Cadmium removal using waste residue generated after recovery of base metals from manganese nodules

Abstract

The laboratory scale investigations on Cd2+ removal characteristics of waste manganese leach residue (wMNR), generated by reduction roasting – ammonia leaching of manganese nodules, are described in this paper. Adsorption studies showed rapid kinetics of Cd2+ adsorption. About 90% of total Cd2+ adsorption occurred within 15 min contact time and equilibrium was attained within 30 min. The quantity of Cd2+ adsorption increased with increase of leached residue dose but decreased with increase of initial Cd2+ concentrations. The adsorption was found to be dependent on initial pH of Cd2+ solution, which increased with increase in initial pH of the solution. Adsorption data were satisfactory fitted to the Langmuir isotherms. The loading capacity of Cd2+on leached residue calculated from Langmuir data was 32.26 mg g-1 at pH 5.5and 303 K, which improved to 38.17 at 323 K. Pseudo second-order kinetics was applicable for the Cd2+ adsorption. Thermodynamic studies indicated spontaneous (ΔG0, -3.88, -5.04 and -6.0 kJ mol-1 at 303, 313 and 323 K respectively) and endothermic (ΔH0, 28.3 kJ mol−1) nature of adsorption. The activation energy for Cd2+ adsorption onto wMNR, calculated to be 50.76 – 65.14 kJ mole-1, suggested chemisorption type adsorbate-adsorbent interaction.