Acid-base modification of zeolite and environmental protection applications of modified zeolite

rv ABSTRACT The natural clinoptilolite can be used as an ion exchanger for the removal of heavy metals and for the treatment of environmental pollution because of its desirable characteristics of high ion exchange selectivity and resistance to different media. The modification of zeolites is realized by treatment with acid and base solutions as well as inorganic compounds during which ion-exchange process is utilized.. In this way zeolites gain new valuable properties while they preserve some of their original characteristics. A structural change including physical, chemical, thermochemical and mechanical aspects takes place in chemically modified zeolites. Mostly, the modified zeolite possess more useful characteristics for environmental problems (Földesova ve ark., 1999; Kang ve Egashira, 1997; Ortega ve ark., 2000; Gates ve ark., 2000; Kooyman ve ark., 1997; Ponthieu ve ark., 1992). In this study the sorption effectiveness of Manisa-Gördes clinoptilolite which present a vast reserve has studied. The mineralogical structure (XRD, XRF, SEM), the chemical composition, and the effect of the chemical modification on the structure of the zeolite were carried out. Also, the sorption and cation exchange capacities of the zeolites for Cu2+, Zn2+, Fe3+ ve Pb2+ were improved using acid/base and chemical modifications. Finally, the sorption and desorption mechanisms and optimal conditions (the particle size, the initial cation and/or anion concentration, initial pH, contact time, liquid/solid ratio) for these cations were outlined using Batch method. The sorption kinetics of metals were investigated using Freundlich and Langmiur isotherms. AAS and UV-vis Spectrophotometric methods were used for the determination of metal concentrations. The Si/Al ratio, theoretic (TCEC) and experimental (CEC) cation exchange capacity of natural and modified zeolites were calculated. Maximum sorption with all metals is supplied with natural and base modified zeolites. The order of metals according to cation exchange capacities is found as Pb2+>Fe3+ >Zn2+>Cu2+.