Removal of the residual xanthate from flotation plant tailings using bentonite modified by magnetic nano-particles

Abstract

The residual organic reagents (including xanthates) in the flotation tailings can cause environmental issues during their disposal, besides their deleterious influence on the flotation performance during recycling. In this study, the adsorption characteristics of bentonite modified with copper and manganese ferrite nanoparticles (BeeCuFe2O4, BeeMnFe2O4) for xanthate removal from the synthetic and real solutions was studied. The characterization studies by XRF, XRD, BET, SEM, EDX, VSM and FTIR techniques confirmed the formation of magnetic nanoparticles. The adsorption capacity of BeeCuFe2O4 was found to be higher than BeeMnFe2O4 and at optimum conditions (adsorbent dosage: 4 mg/mL; xanthate concentration: 1000 mg/L; pH=9.2; time=40 min) more than 94% of the residual xanthate was removed by this adsorbent. The kinetic studies showed that rate of xanthate adsorption on both adsorbents followed the pseudo-second order model. The intraparticle diffusion was not the only rate-limiting step of the adsorption process. The equilibrium isotherms were best fitted to the Langmuir model. This suggests monolayer adsorption of xanthate on homogenous sites of the adsorbents. The thermodynamic studies revealed that the adsorption process was spontaneous, endothermic and entropy-driven. The synthesized adsorbents were capable of completely removing xanthate from the actual samples taken from the tailings of a copper flotation plant (Qaleh-Zari, Iran).