Competitive adsorption of Pb~(2+) and Zn~(2+) ions from aqueous solutions by modified coal fly ash

摘要

Coal fly ash (CFA), which is a solid waste generated in large amounts worldwide, is mainly composed of some oxides having high crystallinity, including quartz (SiO_2) and mullite (3Al_2O_3 2SiO_2), and unburned carbon as a mesopore material that enables it to act as a dual site adsorbent. To decrease the crystallinity, CFA was modified by sodium hydroxide treatment. The modified fly ash (MFA) contains lower amount of Si and Al and has a higher specific surface area than the untreated fly ash (CFA). The objective of this study is to investigate the competitive adsorption of Pb~(2+) and Zn~(2+) from aqueous solutions by CFA and MFA. The effect of pH, contact time and initial concentration was investigated. Effective pH for Pb~(2+) and Zn~(2+) removal was 4. A greater percentage of Pb~(2+) and Zn~(2+) was removed with a decrease in the initial concentration of Pb~(2+) and Zn~(2+). Quasi-equilibrium reached in 240 min.