Study On Pre-treatment Of N-PHenylglycinonitrile Production Wastewater

N-phenylglycinonitrile chemical wastewater is one of the refractory wastewater with high concentration, low biodegradability and high toxicity; the main components are anilines and cyanides which are harmful to organisms at low concentration and classed as hazardous pollutants. Experiments study on the pre-treatment of this wastewater before the biological-treatment was introduced in this paper.Montmorillonite, the primary constituent of bentonite, is an aqueous aluminosilicate clay mineral with expandable layer structure. With its special physical and chemical properties, the bentonite has better effect for wastewater treatment by the course of organic or heavy metal modification, modified bentonite is an effective adsorbent for the removal of organic contaminates and heavy metals from wastewater. Therefore, the application of modified bentonite in wastewater treatment has been emphasized and investigated by environmentalists.First, using Ca-bentonite as raw material, Na-bentonite was prepared by microwave radiation after purification, and the preparation conditions were follows: use NaCl as modified regents, the reagent volume of 50% C2H5OH to the bentonite quality is 7:5(ml/g)and the reaction time is 4min, the experimental results showed that the CEC of Na-bentonite increased to 93mmol/100g after modification from 62.4mmol/100g which is useful to the organic modified and the Fe-pillared modified.Secondely, the organo-bentonite was prepared from Na-bentonite by cation surfactant CTMAB. The preparation conditions were optimized and the ability of organo-bentonite to remove organic compounds in N-pHenylglycinonitrile chemical wastewater was investigated. The experiment results show that the appropriate preparation conditions of organic bentonite were follows: the amount of surfactant is 90CEC, the microwave radiation time is 2min,the reagent volume of H2O2 to the bentonite quality is 6:1(ml/g); the feasible treating conditions of N-pHenylglycinonitrile chemical wastewater by organo-bentonite were follows: the organo-bentonite concentration is 20g/L, the pH of wastewater is 6.0, the adsorption temperature is 30℃and the adsorption time is 60min. The organo-bentonite has a high ability of adsorption compared to Na-bentonite, the removal rate of CODcr and anilines can reach 23.3%, 54.4% and the BOD5/CODcr increased to 0.11, the adsorption can be well represented by linear isothermal adsorption model and pseudo secondary kinetics model, however, the removal rate only can reach 3.4%and 8% if using the raw bentonite as adsorption regent. However, the organo- bentonite adsorption ability to the N-pHenylglycinonitrile chemical wastewater was rather limited, the removal rate didn't achieve the ideal degree to meet the requirement of subsequent biochemical treatment.For the wastewater treatment limitation of organo-bentonite, using the Fe-pillared bentonite and H2O2 to treat the N-pHenylglycinonitrile chemical wastewater by oxiditon was tried, and the removal ability was investigated, too. The experimental results showed that the optimal treatment conditions were obtained as follows: pH value is about 4.0, added amount of H2O2 is 6.66g/L, amount of Fe-pillared bentonite added is 20g/L, temperature is 30℃, and treatment time is 60min, he removal rate can reach 23.3%, 54.4% and the BOD5/CODcr increased to 0.11 which meet to the requirement of subsequent biochemical treatment. Comparing to the ogano-bentonite adsorption, the effect of oxidation method by Fe-pillared bentonite and H2O2 had been improved effectively. Simultaneously, the reaction kinetics was studied.Thirdly, the structures of Na-bentonite, organo-bentonite and Fe-pillared bentonite was investigated by XRD, IR and SEM respectively. Studies on X-ray diffraction date (XRD) demonstrated that the interlayer spacing were obviously enlarged through organic modification or Fe-crosslinked modification ; results of infrared spectrum (IR) discovered that some new characteristic peaks appeared, and the basic structure didn't destroy; SEM indicate that the bentonite surface was packed modified groups via modification, which improved the treatment effect, therefore, the change of structure and properties of bentonite is usful to the treatment effeciecy during modification.Finally, this paper put forward using Fe-pillared bentonite-H₂O₂ to treat N-pHenylglycinonitrile chemical wastewater by comparing the treatment effect of each method, including purified bentonite, Na-bentonite, organo-bentonite and Fe-pillared bentonite-H₂O₂, and determined the optimal pH of the pre-treatment process effluent which is about 6.0～6.5 through testing the sludge activity in hydrolysis-acidification reactor.