1 Waste Re-processing Division, CSIR- National Environmental Engineering Research Institute (NEERI), Nehru Marg, Nagpur, 440 020, India. Electronic address: s_kumar@neeri.res.in.
2 Department of Chemistry, College of Science, King Saud University (KSU), Riyadh, 11451, Saudi Arabia.
3 Department of Chemical Engineering, School of Mining, Metallurgy and Chemical Engineering, University of Johannesburg, P. O. Box 17011, Doornfontein, 2028, South Africa.