Arsenic removal from aqueous system using natural and modified (Kula ebonite and zeolite) adsorbents



Natural adsorbents (Kula ebonite, zeolite and zeolite treated with Al2(SO4)3; Al2(SO4)3+NaOH; FeCl3 and FeCl3+NaOH) were prepared and employed by means of batch method for selective adsorption and removal of arsenic from aqueous system. The influences of different parameters such as, contact time, pH, temperature, and concentration of adsorbate on adsorption performance of zeolite and zeolite treated with FeCl3 and FeCl3+NaOH were studied in order to optimize the adsorption conditions. Batch adsorption studies have shown that removal capacity of zeolite from aqueous solutions can be increased by FeCl3 and FeCl3+NaOH treatment. The maximum adsorption capacities were 1.99 and 3.43 mg g−1 of zeolite which was treated with FeCl3 and FeCl3+NaOH for arsenic, respectively. The adsorption data obtained follows a first-order rate expression and fits the Langmuir isotherm that has been used to obtain thethermodynamic parameters. In addition, the thermodynamic parameters, standard free energy (ΔG°), standard enthalpy (ΔH°), standard entropy (ΔS°) of the adsorption process were calculated. It was found that the adsorption of arsenic on zeolite was exothermic. © 2011 American Institute of Chemical Engineers Environ Prog, 2011