Research On Removal Effect And Mechanism Of Typical Pharmaceutical And Personal Care Products By Reverse Osmosis Membranes

Pharmaceutical and personal care products（PPCPs）have become widespread in the environment as an emerging pollutant,and their unique biological toxicity and ecological risks have attracted attention.Conventional water treatment can hardly meet the requirements of removing PPCPs,and there is still a large potential safety risk in conventionally treated water.This paper mainly studied the removal characteristics of typical PPCPs by reverse osmosis.Three typical PPCPs（ibuprofen,carbamazepine,triclosan）were selected as the research objects to analyze the removal mechanism of PPCPs by reverse osmosis membrane,and the treatment process conditions were optimized through the factor design,providing reference for the practical application of PPCPs removal by reverse osmosis.And the effect of simulated DOM and Ca²⁺coexistence water conditions on the removal of PPCPs by reverse osmosis was studied on this basis.By studying the effect of ultrafiltration pretreatment on the reverse osmosis removal effect of organic matter in the three kinds of actual water bodies（MBR effluent,tap water,surface water）,the content and variation rule of dissolved organic matter in the process of ultrafilter-reverse osmosis were analyzed.The main conclusions are as follows:（1）The removal rate of PPCPs increases with the increase of initial influent concentration and pre-membrane pressure.p H affects the removal effect by affecting the electrostatic interaction between PPCPs and the membrane.The removal effect of PPCPs in water is the result of the combined effect of dimensional repulsion and electrostatic repulsion.The process was optimized by the factor design method,and it was found that the removal rates of reverse osmosis on IBU,CBZ,and TCS could reach98.93%,97.47%and 99.01%respectively under the optimal conditions（with an influent concentration of 500μg/L,pre-membrane pressure of 16 bar and p H=10）.The dynamic adsorption of PPCPs by reverse osmosis membrane satisfies the primary reaction kinetic adsorption model.Through model fitting,it was found that the adsorption capacity of PPCPs on the membrane is affected by the initial concentration,pre-membrane pressure and p H.The hydrophobic affinity between PPCPs and the membrane surface is the driving force of adsorption,and electrostatic repulsion also affects the adsorption effect of PPCPs on the membrane surface.（2）Ca²⁺can promote the accumulation of humic acid（HA）and sodium alginate（SA）on the surface of reverse osmosis membrane,but has little effect on the morphology of contaminated layers of bovine serum protein（BSA）membrane.In a certain concentration range,Ca²⁺can intensify the organic contamination on reverse osmosis membrane,leading to a decrease in flux.The increase of Ca²⁺concentration can also promote the formation of dense organic contamination layer,increase the hydrophobicity of the membrane surface,and decrease the charge density of the membrane surface.The removal effect of PPCPs under water quality conditions of DOM and Ca²⁺coexistence is mainly influenced by two mechanisms:the sieving effect of the organic contamination layer on the membrane surface and the complexation of PPCPs with organic and inorganic ions.The sieving effect of the organic contamination layer prevents the distribution and transport of PPCPs molecules in the membrane pore channels,thus enhancing the removal rate of PPCPs;Ca²⁺can reduce the charge density of membrane surface and organic matter,weaken the electrostatic repulsion between the membrane,organic matter and PPCPs,and promote the formation of dense contamination layer;it can also affect the removal rate by bridging or changing the organic matter conformation to influence the complexation effect of PPCPs and organic matter.The effect of Ca²⁺concentration on PPCPs removal rate is the result of multiple mechanisms.The kinetics of adsorption of PPCPs on reverse osmosis membranes under the conditions of DOM and Ca²⁺coexistence in water is also consistent with the primary reaction model.With the increase of Ca²⁺concentration,the stable adsorption capacity of IBU and TCS increased,while the stable adsorption capacity of CBZ decreased.The electrostatic repulsion between IBU,TCS and the membrane was weakened,resulting in an increase of adsorption on the membrane;the dense organic contamination layer hindered the adsorption of CBZ on the membrane.（3）MBR effluent water,tap water and surface water mainly contain five DOM types:high and low excitation tyrosine,high and low excitation tryptophan,and ultraviolet fulvic acid.Due to the different water quality,the same pore size ultrafiltration membrane for the same kind of DOM removal rate in different water bodies vary greatly.Ultrafiltration had the highest DOM removal rate for tap water,and the removal rates of protein-like substances and fulvic acid-like substances could reach more than 80%;while the highest removal rates of protein-like substances and fulvic acid-like substances in MBR effluent water were only about 40%;the highest removal rate of fulvic acid-like substances in surface water was 28.07%,and the removal rates of protein-like substances were 70%～80%.The removal rate of all kinds of DOM can reach more than 80%after ultrafiltration with different pore size and reverse osmosis double membrane treatment.