Study On Ability Of Phosphorus And Nitrogen Fixation Of Synthetic Zeolite From Coal Fly Ash Under Different Synthetic Conditions

Coal fly ash have hogged the number one spot among three solid waste in China. Annual emissions of fly ash have reached 5.7 tons, while the utilization rate is only 69%. So much fly ash needs a large of cropland to deposit and cause many environment problems in water, atmosphere and soil environment. In addition, eutrophication is the key point of water pollution control. It’s the basic to control the content of nitrogen, phosphorus and other pollutants in a reasonable range. In this study, fly ash were used to synthesize zeolite adopting alkaline fusion method. The purpose is to investigate the effect of different synthesis conditions on quality of the synthetic zeolite、 phosphorus immobilization capacity and cation exchange capacity of the synthetic zeolite. The main conclusions are as follows:(1) Different calcium content leads to the different synthetic product from coal fly ash. The main synthetic product from the high calcium* middle calcium 、low calcium coal fly ash are respectively Katoite, Na6[AlSiO4]64H2O and NaP1 zeolite.(2) High calcium fly ash could be used as raw material to synthesize zeolite for phosphorus removal, while synthetic zeolite from low calcium coal fly ash could be suitable for the removal of nitrogen. In this research, the maximum phosphorus immobilization capacity is 92.24mg/g and the maximum adsorption capacity for nitrogen obtained is 41.37mg/g.(3) Considering NaOH/fly-ash mass ratio、melting temperature、melting time、solid-liquid ratio and crystallization time, the effect of NaOH/fly-ash mass ratio and melting time on phosphorus uptake of synthetic zeolite is relatively larger than others, and the effect of solid-liquid ratio and crystallization time on nitrogen uptake of synthetic zeolite is larger. The mechanism of phosphorus immobilization is Ca2+ in zeolite precipitated with PO43- as calcium phosphate precipitation. Besides, the nitrogen fixation ability is controlled by the cation exchange capacity.