Studies on the removal of nickel(II) ions by adsorption using various carbons - A comparative study

Studies on the removal of nickel(II) ions by adsorption on various carbons (commercial activated carbon (CAC) and chemically prepared ACs (CPACs) from raw materials like straw, saw dust and dates nut) have been carried out under batch mode of adsorption at 30 degrees C with an aim to obtain information on treating effluents containing Ni(II) ions. The effect of various experimental parameters such as (i) initial concentration (ii) contact time, (iii) dose of adsorbent, (iv) initial pH of the solution, with CAC and CPACs, (v) particle size of CPACs (except CAC) and (vi) ionic strength (with CAC and CPACs) at 200 rpm speed of agitation has been investigated. The percentage removal of Ni2+ ions increased with the decrease in initial concentration and particle size of the adsorbent and increased with the increase in contact time, dose of adsorbent and initial pH (6) of the slurry. Ionic strength decreased the extent of adsorption. The adsorption data were modelled with the Freundlich, Langmuir, Dubinin-Radushkevich and Redlich and Paterson adsorption isotherms and first-order kinetic equations such as of Natarajan and Khalaf, Lagergren, Bhattacharya and Venkobachar and modified Elovich equations and intraparticle diffusion model. The kinetics of adsorption is found to be of first order with intra-particle diffusion as one of the rate determining steps. Thermodynamic parameters were evaluated from the equilibrium studies carried out at 30 degrees, 35 degrees and 40 degrees C. Investigations on the desorption of Ni(II) ions from metal loaded ACs with various eluents and the possibility of reuse of regenerated ACs have also been carried out at 30 degrees C. The results on the removal of Ni(H) ions by CPACs are compared with CAC and cationic resin, Tulsion CXO-9(H). The results conclude that these carbons could be employed as low-cost alternative adsorbents to CAC in wastewater treatment for the removal of metal ions, in general, and nickel(R) ions, in particular.