The Degradation Of Tetrabromobisphenol A And Tetrachlorobisphenol A In Soils By Copper/Nanoscale Zero-valent Iron(Cu/nZVI) Bimetallic Particles

Halogenated flame retardant tetrabromobisphenol A(TBBPA) and tetrachlorobisphenol A(TCBPA) have the advantages of preventing the burning, lower dosage and lower cost, which are the most widely used flame retardant. TBBPA and TCBPA unable to be recycled and may produce toxic and harmful substances in the process of combustion and heating. With the characteristics of environmental persistence, lipophilic and hydrophobic, refractory, TBBPA and TCBPA are potential environmental endocrine disruptors for they can interfere with thyroid hormone, estrogen activity and have the potential carcinogenic. They are harmful to humans and the environment so they gradually caused people’s attention. Since there is no new type of flame retardant can replace the halogenated flame retardant completely, TCBPA and TBBPA will continue be used as flame retardant materials in electronic and other plastic products, it is necessary to seek appropriate methods and advanced technology to deal with TCBPA and TBBPA.There are few studies on nano zero value iron degradate TCBPA and TBBPA in the soil. In this paper, we used the liquid phase reduction method to prepare the 0.5 wt% copper loading of Cu/nZVI particles and degradated the typical halogenated flame retardant TBBPA and TCBPA in the soil. The surface structure, properties and chemical constituents of the Cu/nZVI bimetallic materials were analyzed by means of scanning electron microscopy, X ray diffraction, X ray photoelectron spectroscopy, etc. The effects of different factors such as TCBPA, TBBPA concentration, Cu/nZVI dosage, pH, temperature on the contaminants degradation rate and reaction kinetics. The reaction mechanism of TBBPA and TCBPA in the soil was discussed by analysed the degradation products of TBBPA and TCBPA.Fresh prepared nZVI and Cu/nZVI particles into regular spherical, distribution of particles size were uniform, particles reunited together due to the magnetic force and the surface tension. nZVI particles were slightly larger than Cu/nZVI particles. Both two kinds of particles had a core-shell structure, particles center were Fe0 with a strong reduction, the surface of the nZVI particles were mainly composed by divalent iron oxide, Cu/nZVI particles surface were mainly composed by divalent iron oxide and ferric oxide, it may be Fe3O4. After the reaction of Cu/nZVI with TBBPA and TCBPA, the spherical particles became irregular and the particle size was increased, the surface oxidation was serious, iron oxide was formed in the reaction process. The surface of the sample was composed by divalent iron oxide and ferric oxide, which might be Fe2O3 and Fe3O4.The reactions of Cu/nZVI degradated TBBPA in soil followed pseudo first-order kinetics, when the initial concentration of the soil TBBPA <5mg/g, TBBPA degradation rate and kobs increased with the increases of TBBPA initial concentration, when TBBPA initial concentration > 5 mg/g, TBBPA degradation rate and kobs decreased with the increase of TBBPA initial concentration; TBBPA degradation rate and kobs increased with Cu/nZVI dosage increased gradually, there were a linear relationship between the rate of kobs and Cu/nZVI dosage; TBBPA degradation rate and kobs gradually decreased with the initial pH increased, and increased with the increase of temperature.The reactions of Cu/n ZVI degradated TCBPA in soil followed pseudo first-order kinetics, TCBPA degradation rate and kobs decreased with the increases of TCBPA initial concentration, increased with the increases of the number of Cu/nZVI particles. The degradation rate and kobs of TCBPA gradually reduced with the increases of the initial pH, acidic environment was conducive to the reaction of Cu/nZVI particles on TCBPA in soil, followed by a neutral environment, and alkaline environment will hinder the reaction; TCBPA degradation rate and kobs gradually increased with the increases of the temperature, increase the reaction temperature appropriately was conducive Cu/nZVI particles degrade TCBPA in soil, the low temperature will reduce the reactivity, resulting in the decreases of reaction rate. The degradation rate and kobs of TBBPA in soil was higher than TCBPA by Cu/nZVI under the same experimental conditions, the apparent activation energy of TBBPA and TCBPAwas 21.02 kJ / mol, 53.55 kJ / mol respectively, TCBPA was more difficult to be degraded by Cu / nZVI than TBBPA.TBBPA debromination products were TriBBPA, DBBPA, MBBPA and BPA; due to soil composition was complex, detected in the degradation products of TCBPA dechlorination were TriCBPA and BPA; degradation is the main process of TBBPA,TCBPA removed in soil, main the process of dehalogenation is the reduce of hydrogen, the hydrogen ions play an important role in the reaction. This study speculated the degradation of TBBPA, TCBPA in soil were a gradual dehalogenation process, dehalogenate degradation mechanism might have three reasons: Cu element promoted dehalogenation, the galvanic effect of Cu/nZVI bimetallic system, the hydrogen produced during the reaction adsorbed on Cu surface and dissociated to hydrogen atom.