Study On Supercritical Water Oxidation Of 4-chlorophenol And Advanced Treatment Of Coking Wastewater

Despite of biochemical treatment of coking wastewater, the concentration of suspend, organic contaminants amd chroma were still high. Advanced effective treatment process was carried to remove or reduce the impurity composition for the purpose of reusing the wastewater as circulating cooling water. Based on effluent of A/O/H/O (anaerobic/oxidation /hydrolysis/oxidation) process, the process of oxidation/adsorption/coagulation was carried out to meet the standard and reduce toxicity. The water quality analysis was put into practice to different process unit, discussing the factors of determining the treatment effect and optimal parameters. A part of chlorinated organic compounds were found afer advanced treatment. The supercritical water oxidation(SCWO) of 4-CP was carried out in the self-designed flow-type SCW apparatus processed by Supercritical Fluid Technologies Inc., the kinetic characteristics, reaction pathway and reaction mechanism of 4-CP SCWO were studied.The results showed that the process of oxidation/adsorption/coagulation collaboration had good effect on coking wastewater after biological treatment. In the reaction condition of PFS concentration 300 mg·L-1, NaClO concentration 40 mg·L-1, AC concentration 500 mg·L-1, reaction time 0.5 h and pH7.0, the COD and chroma moval rate were above 75 % and 80 % separately, besides the COD and chroma droped to 60 mg·L-1and 20 below separately after the treatment of oxidation first and then absorption and coagulation to the coking wastewater. In addition, GC/MS was used to carry out the qualitative analysis of organic compositions in wastewater, removing the majority of wastewater monocyclic aromatic compounds and polycyclic aromatic compounds, some heterocyclic chemicals, organic chlorides and bromides, but part of long-chain alkanes and aromatic hydrocarbons was almost non-functional.The result showed that the effect of the process of oxidation/adsorption/ coagulation had the structure-activity relationship with the structures and the forms of the organic compounds, the synergy of oxidiation and catalytic was the key to efficient removal.The degredation of 4-CP had good effect in SCWO. In the reaction condition of temperature from 400 to 460℃, pressure 24 MPa, reactor residence time from 30 to 200 s, excess oxygen from 100% to 500%, the removel of COD 4-CP and dechlorination rate of 4-CP increased with the increase of temperature, residence time; The removel and dechlorination of 4-CP was increased with the excess H2O2 with certain range in the other same condition. From the influence factor of temperature, residence time,concentration of 4-CP and oxidant, the temperature and residence time were the main influence factors but the concentration of 4-CP was not sigifcant, the influence of oxidant depended on the reaction process and the optimal value of excess H2O2 was 375%.In this paper, the kinetics of oxidative degredation and dechlorination of 4-CP in SCW was studied. The results were as follows: ; the kinetic of 4-CP dechlorination: the relation between the removel and dechlorination of 4-CP was suggested as follows: .9036ex . In the analysis of 4-CP kinetic, the equation was described by power exponent and first-order kinetic was builded by using the experimental data, found that the predicted data was in accordance with the experimental data, 4-CP was the first-order kinetic, apparent activation energy was Ea=92.978 KJ·mol-1, frequency factor was 104.6302, induction time was not exist. The experimental data and calculated data of 4-CP dechlorination were linear correlativity at different initial concentration and residence time (R2=0.999).Based on the GC/MS analysis of the liquid product, the pathway and mechanism of 4-CP reaction in SCW were proposed and explained. Free radical reaction was the common feature in SCWO and the final products of HCl, CO2 and H2O was found after a series of complex oxidation reaction. The evidences of the 4-CP oxidation action pathway were provided by intermediate products such as hydroquinone, pyrocatechol, para-benzoquinone and biopolymer.Research results showed that oxidation/adsorption/coagulation collaboration process had great engineering application prospect in the advanced treatment of coking wastewater, and SCWO was provided to the treatment of CPs organism because of the advantage such as high efficiency, fast reaction rate and compactive apparatus.