Study On Adsorption And Desorption Behavior Of Polar Halogenated Disinfection By-products In Reclaimed Water In Soil

Regenerated water replenishes groundwater is one of the effective measures to mitigate disasters such as regional groundwater resource shortages and ground collapses.Disinfection is the necessary process of regenerative water treatment,wherein the chlorine disinfection is good,and the cost is low,but the disinfection process has a large number of emerging polar halogenic disinfection by-products with strong carcinoma,teratogenicity and mutagenicity,toxicity.It is much higher than the traditional halogenic disinfection by-products.In recent years,they have been concerned by research scholars,but they have a fresh migration in the soil during the replenishment of groundwater.In this paper,2,4-dichlorophenol(2,4-DCP),2,4-dibromophenol(2,4-DBP)and2,4,6-tribromophenol(TBP),three emerging polar halogenated disinfection by-products with high frequency and high toxicity in wastewater and reclaimed water,were selected to study their migration behavior in typical soils in different regions.The main influencing factors and mechanisms of adsorption and desorption are explored,and the main conclusions are as follows:(1)Establish and optimize 2,4-DCP,2,4-DBP and TBP analysis methods based on high performance liquid chromatography(HPLC),and the detection limit is0.0340mg/L,0.0556mg/L and 0.0175mg/L.The four fences of Beijing,Anyang,Hangzhou and Harbin were collected,characterized by the physical and chemical properties such as soil pH,organic matter content(OC),cation exchange(CEC),mechanical composition and specific surface area.(2)Adsorption kinetic studies have shown that 2,4-DCP,2,4-DBP and TBP are rapid in the soil in the soil,and the suction rate is slow after 4h,and gradually reaches balance,the adsorption equilibrium time is 24h.Adsorption kinetics complies with the secondary rate equation,R~2 is between 0.9848 to 0.9998,and the adsorption process is based on chemical adsorption of chemical reaction or electron loss.(3)Adsorption thermodynamics has shown that 2,4-DCP,2,4-DBP and TBP can better meet the Henry and Langmuir models in four soils,most R~2 can reach 0.9.The maximum adsorption amount cm in the four soils in Beijing,Anyang,Hangzhou and Harbin were 0.1484 mg/g,0.0079 mg/g,0.0513 mg/g,and 0.3797 mg/g.The adsorption constant K_fin the Freundlich model can describe the size of soil adsorption capacity,the adsorption capacity of Beijing and Harbin soil is much higher than that of Anyang and Hangzhou soil.The lag coefficient H in Beijing and Harbin soil is less than 0.7,and there is obvious hysteresis,reflecting the irreversibility of the adsorption process.(4)The adsorption effect of environmental factors and soil physicochemical properties on 2,4-DCP,2,4-DBP and TBP in soil showed that temperature increase inhibition soil adsorption,adsorption reaction was exothermic reaction.Increased pH will inhibit soil adsorption.There is a competitive role between calcium ions and solutes,and the amount of adsorption is reduced during ion intensity.The soil pH and K_fvalue present a negative correlation relationship,OC and CEC and K_fvalue show a high positive correlation relationship.The soil adsorption is not the result of a single factor,but two or more factors together,when the number of factors is two,the resulting correlation coefficient is significantly higher than the correlation coefficient of a single factor,when the number of factors reaches three when or more,the correlation coefficient R~2 can reach 1.