Synthesis Of PAC-Fe₃O₄ And Its Application In Dyeing Wastewater Treatment

The COD of the secondary biochemical effluent which came from a printing and dyeing company in Jiangsu Province cannot satisfy the grade A of the national discharge standard of GB18918-2002.Its BOD5/COD was 0.18,so it’s unsuitable to use the conventional biological technology for treatment,the physicochemical metholds was considered as the proper metholds for advanced treatment.PAC was difficult to separate with the treated wastewater,the cost was high and it’s hard to regenerate,besides,the traditional Fenton method can cause the problem of large amount of sludge production,the topic studied the adsorption characteristics and put forward a magnetic activated carbon-H2O2 combined system by PAC-Fe3O4 preparation.We proposed a feasible method for the improvement of wastewater treatment process by optimizing the operation parameters of the system to the printing and dyeing wastewater.Firstly,three kinds of magnetic activated carbon were prepared using chemical co-precipitation,the mass ratio of PAC/iron oxides were 1#1:1、2#1:2 and 3#1:3, respectively.The surface properties had made obvious changes,the iron oxides were determined as Fe3O4,its existence didn’t make much effect on the internal pore structure of PAC.Besides,compared the recyclable performance with PAC,the magnetic activated carbon had made a significant improvment,it could complete precipitation in 10 minutes under the condition of the natural gravity setting,and it could be quickly separated in 30 seconds under the action of outsid e magnetic field.Then,the wastewater was prepared by methylene blue as the target pollutant,and the adsorption characteristics of magnetic activated carbon were discussed.The results showed that the adsorption capacity of 1# was improved than PAC,p H value was the key factor influencing treatment efficiency, the higher p H value and adequate contact time were favorable for the removal of pollutants.Under the condition of initial concentration of methylene blue of 100mg/L,dosage of magnetic activated carbon of 0.4g/L,p H 9 and the reaction time of 300 minutes,the removal rate of methylene blue reached 98.9%.The adsorption behavior of methylene blue on magnetic activated carbon conformed to the Langmuir isotherm and Elovich dynamics model,the thermodynamic analysis indicated that the adsorption was spontaneous endothermic reaction,and the chemical adsorption played an important role in the adsorption process. Then the treatment efficiency of the magnetic activated carbon-H2O2 system was discussed.The optimal operation parameters of the composites of 1#, 2#, 3#:dosage of the composites of 0.5g/L,the ratio of H2O2/magnetic activated carbon of 0.6m L/g、0.6m L/g and 0.8m L/g, p H 3,the reaction time of 180 min.Under the condition,the removal rate of methylene blue were all close to 100%,the removal rate of COD could reach 85.23%、86.96% and 86.87%,respectively.The reuse stability of 1# was the best,2# followed by,3# was the worst.Finally,investigated the treatment efficiency of the system to the printing and dyeing wastewater,the optimal operation parameters of the composites of 1#, 2#, 3#: dosage of the composites of 0.5g/L,the ratio of H2O2/magnetic activated carbon of 1.0m L/g、1.0m L/g and 1.4m L/g,p H 3,the reaction time of 180 min.The removal rate of TOC could reach 61.74%、72.48% and 75.22%,the effluent COD value was below 50mg/L,satisfied the criteria of discharge.Treatment efficiency and reuse stability were factored into the comparison of composites,2# was the best.Under the best condition of static experiment,2# was applied in the continuous operation of the reactor,the final effluent TOC value was about 15~20mg/L, satisfied the criteria of discharge.The innovations of the topic were the application of PAC-Fe3O4 composites and magnetic activated carbon-H2O2 system in actual printing and dyeing wastewater treatment,it’s a kind of physicochemical methold combined adsorption and chemical oxidation regeneration.Compared with the PAC process and conventional Fenton process,the method had obvious advantages,it combined the both advantages of them, and improved the insufficient of their own.The research of this thesis proposed a feasible method for the improvement of the printing and dyeing wastewater treatment process,and provided the guidance for the feasibility of the engineering application of the composites.