Heavy metals (Pb, Cr) removal from aqueous solution by modified clinoptilolite

摘要

One of the most required characteristics of natural zeolites is the ability to selectively sort molecules. Zeolites preferentially adsorb certain molecules while excluded others. The ion exchange functions occurs when cations present in the solution are exchanged for cations in the structure (sodium, potassium, magnesium and calcium). Each zeolite has distinction exchange selectivity and adsorption capacity that can be more effective after modification. Physical and chemical regeneration can recover adsorption capacity of used zeolite. The scope of this study was to modify the natural zeolite clinoptilolite for its lead and chromium (Ⅲ) retention capacity. Clinoptilolite was pretreated by sodium chloride solution and sodium hydroxide solution under thermal and microwave irradiation. The removal of heavy metals were investigated by conducting as series of batch experiments. The lead and chromium (Ⅲ) ions retention capacity of thus obtained modified clinoptilolites were found to be good material for these heavy metals removal from aqueous solutions. For lead, the zeolite treated under microwave irradiation and NaCl had the highest heavy metal adsorption capacity value, followed by the zeolite obtained by thermal process and NaCl and by thermal process and NaOH. For chromium (Ⅲ), the clinoptilolite treated under thermal process and NaOH had the highest heavy metal adsorption capacity value, followed by the zeolite obtained by thermal process and NaCl and microwave irradiation and NaCl. Based on the obtained results, it was concluded that the thermal and/or microwave treated natural zeolite was a promising adsorbent for heavy metals such as lead and chromium (Ⅲ) removal from water. Due to their low cost and high adsorption capacity, the modified clinoptilolite has the potential to be utilized for cost-effective removal of lead and chromium (Ⅲ) from aqueous solution.