Study On Oxidation Of Chlorinated Hydrocarbons By Potassium Permanganate Supported On Montmorillonite K-10

Chlorinated aliphatic hydrocarbons is the organic who with the highest detection rate in groundwater pollutants, and trichloroethene(TCE) and tetrachloroethene(PCE) is the most famous in chlorinated aliphatic hydrocarbons, not only widely distributed, and greatly harmful, the repair of such pollutants in the groundwater environment is imminent. Through indoor controlled batch experiments, the research of oxidation degradation of trichloroethene and tetrachloroethene by potassium permanganate supported on montmorillonite K-10is carred out, to reveal capacity and kinetics characteristics of the oxidative degradation reaction, and provide a scientific basis for groundwater pollution remediation.Potassium permanganate is a strong oxidant for trichlorethylene and tetrachlorethylene, while montmorillonite has the function of adsorption and flocculation. potassium permanganate supported on montmorillonite can take advantage of oxidation of potassium permanganate, also can make use of adsorption, flocculation of montmorillonite, to solve the problem of manganese dioxide blockage and recycling of manganese dioxide.Potassium permanganate supported on montmorillonite is prepared by milling legal system, take20g montmorillonite,0.5g potassium permanganate, were ground together in a mortar until a fine homogeneous powder was obtained.In100min, supported potassium permanganate could removal more than97%TCE, and nearly50%PCE, the effect is very obvious. The rate of oxidative degradation of supported potassium permanganate is slightly slower than the potassium permanganate, proving the sustained release effect of montmorillonite. Montmorillonite also has function of flocculation and adsorption. Filtering the reaction residue, basically could not find black floc in the filter material, indicating the flocculation effect of montmorillonite to manganese dioxide, using supported potassium permanganate on montmorillonite to remove trichlorethylene and tetrachlorethylene is feasible.The effects and kinetic characteristics of the oxidative degradation reaction under different environmental conditions were studied:(1) With the increase in the amount of supported potassium permanganate, the reaction rate became higher. When the dosage was0.1g, the degradation of trichlorethylene was incomplete, and the degradation of tetrachlorethylene basiclly no occur; When the dosage was0.5g,1g,2g, the degradation of trichlorethylene was complete, the degradation of PCE was partial, and the degradation rate of PCE was increased with the increase of dosage. Experimental results have shown that the reaction appears to be first order under the difference of dosage conditions. With the increase in the amount of supported potassium permanganate, The reaction rate constant Kobs of TCE and PCE degradation reaction gradually become larger, the half-life gradually become smaller, the reaction rate constant Kobs and the amount of dosage have shown linear relationship.(2) With the increase in the concentration of chlorinated hydrocarbons, the time required for complete degradation of TCE became longer, the amount of PCE degradation was increased, but the rate of PCE degradation was reduced. Experimental results have shown that the reaction appears to be first order under the difference of initial concentration of chlorinated hydrocarbons. With the increase of initial concentration of trichlorethylene, tetrachlorethylene, The reaction rate constant Kobs of TCE and PCE degradation reaction gradually become smaller, and the two have shown obvious logarithmic correlation.(3) With increasing temperature, the reaction rate is increased, the time required for complete degradation of TCE became shorter, the rapid degradation of PCE ahead of time. Temperature of15℃to45℃, TCE degraded completely;25℃to45℃, PCE degradation rate increases with temperature rise. Experimental results have shown that the reaction appears to be first order under the difference of temperature conditions. Temperature between15℃to45℃, the reaction apparent rate constant Kobs are larger with increasing temperature. According to the Arrhenius equation, to draw the curve to show the correlation of the lnKobs under different temperatures and105/T, and then obtain the reaction activation energy Ea. The Ea of the degradation reaction of TCE and PCE were both less than40kJ-mol-1, indicating that the reaction more likely to occur, the reaction rate is relatively fast.(4) Under the the difference of initial pH values, the reaction rate were basically unchanged. This is because the first of the degradation reactions are both generating manganese cyclic ester, which is the step determining the reaction rate, then according to the different pH environment, the reaction path will be different, but the subsequent reaction rate had no significant effect on the overall reaction rate.(5) Analyzing the kinetic characteristics of the oxidation of trichlorethylene and tetrachlorethylene under the same conditions, we could found that the trend of the degradation rate of trichlorethylene and tetrachlorethylene with the changes of dosage is basically the same. PCE is more sensitive to the changing conditions of the concentration of chlorinated hydrocarbons, with the reduction of the concentration of chlorinated hydrocarbons, the reaction between potassium permanganate and PCE is more likely to occur. And PCE is more sensitive to temperature changes, with increasing temperature, the reaction between potassium permanganate and PCE is more likely to occur. In addition, this paper also studied the degradation characteristics of the one-component solution TCE and the one-component solution PCE by potassium permanganate supported on montmorillonite K-10, and compared these with the mixed solution. Coexistence of TCE and PCE may reduce the rate of degradation of each component, which TCE is shown easier to be degraded by potassium permanganate supported on montmorillonite.