Removal Of Cr(?) From Environment And Food By High Energy Electron Beam Irradiation And Composites

Nowadays,large amounts of organic and inorganic pollutants such as chromium?Cr?can be released into the environment from chemical industry,textiles,tannery,mining,battery manufacturing,coatings and pigments,paper and pulp industries,etc.These industrial activities have increased the use of Cr,leading to a gradual increase in Cr concentration in industrial wastewater.However,the concentration of chromium ions in the discharged sewage is higher than the minimum allowable.The long-term discharge of Cr-contaminated wastewater results in a large amount of Cr enrichment in the soil.In the environment,Cr mainly exists in two forms of Cr???and Cr?III?,which are easily absorbed by the human body through food chain.After that,Cr is enriched in the human body and poses a threat to human health.In recent few decades,scientists have developed various functional composites to remove Cr???in water and soil.Although these composites are able to remove Cr???from the water and soil to different degrees,but they have some shortcomings including high cost,complex procedures and secondary pollution to the environment.However,high-energy electron beam irradiation has the advantages of high efficiency,in situ and low cost,so it has attracted wide attention in the reduce of Cr???and modification of composites.In this thesis,high-energy electron beam irradiation is used to reduce highly toxic Cr???in pork,and porous magnetic cornstalk is prepared based on high-energy electron beam irradiation to remove Cr in water and soil,and release ammonium to promote the growth of plants.The main arrangements of this paper are as follows:1.In order to reduce the toxicity of pork containing Cr???to human body,high-energy electron beam?HEEB?irradiation was used to reduce the highly toxic Cr???in pork to low-toxic Cr?III?.The results indicated that HEEB irradiation could effectively and non-destructively reduce free and adsorbed Cr???in pork,and its maximum reductive efficiency?RE?is 98.03%.Hydrated electrons(e^-_aq)and hydrogen radicals?·H?generated during HEEB irradiation may play a key role in the reduction process.To obtain the optimal conditions for reduction of Cr???,the effects of irradiation dose,initial concentration of Cr???,pH, temperature,salinity and soybean oil on reductive efficiency were explored,and the results proved that the method is universal.This work provides a clean and low-cost method for removing Cr???from pork,which is important for food safety.2.Cornstalk?CS?was irradiated by high energy electron beam to obtain honeycomb porous corn stalk?PCS?,then PCS was loaded with ammonium sulfite?AS?.Finally,PCS-AS was coated with polyvinyl alcohol?PVA?-Fe₃O₄ to obtain PCS-AS@PVA-Fe₃O₄ which could reduce Cr???to Cr?III?through SO₃^2-,and then Cr?III?co mbines with PCS-AS@PVA-Fe₃O₄ through hydrogen bonding.Besides,PCS-AS@PVA-Fe₃O₄/Cr could be separated from water by a magnet.In addition,the results showed that PCS-AS@PVA-Fe₃O₄/Cr could effectively control the migration of Cr???in soil and plant uptake.Meanwhile,PCS-AS@PVA-Fe₃O₄ could release ammonium to promote plant growth.Therefore,this work not only provides a promising and low-cost method to simultaneously remove Cr???and promote plant growth,but also provides a new idea for cornstalks reapplication,which may have potential application value.