Application of Shewanella xiamenensis Placed on Zeolite in Treatment of Silver-Containing Effluents

Abstract

The adsorption properties of Shewanella xiamenensis immobilized on zeolite have been evaluated in order to determine its applicability for remediation of silver-containing effluents with different chemical composition. The effects of pH (2.0–6.0), contact time (15–150 min), silver concentration (10–100 mg/L) and temperature (20–50 °C) on the bio-zeolite adsorption efficiency were investigated in batch experiments. The optimal pH for metal ions removal was in the range of 4.0–6.0, while the time required to attained equilibrium lay between 60 and 150 min. The adsorption of silver was described by a pseudo-second-order kinetic model in Ag- and Ag-Cu-Ni-Zn systems, while in Ag-Cu systems, it fitted well the pseudo-first-order kinetic model. The maximum adsorption capacities of silver on bio-zeolite calculated from the Langmuir model were 14.8 mg/g (Ag system), 32.5 mg/g (Ag-Cu system) and 12.8 mg/g (Ag-Cu-Ni-Zn system). The thermodynamic parameters showed that the adsorption of metal ions onto bio-zeolite was a spontaneous entropy-driven process.