Esearch On Coggulation Behavior And Coagulation Mechanism Of Zirconium Salt Coagulant

The coagulation process is one of the most commonly used processes in watertreatment,and its treatment effect is mainly determined by the type of coagulant and the water environment.In today’s domestic and foreign water treatment processes,the most widely used inorganic coagulants are aluminum salts and iron salts.However,this type of conventionalcoagulant has many shortcomings.With the improvement of effluent water qualityrequirements,its shortcomings are gradually exposed.Therefore,it is urgent to develop a new type of high-efficiency coagulant to meet the needs of current water treatment.Zirconium salt is a new type of flocculant with excellent coagulation characteristics.It has received certain attention in recent years due to its environmental protection characteristics,but relevant basic research has not yet been systematically carried out.This article mainly studies thecoagulation behavior of zirconium salt coagulation and its coagulation mechanism.At the same time,the application effect of zirconium salt coagulant in the treatment of differentwater samples is studied,and the coagulation effect is further proposed for water samples with poor coagulation effect.A coagulation scheme was formulated,and the coagulation behavior of zirconium salt under the improved scheme was studied.The main experimental contentsand conclusions are as follows:（1）Prepare polymeric zirconium sulfate coagulant（PZS）and polymeric zirconiumchloride coagulant（PZC）coagulant by the micro-drop alkali method,and the alkalinitygradient is set to（0.5,1.0,1.5,2.0,2.5）.The effects of PZS and PZC alkalinity,dosage,and initial p H value of water samples on the coagulation effect of simulated domestic sewage were explored.Experimental data shows that the best coagulation conditions for PZScoagulant are:the best alkalinity is 1.0,the best dosage is 32mg/L,and the best initial p H is 6.Under the optimal conditions,the remaining turbidity of the coagulated effluent is 0.55NTU,the TOC removal rate is 89.3%,and the total phosphorus removal rate is 98.2%;but theeffluent p H is 3.58,and subsequent treatment is required.The best coagulation conditions for PZC are:the best alkalinity is 1.5,the best dosage is 24mg/L,and the best initial p H is 6.Under the optimal conditions,the remaining turbidity of the coagulated effluent is 0.67NTU,the TOC removal rate is 77.9%,and the total phosphorus removal rate is 85.1%;the p H of the effluent at this time is 6.74 and no subsequent treatment is required.Through Zeta potential analysis,it is concluded that the main coagulation mechanism of PZS and PZC coagulants in the treatment of simulated domestic sewage is the principle of electric neutralization.Themaximum size of the flocs produced by PZS can reach 1680μm,the maximum size of the flocs produced by PZC can reach 1600μm,and the flocs produced by the amount ofcoagulation have higher strength factors and recovery factors.（2）The effect of zirconium oxychloride coagulant（ZOC）on the treatment ofsecondary effluent from simulated sewage plants,oily wastewater,fluorine-containingwastewater,cadmium-containing wastewater,dye wastewater,and surface water was studied.Among them,fluorine-containing wastewater,dye wastewater and surface water have better coagulation effects.When the initial p H of fluorine-containing wastewater is 6,the fluorine removal rate can reach 65%;the removal rate of dye wastewater（methylene blue）can reach up to 92%;the remaining turbidity after the treatment of surface water is 1.5NTU,and UV₂₅₄removal The rate is close to 70%.The coagulation effect on other water samples is poor.Although ZOC has a removal rate of 90%for the turbidity of the secondary effluent,theremoval rate for UV₂₅₄is only about 30%;the removal efficiency for oily wastewater is close to 65%,but The formed flocs are not easy to settle and require further treatment;the removal efficiency of cadmium-containing wastewater is poor,and the maximum is only about 25%.（3）Researched the use of ZOC and other coagulants to solve the problems of ZOCin the treatment of secondary effluent,oily wastewater,and cadmium-containing wastewater.The ZOC and chitosan（CTS）coagulant are compounded and used to improve the oil removal rate.The optimum compound ratio is ZOC/CTS=1:1,and the optimum dosage（calculated as Zr）is 2mg/L,the best initial p H is 6,the oil removal rate of ZOC/CTS is increased by nearly50%compared to ZOC.,The maximum size of flocs produced by compounding is 3 times of the size of ZOC flocs used alone.ZOC/CTS is used to treat secondary effluent,and the best combination ratio is ZOC/CTS=1:2.After use,the UV254 removal rate is increased by 55%compared with ZOC alone,and 25%compared with CTS alone.;At the same time,ZOCcoagulant has poor temperature resistance and low low temperature coagulation effect,while ZOC/CTS has strong temperature resistance,and its coagulation effect is basically unchanged at low temperatures.For the cadmium-containing wastewater,the ZOC coagulant and PAC coagulant are used for compounding.The best compound ratio is Al:Zr=1:4,and the bestcadmium removal rate can reach 70%.The influence of different initial p H on the coagulation effect was investigated,and it was found that the higher the initial p H,the best removalefficiency of cadmium.The maximum size of the flocs produced by compounding can reach1200μm,and the strength factor is the largest.