Research Of Degradation Of Phenolic Wastewater By ZSM-5 Sieve Photocatalysis Coupled With Persulfate

The Phenolic wastewater is a kind of industrial waste water sources more widely and universal,Phenolic material actually is a general term for a large class of similar compounds, including phenol substituted compounds, polyphenols, Chlorophenol and nitrophenol etc.P-nitro-phenol is one of the most common phenols, which can be detected in many industrial and agricultural wastewater.Due to its unique chemical structure,it has good chemical stability. it is difficult to degrade in the natural environment, long-term stay in the environment, serious damage to the ecological environment and human health impact.At present, the treatment technology of phenolic wastewater can be divided into three major categories:physical treatment, biochemical treatment and chemical treatment.Advanced oxidation technology is the most popular treatment methods in recent years, the processing method is simple, easy to implement, and get a quicker development.Due to the advantages of TiO₂ of excellent chemical stability, price cheap, non-toxic harmless, safe use and high photocatalytic activity etc.However,the photocatalytic process is more complex.there are still many theoretical and practical problems cannot be solved, largely restricted the large-scale application of TiO₂.Such as the wide band gap of TiO₂ photocatalyst and low quantum yield is still the main reason to restrict its development. The nano materials is a better way to improve the performance of the catalyst,but it is difficult to recover the nano materials with the loss of water.In this paper, according to the existing problems, the content of the study will be divided into three directions as follows.（I）Modified ZSM-5 molecular sieve and the preparation of supported catalytic materials.Because of its unique crystal structure and pore structure, ZSM-5 molecular sieve has been widely used in adsorption, catalysis and immobilization, but ZSM-5 is a microporous molecular sieve, which limits its wider application.This study will be modified to expand the pore size and enhance the transfer performance of organic macromolecules.Preparation of composite catalysts TiO₂/ZSM-5, TiO₂ loading on modified molecular sieve by sol gel method and composite catalyst CuO/ZSM-5 was prepared by impregnation loading method.Catalytic materials was characterized by scanning electron microscope （SEM）, N2 adsorption desorption isotherms and X-ray diffraction （XRD）.（Ⅱ）Study the performance of TiO₂/ZSM-5 coupled with the catalytic degradation of phenol.In this research sulfate as electron acceptor, in order to reduce the electron hole recombination probability, and thus indirectly improve the hydroxyl radical （HO-） content.Persulfate can not only to accept electronic reduced electron hole recombination probability, will also generate sulfate radical （SO4-·）. Synergistic treatment of phenolic wastewater with two free radicals.The influence of initial pH, TiO₂/ZSM-5m dosage, concentration of FeSO4, Na2S2O8 and the initial concentration were investigated using p-Nitrophenol （pNP） as a object pollutant. The results show that the removal rate of pNP （50 mg/L） reached 99.31% under the optimization conditions: TiO₂/ZSM-5 dosage of 0.8 g/L, pH of 4.0, FeSO4 of 0.2g/L, Na2S2O8 of 2.4 g/L and reaction time of 240 min at room temperature, Degradation dynamics of pNP fits well Langmuir-Hinshelwood model.（Ⅲ）The effect and mechanism of degradation of phenol wastewater by CuO/ZSM-5/sulfate system were investigated by sequencing batch test. The results showed that the catalyst copper is mainly in the form of CuO exist with Cu/ZSM-5 molecular sieve, phenol conversion rate with the increase of catalyst concentration and reaction temperature, the removal rate of phenol increases, after reaching a steady value.PH is one of the biggest factors affecting the removal rate of phenol.The removal rate of phenol reached 98.3% at initial average concentration of phenol was 50 mg/L,CuO/ZSM-5 was 2g/L, pH was 7, C （Na2S2O8） was 3.2 g/L,temperature was 70, reaction 90 min.GC-MS was used to measure the wastewater before and after treatment to reveal the law of degradation and transformation. It was found that the phenol could be degraded effectively, but the intermediate products were significantly increased.