Study On Preparation,Characterization Of Phosphorus-Doped Boron Nitride And Its Adsorption Properties Of Heavy Metals

The heavy metals contained in solid waste will be accumulated on fly ash particles or directly transferred and transformed by gaseous forms during incineration,thereby causing heavy metal pollution in the environment.In this paper,the phosphorus-doped boron nitride material(P-BN)was successfully prepared by introducing red phosphorus as a dopant for the preparation of that the use of boric acid and melamine as boron source and nitrogen source of precursor.Using P-BN as an adsorbent,adsorption experiments of heavy metal flue gas were carried out on an independently designed experimental platform,and the adsorption characteristics of P-BN for Zinc and Copper were obtained through dynamic simulation analysis.The results show that the phosphorus content in the P-BN sample prepared by doping activation is>30 mg/g,and its maximum specific surface area is 837.08 m~2/g.Through the mixed adsorption experiment of heavy metal flue gas,it was found that the order of adsorption capacity of P-BN for heavy metals is Zn>Cu>Pb>Cd>Cr.In particular,P-BN has the adsorption capacity of 45.33 mg/g for heavy metal Zn,wherein the adsorption capacity of P-BN for Zinc reached 5～38 times higher than that of other heavy metals.The single-flue gas adsorption experiments were performed on heavy metal Zn and Cu.During the adsorption experiments,it was found that P-BN exhibited a transition phenomenon of adsorption capacity to Zinc and Copper in different adsorption time periods.The maximum adsorption capacities of P-BN for heavy metal Zinc and Copper in the single heavy metal atmosphere were 69.45 mg/g and 53.8 mg/g,respectively.In addition,P-BN also has a certain adsorption capacity under high temperature adsorption environment.When the adsorption temperature rises to 250°C,the adsorption capacity of P-BN for mixed heavy metal flue gas can reach about 60 mg/g.Under the same experimental conditions,the adsorption capacity of P-BN reached more than 12 times that of activated carbon and the adsorption capacity of P-BN also reached more than 4 times that of ordinary boron nitride.When the adsorption temperature rose to 450°C,the adsorption capacity of P-BN for heavy metal Zn is still up to29.44 mg/g.Through TG-DSC analytical analysis and dynamics simulation analysis,it was found that P-BN has two adsorption modes in the adsorption process of heavy metal Zn and Cu:physical adsorption and chemical adsorption.The comparative analysis of desorption activation energy found that the activation energy of P-BN for heavy metal Zn is about 2000J/mol lower than that of heavy metal Cu.This shows that P-BN has good adsorption selectivity and strong adsorption capacity for heavy metal Zn,however,its fixation effect is relatively weak,indicating that it is easy to carry out desorption.