Bentonite polymer composite for water purification

[摘要] A polyethylene glycol (PEG)–bentonite (BT) composite was prepared by direct polymerization of PEG in suspensions of BT. Based on detailed analyses using field-effect scanning electron microscopy, X-ray diffraction, surfacearea measurements and chemical methods, the obtained product was mainly composed of Ca-BT with a specific surface area of 4.13 m$2^$ g$^{−1}$. The optimal conditions for adsorption of Pb$^{2+}$ and Cd$^{2+}$ ions were found to be a PEG content of 0.1% and a contact time of 60 min. The sorption experiments were performed under various operating variables, including polymer concentration, pH and temperature. For both Pb$^{2+}$ and Cd$^{2+}$%, the adsorption equilibrium was described by the Freundlichmodel, which confirmed the presence of a heterogeneous system with irregular filling of the active centres. The maximum sorption capacities of BT–PEG for removal of Pb$?^{2+}$ and Cd$^{2+}$ were found to be 22 and 18 mg g$^{−1}$, respectively. The rate constants calculated for the sorption of Pb$^{2+}$ and Cd$^{2+}$ were 6.29 and 6.67 g mg$^{−1}$ min$^{−1}$, respectively, at 25$^{\circ}$C. This study shows that the obtained sorbents based on BT may be used for treatment of waste water and could help resolve environmentalprotection issues.

[学科分类] 材料工程

[关键词] Bentonite clay;polyethylene glycol;lead;cadmium;sorption;composite materials.