Effect Of Several Surfactant On Leaching And Adsorption Of Bentazon In Soil

Bentazon is a widely used herbicide in China,and there is a great threat to the pollution of groundwater and deep soil.By strengthening the organic pollutants in the soil adsorption and immobilization,the surfactant can regulate the adsorption and distribution behavior of organic matter in soil-water system,thereby surfactant can reduce the risk of contaminated deep soil or groundwater.In this paper,two kinds of soils,yellow brown soil and red soil,which were the most widely distributed in Anhui Province,were selected for the adsorption test of Bentazon in soils,andby studying the effects of cationic surfactants CTAB,nonionic surfactants TX-100 and CTAB-TX-100 mixture on the adsorption behavior of Bentazon in soil,and the effects of four nonionic surfactants of TX-100,TW-20,SPAN20 and AEO-9 on the leaching of bendasone in yellow brown soil,the following conclusions were drawn:(1)The adsorption kinetics of bendasone in yellow brown soil and red soil was found that adsorption equilibrium time of Bentazon in the two soils was at 24 h.Adsorption isotherm study found that,regardless of the presence or absence of surfactants,Bendanzon in the two soils are non-linear adsorption.(2)The adsorption constants of Bentazon in yellow brown soil and red soil were 0.36 and 0.45,respectively,when no surfactant was added.The effects of nonionic surfactant TX-100 on the adsorption and distribution of Bentazon was studied in the range of 0mg / L ~ 1000 mg / L in yellow brown soil and red soil,which were both weakness.The adsorption and immobilization of Bendazon in yellow brown soil and red soil was enhanced with the increase of the concentration of cationic surfactant CTAB in the range of 0mg/L ~ 2000mg/ L?(3)In the CTAB-TX-100 mixed system,when the CTAB concentration was constant(500mg /L),the addition concentration of TX-100 was changed to form a mixed surfactant.When the concentration of TX-100 was 1000 mg / L in CTAB-TX-100 mixed system,the adsorption constant Kd of yellow-brown soil was 0.93,which was 1.76 less than that without TX-100.In the red soil,the concentration of TX-100 in the mixed system is in the range of 10 mg / L ~ 100 mg / L,the adsorption constant has a slight increase(10.75 to 11.11).However,from the whole mixed system,the mixed surfactant-100 concentration(0-1000 mg /L)increased the adsorption constant from 11.21 to 2.32,adsorption fixation is still weakened.(4)The results showed that the addition order of CTAB and TX-100 could lead to a different distribution and adsorption behavior of the Bentazon in the soil.In yellow brown soil,when CTAB was added firstly and then TX-100 was added in the system,with the change of TX-100 concentration(0mg/L ~ 1000mg/L),the resulting adsorption constant decreased from 1.8048 to 0.8548,which was lower than that of the mixed surfactant(added in meanwhile)at the same TX-100 concentration,(from 0.98 to 0.9275).And when the addition of TX-100 first and then add CTAB in the system,with the TX-100 concentration changes(0mg/L ~ 1000mg/L),the resulting adsorption constant(from 2.0128 down To 1.1017)is higher than that of the mixed surfactant(added in meanwhile)at the same TX-100 concentration(from 1.98 to 0.9275).In the red soil,the increase of the concentration of TX-100 from 10 mg / L to 100 mg / L,No matter what the addition orders were added in the red soil,the adsorption constant of bendazon will raise 0.4.When the concentration of TX-100 was higher than its CMC(194mg / L),the adsorption constants of bentazon in red soil were decreased with the increase of TX-100 concentration.The adsorption constants of Bentazon were increased from 9.4945 to 2.4484 in the system with adding CTAB first and then adding TX-100,and the adsorption constant of bendasone decreased from 10.6609 to 2.6556 after adding TX-100 first then adding CTAB.At the same time,in the mixed surfactant(added in meanwhile)system,the adsorption constants of bendasone decreased from 9.6367 to 2.3181.From the whole system,the adsorption of Bentazon in the soil by the mixed system is weaker than the single addition of CTAB.(5)Leaching experiments found that the Bentazon in the yellow soil leaching rate is 76.84% without adding non-ionic surfactant.The leaching rate of Bentazon was increased in the soil with the addition of nonionic surfactants.The leaching rates of AEO-9,TX-100 and SPAN20,TW-20 at the 1CMC concentration were 94.13%,92.45%,86.59 and 81.43% respectively.At the 2CMC concentrationof AEO-9,TX-100,SPAN20 and TW-20,the leaching rates of Bentazon were 97.86%,95.80%,97.29%and 94.37% respectively.In the absence of surfactant,Bentazone was detected from15 cm in the soil column.When 1CMC concentration of the surfactant was added,Bentazonewas concentrated at 18 cm-30 cm in the soil column.For 2CMC,Bentazon is mainly concentrated at 24cm-30 cm in the soil column.