Synthesis And Adsorption-Catalytic Performance Of Modified Coke Loaded With Nano Fe₃O₄ As Magnetic Water Treatment Agent

Industrial organic wastewater,which contains refractory organics with high chroma and toxicity,has a major impact on the environment.The degradation efficiency of these pollutants using traditional method is not satisfactory.With the promulgation of"Water pollution control action plan"in 2015,the advanced treatment of industrial organic wastewater,not only meeting the discharge standards but also achieving"zero emissions",has become increasingly urgent.As a new advanced oxidation technology,the heterogeneous Fenton catalysis is widely used in the treatment of organic wastewater.How to develop an efficient,environment-friendly and easy preparation of water treatment agent is the key to promote this technology in industrial application.In this dissertation,a new type of magnetic water treatment agent was prepared via in-situ oxidation precipitation method based on modified coke loaded Fe₃O₄ nanoparticles.The modification of coke,the preparation of Fe₃O₄/MC and its adsorption and degradation mechanism towards organic wastewater were investigated.The study is briefly summarized as follows:The optimum conditions for the modification of coke were determined by the orthogonal test range analysis:the alkali carbon ratio was 4:1,the activation temperature was 850?and the activation time was 1.5 h.The specific surface area of the optimal modified coke increased from 4 m²?g^-1 of unmodified coke to 298m²?g^-1.After modified,the pore structure of coke was developed,the ash content was decreased from 12.04%to 7.87%,the volatile content was increased from 1.23%to 7.10%,the oxygen functional groups increased and graphitization degree decreased.The adsorption process of modified coke towards RhB was confirmed with the pseudo-second-order kinetic model.The saturation adsorption capacity of modified coke at 25?was increased from 13.01 mg?g^-1 of unmodified coke to73.01 mg?g^-1.Langmuir isotherm adsorption model can better reflect the adsorption results.The modified coke had good adsorption performance and load function.The optimal loading of nano Fe₃O₄ in the Fe₃O₄/MC was 40%by in-situ oxidation precipitation.The Fe₃O₄ was dispersed on modified coke by chemical bond,in which the average particle size was decreased from 180 nm to 90 nm.The Fe₃O₄/MC with superparamagnetic,which the saturation magnetization was 40.85emu?g^-1 and the p H_PZC was 7.40.Under the condition of the dosage of Fe₃O₄/MC was 1.0 g?L^-1,the initial concentration of H₂O₂ was 50 mmol?L^-1,initial pH=3.0,T=25?,the degradation of RhB followed pseudo-first-order reaction rate constant that was 0.035 min^-1,The removal rate of RhB for Fe₃O₄/MC,Fe₃O₄/coke and Fe₃O₄are 96.86%,49.00%and 28.60%within 100 min,respectively.The nano Fe₃O₄ and modified coke have synergistic effect,which can significantly improve the catalytic degradation performance of Fe₃O₄/MC magnetic water treatment agent.The adsorption process of the Fe₃O₄/MC to RhB conformed to the pseudo-second-order kinetic model.The saturation adsorption capacity at 25?was 39.71mg?g^-1.Langmuir isotherm adsorption model can better reflect the adsorption results.The adsorption of RhB onto the Fe₃O₄/MC was spontaneous and endothermic process.The adsorption capacity of the adsorbent was higher in a wide range of pH,and the removal rate of RhB reached to 98.32%when the dosage was 4.0 g?L^-1.The optimum conditions were catalytic degradation of RhB as follows:[catalyst]=0.8 g?L^-1,[H₂O₂]=30 mmol?L^-1,the initial pH=3,T=35?.The removal rate of RhB and COD_Cr in 60 min were 98.85%and 93.08%respectively.The Fe₃O₄/MC displayed good stability,and the dissolution rate of Fe was low,showing good magnetic separation and reusability.The effect of advanced treatment of sedimentation tank effluent of coking process using the Fe₃O₄/MC was investigated.The results show that COD_Cr was decreased from 220 mg·L^-1 to 55.78 mg·L^-1 and UV₂₅₄ was decreased from 2.548 to0.103 within 3 h in the following initial conditions:[catalyst]=1.2 g?L^-1,[H₂O₂]=60mmol?L^-1,pH=3.0 and T=45°C,which the removal rate reached 74.59%and 95.56%respectively.The Fe₃O₄/MC showed well stability and the low dissolution rate of Fe.The final of COD_Cr(55.78?78.51 mg·L^-1)and chroma?5?30?in 4 cycles,which reached the discharge standardAbove of all,the magnetic water treatment agent with integrated adsorption,catalysis and magnetic separation,was prepared via in-situ oxidation precipitation.The composite was applied in the the advanced treatment of coking wastewater,which could reached the discharge standard,reusability and pollution-free.It provides a new method for the advanced treatment of organic wastewater.