Sorption of cadmium from aqueous solution by surfactant-modified carbon adsorbents

Sorption capacities for cadmium, Cd(II) on indigenously prepared, steam activated, untreated, surfactant-modified carbon powder, from husk and pods of Moringa oleifera were investigated. The optimized conditions for all the experimental runs were pH 8.0 ± 0.2, temperature 30 ± 0.5 °C, contact time 120 min, agitation speed 160 rpm, initial metal concentration 30 mg L^-1 and adsorbent dosage 1.0 g L^-1, respectively. Maximum Cd(II) removal, 98.0% was observed when cetyltrimethyl ammonium bromide (CTAB), cationic surfactant-treated carbon was used as an adsorbent. The Cd(II) removal percentages for sodium dodecyl sulphate (SDS), anionic surfactant, Triton X-100 (non-ionic surfactant) treated and untreated powder activated carbons were found to be 95.60, 81.50 and 73.36%, respectively. SEM images and BET surface area, porosity and pore volume measurements have revealed that surfactant-treated carbons have superior porosity and enhanced surface area than untreated carbons. The sorption data were correlated better with the Langmuir adsorption isotherm than Freundlich isotherm with R² values ranging from 0.91 to 0.98.