Heterogeneous Fenton-like Oxidation Treatment Coking Wastewater By Pomegranate Leaf Synthesis Of Iron Nanoparticles

Coking wastewater is a high-concentration organic wastewater produced in the process of coal coking,it is a typical refractory wastewater in coal chemical wastewater due to its complex composition,strong toxicity and serious pollution hazard.Recently,advanced oxidation technologies(AOPs)have been gradually applied in the field of wastewater treatment due to its high reactivity and high efficiency.Based on the Fenton reaction of iron nanoparticles-based materials,it can fully utilize the characteristics of iron nanoparticles(Fe NPs)and perform good adsorption property and high reactivity,which shows unique advantages for the treatment of refractory organic wastewater.The green synthesis of iron nanoparticles(Fe NPs)using plant extract has been recently developed as a cost effective,environmental friendly alternative to chemical methods.Fe NPs was synthesized from pomegranate leaf extracting solution and was used as a low-cost Fenton oxidation catalyst to degrade phenol in solution,and the effects of temperature,p H,Fe NPs dosage and H2O2 concentration on phenol degradation were discussed.Then the mechanism of phenol degradation was explored.Finally,it was applied to the actual wastewater.The mian conclusions of this thesis are as follows:(1)The removal rate of phenol adsorbed by Fe NPs reached 63%,and the removal rate of phenol reacted by Fenton-like oxidation increased up to 86%.The removal efficiency of phenol reached the best 86% when the dosage of Fe NPs was 100 m L,the reaction temperature was 323 K,the concentration of H2O2 was 10 m M,the initial p H was 3.(2)The adsorption thermodynamic,adsorption kinetics and oxidative degradation kinetics of nano-scale iron were investigated.The results showed that Langmuir model could better describe the removal process of phenol by Fe NPs.The removal process of phenol by Fe NPs was a reaction process whichwas beneficial to absorption.And the adsorption of phenol by iron nanoparticles followed the pseudo-second-order kinetics model.The adsorption process was a chemical adsorption process.It was a rate control step caused by electrostatic interaction or ion exchange between phenol and iron oxide.The kinetics of phenol degradation by iron nanoparticles Fenton-like oxidation indicated that both kinetic models were suitable for simulating phenol degradation.The iron nanoparticles Fenton-like oxidized phenol was an endothermic reaction due to the migration of electrons from the surface of the iron nanoparticles particles to H2O2 in solution.(3)Then SEM,TEM,FTIR,and other characterization techniques were used to further analyze the degradation mechanism of phenol.The results showed that the iron nanoparticles coated with organic material from pomegranate leaf extracting solution were corroded and agglomerated.The iron nanoparticles were composed by zero-valent iron and iron oxide.On acidic condition,the iron nanoparticles were corroded on its surface and released Fe2+and Fe3+,then reacted with H2O2 to produce hydroxyl radicals that were used to mineralize phenol.Based on the above research,the mechanism of phenol degradation mechanism was proposed.(4)Iron nanoparticles Fenton-like oxidation was applied to the degradation of organic matter in coking wastewater.The results showed that Fenton-like oxidation process had a great effect on the removal of organic materials in raw coking wastewater and the biochemical treatment effluent.The most organic matter were removed,especially the organic compounds with complex structure,stable property,refractory degradation.Thus,the degradability of wastewater was improved,which was conductive to subsequent processing.