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

Seyedein Ghannad, S. M. R., Lotfollahi, M. N.
International journal of environmental science and technology 2019 v.16 no.7 pp. 3697-3706
aqueous solutions, bentonite, cadmium, composite materials, copper, equations, heavy metals, lead, metal ions, pH, sorbents, sorption, strength (mechanics), zinc
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.