Dynamic Adsorption And Regeneration Performance Of Zeolite-biochar Based Composites To Remove Ammonia Nitrogen And Disinfection By-products DBPs Precursors In Micro-polluted Water

For a long time,due to the rapid growth of population,the acceleration of urbanization and the rapid development of society,the problem of water pollution is becoming more and more seriously.Excess nitrite and nitrate concentrations in ammonia nitrogen pollution water will not only produce carcinogenic nitrosamines and probably induce methemoglobin;due to drinking water chlorinated disinfection,disinfection by-products(DBPs)causes higher central nervous system harm.Such threaten the safety of drinking water and human health seriously.Zeolite has high adsorption capacity to ammonia nitrogen,and the price is cheap and easy to get.Biochar has high adsorption characteristics of organic carbon and economic safety.However few studies on the combination of the two materials were reported to remove ammonia nitrogen and DBPs precursors in micro-polluted water simultaneously.Salt modification of natural zeolite was conducted in this study,and the modified zeolite and biochar were combined to prepare zeolite-biochar based composites.Ammonia nitrogen and DBPs precursors,fulvic acid and tryptophan as target pollutants,for the single pollution(ammonia nitrogen,fulvic acid or tryptophan)and mixed pollution(ammonia nitrogen and one DBPs precursor),dynamic adsorption experiments were carried out to investigate the influences of flow velocity,initial pollutant concentration,particle size and initial pH on pollutant adsorption performance,and the penetration performance of the composite adsorption column was also investigated.Based on the results from synthetic water experiment,the actual micro-polluted water was treated by composites to verify the removal effect of DBPs precursor.In addition,the two methods,heating regeneration and microwave regeneration were used to explore the regeneration performance of zeolite-biochar based composites.The main results are as follows:(1)The natural zeolite was modified by salt to prepare zeolite-biochar based composites,the dose of biochar was optimized and the optimal particle size of composites was selected.The results show that when the biochar dose is 20%,the removal rates of ammonium,tryptophan and fulvic acid by composites simultaneously were the best.The adsorption removal rates of various pollutants decreased with the particles size of the composites and at the particle size of 3 mm,the adsorption efficiencies of various pollutants by composites were the best.(2)The dynamic adsorption performance of composites to remove ammonia nitrogen and DBPs precursors were investigated.The adsorption capacities of ammonia nitrogen,tryptophan and fulvic acid on composites changed with the variation of the flow rate.When the flow rate was 0.5 L/h,the removal rates of ammonia nitrogen,tryptophan and fulvic acid were the highest.The particle size of the composites had a great influence on the removal efficiency of pollutants.When the particle size was 3 mm,the adsorption rate of the pollutant on the composites is the highest.The effect of initial pollutant concentration on the adsorption performance of composites differed from pollutant species.The optimal initial concentrations of ammonia nitrogen,fulvic acid and tryptophan were 15,5 and 10 mg/L,respectively,and at the initial concentrations the adsorption rates of various pollutants on composites were optimum.pH had a great influence on the removal of the target pollutants by the composites.When the pH was 6,the adsorption rates of ammonia nitrogen,fulvic acid and tryptophan were the best.The treatment effect of actual micro-polluted water by composites was better.The results showed that the removal efficiencies of ammonia nitrogen in water taken from Yangtze River,Xuanwu Lake and Qinhuai River were 67.0%,48.0%and 53.8%,respectively,and the removal rate of COD were 33.0%,22.2%and 46.0%,respectively.(3)The regeneration performance of composites was investigated.Heating regeneration was used,and when the calcination temperature was 200 ? the adsorption performance of the regenerated composites to adsorb fulvic acid and tryptophan was the best;while at the calcination temperature of 300 ? the adsorption performance of the regenerated composites to adsorb ammonia nitrogen was the best.When the microwave regeneration was used,at the microwave power of 480 W the adsorption capacities of the regenerated composites to adsorb ammonia nitrogen and fulvic acid were the best.While for tryptophan adsorption,the optimal microwave power was 640 W,at this time the adsorption capacity of the regenerated composites was the best.