Applicability Evaluation Of Titanium Coagulation In Antimony Removal From Dyeing Wastewater Before Membrane Filtration For Water Reuse

In recent years,Antimony(Sb)pollution in the printing and dyeing wastewater has aroused widespread concern.In the dyeing process,antimony could be released to varying degrees at different stages of the process,posing a huge threat to human health and the ecological environment.On the other hand,the large water consumption in the dyeing industry makes water reuse very necessary.At present,the water reuse process based on coagulation membrane filtration is commonly used.However,iron-based coagulation,which can effectively remove antimony,is difficult to apply to the reverse osmosis membrane due to its large membrane pollution.Aluminum-based coagulant is commonly used in the reverse osmosis membrane filtration process,but aluminum-based coagulants cannot remove antimony so the concentration of antimony in reverse osmosis concentrate is extremely high(>1 mg/L).As a result,it cannot be discharged until further treatment meets the standard.Therefore,it is of great significance to find a coagulant that can be used as membrane pretreatment and has high antimony removal performance.Aiming at the problem of the removal of antimony from dyeing wastewater and the inability to directly discharge reverse osmosis concentrated water in the conventional coagulation membrane filtration process,this paper uses a new titanium gel coagulant(TXC),as well as the traditionally used polyferric chloride(PFS)and polychlorinated aluminum(PAC),reserached the performance and mechanism of antimony removal by different coagulants,and conducted a pilot test of coagulation-membrane filtration.Through the treatment results of three kinds of antimony-containing wastewater,including simulated and actual dyeing wastewater,it is found that compared with PFS and PAC,TXC has an efficient coagulation removal ability for antimony.In the treatment of the effluent from the biochemical precipitation of the dyeing wastewater,when the p H 3,the dosage of TXC is 100 mg/L,the antimony concentration of the effluent is only 4.25?g/L,which meets the national drinking water standard.Also,TXC has a more stable antimony removal ability than PFS.Among the 11 coexisting substances selected,only CO₃^2-and PO₄^3-have a certain inhibitory effect on the antimony removal effect.Through analysis and characterization methods such as Zeta potential,scanning electron microscope,X-ray diffraction,X-ray photoelectron,etc.,it is proved that the antimony removal mechanism of TXC is mainly through chemical adsorption.The combination of TXC coagulation and ultrafiltration reverse osmosis treatment is in good condition,and it has realized the efficient and stable removal of antimony in the biochemical precipitation effluent of dyeing wastewater.During the entire pilot experiment,the average antimony concentration of TXC coagulation effluent,ultrafiltration effluent,reverse osmosis effluent,and reverse osmosis concentrated water were 34.4,25.4,1.0,and 77.5?g/L,respectively.The reverse osmosis concentrated water meets the discharge limit of 100?g/L specified in the"Water Pollutant Discharge Standard for Textile Dyeing and Finishing Industry"(GB 4287-22),and no need for further antimony removal treatment.During PAC pilot experiment,only the reverse osmosis treatment can effectively remove antimony,the rest of the process units have no antimony removal effect.The average concentration of antimony in the reverse osmosis concentrated water is as high as 1240?g/L.It needs to be coagulated by PFS to remove antimony to meets the standard before discharge.At the same time,the membrane fouling degree of the TXC pilot plant is smaller than that of the PAC plant.The flux of the ultrafiltration membrane after TXC coagulation decreases slowly,the flux can be restored to 70%after citric acid cleaning,which indicates the reversibility of TXC membrane fouling is high.While the flux of the ultrafiltration membrane of the PAC device decreases rapidly,and most of them are irreversible fouling.For the reverse osmosis membrane,the filter cake layer of the reverse osmosis membrane of the TXC device is thinner than that of the PAC,which proves that the surface of the reverse osmosis membrane after the TXC coagulation treatment during operation is less pollutants and the degree of pollution of the reverse osmosis membrane is low.The research results of this article showed that TXC is a coagulant with high antimony removal ability and suitable for combined use with membrane filtration,and it is expected to be used in the treatment and water reuse of antimony-containing wastewater.