Preparation Of OA-Pluronic-Stabilized NZVI And Their Dechlorination Of 2,4-Dichlorophenol In Water

In situ dechlorination by direct injection of nanoscale zerovalent iron(NZVI) into the contaminated subsurface has attracted increasing interest in recent years.To achieve this goal,NZVI particles in water should form stable suspension,and the rate of corrosion by water should slow down.These two points can be achieved by coating the surface of NZVI with some surfactants.In this study,OA-Pluronic-stabilized NZVI were synthesized by coating NZVI with Oleic acid(OA) and Pluronic F-127, then 2,4-DCP was dechlorinated by the nanoparticles in different conditions.The main contents were as follows:1.NZVI was prepared by liquid-phase reduction,then it was Modif-ied by oleic acid,so OA-coated NZVI was made.The OA-coated NZVI particles were characterized by Fourier transform infrared(FT-IR) spectroscopy,transmission electron microscopy(TEM), Thermogravimetry(TG) and the powder X-ray diffraction(XRD). According to this,the best Synthesis conditions of OA-coated NZVI were:T=30℃,stirring 10h,the best addition ratio of OA was 20wt%.2.The OA-Pluronic-stabilized NZVI particles were made by the reaction of Pluronic F-127 and OA-coated NZVI.OA-Pluronic-stabilized NZVI was characterized by FT-IR,XRD,TEM and TG.On this basis, the best Synthesis conditions of OA-Pluronic-stabilized NZVI were: T=30℃,stirring 10 h,the best weight ratio of OA and Pluronic F-127 was 18.3:18.7.3.The OA-Pluronic-stabilized NZVI was used for removal of 2,4-DCP.The effects of some factors on 2,4-DCP removal and yied of phenol,2-CP and 4-CP in solution were discussed,such as initial pH, initial conentration of 2,4-DCP,NZVI loading,and reaction temperature.The products and reaction mechanism were analyzed.The main results were as follows:(1) In high 2,4-DCP initial concentration,the pollutant molecules competed for active site on the surface of NZVI,so the conversion rate decreased.In low 2,4-DCP initial concentration,2,4-DCP was easily dechlorinated to Phenol,2-CP and 4-CP.In high 2,4-DCP initial concentration,the particles probably showed absorption.(2) Initial pH showed great impact on the reaction,and at pH value of 4.8～6.8,dechlorinated reaction progressed well.In weak acid environment,2,4-DCP was inclined to produce 2-CP,in nearly neutral environment,it was conducive to produce 4-CP. (3) At NZVI loading of 6g/L,the concentrations of phenol,2-CP and 4-CP was higher than that in other conditions.At pH value of 10.8, the removal of total organic compounds might be caused by strong adsorption on the surface of OA-Pluronic-stabilized NZVI.(4) At various temperatures,2,4-DCP was easily dechlorinated to 2-CP and 4-CP.At 30℃,the concentrations of products achieved the maximum in 4 h,and in 6 h at 15℃.Thus,30℃was the best reaction temperature.