Selective extraction of manganese using moringa oleifera seeds as bioadsorbent

Abstract

The adsorption of manganese onto Moringa oleifera seeds was optimized as a function of pH, adsorbent mass, particle size and contact time in aqueous solutions in batch tests. The results show that the optimized conditions for manganese adsorption were: pH 3.0, particle size ≤ 180 μm, adsorbent mass 1.0 g and contact time 15 min. Varying the pH allowed the separation of the manganese species, the seeds selectively retained Mn(II) while Mn(VII) remained free in solution. Around 60% of the Mn(II) was removed at an initial pH of 3.0 with a manganese concentration of 4 mg L-1. The adsorption process was evaluated through adsorption isotherms and kinetics studies. The maximum adsorption capacity for Mn(II) was 10.35 mg g-1. The isotherm followed the Langmuir model and the adsorption kinetics followed a pseudo-second-order kinetic model.