Degradation Of BFRs And Cr(?) By Modified Nano-zerovalent Iron

Flame retardants are widely used in electronic products such as coatings and circuit boards due to their excellent time delay or anti-combustion.At the same time,heavy metal devices are also indispensable elements in electronic products.After electronic products are discarded,they will be released into the environment through various channels,causing great harm to the ecosystem and human health,such as interference with biological endocrine and carcinogenicity.Modern technologies for the treatment of flame retardants include adsorption methods,advanced oxidation methods and biological methods.They have the disadvantages of low processing efficiency,toxic and harmful by-products,or long degradation cycles.The main methods for removing heavy metals include physical adsorption methods,electrolytic methods,and biological methods,but these methods have higher costs,longer processing times,or higher energy consumption.Thus,There is a need to develop a stable and efficient technology for the treatment of pollutants in electronic waste.This article selected brominated flame retardants TBBPA and BDE-209 in electronic waste-,and Cr(?)for degradation.In this study,nZVI and composite materials nZVI-BC and nZVI-BC-P were prepared and characterized by biochar and liquid phase reduction methods,respectively.The effects of different materials,dosages,p H and initial concentrations of the solution on the degradation effect were discussed,and kinetic analysis and products analysis were performed.?The main conclusions are as follows:(1)The pore structure of biochar prepared from phosphoric acid-activated grapefruit peel is hollow and uniformly distributed,has a high specific surface area,and improves the dispersibility of nano-zero-valent iron.nZVI and composite materials nZVI-BC and nZVI-BC-P were prepared using biochar and liquid phase reduction methods.The specific surface area of nZVI particles was 27.18 m~2/g and the specific surface area of nZVI-BC particles was 51.58 m~2/g.The specific surface area of nZVI-BC-P particles is 80.36 m~2/g.Both the loading of biochar and the activation of phosphoric acid can significantly increase the specific surface area of nano-zero-valent iron materials.(2)Degradation of TBBPA by nZVI-BC-P:The removal rate of TBBPA with an initial concentration of 5 mg/L can reach the optimal conditions at a temperature of 25?,a p H of3.0,and a dosage of 2.5 g/L.With the increase of the amount of nZVI-BC-P input,the removal efficiency of TBBPA increased.Under acidic conditions,the degradation effect of nZVI-BC-P on TBBPA is better.Properly reducing the initial concentration of TBBPA solution will help to improve the degradation rate of TBBPA.The degradation process of TBBPA by nZVI-BC-P conforms to the quasi-first-order kinetic equation.Kobs increases with the increase of the amount of nZVI-BC-P added;it gradually decreases with the increase of the p H and initial concentration of the solution.small.The process of nZVI-BC-P degradation of TBBPA is that the hydrogen atom gradually replaces the bromine atom,so that it is first debrominated into tri-BBPA and di-BBPA,and finally the bromine atom is further replaced to generate mono-BBPA and BPA.(3)Degradation of BDE-209 by nZVI-BC-P:The degradation efficiency of BDE-209with initial concentration of 0.5 mg/L is close to 80%when the temperature is 25?,p H is3.0,and the dosage is 5 g/L.As the amount of material added increases,its removal efficiency increases.Under low concentration and acidic conditions,the degradation effect of nZVI-BC-P on BDE-209 is more excellent.The degradation of BDE-209 by the nZVI-BC-P system is a step-by-step debromination process.In the end,nZVI can degrade it to dibromodiphenyl ether and monobromodiphenyl ether.Compared with the ortho and para bromine atoms,the meta bromine atom is more easily removed.(4)Degradation of Cr(?)by nZVI-BC-P:Removal rate of Cr(?)solution with initial concentration of 15 mg/L can reach 100%at a temperature of 25?,a p H of 4.0,and a dosage of 2.5 g/L.At the same time,the process of Cr(?)removal by nZVI-BC-P also conforms to the quasi-first order kinetic equation,and the kobs gradually decreases with the increase of the initial concentration of the solution.nZVI-BC-P,which uses readily available and aggregated biochar as the supporting matrix,provides a new material for the treatment of Cr(?)-containing wastewater.In summary,the nZVI-BC-P prepared in this paper can effectively degrade TBBPA,BDE-209,and Cr(?)in solution,and has a broad application prospect for the removal of halogen-containing organic compounds and heavy metals.