Preparation And Adsorption Performance Of Fe/N Inorganic/Organic Composite Adsorbents

With the continuous improvement of human living standards and the continuous development of industrialization,environmental pollution has become one of the main factors restricting the development of society.Thereinto,water pollution is particularly outstanding.Among all kinds of pollutants,heavy metals are both acute poisoning and accumulative toxicity,which pose a great threat to human health and social development.Three Fe/N inorganic/organic composite adsorbents with different structures,Fe/N co-doped lignin(Fe/N-Lignin),N-doped Fe/Mg layered double hydroxide(N-Fe/Mg-LDH)and N-doped Fe/Mg metallic organic nanosheet material(Fe-Mg-BDC),were prepared,achieving the selective adsorption for As(V)anions.The performances of adsorbents were evaluated by selectivity,concentration effect,p H effect,saturated adsorption capacity,adsorption rate and regeneration ability.The adsorption isotherms and kinetics were studied.Related materials were characterized by FT-IR,XPS,XRD and SEM,and the adsorption mechanism was studied.The main work and conclusions of this study are as follows:(1)Using lignin as the substrate,N-doped lignin(N-Lignin)was prepared by introducing aminomethyl to the o-position of phenolic hydroxide groups in lignin through Mannich reaction.Fe/N co-doped lignin(Fe/N-Lignin)was further prepared by doping N-Lignin with Fe element through complexation reaction.Compared with N-Lignin,the selectivity of Fe/N-lignin for As(V)was significantly enhanced.The separation factors,and,were 916 times and 486 times those of N-Lignin,respectively.The saturated adsorption capacity of Fe/N-lignin for As(V)reached 720.96 mg·g^-1,and the adsorption equilibrium was reached within 60 min.After four regenerations,the adsorption capacity of Fe/N-Lignin for As(V)was decreased by only 10.38%.(2)Using glycine as N source,N-doped Fe/Mg layered double hydroxides(N-Fe/Mg-LDH)with different Fe/Mg ratios were prepared.The Fe/Mg layered double hydroxide without the doping of N(Fe/Mg-LDH-1)was also prepared.Among N-Fe/Mg-LDH with different Fe/Mg mole ratios,only N-Fe/Mg-LDH-1(with the Fe/Mg ratio of 1:1)achieved significant improvement in the selectivity for As(V).The separation factors,and,were 620 times and 994 times those of Fe/Mg-LDH-1,respectively.The saturated adsorption capacity of N-Fe/Mg-LDH-1 for As(V)reached 853.44 mg·g^-1,and the adsorption equilibrium was reached within 120 min.After four regenerations,the adsorption capacity of N-Fe/Mg-LDH-1 for As(V)was decreased by only 12.49%.(3)Using triethylamine as N source,N-doped Fe/Mg metal organic nanosheet(Fe-Mg-BDC)was prepared.The saturated adsorption capacity of Fe-Mg-BDC for Pb(?)cation reached 737.81 mg·g^-1,and the adsorption equilibrium was reached within 60 min.The saturated adsorption capacities of Fe-Mg-BDC and Fe-Pb(Mg)-BDC(Fe-Mg-BDC saturated by Pb(?))for As(V)anion reached 122.92 mg·g^-1 and 134.49 mg·g^-1,and the adsorption equilibrium was reached within 60 min and 30 min,respectively.After four regenerations,the adsorption capacity of Fe-Pb(Mg)-BDC for As(V)was decreased by only 23.62%.