V5+和V4+在不同生物炭柱中淋溶特性及其影响因素研究OA北大核心CHSSCDCSTPCD

Biochar has a great retention potential on metal ions and has been widely used to remove heavy metals from sur-face runoff and groundwater.In this study,wood charcoal and bamboo charcoal with particle size of 0.80 mm were used,and the column experiments were conducted to investigate V5+ and V4+ leaching in the two types of biochar columns.The effects of vanadium valence state,initial vanadium concentration,solution pH,types and concentrations of organic acids on vanadium migration were studied.The results indicate that the retention efficiency of V5+ in the wood charcoal and bam-boo charcoal columns was low,while the retention efficiency of V4+ was high in both types of columns.When the injection amount was three times of PV(pore volume,60 mL),the effluent ratios(the ratio of effluent concentration to inlet con-centration)of different initial V5+ concentrations exceeded 0.90 in both types of biochar columns,indicating that V5+ had a high migration rate in biochar columns and the influence of initial V5+ concentration on retention was not significant.When the injection amount was 8 times of PV,the effluent ratio for the V4+ solution with an initial concentration of 5 mg·L-1 was about 0.90,whereas the effluent ratio for the V4+ solution with an initial concentration of 40 mg·L-1 decreased to be-low 0.63.This suggests that the migration rate of V4+ in biochar columns had significantly decreased with the initial V4+ concentration increased.With the increase in leachate pH,the retention rates of V5+ and V4+ in both types of charcoal col-umns decreased,subsequently leading to an increase in the effluent ratios of V5+ and V4+ solutions.At the leachate pH of 5.5,the maximum effluent ratios for V5+ and V4+ in the wood charcoal column were 0.88 and 0.58,respectively,while they were 0.83 and 0.53 in the bamboo charcoal column.When different concentrations of oxalic acid and citric acid were added into the leachate,it was observed that high concentration organic acid promoted V5+ leaching,whereas low concen-tration organic acid inhibited V5+ leaching.Compared to oxalic acid,citric acid had exhibited stronger effect in inhibiting V5+ leaching in both the two types of biochar columns.Fourier-transform infrared spectroscopy(FTIR)analysis had re-vealed that the surfaces of biochar were predominantly characterized by acidic oxygen-containing functional groups,such as carboxyl groups,carbonyl groups,hydroxyl groups,and other functional groups,which readily formed the complexes and facilitated the deposition of V5+ and V4+.Under the condition of low pH value of the solution,the content of these acidic oxygen-containing functional groups on the biochar surface had increased,thereby significantly promoting the adsorption of V5+ and V4+ on biochar.