Removal of the residual xanthate from flotation plant tailings using modified bentonite

Abstract

Xanthates are the most widely used collectors for flotation of sulfide minerals. It has been estimated that about half of the organic reagents (including xanthate) added to the flotation circuits are consumed, while the remaining half are discharged into the plant tailing. The residual xanthate in the flotation tailing can cause environmental issues through contaminating of the nearby water resources as a result of poor design of the tailings dams. In this communication two modified bentonite adsorbents, namely acid-activated (H-Be) and aluminumpillared (Al-Be) bentonite, were synthesized and used for the removal of the residual xanthate (potassium amyl xanthate) from the synthetic and real solutions. Al-Be was found superior to H-Be in terms of adsorption performance and under optimum conditions (adsorbent dosage: 7500 mg/L; xanthate concentration: 2000 mg/L; pH=12.2; time=45 min) and more than 99% of the residual xanthate was removed. The kinetics data were best described by pseudo-second order model for the both adsorbents. The adsorption equilibrium isotherms were fitted by Freundlich, Langmuir, and Temkin models. The isotherm data were best-fitted to the Langmuir model, indicating monolayer adsorption of the xanthate on homogenous surfaces of the both adsorbents. The thermodynamics studies indicated that the adsorption was spontaneous, exothermic with the reducing entropy. The adsorption tests on the real samples taken from the tailing stream of a copper flotation plant (Qaleh-Zari in Iran) proved that both adsorbents are capable of removing more than 90% of the residual xanthate.