金属-炭黑调控增强金属有机框架（ZIF-8）吸附水体中砷的研究

【作者】 王恒；

【导师】 祁先进； 尧世文；

【作者基本信息】 昆明理工大学 ， 材料与化工（专业学位）， 2023， 硕士

【摘要】 砷污染治理是现阶段实现可持续发展的一个重点难点。尤其是水体中的砷污染,包括地下水砷含量超标以及工业含砷废水排放。这两种污染途径导致的水体污染不仅会对环境造成极大的危害还会直接或间接危害人体健康。常见的含砷水体的处理技术虽然操作简单,但是通常会产生大量的固体废渣,这些废渣因为稳定性差会造成二次污染。为了实现保护经济环保的目的,有必要开发出一种经济、高效、操作简单的除砷技术。ZIF-8是MOFs材料的一种,主要是由锌离子与咪唑配体组成。ZIF-8在水处理方面有很好的表现,但是单独使用ZIF-8材料作为吸附剂去除水体中的砷时,效果不是很理想,并且在酸性条件下,几乎起不到除砷的作用。因此提出以ZIF-8框架为主体,在制备过程中引入其他金属原子以及炭黑和PVP制备出M-ZIF-8和CB@M-ZIF-8吸附剂以提高其吸附能力,提升酸性条件下的除砷性能,实现含砷水体无害化处置,主要研究内容及结论如下:（1）在ZIF-8制备过程中,通过掺杂铜原子以及钴原子,制备出Cu-ZIF-8和Co-ZIF-8吸附剂,金属原子替代部分锌原子可以增加吸附位点,提升吸附性能。在中性条件下,在初始As（Ⅴ）浓度为25 mg/L的溶液中,Cu-ZIF-8和Co-ZIF-8的最大吸附容量分别为238.736 mg/g和250.088 mg/g,是ZIF-8的三倍,除砷率可以达到99.2%和99.43%。在经过四次循环使用之后,吸附剂仍能保持75%以上的除砷率,有很强的重复使用性。在处理含砷废水时,M-ZIF-8吸附剂也表现出不错的除砷性能,并且对废水中的多种金属离子都有一定的去除能力。（2）通过在M-ZIF-8的制备过程中加入PVP和炭黑进行改性之后,吸附剂对砷的吸附能力有了进一步的提升。在pH=4时,吸附效果最好,CB@Cu-ZIF-8和CB@Co-ZIF-8最大吸附容量分别为1705.05 mg/g和2659.67 mg/g。在初始As（Ⅴ）浓度为25 mg/L的溶液中除砷率均可以达到99.99%,处理之后的水体中As（Ⅴ）浓度可以降至0.01 mg/L以下,符合饮用水标准。CB@M-ZIF-8在处理含砷工业废水时同样表现出优异的除砷性能,并且还对废水中其他的金属离子有很好的去除效果。（3）M-ZIF-8和CB@M-ZIF-8对As（Ⅴ）的吸附更符合伪二阶动力模型和Langmuir等温模型,说明吸附过程是单层吸附且以化学吸附为主。在溶液中存在SO₄^2-和CO₃^2-时吸附受到明显的抑制。通过机理分析可知两种吸附剂是通过形成含砷络合物达到除砷的目的。更多还原

【Abstract】 Arsenic pollution control is a key and difficult point to achieve sustainable development at this stage.In particular,arsenic pollution in water bodies,including excessive arsenic content in groundwater and discharge of industrial arsenic-containing wastewater.The water pollution caused by these two pollution pathways will not only cause great harm to the environment,but also directly or indirectly endanger human health.Although the common treatment technology of arsenic-containing water is simple to operate,it usually produces a large amount of solid waste,which usually causes secondary pollution due to poor stability.In order to achieve the purpose of protecting the ecological environment,it is necessary to develop an economical,efficient and simple arsenic removal technology.ZIF-8 is a kind of MOFs material,which is mainly composed of zinc ions and imidazole ligands.ZIF-8 has a good performance in water treatment,but when ZIF-8 material is used alone as an adsorbent to remove arsenic in water,the effect is not very ideal,and under acidic conditions,it can hardly remove arsenic.Therefore,M-ZIF-8 and CB@M-ZIF-8 adsorbents were prepared by introducing other metal atoms,carbon black and PVP in the preparation process to improve their adsorption capacity and arsenic removal performance under acidic conditions.The main research contents and conclusions are as follows:（1）In the preparation process of ZIF-8,Cu-ZIF-8 and Co-ZIF-8 adsorbents were prepared by doping copper atoms and cobalt atoms.Under neutral conditions,in the solution with an initial As（Ⅴ）concentration of 25 mg/L,the maximum adsorption capacity of Cu-ZIF-8 and Co-ZIF-8 was 238.736 mg/g and 250.088 mg/g,respectively,which was three times that of ZIF-8.The arsenic removal rate can reach 99.2%and99.43%.After four cycles of use,the adsorbent can still maintain more than 75%of the arsenic removal rate,and has strong reusability.In the treatment of arsenic-containing wastewater,M-ZIF-8 adsorbent also showed good arsenic removal performance,and had certain removal ability for various metal ions in wastewater.（2）After adding PVP and carbon black to the preparation of M-ZIF-8,the adsorption capacity of the adsorbent to arsenic was further improved.The maximum adsorption capacity of CB@Cu-ZIF-8 and CB@Co-ZIF-8 was 1705.05 mg/g and2659.67 mg/g,respectively.The arsenic removal rate can reach 99.99%in the solution with an initial As（Ⅴ）concentration of 25 mg/L,and the As（Ⅴ）concentration in the treated water can be reduced to less than 0.01 mg/L,which meets the drinking water standard.CB@M-ZIF-8 also exhibits excellent arsenic removal performance in the treatment of arsenic-containing industrial wastewater,and also has a good removal effect on other metal ions in wastewater.（3）The adsorption of As（Ⅴ）by M-ZIF-8 and CB@M-ZIF-8 was more in line with the pseudo-second-order kinetic model and Langmuir isotherm model,indicating that the adsorption process was monolayer adsorption and dominated by chemical adsorption.The adsorption was significantly inhibited in the presence of SO₄^2-and CO₃^2-.Through mechanism analysis,it can be seen that the two adsorbents achieve the purpose of removing arsenic by forming arsenic-containing complexes.更多还原