The Study Of Ammonia Nitrogen Adsorption By Modification Fly Ash In Eutrophication Water

In eutrophic water, ammonia is one of the main factors that cause eutrophication. Fly ash, as a solid waste,in the thought of pollution control "waste controled by waste", will be used by us as adsorbent to absorb ammonia in eutrophic water. Through simulation experiments, this essay studies different methods of fly ash modified, and analyzes how the different factors, such as gray water ratio, pH, particle size etc, influence ammonia adsorption.Studies have shown that different modified methods have different effects on enhancing fly ash to adsorb ammonia nitrogen, and modified fly ash can improve ammonia adsorption performance indeed. The experiments show that the order of how modified fly ash increased ammonia adsorption is:double-modified> modified> microwave modified>heated modified-unmodified, double-modified fly ash can increase the maximum ammonia adsorption capacity, and in order to improve fly ash ammonia adsorption capacity better, we combine two methods in the experiment, which proves to be the best method to absorb ammonia nitrogen First, use microwave modified, then double-modified. Microwaved Double-Modified Fly Ash (MMMFA) does not release ammonia; pH impact greater on MMMFA’s adsorbing ammonia. When the solution is neutral, MMMFA has the maximum removal rate; MMMFA’s dosage also have relatively great impact on adsorbing, when the gray water ratio is1:50, the ammonia nitrogen removal rate reached more than75%. If we continue to increase the amount of adsorbent, the ammonia nitrogen removal rate increases marginally; particle size is an important parameters which affect the adsorption properties, from experiment we know that:fly ash whose particle size is bigger than200mesh have bigger removal rate than less than100mesh and100-200mesh fly ash; when the nitrogen and phosphorus co-exist, phosphorus will affect MMMFA to adsorb ammonia nitrogen, as the phosphorus concentration increases to2mg/L, the ammonia adsorption unit amount gradually decreases from1mg/g to0.8mg/g..In accordance with the correlation coefficient of the dynamics, we can see the pseudo-first-order kinetic model is more accurate to describe MMMFA’s characteristics of adsorpting ammonia, the correlation coefficient is more than97%, and though dynamics simulation we know that MMMFA adsorbing ammonia has characteristic "rapid adsorption, slow balanced", and at the initial stage has the maximum adsorption rate in entire adsorption process, the rate gradually decreases when the adsorption amount increases.At room temperature, from the isothermal adsorption curve analysis experiment,we can see:Langmuir can fit best on MMMFA adsorbing ammonia, then is Freundlich,and Henry is the worst, the first two pertinence are up to0.95. Langmuir isotherm equation can calculate the maximum theoretical adsorption capacity that MMMFA adsorb ammonia is39.68mg/g. Also MMMFA absorbs ammonia consistent with the Freundlich adsorption isotherm, which means the adsorption is the multi-layer adsorption too. And empirical constants n>1, Description MMMFA has good adsorption activity. Therefore, it can be used as a good adsorbent, inhibiting the development of eutrophic water.