【作者】 张娟；

【导师】 谢逢春；

【作者基本信息】 华南理工大学 ， 化学工程与技术， 2022， 硕士

【摘要】 工农业的快速发展加剧了水体重金属污染,这些重金属因具有不可降解性而在环境中持续存在,一旦超过地表水或饮用水排放标准,会对环境和人体造成巨大威胁。因此,开发低成本、高性能的吸附材料,实现吸附剂的再生利用具有重要意义。本文以ZHN和氯化钠(NaCl)为原料,改变它们之间的摩尔比,在酸性条件下合成了ZHO,并通过SEM、TEM、BET、XRD、FTIR和XPS等表征手段对材料进行了分析。从pH、ZHQ的加入方式、重金属离子初始浓度等方面探讨了ZHQ的加入对Cd(Ⅱ)吸附行为的影响,并利用ZHN与ZHQ之间的氧化还原反应再生了ZHO,探讨包覆对Cd(Ⅱ)的深度去除及脱附的影响,最后从宏观和微观两方面分析了ZHO对于Cd(Ⅱ)和ZHQ的吸附机理。主要结论如下:(1)当ZHN与NaCl按摩尔比1:3反应时,得到的B-ZHO具有更大的比表面积、更低的结晶度和更高含量的Mn(IV),对Cd(Ⅱ)表现出更强的吸附能力。(2)ZHQ的加入会对Cd(Ⅱ)的吸附行为产生影响。其中,pH值的增大有利于ZHQ的吸附同时也减少了Cd(Ⅱ)的脱附,间歇式加入ZHQ会在一定程度上降低Cd(Ⅱ)的脱附,较低初始浓度的重金属离子也会降低Cd(Ⅱ)的脱附。ZHO对Cd(Ⅱ)的吸附更符合Langmuir模型和准二级动力学模型,表明吸附是均匀的化学吸附过程,但对ZHQ的吸附更符合Freundlich模型和准二级动力学模型,表明吸附是非均匀的化学吸附过程。颗粒内扩散模型表明Cd(Ⅱ)和ZHQ的吸附受膜扩散和颗粒内扩散的联合控制。(3)ZHO的再生是通过ZHN与吸附在ZHO表面的ZHQ间的氧化还原反应完成的,新生成的ZHO包覆在外层,一方面进一步降低了溶液中Cd(Ⅱ)的浓度,另一方面也减少了Cd(Ⅱ)的脱附,实现ZHO的循环利用。根据XRD、FTIR和XPS的表征分析结果,Cd(Ⅱ)与ZHO表面的羟基相互作用形成Cd-O键,而后加入的ZHQ则是优先吸附在ZHO表面剩余吸附位点,待吸附位点被占满后,ZHQ会部分取代Cd(Ⅱ)的吸附位点,形成ZHO键,ZHO对ZHQ的高亲和力则是由于与其结构中的ZHO发生了反应。更多还原

【Abstract】 The rapid development of industry and agriculture has aggravated the pollution of heavy metals in water.These heavy metals persist in the environment due to their non-degradability.Once they exceed the discharge standards of surface water or drinking water,they will pose a great threat to the environment and human beings.Therefore,it is of great significance to develop low cost and excellent performance adsorption materials and realize the recycling of adsorbent.In this work,different ZHOwas synthesized by changing the molar ratio of ZHN and sodium chloride(NaCl)under acidic conditions,and the materials were characterized by SEM,TEM,BET,XRD,FTIR and XPS.Besides,the influence of ZHQ addition on the adsorption behavior of Cd(Ⅱ)was investigated in terms of pH,ZHQ addition mode and initial concentration of heavy metal ions.The regeneration of manganese dioxide was realized through the redox reaction between ZHN and ZHQ,at the same time,we also discussed the effect of coating on the depth removal and desorption of Cd(Ⅱ).Finally,the adsorption mechanism of ZHO for Cd(Ⅱ)and ZHQ was analyzed from both macroscopic and microscopic aspects.The main conclusions were as follows:(1)When the molar ratio of ZHN and NaCl was 1:3,the synthesized B-ZHO had larger specific surface area,lower crystallinity and more Mn(Ⅳ),showing higher adsorption capacity for Cd(Ⅱ).(2)The addition of ZHQ had a great influence on the adsorption behavior of Cd(Ⅱ).Specifically,the increase of pH value was beneficial to the adsorption of ZHQ and reduced the desorption of Cd(Ⅱ).The intermittent addition of ZHQ weakened the desorption of Cd(Ⅱ)to a certain extent,and the lower initial concentration of heavy metal ions would also reduce the desorption of Cd(Ⅱ).In addition,the adsorption of Cd(Ⅱ)by ZHO was more consistent with Langmuir and pseudo-second-order kinetic model,indicating that the adsorption was uniform chemisorption process,while that of ZHQ could be better in line with Freundlich and pseudo-second-order kinetic model,demonstrating that the adsorption was non-uniform chemisorption process.The intra-particle diffusion model showed that the adsorption of Cd(Ⅱ)and ZHQ was controlled by film diffusion and intra-particle diffusion.(3)The redox reaction between ZHN and ZHQ adsorbed on the surface of ZHO could generate new ZHO,coating outside of original ZHO.Not only could the regenerated ZHO reduce the concentration of Cd(Ⅱ)in the solution further,but also weakened the desorption of Cd(Ⅱ),realizing the recycle of ZHO.According to XRD,FTIR and XPS characterization analysis,Cd(Ⅱ)could interact with hydroxyl groups on the surface of ZHO to form Cd-O bond,and ZHQ was preferentially adsorbed on the remaining adsorption sites on the surface of ZHO.When the remaining adsorption sites were fully occupied,ZHQ would partially replace the adsorption sites of Cd(Ⅱ)to form ZHO bond.The high affinity of ZHO to ZHQ was attribute to its reaction with ZHO in the structure.更多还原