348	0.999

Sorbent	Heavy metal	Parameters	q_eq (mg/g)	Ref.
Chocolate B clay	Pb²⁺	C₀ (10, 30, 50 mg.L^-1), pH (3.0, 4.0, 5.0)	3.36	This work
Chocolate B clay	Zn²⁺	C₀ (10, 30, 50 mg.L^-1), pH (3.0, 4.0, 5.0)	3.72	This work
Gray clay	Zn²⁺	Mechanical agitation (100 to 200 rpm), pH (6.0 to 8.0), C₀ (10 to 50 mg.L^-1)	4.37	³⁵35 P.N.M. Vasconcelos, W.S. Lima, M.L.P. Silva, A.L.F. Brito, H.M. Laborde, M.G.F. Rodrigues, Am. J. Anal. Chem. 4 (2012) 510.
Chocobofe clay	Pb²⁺	C₀ (10, 30, 50 mg.L^-1), pH (3.0, 4.0, 5.0)	3.36	⁵⁰50 W.S. Lima, A.L.F. De Brito, M.G.F. Rodrigues, M.F. Mota, M.M. Silva, Mater. Sci. Forum 805 (2015) 662.
Natural zeolite	Pb²⁺	C₀ = 20 mg.L^-1, pH = 7.5	7.80	⁷⁵75 M. Sprynskyy, B. Buszewski, A.P. Terzyk, J. Namieśnik, J. Colloid Interface Sci. 304 (2006) 21.
	Ni²⁺		5.40
	Cu²⁺		1.40
Brasgel clay	Cd²⁺	C₀ (10, 30, 50 mg.L^-1), pH (3.0, 4.0, 5.0)	2.63	⁷⁶76 J.D. Mota, R.S.S. Cunha, P.N.M. Vasconcelos, M.G.F. Rodrigues, Mater. Sci. Forum 912 (2018) 202.
Activated carbon	Cu²⁺	C₀ = 100 to 500 mg.L^-1, pH = 5.0, T = 30 °C	4.00	⁷⁷77 P.S. Kumar, V. SathyaSelvaBala, K. Ramakrishnan, P. Vijayalakshmi, S. Sivanesan, Russ. Chem. Bull. 59 (2010) 185.

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Removal of Pb2+ and Zn2+ using modified Chocolate B clay: a study using statistical analysis, equilibrium isotherms, and adsorption kinetics

Abstract

Removal of Pb²⁺ and Zn²⁺ using modified Chocolate B clay: a study using statistical analysis, equilibrium isotherms, and adsorption kinetics