Efficient and selective removal of Ag+ as nano silver particles by the composite of SiO2 supported nano ferrous oxalate

Abstract

Developing novel environmentally materials with high capacity and selectivity for Ag+ adsorption by transforming Ag+ to nano silver is important for the recovery of precious metals from Ag-containing solution. The present study systematically studied the Ag + adsorption process from solution by the composite of SiO2 supported nano ferrous oxalate (SNFO) synthesized from biotite-containing minerals. Batch experiments, dynamics and isothermal adsorption fitting results showed that Ag+ removal behaviours were in accordance with the pseudo-first-order kinetic model and Langmuir model, and the maximal Ag+ removal capacity was 223.68 mg/g. Thermodynamic fitting results suggested that Ag + removal by the composite was a spontaneous and endothermic reaction process. XRD and TEM revealed that the reaction products were consisted of SiO2 and nano silver particles, and FTIR and XPS results indicated that the Ag+ removal mechanisms were attributed to the synergistic reduction interaction between ferrous and the anions of oxalate. Meanwhile, the composite possesses high selectivity for Ag+ removal even at low Ag+ concentration. Moreover, the size of nano silver particles could be adjusted by different pH values. All above results demonstrated that the composite was an ideal material for selective recovery of Ag+ from Ag+ containing effluents in the form of nano silver.