Removal of Some Cationic Contaminants from Aqueous Solutions Using Sodium Dodecyl Sulfate-Modified Coal Tailings

A sample coal tailings activated by Sodium Dodecyl Sulfate (SDS) surfactant was used as an efficient adsorbent for the removal of lead from an aqueous solution. The effects of three factors, namely, initial solution pH (3-11), absorbent to lead ratio (12.5-162.5), and contact time (3-31 h), on lead removal, were studied and optimized using response surface methodology. Statistical analyses showed that all factors significantly affect lead removal. Process optimization resulted in maximum lead removal of 99.64% at initial solution pH of 6.75, absorbent to metal ratio of 91.33 and 20 h equilibrium contact time, and 97.4% removal after about 40 min. Kinetic studies revealed that lead adsorption follows the first-order model with a rate constant of 10.39 h^-1 . The selectivity study in bimetal aqueous systems using copper, lead and zinc metals showed the adsorption order of Cu^2+ Pb^2+, Pb^2+ Zn^2+ , and Zn^2+ Cu^2+ with some unusual trends. The lead adsorption on activated coal tailings was also found to follows the Freundlich isotherm model. The interaction mechanisms between SDS and the surface of coal tailings particles were also discussed. This study demonstrates that SDS-activated coal tailings could be considered as a promising efficient, low-cost, and easily available adsorbent for the treatment of heavy metal polluted wastewaters.