Removal Effect And Mechanism Of Micro-polluted Organics By MIEX Combination Process

Recently,emerging contaminants are gradually becoming the focus of environmental research,among which pharmaceuticals and personal care products(PPCPs)are among the most important groups.Excessive usage and incomplete metabolism lead to the discharge of PPCPs into the aquatic environment.Certain PPCPs impose a long-term threat to humans,wildlife,and aquatic ecosystems.PPCPs cannot normally be effectively removed by traditional water treatment plants,and have been detected in wastewater effluent,seawater,surface water,and drinking water worldwide.There are two kinds of substances in natural water,one is natural organic matter and the other is inorganic turbidity substance.Natural organic matter and inorganic turbidity substance can influence the environmental distributions of various organic compounds between natural solids and water.In this master’s thesis,composite micro-polluted water is treated by coagulation,MIEX resin,ultrafiltration and its combination process.A variety of characterization methods were used to investigate the treatment effects and reaction mechanisms of pollutants.The specific research contents are as follows:Natural organic matter(NOM)in aquatic environments have a significant impact on NOM-organic compound interactions,which could strongly affect the distribution and transformation of organic compounds during water treatment.This study focused on the removals of NOM(humic acid,HA)and synthetic organic matter(ibuprofen,IBP)through enhanced coagulation and magnetic ion exchange(MIEX)resin adsorption in single and bi-component systems.Two coagulants,traditional aluminum sulfate(AS)and lab-prepared polyaluminum chloride(PACl),were employed.The charge properties,particle size distribution,and fractal dimension(D_f)during organic matter removal were studied in both the single and bi-component systems to explore the purification behaviors and mechanistic effects of interactions between coagulants,MIEX,and organic matters.The experimental results indicated that the Al-based coagulants could remove over 80%of HA in both the single and IBP-HA combined systems,while the presence of HA could considerably improve the IBP removal rate.The aggregates formed during single-component coagulation were larger,but weaker and more loosely structured than those formed in the bi-component system under the same coagulation conditions.In the single-component system,the maximum removal efficiencies of IBP and HA by MIEX adsorption were 65%and 72%,respectively,at a resin dosage of 20.0 mL/L and mixing time of 60 min.Under the same conditions,the removals of these components in the bi-component system were improved to 68%and 98%,respectively.The reaction rate between IBP and MIEX resin was found faster than that between HA and MIEX resin.Effect ofturbidity on the removal of organic micropollutant(carbamazepine,CBZ)through magnetic ion exchange(MIEX)resin combined with ultrafiltration(UF)was investigated in this study.The purification behaviors of the MIEX/UF processes were studied through scanning electron microscopy,high-performance liquid chromatography,Zeta potentialand particle size distribution analyses.The experimental results show that 64-74%of CBZ in different turbidities could be removed by MIEX resin under the optimum dose and contact time,while water sample with turbidity of 20±1.1 NTU present minimum CBZ removal rate of 64%and turbidity of 60±1.0 NTU led to maximum removal efficiency of 74%.The results of UF experiments showed that UF could not efficiently remove CBZ.Alternatively,UF wasmore suitable for removing turbidity than MIEX resin.In a separate UF system,the turbidity(20±1.1 NTU)led to a flux reduction of 60%at the first filtration cycle,while the reduction for 1.0±0.1 NTU,40±1.0 NTU and 60±1.0 NTU were 48%,52%and 45%,respectively.For the water sampleswith different turbidities,obvious decrease in membrane fouling was observed after MIEX pretreatment,meanwhile the CBZ/turbidityremoval could be improved.The UF membrane was used four times after backwashing to research the reusability of membrane.The integrated processes combining MIEX resin with UFcould significantly improve membrane recycling effect and prevent secondary pollution caused by resin.Removals of salicylic acid(SA),humic acid(HA)and turbidity particlein single-component and bi-component systemsby coagulation employing aluminum sulfate(alum)and lab-prepared polyaluminum chloride(PACl),adsorption using magnetic ion exchange(MIEX)resin and ultrafiltration(UF),werecomparatively investigated in this study.In single-component system,alum at sufficient dose,although efficient in removing HA,was not desirable in removal of SA.Conversely,higher SA removal rateinthe adsorptionprocess was achieved due to its superior adsorption tendencies and size-exclusion effects than that of HA.In the bi-component system,the SA and HA removal rates were observed to decrease to varying extents.The results demonstrated high molecular weight HA-Alcomplex could grow into enough large sizeand consequently tended to separate in water.For MIEX resin,parts of adsorption sites were preoccupied by HA and thereby result in the low SA removal efficiency.Furthermore,combination of MIEX resin and coagulation could significantly enhance organic matter removal.UF experimental results show that the removal efficiency of SA by UF is worse than that of MIEX resin but better than that of coagulation.Alternatively,UF wasmore suitable for removing turbidity than MIEX resin.The integrated processes combining MIEX resin with UF could significantly prevent secondary pollution caused by resin.