Preparation Of Composite Zeolite And Its Performance On Removal Of Ammonia Nitrogen And DBPs Precursors From Micro-polluted Water

In recent years,due to the population growth,the rapid development of economy and society and the speeding up of urbanization,the problem of source water pollution is becoming more and more serious.Because of the source water pollution,the concentrations of both ammonia nitrogen and disinfection by-products(DBPs)precursors go up,and the regular water treatment technology is difficult to make water quality meet the drinking water standards.Once the concentration of ammonia nitrogen and DBPs precursors are too high,the concentrations of nitrite and DBPs in drinking water are likely to rise,which seriously threaten the safety of drinking water and human health.As the zeolite is cheap,readily available and high selective adsorption to ammonia nitrogen,as well as the biochar is economic,safe and effiective,both of them have attracted extensive attention in recent years.Much progress has been made in the research of using zeolite or biochar to adsorb single pollutant such as ammonia nitrogen or DBPs precursors in water body,while the study of combing the two materials to remove the ammonia nitrogen and DBPs precursors from micro-polluted water synchronously is rarely reported,and need to be researched and discussed.Natural zeolite was modified,and the modified treatment zeolite was combined with biochar to prepare composite zeolite in this paper.Then take the modified zeolite,biochar and composite zeolite as adsorbents,and ammonia nitrogen,DBPs precursors such as-humic acid,fulvic acid and tryptophan as target pollutants,to compare the adsorption properties of each adsorbent on the target pollutants;experimentings respectively under the condition of ammonia nitrogen pollution,the single pollution of DBPs precursors and mixed pollution which means ammonia nitrogen mixed with a certain kind of DBPs precursors pollution,were made to analyze the effect of initial pH,temperature,composite zeolite concentration,initial concentration of pollutants and adsorption time on the adsorption properties of composite zeolite;and carry out application research on composited zeolite for actual micro-polluted water treatment,including removal effect of ammonia nitrogen,DBPs precursors,CODMn and turbidity,and also analyze the DBPs generation in both treated and untreated water samples after chlorination,especially the adsorption performance of composite zeolite on DBPs precursors.The main results are as follows.(1)First,the better method between the methods of heating salt modifying method and microwave salt modifying method was chosen and the optimum modifying conditons were found.And then we prepare the composited zeolite mainly using the modified zeolite with a defined amount of biochar,and compared the adsorption efficiency of modified zeolite,biochar and composited zeolite.The results indicated-that the adsorption efficiency of modified zeolite prepared using heating salt modification method was better,and the optimum temperature of this modified method was 65-70?;the smaller zeolite particle size had the better adsorption performance,and the proper particle size was less than 100 mesh;the optimal dose of biochar was 20%(biochar accounts for 20%of the amount of modified zeolite)to prepare the composited zeolite;and compared with modified zeolite and biochar,composited zeolite had the best ability to remove ammonia nitrogen and DBPs precursor synchronously.(2)pH value had large and different effects on adsorption of different target pollutants,and for adsorption treatment by composited zeolite,pH value of 7 was approprite to synchronously meet the target pollutants removal requests.Rising temperature could facilitate the adsorption indicating that the adsorption was endothermic reaction,and the appropriate temperature is 25? considering many factors.When the dose of composited zeolite was 18 g·L-1,the removal efficiencies of target pollutants could basically meet the requirements of effluent's concentration standard.In addition the adsorption kinetics conforms to second-order kinetic equation,and the adsorption isotherm was similar to Langmuir isotherm model.(3)Composited zeolite had a good performance on the treatment of actual micro-polluted water,and during the investigated water quality index,the removal rate of ammonia nitrogen,CODMn and turbidity reached to 58.87%,39.82%and 53.12%respectively.But due to the complexity of actual water sample,the treatment effect was slightly worse than that of simulated water.After treated by composited zeolite,the production of DBPs of the water sample was significantly reduced.When the concentration ratio of sodium hypochlorite and humic acid in the water was 0.5 and 1 during the chlorination,the amount of dibromoacetic acid(DBAA)produced in raw water is 14.98 and 23.41 ?g·L-1 respectively,while it reduced to zero after treated by composited zeolite.The results showed that composited zeolite has significant performance on the removal of DBPs precursor in micro-polluted water.