Study On Treatment Of Caprolactam Wastewater With Biochar Based Heterogeneous Fenton Catalyst

Caprolactam wastewater has the characteristics of high toxicity,complex composition,high oxygen consumption,and large fluctuations in water quality.Direct discharge of untreated caprolactam wastewater is harm to the environment and human body.Advanced oxidation technology can effectively reduce the toxicity of wastewater,which can quickly reduce the potential risks of wastewater originally.In this paper,a biochar carrier is prepared by using waste agricultural peanut shells as a raw material,an iron-cerium bimetallic heterogeneous Fenton-like catalyst is synthesized by ultrasonic impregnation,and a micro-nano bubble assisted heterogeneous Fenton-like reaction technology is used to degradation caprolactam wastewater.It provides a research basis for the efficient treatment of caprolactam wastewater and reducing its risks.The main research conclusions are as follows:（1）Pyrolyze waste agricultural peanut shells at 600℃ for 2h under nitrogen atmosphere to prepare peanut shell biomass charcoal carrier,and mix it with iron-cerium bimetallic salt solution by ultrasonic for 30min and immersion for 24h.In nitrogen and air atmosphere Different kinds of biochar-based heterogeneous Fenton catalysts were prepared by calcination at 300℃for 2h.Through a series of characterization and other means to analyze the catalyst,it is found that the catalyst has the characteristics of rich pores,high specific surface area,wide pH adaptation range and many kinds of surface functional groups,and the iron-cerium bimetallic oxide is uniform in amorphous form.Distributed on the biochar carrier,it can increase the activation sites of hydrogen peroxide.（2）Through various factors on the all Fenton reaction of caprolactam wastewater treatment effect,the study makes a conclusion that the best ratio of iron cerium bimetallic catalyst precursor salt is 3:1,and the optimum reaction system is micronano bubbles aided heterogeneous Fenton system.The optimum reaction condition is:hydrogen peroxide concentration is 1.2 M,the initial pH is 2,the catalyst dosing quantity is 1g/l.Under condition of reaction after 120min,The COD,TOC,ammonia nitrogen,SS and chroma removal rate of wastewater can reach 93.26%,90.4%,40%,99.3%and 83%.Besides,using catalyst for continuous loop test 5 times in a row,the COD removal rate can reach 87%,so it proves the catalyst has good stability and can be repeated use.（3）Through the detection and analysis of wastewater and catalyst by EPR,XPS,FTIR and GC-MS,it was determined that·OH was the main active species in the reaction system.It was found that the types of functional groups in the catalyst increased,the positions of ferium-cerium functional groups shifted,part of Fe²⁺and Ce³⁺were oxidized to Fe³⁺and Ce⁴⁺,and part of metal ions were consumed and dissolved out.It is speculated that in the process of wastewater degradation,biochar bimetal catalysts and micronano bubbles activate hydrogen peroxide to generate hydroxyl radicals through synergistic action.Under the action of hydroxyl radicals,the annular organic compounds in wastewater are degraded to substances such as long-chain alkanes,organic acids and organic amines,and finally to carbon dioxide and water.