Adsorption and ion exchange of toxic metals by Brazilian clays: clay selection and studies of equilibrium, thermodynamics, and binary ion exchange modeling

In this study, four Brazilian clays (Bofe, Verde-lodo, commercial Fluidgel, and expanded commercial vermiculite) were evaluated for their adsorptive capacity and removal percentage in relation to different toxic metals (Ni 2+ , Cd 2+ , Zn 2+ , and Cu 2+ ). The best results were obtained by expanded...

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Published in:Environmental science and pollution research international 2024-08, Vol.31 (38), p.50857-50873
Main Authors: da Silva, Thiago Lopes, da Costa, Talles Barcelos, de Carvalho Neves, Henrique Santana, da Silva, Meuris Gurgel Carlos, Guirardello, Reginaldo, Vieira, Melissa Gurgel Adeodato
Format: Article
Language:English
Subjects:
Adsorption
Adsorptivity
Aquatic Pollution
Atmospheric Protection/Air Quality Control/Air Pollution
Cadmium
Chemisorption
Clay
Earth and Environmental Science
Ecotoxicology
Endothermic reactions
Environment
Environmental Chemistry
Environmental Health
Equilibrium
Heat resistance
Heat treatment
Heavy metals
Ion exchange
Metals
Research Article
Thermal analysis
Thermal resistance
Thermodynamics
Vermiculite
Waste Water Technology
Water Management
Water Pollution Control
Zinc
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Summary:In this study, four Brazilian clays (Bofe, Verde-lodo, commercial Fluidgel, and expanded commercial vermiculite) were evaluated for their adsorptive capacity and removal percentage in relation to different toxic metals (Ni 2+ , Cd 2+ , Zn 2+ , and Cu 2+ ). The best results were obtained by expanded vermiculite, with cadmium removal reaching values of 95%. The most promising clay was modified by the sodification process, and the metal cadmium was used to evaluate the ion exchange process. The clays expanded vermiculite (EV) and VNa-sodified vermiculite were evaluated by equilibrium study at 25, 35, and 45 °C. At 25 °C, EV obtained a maximum adsorption capacity of 0.368 mmol/g and sodified vermiculite 0.480 mmol/g, which represents an improvement of 30.4% in modified clay capacity. At 45 °C, the sodified vermiculite reached 0.970 mmol/g adsorption capacity. The Langmuir, Redlich-Peterson Freundlich, and Dubinin-Raduskevich models were adjusted to the results. Langmuir provided the best fit among the models. The thermodynamic quantities (Δ S , Δ H , and Δ G ) demonstrated that the process is spontaneous and endothermic and the metal is captured by physisorption and chemisorption in the studied temperature range. For the ion exchange equilibrium, the binary Langmuir and binary Langmuir–Freundlich models were adjusted to the expanded vermiculite and sodified vermiculite isotherms, respectively. Both models were predictive. Thermal analysis indicated good heat resistance even after material modification. The apparent and real densities demonstrated that after each treatment or contamination, the clayey material undergoes contraction in its structure. An improved efficiency of the adsorbent was found after sodification. Graphical Abstract
ISSN:1614-7499
0944-1344
1614-7499
DOI:10.1007/s11356-024-34496-z