Analysis Of Antimony(?) Removal Efficiency By Combined Process Of Coagulation And Floc-preloaded And Ultrafiltration And Mechanism Of Membrane Fouling

Antimony(?)can cause chronic or acute poisoning to plants and animals.The antimony's remaval effect of coagulation-sedimentation process is limited.The ultrafiltration process combined with coagulation process can enhance the its effect,but membrane fouling b ecomes a limiting condition for its promotion and application.When the floc is preloaded on the the membrane suirface,it can become a barrier between the contaminant and the ultrafiltration membrane,which has high removal efficiency for metals and organic matter and can effectivel y alleviate membrane fouling.In this paper,the flocs produced by the pre-loaded water sample during the coagulation process are preloaded on the surface of the ultrafiltration membrane,and the combination of Coagulation-Floc-Preloaded-Ultrafiltration(CFPLU)is proposed,its pollutant removal efficiency and membrane fouling mechanism are explored.In this paper,the characteristics of pre-loaded floc layer on the surface of ultrafiltration membrane were investigated,which formed b y pre-loaded floc water samples with different solid content s.The thicker the pre-loaded floc layer,the larger the section cra ck width and the lower the interception ability of the contaminant,then the contaminant can directly contact the ultrafiltration membrane and causes pollution.The pre-loaded floc layer is loose and porous,and the Zeta potential is negative.So,there is an electrostatic repulsion between the the pre-loaded floc la yer and the surface of the ultrafiltration membrane,which is easily removed by h ydraulic backwashing.The PFS dosage,slow stirring time,pH of the water sample and the solid content of the pre-loaded floc water sample were taken as the experiment's conditions.The test results showed that the effluent antimony(V)concentration of the CFS process under each coagulation condi tion was much higher than 5 ?g/L.However,the removal efficiency of CFPLU process is much higher than CFS process 's,the humic acid removal rate is above 95%,and the effluent antimony(V)concentration under optimal conditions is less than 1?g/L.The slow stirring time and solid content have little effect on the removal efficienc y of antimony(V).When the pH of the water sample is in the range of 4-6 and the dosage is 30-70mg/L,the antimony(V)'s removal effect of the CFPLU process is best.Under the reaction conditions,the irreversible pollution,reversible pollution an d total pollution of the ultrafiltration membrane showed a trend of decreasing at first and then increasing,and the surface morphology of the ultrafiltration membrane was also different.The slow stirring time is short and the pollutant adsorption reactio n does not reach equilibrium.Under suitable slow stirring time,when the water sample is weak acid and the PFS dosage is large,the more adsorption sites are generated,the competition between humic acid and cerium(V)is weaker,and the adsorption of pol lutants is more complete.The smaller the floc particle size,the larger the specific surface area,then the more the contact point of the adsorption site with the contaminant,and the stronger the adsorption.When the dosage is excessive,the floc growth time is dela yed and the floc particle size is ver y small,then the pre-loaded floc layer and the ultrafiltration membrane transport channel are blocked in the filtration process.When the water sample is alkaline,the removal efficienc y of the contaminant was low,which results that most of the humic acid is not removed and existed in aqueous solution,and small molecule humic acid will be adsorbed in the ultrafiltration membrane through the preloaded floc la yer.Both of the above conditions can cause membr ane fouling.Under the same conditions,the pollutant's removal efficienc y and membrane fouling degree of the coagulation-sedimentation(CFS)process,direct ultrafiltration(UF)process,floc pre-loaded ultrafiltration(PL-UF)process and coagulation-ultrafiltration(CF-UF)process were compared with coagulation-floc pre-loaded-ultrafiltration(CFPLU)proces.The result shows that the CFPLU process has the highest pollutant removal rate and the lowest membrane fouling,indicat ing that the pre-loaded floc la yer has the functions of retention,electrostatic attraction with ultrafiltration membrane and chemical bond adsorption,which separated the coagulated water sample and the ultrafiltration membrane surface.the small particle size contaminants of the coagulated water sample can be left on the pre-loaded floc layer 's surface and inside.The ultrafiltration membrane plays a role of further interception and adsorption,which strengthens the removal rate of pollutants.Futhermore,the pre-loaded floc layer red uces the number of the pollutants in coagulated water sample reaches the surface of the ultrafiltration membrane,and reduces the adsorption and clogging pollution of the ultrafiltration membrane.The pre-loaded floc la yer is also easi er to remove during b ackwashing,which reduces irreversible pollution and improves the recover y rate of membrane flux.