COMPETITIVE ADSORPTION OF NICKEL, MANGANESE, CHROMIUM AND CADMIUM FROM AQUEOUS SOLUTIONS BY DIFFERENT ADSORBENTS

摘要

Landfilling is the primary solid waste disposal method in Jordan. Since Jordan is considered oneof the poorest countries with water resources, it is crucial to protect its groundwater resources from anypossible risk of contamination from landfill leachates. A survey on leachates from landfills of differentages and control systems in Jordan, performed by our group during the years 2009 and 2010, showedthat heavy metals concentrations in leachates were high exceeding the allowable limits of both JordanIndustrial wastewater and US Environmental Protection Agency. The main heavy metals with high riskare identified to be: Cr (0.66-20.5 mg/L), Mn (0.41-10.37 mg/L), Cd (0.48-4.5 mg/L), and Ni (0.74-6.69mg/L). In the present study, competitive adsorption of these four metals on different adsorbentsincluding: natural untreated shrimp shells (SH), granular activated carbon (GC), acid-treated granularactivated carbon (AGC) and acid-treated powder activated carbon (APC) were investigated undersimulated conditions. All adsorption isotherms were generated using the bottle point method, followingthe ASTM standard procedure (ASTM D3860-89a). Untreated granular carbon (GC) was the bestadsorbent for Ni removal from a simulated solution with 90% removal efficiency. AGC and APC bothshowed very high selectivity for Cr over other present metals with removal efficiency of 99%. For Mn,shrimp shells (SH) was the best adsorbent with 79% removal efficiency, while both GC and SHadsorbents have comparable efficiency for Cd removal from the simulated solution (92%). Order ofmetals selectivity for SH adsorbent was Cd ＞ Mn ＞ Ni ＞ Cr, for GC the selectivity was Cd ＞ Ni ＞ Cr ＞Mn, for both AGC and APC the order was Cr ＞ Cd ＞ Ni ＞ Mn.