Study On The Treatment Of Mixture Pollutions Of Hydrocarbons And Petroleum Hydrocarbons By Granular Iron System

Groundwater pollution may consist of complex mixtures of compounds. Chlorinated solvents and petroleum hydrocarbons are two common classes of toxic organic contaminants that are often detected together in the contaminants. The sorption and degradation of trichloroethene(TCE) and tatrachloroethene(PCE) were investigated in zero-valent iron systems in the presence of benzene, toluene and xylene(BTX). The followings were the main results.(1) The sorption of benzene, toluene and xylene to iron surface could be described quite well by nonlinear Freundlich sorption isotherm expressions respectively. The extent of sorption followed the trend xylene>toluene>benzene.(2) The sorption of TCE, PCE to iron surface could be considered as quasi-equilibrium sorption isotherms since chemical degradation reactions are also taking place. The sorption could be described quite well by nonlinear Freundlich sorption isotherm expressions respectively. The extent of sorption followed the trend PCE>TCE. The reductive dechlorination of TCE, PCE could be described quite well by a pseudo-first-order model, respectively.(3) Compared with they existed singly, the Freundlich isotherm coefficients for TCE and PCE sorption decreased by 30% and 8% respectively, the rate constant for TCE and PCE degradation decreased by 31% and 33%, respectively, when mixed the TCE and PCE together.(4) In the presence of mixed BTX at low concentration and high concentration, the Freundlich isotherm coefficients for TCE sorption decreased by 78% and 84%, respectively, and the degradation rates have no significant change.(5) In the presence of mixed BTX at low concentration and high concentration, the Freundlich isotherm coefficients for PCE sorption decreased by 38% and 85%, respectively, and the degradation rates all increased by 50%.(6).Both TCE and PCE were affected by the competition for reaction sites, while only TCE was affected by competition for sorption sites, suggesting that reaction and sorption sites are different physicochemical entities on iron surface.(7) Groundwater co-contaminants could impact the sorption and degradation of chlorinated ethenes in zero-valent iron system by competition for a finite number ofreaction or sorption sites at the surface, depending on the physicochemical properties of the competitors.(8) It is necessary for designing and evaluating the performance of the permeable reactive barrier to think about the nonreactive sites sorption at iron surface.