Bentonite polymer composite for water purification

Abstract

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, surface area measurements and chemical methods, the obtained product was mainly composed of Ca-BT with a specific surface area of $$4.13 \hbox { m}^{2} \hbox { g}^{-1}$$ . The optimal conditions for adsorption of $$\hbox {Pb}^{2+}$$ and $$\hbox {Cd}^{2+}$$ 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 $$\hbox {Pb}^{2+}$$ and $$\hbox {Cd}^{2+}$$ , the adsorption equilibrium was described by the Freundlich model, 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 $$\hbox {Pb}^{2+}$$ and $$\hbox {Cd}^{2+}$$ were found to be 22 and 18 mg $$\hbox {g}^{-1}$$ , respectively. The rate constants calculated for the sorption of $$\hbox {Pb}^{2+}$$ and $$\hbox {Cd}^{2+}$$ were 6.29 and 6.67 g $$\hbox {mg}^{-1} \hbox { min}^{-1}$$ , respectively, at $$25^{\circ }\hbox {C}$$ . This study shows that the obtained sorbents based on BT may be used for treatment of waste water and could help resolve environmental protection issues.