Study On Adsorption Performance Of Modified Aminated Cotton Material For Disinfection By-products In Drinking Water

Water disinfection is an essential water treatment process in order to control the harmful pathogens and protect human health.However,the reaction between disinfectant and natural organic matter(NOM)in raw water would produce various disinfection by-products(DBPs),which pose a potential threat to human health.Therefore,it is necessary to take effective measures to control DBPs in drinking water.Adsorption method is widely used in the control of water pollutants in industry.Therefore,this study aims at investigation of the DBPs removal performance and mechanism with the adsorption method.In the first part of this study,the aminated cotton was prepared via the surface-initiated polymerization of the the PGMA polymer brush through UV irradiation and redox reaction,and the subsequent amination reaction with diethylenetriamine(DETA).The aminated cotton was characterized by SEM,FTIR,XPS and element analyzer.The best preparation condition was obtained with the nitrogen content of up to 7.2%.Then,the prepared aminated cotton was used as the adsorbent to investigate the dynamic adsorption performance of eight DBPs in the column adsorption mode,and the derived breakthrough curve was fitted by the Thomas model.With the sodium hydroxide solution as the desorption agent,the desorption and regeneration performance of the aminated cotton adsorbed with DBPs was investigated.In the second part of this study,the aminated cotton was used to adsorb the natural organic matter(NOM)in the simulated raw water.In addition,the aminated cotton was also used to study the removal of the brominated disinfection by-products(Br-DBPs)and chlorinated disinfection by-products(Cl-DBPs)in the simulated drinking water after chlorine disinfection,and the iodine disinfection by-products(I-DBPs)in the simulated drinking water after chloramine disinfection.The removal effect of the aminated cotton on the DBPs and its precursor NOM in the simulated drinking water was investigated.The main results are as follows:(1)For the column adsorption test,At the initial influent concentration of 100μg/L and the flow rate of 40 m L/min,the aminated cotton showed greater breakthrough adsorption capacity and longer breakthrough time for the eight DBPs with low concentrations,including2,4,6-trichlorophenol(TCP),2,6-dichloro-4-bromophenol(DCBP),2,4,6-tribromophenol(TBP),2,4,6-triiodophenol(TIP),2,6-dichloro-4-nitrophenol(DCNP),2,6-dibromo-4-nitrophenol(DBNP),3,5-dichlorosalicylic acid(DCSA)and 3,5-dibromosalicylic acid(DBSA),as compared with the original cotton and activated carbon.All the breakthrough curves obtained were successfully fitted by the Thomas model.The simulated adsorption capacity derived from the fitting of the Thomas model ranged from 14.76-89.47 mg/g,and the linear correlation coefficient of the fitting ranged from 0.915 to 0.998.In the neutral solution,the adsorption mechanism of the aminated cotton for phenolic DBPs was mainly due to the intermolecular hydrogen bonding between the amino groups of the aminated cotton and the phenolic hydroxyl groups of DBPs.In addition,the protonated amino groups also improved the adsorption performance through the electrostatic attraction.0.1%Na OH solution was used as the desorption agent for DCBP,TCP,TBP,TIP,DCSA and DBSA desorption from the aminated cotton,while 0.5%Na OH solution was used for DCNP and DBNP.(2)The overall levels of DBPs in disinfected drinking water decreased significantly after the adsorption by the aminated cotton.The total ionic strength(TII)and the total organic halogen(TOX)of the polar halogenated DBPs showed that the removal efficiency of I-DBPs and Br-DBPs were over 80%,while the removal efficiency of Cl-DBPs was lower at about 50%.The aminated cotton showed different removal efficiency on different kinds of DBPs in drinking water.The DBPs removal efficiency(>85%)for triiodophenol,tribromophenol and diiodiohydrobenzoic acid as emerging aromatic compounds with strong toxicity was significantly higher than that for the common haloacetic acid-based DBPs(<40%).This was mainly due to the intermolecular hydrogen bonding between the aminated cotton and the unionized phenol hydroxyl and carboxyl groups.While the DBPs with lower p K_a values in drinking water at the neutral p H condition were not easy to form hydrogen bond with the amino groups.The aminated cotton showed a good adsorption effect not only for the formed DBPs but also for the natural organic matter(NOM)as DBP precursors.After disinfection,the overall generation level of the polar Br-DBPs in the simulated drinking water with the NOM removed by the pre-adsorption treatment was 94.3%,lower than that of the water without NOM removed.