Treatment of monazite processed effluent to recover rare earth metals (REMs)

Abstract

Improper disposal of effluent generated in rare earth mining areas and ore processing industries results in loss of REMs and miserably affects the ecosystem. Thus, their appropriate treatment is required, which can be achieved via environmentally feasible processes. In this connection, systematic scientific adsorption studies were carried out to separate REMs using cationic resin, Amberlite IR120 Na from the effluent generated during monazite processing for REMs recovery. To optimize feasible conditions for REMs recovery, bench scale studies were carried out varying different process parameters viz. pH, contact time, resin dose, etc. It was observed that adsorption of 92.63% La, 92.79% Ce, 91.45% Nd, 90.95% Pr and 95.09% Sm was achieved at aqueous/ resin (A/R) ratio 25 mL/g, pH 1.3 and contact time 10 min. Loading capacity of resin was found to hold 48.57 mg REMs/g resin. The adsorption data followed the second order reaction ((t/q) =  (1/h) + (1/qe)(t)) and Langmuir adsorption isotherm (1/q = [(1/k1 qm)(1/Ce)] + (1/qm)). The loaded REMs was effectively eluted using 15% H2SO4 in 10 min. The REMs enriched solution was treated to get pure REM oxides as precipitate. This technical application will be useful for REMs recovery as well as to mitigate environmental pollution.