汽油中典型苯系物在静止水相中的溶解及乙醇增溶效应研究

Study on dissolution of gasoline typical benzene series in static aqueous phase and solubilization effect of ethanol

汽油中典型苯系物(苯、甲苯、乙苯和3种二甲苯的同分异构体,统称BTEX)在含水介质中的溶解情况直接关系到下游BTEX污染程度和污染范围,是汽油泄漏区制定污染场地修复计划的关键资料。为探究汽油BTEX在静止水相中的溶解情况及乙醇对BTEX溶解的影响,利用微元体开展了传统汽油和乙醇汽油(乙醇体积分数10%)静态溶解批实验。结果表明:在静止水相中,油水体积比为1∶70的条件下,水相中BTEX浓度在前9天呈线性快速上升,第13天后进入平衡状态,平衡质量浓度为119.63~130.76 mg/L,溶解速度为8.39~13.75 mg/(L·d)。乙醇对汽油中的BTEX有一定增溶作用,但效果不明显,且BTEX在乙醇汽油中的溶解速度比传统汽油慢。砂层对BTEX存在吸附作用,可以增强BTEX的溶解。Raoult定律能较好地预测汽油BTEX在静止水相中的溶解,其中高溶解度组分苯和甲苯的实测浓度与预测浓度较为接近。

The dissolved situation of typical benzene series(benzene,toluene,ethylbenzene and 3 xylene isomers,collectively referred to as BTEX)of gasoline in the aqueous medium is directly related to the degree and scope of downstream BTEX pollution,which is the precondition and key to the restoration plan of contaminated site in gasoline leakage area.In order to investigate the dissolution of gasoline BTEX in static aqueous phase and the effect of ethanol on BTEX disslution,a microcosm experiment by using traditional gasoline and ethanol(volume fraction of 10%)blended gasoline was carried out.The results showed that the dissolution concentrations of gasoline BTEX increased linearly and rapidly in the first 9 days,and entered the quasi-equilibrium state after 13 days under the condition that the oil-water volume ratio was 1∶70.The equilibrium mass concentration of BTEX ranged from 119.63-130.76 mg/L,and the dissolution rate ranged from 8.39-13.75 mg/(L·d).Ethanol stimulated the dissolution of gasoline BTEX but not obvious.Interestingly,the dissolution rate of BTEX in ethanol blended gasoline was slower than that of traditional gasoline.Sand had an influence on BTEX dissolution maybe due to adsorption.Raoult’s law could well estimate BTEX dissolution in static water,in which the estimated concentrations of benzene and toluene were closer to the measured concentrations.