Efficient removal of Pb(II) ions from aqueous solution by novel PVA-sodium alginate immobilized sulfate reducing bacteria

Abstract

In this study, a novel complex of polyvinyl alcohol (PVA) and sodium alginate impregnated with sulfate-reducing bacteria (SRB) was successfully synthesized and this versatile bio-composite was adopted as a highly efficient biological remover to eliminate toxic Pb(II) in aqueous solution. The immobilized SRB beads were characterized by scanning electronic microscopy-energy dispersive X-ray (EDX), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR). The surface of immobilized SRB beads were altered markedly and become much smoother after Pb(II) removal. Both EDX and XPS results confirmed that some Pb(II) accumulated on the surface of immobilized SRB beads. For a reaction to become a feasible treatment technique, the influences of pH, reaction temperature and initial sorbate concentration on the removal rate of Pb(II) were thoroughly investigated. The sorption results elucidated that the solution pH played an important role for the removal of Pb(II) ions. The Pb(II) sorption increased as the initial Pb(II) ion concentration increased and the optimal temperature for the removal of Pb(II) is 35°C. The greatest removal efficiency of Pb(II) was observed at 35°C and pH 8.0 with 50 mg·L –1 of Pb(II) in the reactive system. The bio-removal kinetics of Pb(II) by immobilized SRB beads were described well by Lagergren pseudo-second order and Langmuir model, as good kinetic fitting results and isotherms analyses achieved. Maximum adsorption capacity was determined to be 707.3 mg·g –1 under optimal conditions. The sorption results of PVA-sodium alginate immobilized SRB was compared with other forms of different adsorbents. The membrane diffusion phase is a rate-control step. FT-IR and XPS analyses implied that biosorption is the main mechanism for removal of Pb. Our findings demonstrated that the immobilized SRB beads had great potentials for the remediation of Pb(II) contaminated wastewater stream.