Investigation Of Bisphenol A In Wastewater Removed By The Nitrogen-doped Graphene-like Plates Prepared Of Green Petroleum Coke

In recent years,with the increasing production and utilization of epoxy resins and polycarbonate plastics,a large amount of bisphenol A(BPA)is discharged into water,resulting in serious environmental pollution.BPA in sewage is an important factor affecting human health.Adsorption is one of the most effective technologies for the removal of BPA in wastewater,and the adsorption effect of carbonaceous materials is the most excellent,which has a great application prospect.In this study,green petroleum coke,a carbonaceous solid waste,was modified by calcination and nitrogen doping with melamine as nitrogen source.The influence of nitrogen doping time and temperature on the modification effect was also investigated.Analyses of SEM,XRD,XPS,FT-IR,BET and ξ-potential indicated that green petroleum coke obtained a more regular graphene-like layer structure after calcining and nitrogen doping,thus having a larger specific surface area.The nitrogen-doped petroleum coke with high graphitization degree can be obtained by calcining and nitrogen doping at 750℃ for 6 h.Besides,the nitrogen-doped petroleum coke contained an electropositive surface,which greatly improved BPA adsorption efficiency,and BPA removal efficiency exceeded 95%.The effects of environmental factors on the adsorption of BPA were investigated in the adsorption experiments.It was found that the best adsorption effect could be obtained under the conditions of 50℃,pH=6 and 48 h contact time.Langmuir isotherm can better explain the adsorption process.Thermodynamic parameters proved that the adsorption process was a spontaneous endothermic physical process.Electrostatic adsorption,π-π interaction and hydrogen bonds are the main mechanisms of the high efficiency adsorption of BPA by nitrogen doped petroleum coke.This study provides a theoretical basis for the design of low-cost,easy-prepared and high-efficiency carbonaceous adsorbents by utilizing green petroleum coke,a kind of solid waste.The main experimental results are as follows:(1)The results of FT-IR analysis showed that there were stable nitrogen-containing groups in the modified petroleum coke samples,which proved that nitrogen doping modification was successfully realized.SEM analysis results showed that petroleum coke obtained regular and smooth lamellar structure after calcination and nitrogen doping,and the lamellar structure became more obvious with the increase of calcination temperature and time.XRD analysis results showed that nitrogen doping and calcination can make petroleum coke obtain more obvious graphitization structure,and the degree of graphitization increased with the increase of calcination temperature and time.BET experiments showed that nitrogen doping and calcination significantly increased the specific surface area and pore volume of petroleum coke.The specific surface area increased from 8.0 m2/g to 96.6 m2/g,and the pore volume increased from 0.013 cm3/g to 0.082 cm3/g.Zeta potential measurements showed that the nitrogen-doped petroleum coke had a positively charged surface.(2)The results of adsorption experiments showed that when the dosage of nitrogen-doped petroleum coke was 7 g/L,the initial pH of wastewater containing BPA was 6.0,the contact time was 48 h,and the adsorption temperature was 50℃,the removal rate exceeded 95%.(3)Through Langmuir isotherm simulation,the R2 values of BPA adsorption by nitrogen-doped petroleum coke were 0.9982-0.9922.Therefore,Langmuir isotherm model was suitable for analyzing and explaining this adsorption process.(4)Electrostatic attraction and π-π interaction were the main forces in the adsorption process of BPA onto nitrogen-doped petroleum coke.Hydrogen bonding between nitrogen-doped petroleum coke and bisphenol A further enhanced the adsorption effect.(5)Calculated by thermodynamics,the value of ΔG0 was between-0.97 and-7.13,indicating that the adsorption process was spontaneous physical adsorption.The values of ΔH0 and ΔS0 were>0,which showed that the adsorption process was endothermic.(6)The regeneration experiment showed that the adsorption capacity of the nitrogen-doped petroleum coke to BPA gradually decreased with the increase of cycle times,but after six cycles,the removal rate of BPA could still be maintained at 80%.