[show abstract][hide abstract] ABSTRACT: 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.
[show abstract][hide abstract] ABSTRACT: An indigenously prepared, steam activated and chemically modified carbon from husk and pods of Moringa oleifera (M. oleifera), an agricultural waste, was comparatively examined as an adsorbent for the removal of lead from aqueous solutions. Studies were conducted as a function of contact time, initial metal concentration, dose of adsorbent, agitation speed, particle size and pH. Maximum uptake capacities were found to be, 98.89, 96.58, 91.8, 88.63, 79.43% for cetyltrimethyl ammonium bromide (CTAB), phosphoric, sulfuric, hydrochloric acid treated and untreated carbon adsorbents, respectively. Bangham, pseudo-first- and second-order, intra-particle diffusion equations were implemented to express the sorption mechanism by utilized adsorbents. Adsorption rate of lead ions was found to be considerably faster for chemically modified adsorbents than unmodified. The results of adsorption were fitted to both the Langmuir and Freundlich models. Satisfactory agreement between the metal uptake capacities by the adsorbents at different time intervals was expressed by the correlation coefficient (R(2)). The Langmuir model represented the sorption process better than the Freundlich one, with R(2) values ranging from 0.994 to 0.998.
Journal of Hazardous Materials 01/2007; 138(3):604-13. · 3.93 Impact Factor