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.