Conversion of Volcanic Tephra to Zeolites for Calcium Ion Cross-Linked Alginate-Zeolite Composites for Enhanced Aqueous Removal of Cu(II) Ions
2015
Wang, Yifan | Luo, Min | Xu, Fang | Zhang, Wenzhong
After alkaline hydrothermal conversion of volcanic tephra to zeolite (VT-Z) particles, calcium ion cross-linked alginate-zeolite composites (VT-Z/CA) were subsequently fabricated as sorbents for enhancing removal of Cu(II) ions from aqueous solution. The naturally occurring VT minerals were used as silica and alumina sources for zeolite crystallization. The conversion conditions were optimized by altering the alkaline concentration, conversion time, temperature and addition of ethanol. After the synthesized VT-Z particles were entrapped into CA biopolymer template, the developed VT-Z/CA composites not only make full use of the excellent adsorption capabilities of zeolites but also prevent the major problems of mobility/agglomeration for zeolite particles in aqueous media. The VT-Z/CA composites were characterized and studied for aqueous removal of Cu(II) ions in a batch mode. Solution pH 5.5 was found to be the best choice. The kinetic data were evaluated by the pseudo-first, pseudo-second order, and Elovich model. The adsorption kinetics followed the pseudo-first model. Langmuir isotherm best described the adsorption behavior with the maximum adsorption capacity for Cu(II) at 121.1 mg g⁻¹ (45 °C). The composites were successfully explored for treatment of Cu(II)-bearing livestock farm wastewater in China. The VT-Z/CA composites offer a highly attractive alternative for remediating heavy metal contaminated water with advantages of being easy to operate, cost-effective, biodegradable, and environmentally benign.
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