【作者】 于春光；

【导师】 杜茂安；

【作者基本信息】 哈尔滨工业大学 ， 市政工程， 2013， 博士

【摘要】 随着工业的迅速发展,产生了大量的有毒的重金属废水。这些废水对环境和人体健康及生态系统都造成了很大的危害。因此,去除废水中的重金属成为当今环境的重要问题之一。利用农林废弃物吸附剂是一种新的技术利用生物质去除水中的重金属,因其成本低廉,对环境无二次污染,取材来源广泛等特点,与其它传统的方法相比有较大的优势。本论文选用农林废弃物质山核桃壳为材料,对其进行化学改性后,得到改性后的山核桃壳(MCWS)。通过对水溶液中Cr6+、Cu2+、Hg2+、Cd2+单一金属溶液和混合金属溶液的吸附行为的研究,考察了山核桃壳吸附剂的吸附性能。采用红外光谱FTIR分析、比表面积分析仪、元素分析仪和扫描电镜等分析检测技术,对山核桃壳的结构、形貌进行了表征,通过对MCWS吸附重金属离子的最佳条件的研究,如金属溶液的pH、金属离子的初始浓度、MCWS投入量、溶液温度及不同吸附时间等,利用吸附动力学模型及吸附等温方程对实验数据进行分析,探讨MCWS吸附重金属的机理。利用FTIR对山核桃壳进行红外光谱分析,显示MCWS有很多化学基团或化学键。在波数3423.3cm-1处的峰值是羟基的振动,而在2937.5cm-1吸收峰处是亚甲基的C-H伸缩振动。1738.4cm-1是羧基上的羰基振动。1638.2cm-1为分子内部羧基上的羰基的伸缩振动,1513.7cm-1是芳香环上的C-C伸缩振动。1462.6cm-1是证明了芳香环上的C-C伸缩振动。1372.5到1046.2cm-1是酚基上的C-O键振动,不同的酚基上不同的C-O说明MCWS富含单宁。605.7cm-1是芳香化合物的振动。这些基团如-OH和-COOH可能与吸附重金属有关。MCWS吸附水溶液中的单一金属实验结果表明,Cr6+离子的去除率随着pH的增高而降低,最大去除率在pH=1时,可以达到82.88%；Cu2+离子的去除率随着pH值的升高增大,去除率最高时的pH5.0,去除率可以达到80.44%；Cd2+离子的去除率随着pH的增大而增加,pH7.0时候达到最大95.64%；MCWS吸附Hg2+的吸附量随着pH的增加而增加,pH5.0达到最大吸附率92.30%,然后吸附量开始下降。MCWS吸附水溶液中的单一Cr6+、Cu2+、Hg2+、Cd2+离子吸附的实验数据都符合Langmuir吸附模型,MCWS对Cr6+、Cu2+、Hg2+、Cd2+离子的最大吸附量分别为：41.7mg/L、15.87mg/L、8.06mg/L、37mg/L。MCWS对水溶液中的Cd6+、Cu2+、Hg2+、Cd2+的吸附过程都是符合拟二级动力学方程的快速吸附过程,30-45min内对四种金属的吸附均达到吸附平衡。利用解吸附实验、FTIR分析、SEM分析MCWS吸附机理,结果表明MCWS吸附Cd6+的机理的吸附过程属于化学吸附,-OH、-COOH的H+与Cr6+离子进行离子交换或者络合作用完成主要吸附过程。MCWS吸附Cu2+离子的吸附过程由化学吸附控制,是吸热反应。羟基在吸附过程中起主要作用,与Cu2+离子进行离子交换,新形成的化学键键能较低,容易被破坏。MCWS吸附Cd2+离子过程属于化学吸附,Cd2+离子与C=O进行吸热的化学反应,新生成的化学键较弱,容易解吸附。MCWS吸附Hg2+离子的机理可能是羟基的H+与Hg2+离子进行离子交换的结果,属于吸热反应,新形成的键能较低。MCWS吸附Cr6+、Cu2+、Hg2+、Cd2+混合离子的最适pH在5.0-7.0之间,相对于Cr6+、Cu2+、Hg2+、Cd2+单一金属存在的最大吸附率都有所下降。最佳吸附时间可为30-90min。随着金属离子初始浓度的增大,吸附率降低,Cr6+、Cu2+Hg2+、Cd2+离子的初始浓度为25mg/L时,吸附率最大。混合金属离子的吸附率随温度升高而增加,混合金属的最佳吸附温度为30℃。MCWS对混合金属溶液的吸附过程比较适合用Langmuir方程拟合,说明吸附过程为均匀的单层吸附。Cr6+、Cu2+、Hg2+、Cd2+最大吸附量分为18.24mg/L,12.8mg/L、7.12mg/L13.32mg/L,均小于单一金属吸附量过程。MCWS吸附Cr6+、Cu2+、Hg2+、Cd2+混合离子的机理涉及到多个化学基团或化学键如-COOH、-OH、C-H、C-O通过离子交换或络合作用完成吸附。更多还原

【Abstract】 The rapid development of industry, produces large amounts of toxic heavy metalwastewater. These waste on the environment have caused great harm to human healthand ecosystems. Therefore, removal of heavy metals from wastewater has become oneof the important environmental problems. The use of agricultural and forestry wasteadsorbent is a kind of new technology and utilization of biomass for removal of heavymetals in the water, because of its low cost, no environmental pollution, abundantsources, it has an advantage over other traditional method.This paper selects the agricultural and forestry waste material Chinese Walnutshell （MCWS） as raw material, through to the aqueous solutions of Cr⁶⁺, Cu²⁺, Hg²⁺,Cd²⁺single metal solution and the mixed solution of metal adsorption behaviorresearch, examines the MCWS adsorbent adsorption properties. The structure,morphology of MCWS were characterized using Fourier Transform InfraredSpectroscop（FTIR）, Specific Surface Area Analyzer, Elemental Analyzer and ScanningElectron Microscopy（SEM）. The optimum sorption conditions such as a metal solutionpH, initial concentration of metal ions, MCWS dosage, solution temperature andadsorption time,were studied. Adsorption mechanism were analysis using the modelon the adsorption kinetics and adsorption isotherm equation to the experimental dataanalysis.The FTIR showed that MCWS has many chemical group or chemical bond. Inthe wave number3423.3cm^-1peak is hydroxyl vibration, while in2937.5cm^-1absorption peak is the C-H stretching vibration of methylene.1738.4cm^-1is carboxylgroups on the carbonyl vibration.1638.2cm^-1is molecules inside of carboxyl groupson the carbonyl stretching vibration,1513.7cm^-1is on the aromatic ring of the C-Cstretching vibration.1462.6cm^-1is proved on the aromatic ring of the C-C stretchingvibration.1372.5to1046.2cm^-1are phenolic groups on C-O bond vibration, differentphenol based on a different C-O MCWS rich in tannin.605.7cm^-1is aromaticcompound vibration. These groups such as-OH and-COOH may be related to theadsorption of heavy metals.The adsorption of MCWS in aqueous solution of single metal experimental resultsshow that, Cr⁶⁺ion removal rate decrease with increased pH, the maximum removal rate in pH=1, can achieve82.88%; Cu²⁺ion removal rate increase with the increase ofpH value, the highest removal rate of pH5, removal rate can reach80.44%; Cd²⁺ionremoval rate increase with increasing of the pH, pH=7reaches the maximum95.64%; MCWS adsorption adsorption amount of Hg²⁺with pH increased, pH=5reaches the maximum adsorption rate of92.30%, then the adsorbed began to decline.Experimental data of adsorption of MCWS in aqueous solution of single Cr⁶⁺,Cu²⁺, Hg²⁺, Cd²⁺ion are consistent with the Langmuir adsorption model, Adsorptioncapacity of MCWS on Cr⁶⁺, Cu²⁺, Hg²⁺, Cd²⁺ion are as follows:41.7mg/L,15.87mg/L,8.06mg/L,37mg/L.Adsorption process of MCWS on aqueous solutions of Cd⁶⁺, Cu²⁺,Hg²⁺, Cd²⁺is consistent with the pseudo-second-order dynamic equation. Adsorptionprocess is quickly in the first short time, the adsorption equilibrium time is30-45min.Adsorption mechanism of MCWS were analysed using desorption experiment,FTIR, SEM.The results show that the adsorption mechanism of Cd⁶⁺adsorptionprocess is chemical adsorption,-OH,-COOH,H+and Cr⁶⁺ions by ion exchange andcomplexation in main adsorption process. Cu²⁺adsorption ion adsorption process iscontroled by chemical adsorption, the reaction is endothermic. The hydroxyl groupplay the main role in adsorption process of Cu²⁺ion through ion exchange, theformation of the new bond energy is low, easy to be destroyed. Cd²⁺ion adsorptionprocess is chemical adsorption, Cd²⁺ion and C=O undergo endothermic chemicalreaction, the new generation of chemical bonding is weak, easy desorption. Themechanism of Hg²⁺ion adsorption may be the the H+and Hg²⁺of hydroxyl groups ionby ion exchange, which belongs to the endothermic reaction, the newly formed key arelower.The optimum pH of adsorption of Cr⁶⁺, Cu²⁺, Hg²⁺, Cd²⁺mixed ion using MCWSis between5.0-7.0, the maximum adsorption rate of mixed Cr⁶⁺, Cu²⁺, Hg²⁺, Cd²⁺arelower than metal solution. The best time of adsorption is30-90min. As the metal ionconcentration increases, the adsorption rate decreased. The initial concentration of25mg/L can reach maximum adsorption rate. Mixed metal ion adsorption rate increaseswith the rise of temperature, mixed metal best adsorption temperature is30.MCWS on the adsorption process of mixed metal solutions for Langmuir equation, thedescription of the adsorption process for the uniform monolayer adsorption. Cr⁶⁺, Cu²⁺,Hg²⁺, Cd²⁺maximum adsorption is18.24mg/L,12.8mg/L,7.12mg/L,13.32mg/L, wereless than single metal adsorption process. Mechanism ofadsorption of Cr⁶⁺, Cu²⁺, Hg²⁺, Cd²⁺mixed ionic by MCWS involves a number of chemical groups such as-COOH,-OH or chemical bonding, C-H, C-O by ion exchange or complexation adsorption.更多还原