Study On Reduction Of Pb,As And COD In Industrial Wastewater By Titanium Coagulants

Industrial wastewater contains a large number of heavy metal ions and high concentrations of organic substances with persistent environmental damage effects.If the organic matters be directly discharged into the river without proper treatment,they would consume a large amount of oxygen in the water body and induce a serious black body odor effect.Heavy metals are more harmful.The most representative ones are lead,arsenic,etc.,which present different ion forms and exiting forms,and they are difficult to be handled.At the same time,only a small amount of such water discharged into the water body will cause extremely serious damage to the ecological environment and surrounding organisms.Aiming at this problem,this paper,based on simulated industrial wastewater,the removal effects of divalent lead(Pb(II)),trivalent arsenic(As(III))and organic substances pollutants by using polyaluminum chloride(PAC),polytitanium chloride(PTC)and titanium sulfate as coagulants through batch experiment were studied;the effects of initial pH,coagulant dosage and coagulant aids dosage on the removal efficiency of heavy metal ions and organic substances were analyzed;based on the previous researches,the optimal method of the treatment process were comprehensively analyzed by structuring response surface method experimental scheme;the effects of pH and coagulant dosage on floc size were analyzed;and the coagulants were evaluated from the aspects of treatment effects,application cost and environmental effects.This research showed that:(1)PAC,PTC and titanium sulfate had the better removal effect on heavy metal ions,and the lower removal rate of organic matter.(2)In single-factor experiments,higher pH and PAM dosages reduced the removal rates of some pollutants,and excessive dosage of coagulants did not have a negative impact.(3)Based on the results of the previous single-factor experiments and combined with the optimal experimental process by Design Expert,a response surface optimization experiment plan was designed.After a systematic analysis,it can be seen that the pH of the water body was the main factor affecting the removal effect of Pb(II).The amount of coagulant added has a greater effect on the removal of As(III)and organic matter.(4)When comparing the results of orthogonal experiments,the conclusions of the single-pollutant orthogonal experiment and the three-pollutant orthogonal experiment showed consistency,that is,PTC was better in treating heavy metal pollutants,and PAC removes organic matter better,however,the difference between PTC and PAC in the removal of organic matter was smaller.(5)According to the analysis of the particle size of the floc,it is known that the particle size of the titanium salt coagulant is generally larger than that of the PAC,and the pH has a great influence on the particle size of the floc.(6)Through comprehensive evaluation,it can be seen that the advantages of PTC compared with PAC are mainly reflected in the removal effect,settlement performance,Pb(II)removal cost and environmental impact,while the advantage of PAC removing As(III)and COD mainly reflected in coagulant adding cost.Therefore,PTC is considered as the coagulant with a broad application prospect.