Rapid removal of heavy metal ions from aqueous solutions by low cost adsorbents

In the present investigation, different agricultural solid wastes namely: eggplant hull (EH), almond green hull (AGH), and walnut shell (WS), that are introduced as low cost adsorbents, were used for the removal of heavy metals (cobalt, strontium and mercury ions) from aqueous solutions. Activation process and/or chemical treatments using H2O2 and NH3 were performed on these raw materials to increase their adsorption performances. The effectiveness of these adsorbents was studied in batch adsorption mode under a variety of experimental conditions such as: different chemical treatments, various amounts of adsorbents, initial metal-ion concentrations, pH of solutions, contact times, and solution temperatures. High metal adsorption efficiencies were achieved for all cases only in the first two to three minutes of adsorbents' contact time. Maximum adsorption capacity of AGH sorbent for cobalt and EH for mercury were found to be 45.5 mg/g and 147.06 mg/g, respectively. The adsorption capacity of mercury for WS was also obtained as 151.5 and 100.9 mg/g for two different treated sorbents.