由于重金属的难降解性，为避免治理过程中的污染转移，重金属的资源化回收是实现环境与经济效益双赢的有效途径，这就要求吸附剂对目标重金属具有一定的吸附选择性。通过羟甲基化改性提高煤系腐植酸(HA)表面含氧基团密度，形成对重金属吸附的多齿配位结构，来提高HA吸附选择性。改性后的腐植酸进一步与Fe₃O₄共沉淀，生成具有吸附速率快、选择性高且易于固液分离的羟甲基化煤系腐植酸磁性颗粒(OHA-MNPs)，用于废水中重金属的深度分离。对吸附剂进行系统表征，并研究其吸附动力学、吸附热力学、微观吸附机制和多金属共存溶液体系中Pb²⁺和Hg²⁺的吸附选择性。结果表明OHA-MNPs表面腐植酸含量约为9.81%，颗粒粒径主要分布于7~11 nm，具有很好的溶液分散性;Langmuir和准二级动力学模型能够准确的描述OHA-MNPs对Pb²⁺或Hg²⁺的吸附热力学和动力学;OHA-MNPs对Pb²⁺或Hg²⁺的吸附作用以高密度含氧基团多齿络合配位为主，还伴有酸性基团离子交换和静电吸附;在模拟多金属离子共存废水中，OHA-MNPs对Pb²⁺和Hg²⁺均表现出较高的吸附选择性，吸附序列满足Hg²⁺>Pb²⁺Cu2+ Ni²⁺/Cd²⁺，且在总阳离子质量浓度是Pb²⁺的44.78倍的实际酸性矿井废水中，能够对93.76%的Pb²⁺选择性去除。OHA-MNPs同时具有良好的再生能力，是一种高效、绿色、低成本重金属吸附剂。

Because of the non-degradation of heavy metals (HMs),the control on the pollution transfer of HMs in water treatment,and their recycling utilization would be an effective way to achieve a win-win situation of envi-ronmental and economic benefits.In this case,the adsorbent with a selectivity for the target heavy metals is required.Therefore,the density of oxygen-containing functional groups on the surface of humic acid (HA) was improved by hydroxymethylation modification to promote the formation of multi-coordination structure,which had a high adsorption stability and affinity towards certain HMs.Finally,the hydroxymethylated HA magnetic nanoparticles (OHA-MNPs) with high selectivity and easy solid-liquid separation were prepared by co-precipitation,which was used for the deep removal of heavy metals in wastewater.The characterization of adsorbent,adsorption kinetics,adsorption thermodynamics,adsorption mechanism,adsorption selectivity for Pb²⁺ and Hg²⁺ under competitive adsorption,and the regeneration of adsorbent were studied.The results show that the content of HA attached on the surface of OHA-MNPs is about 9.81%.The particle size of adsorbent is mainly distributed in 7-11 nm,which shows good dispersion.The pseudo-second order kinetics and Langmuir adsorption model could well describe the adsorption kinetics and thermodynamics of Pb²⁺ or Hg²⁺ on OHA-MNPs.The adsorption of OHA-MNPs towards Pb²⁺ or Hg²⁺ is mainly attributed to the coordination of oxygen-containing functional groups,accompanied by ion exchange and electrostatic adsorption.In the solution with mixed metals,OHA-MNPs has a high selectivity for Pb²⁺ and Hg²⁺ and the selective adsorption sequence is Hg²⁺> Pb²⁺ Cu²⁺ Ni²⁺/Cd²⁺.About 93.76% of Pb²⁺ can be selectively removed in acid mine wastewater with total cation concentration 44.78 times that of Pb²⁺.Besides,OHA-MNPs also has good regeneration ability.Therefore,OHA-MNPs is a kind of efficient,green and low-cost adsorbent for the removal of heavy metals in wastewater.

1 实验部分

   1.1 煤系腐植酸的提取与羟甲基化改性

   1.2 羟甲基化煤系腐植酸磁性纳米颗粒(OHA-MNPs)的共沉淀制备

   1.3 OHA-MNPs对重金属的吸附实验

2 结果与讨论

   2.1 OHA-MNPs吸附剂表征

   2.2 吸附等温线

   2.3 OHA-MNPs对Pb2+和Hg2+吸附动力学

   2.4 吸附机制

   2.5 OHA-MNPs对Pb2+和Hg2+吸附选择性

   2.6 吸附剂再生

3 结论