| With the rapid development of industrialization in human society in recent decades,the pollution of water environment has intensified,and the types of pollutants in water have become more complex and diverse,among which hydrophilic pollutants are significantly higher than hydrophobic pollutants due to their high water solubility.Therefore,the removal of hydrophilic pollutants in the water environment is a key research priority in the field of water treatment.It is well known that phosphorus(P)is the main pollutant of eutrophication in water bodies and exists mainly in ionic form in water bodies.Phosphorus-containing wastewater seriously damages water ecosystems.At the same time,phosphorus is a valuable resource,and it is of practical significance to target the efficient removal and recovery of phosphorus enrichment in water bodies.Phenol and its derivatives are a class of small molecule hydrophilic aromatic compounds,which are widely used as raw materials for industrial and household products,and the pollution of water bodies by phenols is extremely common and harmful.There is an urgent need for new technologies for the removal of phenolic pollutants from water bodies.Currently,there are still many problems with the methods of phosphorus removal and phenolic pollutant removal in water bodies,such as high cost of removal materials or processes,and even the risk of secondary pollution to the environment.Adsorption is one of the water treatment methods that can be easily applied industrially,especially the adsorption membrane water treatment technology has a series of advantages,including good self-supporting,high water flux,low energy consumption,and good recycling performance.For the removal and enrichment of phosphorus and the removal of phenolic pollutants in water bodies,this study uses inexpensive and readily available polypropylene fiber membrane(PPM)as the substrate and N-vinylformamide(NVF),which can be hydrolyzed to provide positively charged adsorption sites after graft copolymerization,as the modified monomer to obtain modified PPM adsorption membranes for the efficient adsorption capture and leaching concentration of phosphate negative ions in water bodies.The adsorption performance of the modified membranes on phenol was investigated,and modified polypropylene fiber membranes with anti-fouling properties were obtained by copolymer grafting of amphiphilic monomer N-vinylpyrrolidone(NVP)with NVF to achieve the removal of phenol pollutants from water.Main contents are as follows:1.The modified membrane PPM-VA with high amine loading was prepared by a two-step UV grafting-hydrolysis method,and the surface element composition and membrane surface morphology of the modified membrane were characterized.2.Phosphorus removal and recovery in flow-through mode.Using 0.04 g of PPM-VA to treat river water containing 0.1 mg/L of phosphorus,the cumulative phosphorus removal rate reached 90%when the water flow volume reached 2 L.The total removal rate was still up to 69%when the water flow volume reached 12.47 L.Using 3.6 m L of 0.8 mol/L aqueous Na OH solution as the eluent,95.5%of the adsorbed phosphorus could be eluted with a concentration multiple of up to 2290 times,when the eluent flow volume reached 4.8 m L,the elution rate of adsorbed phosphorus reached 97.7%and the recovery rate of corresponding phosphorus reached 67%.Analysis of the regenerated treated PPM-VA membrane using FTIR and XPS showed no significant changes in the composition and structure of the regenerated membrane,exhibiting excellent structural stability,which implies that PPM-VA is expected to be applied to the phosphorus removal remediation of water bodies.3.For the adsorption removal of phenol compounds from water bodies,the interaction between modified polymers and the target pollutants was investigated using conductivity titration to guide the adsorption membrane design.Among the copolymers of different compositions examined,the strongest interaction of the copolymer with phenol was found at a molar share of NVP links of about 50%.It was also found that the increase in molecular weight of the copolymer helped to enhance the interaction with phenol in the aqueous phase and strengthen the adsorption performance.The results of conductivity titration experiments provide a basis for the design of graft modification of adsorption membranes.4.The NVP-NVF copolymerized graft-modified film PPM-VPVF was prepared by UV graft copolymerization(molar content of NVP units was about50%,and the heavy average molecular weight of graft chains was about 30,000g/mol).The resulting modified membranes were characterized by surface elements and morphology.The adsorption membranes exhibited ultra-high water permeability with a monolayer water flux of 70,600 L/(m~2·h)at a transmembrane pressure difference of 14 cm(140 Pa).Protein adsorption experiments demonstrated that PPM-VPVF has better fouling resistance than the original PPM membrane and the NVF homopolymerized graft membrane PPM-VF.5.The effects of grafting rate and aqueous phase ionic strength of the modified membranes on the adsorption of phenol in water were investigated.The results showed that the optimum grafting rate of PPM-VPVF was 38.0%,at which the adsorption amount of phenol was 17.02 mg/g(0.181 mmol/g),and the aqueous phase ionic strength had no significant effect on the adsorption performance of the modified membranes.the adsorption amount of p-cresol with hydrophobic methyl groups was higher for PPM-VPVF(up to 22.07 mg/g,0.204 mmol/g),indicating that the hydrophobic interaction could increase the adsorption amount.This indicates that hydrophobic interactions can increase the adsorption capacity.The adsorption kinetics and isothermal adsorption experiments showed that the adsorption of phenol on PPM-VPVF was in accordance with the proposed secondary kinetic model and Freundlich model,showing multilayer adsorption characteristics.15 and 10 adsorption-elution cycles of PPM-VPVF were performed in pure water and river water bodies,respectively,and the removal rates were maintained above 95%,showing excellent anti-fouling and cycle regeneration reuse performance.The PPM-VPVF membrane was immersed in common acids,alkalis and organic solvents for a long time,and no compositional and structural changes were detected by FTIR and XPS,showing that the membrane has excellent stability. |
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