Preparation of granular composite materials as novel sorbents and their application for removal of heavy metals from solution

Abstract

A granular composite material (GCM) consisting of beta-zeolite-/powder activated carbon (PAC), organic binder (MC) and inorganic binder (bentonite) was prepared from powdered samples. GCMs were prepared successfully at a constant concentration of MC (10 wt%) and bentonite (30 wt%) and at various ratios of β-zeolite/PAC (0.05–0.5). The results indicated that the GCMs had high iodine values (981.9–1170.1 mg/g) and suitable mechanical strength (180.55–323.86 N). A series of batch sorption experiments for removal of Zn2+, Cd2+, Cu2+ and Pb2+ from aqueous solutions were performed with two selected composites of GCM2 (β-zeolite/PAC ratio = 0.05) and GCM9 (β-zeolite/PAC ratio = 0.4) under various conditions (contact time and pH). Maximum sorptions of Zn, Cd and Pb at pH 5.5 and that of Cu at pH 6 were attained at equilibrium time of 80 min and initial metal ions concentration of 20 mg/L. The results showed that the sorption of Zn2+, Cu2+, Cd2+ and Pb2+ by GCMs increased by increasing the β-zeolite/PAC ratio. The maximum sorption occurred at the β-zeolite/PAC ratio of 0.4. The maximum sorption capacity order of GCM2 in unit of mg g−1 was: Pb2+ (13.684) > Cu2+ (13.300) > Cd2+ (12.717) > Zn2+ (12.590). The maximum sorption capacity order of GCM9 in unit of mg g−1 was: Pb2+ (15.983) > Cu2+ (15.066) > Cd2+ (14.760) > Zn2+ (14.481). Three equations of Morris–Weber, pseudo-first order and pseudo-second order were investigated to study the kinetics of sorption process. The kinetic data showed that sorption of heavy metal ions was well described by pseudo-second-order equation.