Degradation Of Phenol By Activated Persulfate From Zero-Valent Ferric Tungstosilicate Prepared By Mechanical Ball Grinding

Phenol is a common pollutant in the environment.It is widely found in the industrial wastewater of oil refineries,pharmaceuticals,pesticides and so on.With strong toxicity,once exposed in the environment,it will not only seriously pollute the groundwater and soil environment,but also endanger human health.Activation of phenol degradation based on persulfate is one of the effective techniques.Zero-valent iron has been widely used in activated PS removal of organic matter due to its low cost,environmental friendliness and low toxicity.However,excessive Fe²⁺produced during the reaction consumes oxidizing free radicals in the process of activating PS,thus hindering the activation efficiency of practical application.In addition,zero-valent iron particles are easy to react with water,resulting in difficulty in long-term action.Meanwhile,the surface of Fe⁰ is easy to be oxidized,resulting in passivation layer,which hinders the release of Fe²⁺and the transfer of electrons.To solve the above problems,this study adopted mechanical ball milling to prepare micron zero-valent iron tungsten-silicated treatment,and prepared zero-valent iron tungsten-silicated（m-WZVI）,to explore the effect of m-WZVI activated persulfate system on the degradation of phenol,the mechanism and the influence of water substrate.The results of SEM,EDS,XPS and XRD show that the m-WZVI material is successfully combined with tungstic acid and zero-valent iron,and the addition of tungstic acid affects the morphology and structure of zero-valent iron,so that m-WZVI has higher and higher activation properties.Tafel and EIS results showed that the reaction rate of m-WZVI with H₂O decreased,so that it could react better with target pollutants.The results of ultraviolet spectrum showed that the tungstic acid and zero-valent iron ball milling had better long-term activation efficiency to avoid the excessive release of zero-valent iron resulting in Fe²⁺consumption of free radicals and iron oxide covering the surface,which affected the degradation effect.FT-IR results show that the surface of m-WZVI material has rich functional groups,which is conducive to the adsorption and contact of PS and phenol pollutants on the surface of m-WZVI material.m-WZVI material enhances the performance of activated PS.Compared with other systems,m-WZVI activated persulfate system has a good degradation effect on phenol.Under the conditions of 0.25 g/L m-WZVI and 2.0mmol/L PS dosage,the degradation rate of phenol with initial concentration of 25mg/L can reach 91.82%within 100min,and the degradation process conforms to pseudo-first-order kinetics.With the increase of the dosage of m-WZVI and the concentration of PS,the removal of phenol firstly increased and then decreased.With the increase of the concentration of phenol in the reaction system,the activation degradation efficiency of phenol in m-WZVI/PS system gradually decreased,and the overall removal efficiency was more easily affected by the concentration of phenol.In the range of p H 3.0～9.0,m-WZVI catalytic material can effectively activate persulfate to degrade phenol.m-WZVI（0.08%molar ratio）has the best effect on persulfate activation.The degradation of nitrobenzene（NB）,benzoic acid and phenol by m-WZVI/PS system under the same experimental conditions verified the universal degradation ability of organic pollutants by m-WZVI/PS system.The activation mechanism of m-WZVI/PS system is different from the traditional zero-valent iron activation PS,which is activated by the preparation of m-WZVI material with electron donating ability of reduced state POM^-([SiW₁₂O₄₀]^5-)as the electron donor,so as to improve the electron activation efficiency.The results of radical quenching and EPR detection confirmed that singlet oxygen（¹O₂）was the main active substance in m-WZVI/PS system,and Sulfate radical(SO₄^·-),superoxide(O₂^·-)and hydroxyl radical（·OH）played an important role in the degradation of phenol.In m-WZVI/PS and m-ZVI/PS systems,the effects of different anions in water matrix showed that Cl^-promoted the reactivation efficiency,while HCO₃^-,CO₃^2-and SO₄^2-inhibited the reactivation efficiency.In addition,the prepared m-WZVI material activated PS shows very good recycling efficiency,and has a good prospect.