Coal fly ash zeolites as adsorbents for effective removal of heavy metals and dyes from contaminated waters

Recently, the purification of enormous amounts contaminated industrial, agricultural and municipal waters increases the demands of low-cost and technologically feasible techniques. The application of natural zeolites in wastewater treatment is known from many years. A feasible approach for processing of zeolite-like materials that possess advantages similar to the natural minerals and can be replaced by them in variety of applications is the alkaline conversion of fly ash (FA) from coal. FA is easily converted to zeolites X, A and Y which are the most important zeolite types for practice due to their surface properties. In this study, fly ash zeolites (FAZ) of Na-X type were synthesized by different laboratory techniques. It was established via nitrogen adsorption/desorption studies that the obtained FAZ possess suitable surface characteristics for adsorption of different contaminants from waters. The adsorption efficiency of FAZ with the highest specific surface value for removal of methylene blue from water media reaches over 60 % for the studied concentration levels. The removal efficiency of FAZ toward Cd2+-ions is in the range 94-98 % and it is not influenced by the pH parameter from 3.0 to 7.0. The obtained results reveal that FAZ are suitable adsorbents in water remediation systems. Acknowledgements This work was financially supported by National Science Funds, Ministries of Education and Science of Republic Bulgaria and Slovak Republic in the frame of bilateral research project under Grant DNTS Slovak Republic 01/6 (SK-BG-2013-0025).