Research On The Treatment Of Wastewater Produced During Synthesizing Copolyether

During the process of synthesizing copolyether produces wastewater which has high COD value, contains high content of difficultly degraded organic substances and has versatile water quality and quantity. Fenton oxidation process is an advanced oxidation technology, which is commonly used to treat organic wastewater. But it is hard to get a good processing effect by using single Fenton oxidation process. In this research, micro-electrolysis-Fenton method, UV-Fenton method, Fenton-coagulation method and micro-electrolysis-UV/Fentoncoagulation method were used to treat the copolyether wastewater. The remove rate of COD and the chroma were taken as indexes to determine the better process conditions of each method. Choose the best combination process and the best experimental conditions to treat the copolyether wastewater.Micro-electrolysis-Fenton method was used to treat the copolyether wastewater, The influences of dosage of H₂O₂（30%）, initial pH value, reaction time, dosage of FeSO₄·7H₂O and ron-charcoal ratio were investigated. The experimental results showed that the optimal conditions were the dosage of H₂O₂（30%） as 40mL/L, initial pH value as 1, reaction time as 4h, the dosage of FeSO₄·7H₂O as 40g/L, and iron-charcoal ratio（weight） as 1:4. After treating copolyether wastewater under the optimal conditions, the removal rate of COD was 93.6%, the chroma value was 2.6 degrees.UV-Fenton method was used to treat the copolyether wastewater. The influences of initial pH value, reaction time, dosage of FeSO₄·7H₂O and H₂O₂（30%） were investigated.The experimental results showed that the optimal conditions were the initial pH value as 2, reaction time as 2.5 h, dosage of FeSO₄·7H₂O as 18g/L, dosage of as 240 m L/L. After treating copolyether wastewater under the optimal conditions, the removal rate of COD was 76.2%, the chroma value was 13.1 degrees.Fenton-coagulation method was used to treat the copolyether wastewater. The influences of the types of coagulants, dosage of FeSO₄·7H₂O, dosage of H₂O₂（30%）, dosage of FeCl₃ and dosage of PAM were investigated. The experimental results showed that the optimal reaction conditions were as followed: using FeCl₃ as coagulant, dose of FeSO₄·7H₂O was 24g/L, dose of H₂O₂（30%） was 160mL/L, dose of FeCl₃ was 5g/L, dose of PAM was 600 mg/L. After treating copolyether wastewater under the optimal conditions, the removal rate of COD was 58.7%, the chroma value was 2.4 degrees.Micro-electrolysis-UV/Fenton-coagulation method was used to treat the copolyether wastewater. The influences of the pH value on the step of UV/Fenton, dosage of FeSO₄·7H₂O, dosage of H₂O₂（30%）, dosage of FeCl₃ and dosage of PAM were investigated. The experimental results showed that the optimal reaction conditions were the pH value on the step of UV/Fenton as 2, dose of H₂O₂（30%） as 420 m L/L, dose of PAM as 200 mg/ L, no FeSO₄·7H₂O and FeCl₃ need be used. Wastewater’s removal rate of COD under the optimal conditions was 98.5%, the chroma value was 6.4 degrees.Considering the efficiency of treating copolyether wastewater, the combined process of micro-electrolysis-UV/Fenton-coagulation method showed the best result in the above four methods, copolyether wastewater’s COD value reduced from 33415 mg/L to 500 mg/L, and the COD value and chroma value of treated copolyether wastewater respectively meet standard Ⅲ and standard Ⅰ of 《Discharge standard of water pollutants》（GB8976-1996）. Micro-electrolysis-Fenton method, UV-Fenton method, Fenton-coagulation method had shown positive effects on treatment of copolyether wastewater, too. Among the three methods, micro-electrolysis-Fenton showed a high removal of organics in wastewater, the removal rate of COD up to 90%. Fenton-coagulation method can be used to treat the copolyether wastewater which possesses high chroma value, contains high concentration of suspended solids, tiny particle and colloid.