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The Basis Of Three-dimensional Electrode Electrolysis Treatment Of Phenol Wastewater

Posted on:2012-09-06Degree:MasterType:Thesis
Country:ChinaCandidate:J YangFull Text:PDF
GTID:2211330371452620Subject:Environmental Engineering
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With the development of coking industry, the components and discharge amout of phenol containing wastewater were increased, which was diffucult to treat because of high COD concentration, stable benzene structure and low biodegrade ability. Research was focused on the development of the effictive technology for phenol containing wasterwater treatment. In this study, the novel technology of electrolysis processes using "three- dimensional electrode reactor" was proposed to treat the simulated phenol wastewater, the process of "caustic washing-three-dimensional electrode electrolysis" was brought out for regeneration of the activated carbon, the correlated conditions were investigated in detail, and then the degradation mechanism of phenol was studied via electrochemical experiments. The conclusions are shown as follows:The degradation technology of phenol in wastewater via the three-dimensional electrode reactor was proposed. The influence factors, including pH value, influent flow rate, temperature, the dosage of NaCl, current intensity and electrolysis time were examined respectively through the single factor experiments and orthogonal experiments. The removal efficiency of total organic carbon (TOC) could reach up to 95% at the conditions of pH of 6-7, influent flow rate of 180 mL/min,25℃, NaCl of 1g/L, electric density of 100 mA and electrolysis time for 1.5 h, the pretreated activated carbon was used as particle electrode. The range analysis showed that the order of relevant factors for TOC degradation efficiency was:pH value> electrolysis time> current intensity> temperature.The "caustic washing-three-dimensional electrode electrolysis"was proposed to regenerate the activated carbon. The influence factors, including stirring time, stirring pH value, influent flow rate, pH value, temperature, the dosage of NaCl, current intensity and electrolysis time were investigated respectively through the single factor experiments. The activity carbon can resume and removal efficiency of TOC could reach up to 95% at the conditions of stirring time of 2 h, stirring pH of 12, influent flow rate of 270 mL/min, pH of 6-7,25℃, NaCl of 8g/L, electric density of 100 mA and electrolysis time for 0.5 h.Adsorption dynamics and adsorption thermodynamics of activated carbon adsorption phenol and adsorption behaviors of phenol on activated carbon were studied. The adsorption observed the second-level dynamic equation, which using the pretreatment activated carbon adsorption phenol. The maxium adsorption capacity was 0.27614 g/g. The experimental results deduced from the adsorption thermodynamics computation and the infrared light spectrogram showed that the adsorption heat was-33.046 KJ/mol, the adsorption bond strength is small, and a phenol adsorption on the two active points of activated carbon surface through the hydrogen bond. Along with the introduction number of phenol copies increase, the infrared spectrum broadens gradually on the 3432cm-1 hydroxyl spectral line by the point, presents the dissemination spectrum. From this extrapolated that the phenol has the association through hydrogen bond on hydroxyl. The activated charcoal adsorption phenol model was proposed according to the obtained data and the related experiment phenomena were explained with the model.The activated carbon anode's electrochemistry behavior in the acid solution, and the phenol degraded mechanism was investigated by the polarized curves and electrochemical impedance spectroscopy (EIS). The experimental results indicated that in the three dimensional electrode electrolysis process the phenol was degraded through two kind reactions, the direct electrolysis and the indirect degradation, the latter played an important role. The relaxation time constant and the polarization resistance were determined through the experiments. The equivalent resistance caused by the adsorption is 5.5 times of charge transfer resistance, the relaxation time constant caused by the adsorption is 104 times of double layer capacitance relaxation time constant, which indicated that hydroxyl free radical·OH has very strong chemical bond on the activated carbon contact surface. Hydroxyl free radical·OH generated in the process of the oxygen evaluation from the activated carbon surface was an intermediary product, and adsorbed on the activated carbon anode surface.Meanwhile, the micro-batteries were formed between the absorbed·OH radicals and the adsorbed phenol. In the micro-cell, firstly phenol is degraded into the intermediates, such as catechol, resorcinol and hydroquinone, and then mineralized into CO2 and H2O.
Keywords/Search Tags:Three-dimensional electrode, Phenol-containing wastewater, soda wash - electrochemistry union regenerative method, Adsorption model, ·OH radical
PDF Full Text Request
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