重金属离子对生物炭吸附水环境中雌激素的影响

Effect of heavy metal ions on environmental estrogens adsorption by biochar

以小麦秸秆为原料制备生物炭(BC),采用批量吸附实验研究BC对水环境中雌激素双酚A(BPA)、17α-乙炔基雌二醇(EE2)的吸附行为,并选用模型污染物菲作对比,探讨了重金属离子(Cu^2+、Cd^2+、Pb^2+)对BC吸附雌激素的影响和作用机制。结果表明:BC对污染物的最大吸附能力为菲>BPA>EE2,其主要吸附机制为疏水性作用、π-π电子供受体作用、孔隙填充作用等。在重金属离子存在条件下,BC对污染物的吸附明显降低,一方面是因为重金属离子与BC表面含氧官能团发生络合作用竞争吸附点位;另一方面是因为重金属离子可与周围水分子之间形成三维水合金属离子进行孔隙堵塞。Pb^2+对BC吸附能力的抑制作用最弱,这主要是因为Pb的水合离子半径最小,孔阻塞和竞争作用最弱。

Biochar(BC)produced from wheat straw was used as absorbent to adsorb estrogens bisphenol A(BPA),17α-ethynyl estradiol(EE2)in aquatic environment.The adsorption process of estrogens was investigated through batch adsorption environment,and compared with that of model contaminant phenanthrene.The effects of heavy metal ions(Cu^2+,Cd^2+,Pb^2+)on the adsorption of estrogens by biochar and mechanism were discussed.The results showed that the maximum adsorption capacity was in the order of phenanthrene> BPA > EE2.The main sorption mechanisms were the hydrophobic effect,π-πdonor-acceptor interactions and pore filling.In the presence of heavy metal ions,the adsorption affinities of the adsorbates on BC were significantly inhibited,this was likely because heavy metal ions could be adsorbed by biochar and occupied the adsorption sites on the surface of biochar via complexation competition.On the other hand,the three-dimensional hydrated metal ions formed between metal ions and surrounding water molecules could block micropores of BC.It was noted that the inhibition effect of Pb^2+ was the weakest,this was because the hydrated ionic radius formed by Pb was the smallest,the pore blocking effect and competition effect were the weakest.