The Study On Removal Of PCB₂₀₉ From Aqueous Solution By Ultra-zero Valent Iron In Modified Bentonite

Polychlorinated biphenyls(PCBs) are a kind of extremely has the representative organic pollutants, due to its stable physical and chemical properties and insoluble in water characteristics of the long-term existence in the environment, and with the migration and transformation happens in the natural and human activities. Nano- zero-valence iron as a new kind of reduction repair material, which has the characteristics of small size, large specific surface area and so on, can accelerate the degradation of PCBs. Through the preparation and characterization of the material, the reduction reaction is revealed from the deep level. The by liquid phase reduction of nanoscale zero valent iron, the bentonite on the load, and by tetramethyl ammonium bromide(TMA), phenyl trimethyl ammonium bromide(PTMA) and cetyl trimethyl ammonium bromide(HDTMA) on Bentonite supported nano zero valent iron is organic modified, tetrahydrofuran analog dense non aqueous phase liquids, decachlorobiphenyl as the object, the organic modification of bentonite bentonite embedded ultrafine zero valent iron for the groundwater heavy repair effect of polychlorinated biphenyls in nonaqueous phase liquids, research has achieved certain effect. The main research contents of this paper are as follows:1. Experiment and of tetrahydrofuran in mixed water solution in decachlorobiphenyl dissolution characteristics, THF and water mixed solution of decachlorobiphenyl has good solubility, even of tetrahydrofuran and water mixing ratio is 1:9, decachlorobiphenyl can in order to dissolve the state exists in thesolution, there will be no precipitation, fully meet the requirements of simulation experiment.2. Experimental study of three kinds of representative organic modifier four methyl bromide, ammonium bromide, phenyl three methyl sixteen alkyl three methyl bromide in the process of modified bentonite ultrafine embedded zero valent iron, modifier in satisfy each molecule alone under the conditions of existence(dissolution the amount is not less than its critical micellar solubility CMC), modifier modified relationship between the amount of dosage, effect, can better control the proportion of different dosage of bentonite ultrafine embedded zero valent iron particles. The results show that with the increase of modifier dosage, particle size smaller, larger specific surface area, particle agglomeration effect has been significantly inhibited, dispersion improved. Among them, the chain scission of tetramethyl ammonium bromide modified superfine bentonite bentonite embedded zero valent iron particles change minimum although particle size decreases, the specific surface area increased, but the effect is not as good as the benzene ring structure of phenyl trimethyl ammonium bromide modified materials, cetyl trimethyl ammonium bromide modified material effect is the most significant, particle size and specific surface area changes most significantly, greatly improve the physical and chemical properties of materials and dispersion morphology, provide rational support for the follow-up study on the degradation reaction.3. using has the better dispersion of cetyl trimethyl ammonium bromide by 95% of the cation exchange capacity(CEC) of bentonite bentonite embedded ultrafine modified zero valent iron particles and heavy degradation in non aqueous phase liquids in ten chlorine biphenyl(concentration of 2.5 ppm) degradation effects and response to environmental factors. The results show that the cast solution with low p H, high temperature, large iron dosage, higher organic solvent ratio and long chain structure is to improve the removal rate of decachlorobiphenyl. In addition, under differentconditions, the removal efficiency of the organic bentonite loaded nano iron to ten is better than that of the unmodified nano iron and ordinary reducing iron powder Organic modified bentonite bentonite embedded ultrafine zero valent iron enhances the particle specific surface area, reducing the particle size, increasing the effective concentration of iron ion and good reduces the effect of agglomeration of nanoscale zero valent iron, is helpful to improve the zero valent iron in the reductive dechlorination reaction in the reductive degradation efficiency rate and on p H changes have buffer action, but also reduce the precipitation of iron ions, which avoids the secondary pollution to the environment. The synergistic effect between the adsorption of organic modified bentonite and the zero valence nano iron reduction effect was significantly improved. Lower solution p H, high temperature, large iron cast dosage, higher organic solvent ratio and long chain structure is to improve the removal rate of decachlorobiphenyl. In addition, under different conditions, the removal efficiency of the organic bentonite loaded nano iron to ten is better than that of the unmodified nano iron and ordinary reducing iron powder. Organic solvent dosage and modified nano zero valent iron dispersion at the same time, disturbance is better than that of the solvent molecules, will be a small amount of bentonite by zero valent iron precipitation, organic modifier dosage increase investment, increase in structure of the chain structure, increase organic surname bentonite iron from precipitation, is not conducive to ten PCBs removal, but better than zero valent iron particles structure change, modifier dosage, the effects of long chain structure is greater than the reduction in the relative amount of zero valent iron.