Removal of Cd(II) Ions from Aqueous Solution by Adsorption Using Manganese Nodules Leaching Residue

The present work reports the feasibility of using leached residue, generated in the process of reduction roast- ammonia leaching of manganese nodules, for removal of Cd(II) ion from its aqueous solution. The leached residue was washed with water to remove the entrapped liquor containing metals from leaching operation, dried and used for adsorption of aqueous Cd(II) under varying experimental parameters. X-ray diffraction patterns of leached residue before and after washing showed characteristics peaks of manganese carbonate and silicate. Particle size analyses showed very fine particles with mean particle diameters (d50) of 17.8 µm. The BET surface areas of leached residue before and after washing were found to be 60.9 and 66.7 m2 g-1, respectively. Adsorption studies by batch equilibrium method indicated that the equilibrium was attained within 30 min. The percentage of Cd(II) adsorption increased with increase of leached residue dose but decreased with increase of initial Cd(II) concentrations. The adsorption was found to be dependent on initial pH of Cd(II) solution, which increased with increase in initial pH of the solution. Adsorption data were satisfactory fitted to the Langmuir isotherms. During uptake of Cd(II) various metal ions, especially Mn and Fe, were found released from leached residue, which decreased with increase of pH and were practically negligible at pH~5-6. The loading capacity of Cd(II) on leached residue was 32.23 mg g-1 at pH 5.5. A pseudo-second order kinetics was applicable for the Cd(II) adsorption.