【作者】 王平；

【导师】 黄占斌；

【作者基本信息】 中国矿业大学(北京) ， 环境科学与工程， 2022， 博士

【摘要】 煤基胡敏素是褐煤和风化煤提取腐植酸后所剩废渣的主要成分,由于废渣缺乏相关利用技术和标准,填埋和乱排已造成严重的环境污染,资源化再生利用成为生产亟待解决的问题。此外,镉（Cd）污染一直被认为是我国农田土壤的主要污染类别,制备高效、环保和成本低廉的镉污染修复材料很有必要。针对我国重金属镉污染严重和废渣中煤基胡敏素利用率低这两个关键的科学问题,本研究以我国腐植酸原料主要产区山西（S）、黑龙江（D）和内蒙古（N）三地的风化煤和褐煤为主,以提取棕腐酸和黄腐酸后的煤基胡敏素（HM）为研究对象,采用Ca（OH）₂和超声辅助水热法制备钙基胡敏素（Ca-SHM、Ca-DHM和Ca-NHM）。将制备的钙基胡敏素作为重金属镉钝化剂,应用于水溶液、土壤和植物体系中,探究其对镉的吸附解吸特性、土壤镉的钝化稳定化效果及镉污染评价等,并结合SEM/EDS、BET-表面、Zeta电位、FTIR、¹³C-CPMAS-NMR和XPS表征手段,揭示煤基胡敏素对镉钝化稳定化的机制。研究结果对促进煤基胡敏素的资源化再生利用和土壤镉钝化稳定化新材料的研发提供重要参考。研究取得以下主要结果:（1）不同来源煤基胡敏素的特征比较。通过对山西、黑龙江和内蒙古的煤基胡敏素进行表征分析。结果表明:煤基胡敏素主要由C、H、O、N、S等元素组成;矿物主要有石英、高岭土、珍珠陶土和二氧化硅等组成;含有羟基、脂肪族、羰基、羧基和醚氧等官能团,且分子量大,芳香度高。此外,山西煤基胡敏素的总腐植酸含量和氧官能团含量最高,分别占11.48和45.39%;山西和内蒙古煤基胡敏素的有机质含量较高,分别为97.35和98.49%;黑龙江煤基胡敏素的氧含量最低,为16.79%。（2）改性煤基胡敏素的制备及其工艺优化。制备巯基化、钙基化和铁基化改性煤基胡敏素,通过对比改性前后煤基胡敏素的比表面积、孔径、红外光谱及镉吸附性能发现,钙基胡敏素对Cd²⁺的吸附效果最好。钙基胡敏素的BET比表面为6.48 m²/g,总孔体积为0.025 cm³/g,平均孔径为15.37 nm。优化钙基改性制备工艺,获得最佳制备条件为:煤基胡敏素和Ca（OH）₂的投加配比为1:1,水热温度为85℃,超声时间为3 h。优化后钙基胡敏素对镉的去除率达到86.43%,提高了22.09%。（3）钙基胡敏素对水中镉的吸附解吸特征和机制。p H值、初始浓度、吸附时间和温度等外界因素均能影响煤基胡敏素对水中镉的吸附性能。钙基胡敏素能显著提高对Cd²⁺的吸附量,在p H为5.5,温度为298.15 K时,通过Langmuir模型计算SHM、Ca-SHM、DHM、Ca-DHM、NHM和Ca-NHM对Cd²⁺的最大吸附量分别为72.46、89.29、15.29、41.84、18.48和64.94 mg/g。吸附过程符合Langmuir模型和准二级动力学模型,表明煤基胡敏素对Cd²⁺的吸附是以单分子层的化学吸附为主,颗粒内扩散是主要限速步骤,同时液膜对煤基胡敏素吸附Cd²⁺的速率产生影响。通过热力学分析表明,增温能够促进煤基胡敏素对Cd²⁺的吸附。煤基胡敏素主要通过离子交换、静电作用、络合反应和物理吸附等途径对Cd²⁺进行吸附。钙基胡敏素能够提高对镉的吸附能力,主要包括三个方面:一是增加煤基胡敏素表面氧烷基碳、芳香族碳和酚碳等活性官能团的含量;二是Ca（OH）₂的腐蚀性导致煤基胡敏素表面的含氧官能团的化学键断裂,Ca²⁺成功负载到煤基胡敏素表面;三是氢氧化钙电离产生OH^-,能够与Cd²⁺形成氢氧化物沉淀;四是孔径的增加,为Cd²⁺向煤基胡敏素结构内部扩散提供了通道。此外,在不同p H、温度和离子强度等外界因素的影响下,钙基胡敏素能显著降低Cd²⁺的解吸率,提高材料对Cd²⁺吸附的稳定性。（4）钙基胡敏素对土壤中镉的钝化稳定化效果。钙基胡敏素对土壤镉具有良好的钝化效果。通过等温线拟合确定钙基胡敏素在土壤环境中对Cd²⁺的最大吸附量为8.62-10.23 mg/g。钙基胡敏素能够降低土壤镉的解吸率,增强土壤镉钝化的稳定性。酸浸试验表明,钙基胡敏素（Ca-SHM、Ca-DHM和Ca-NHM）对镉的浸出质量浓度较改性前（SHM、DHM和NHM）分别降低了3.85、12.90和2.44%,提高了镉在土壤中的稳定性。结合土壤理化特性分析,煤基胡敏素能够增加土壤p H、电导率、阳离子交换量和有机质含量,促进土壤镉的钝化。此外,煤基胡敏素可通过磷酸盐沉淀、碳酸盐沉淀以及含氧官能团的表面络合、离子交换等方式对土壤镉起到稳定化效果。（5）钙基胡敏素对土壤镉的生物有效性影响和综合评价。施用煤基胡敏素能够增加镉胁迫下小白菜的叶绿素含量,提升光合作用,增加小白菜的叶片数、株高、叶面积和根长,促进小白菜生长。与CK相比,SHM、DHM和NHM处理组小白菜地上部鲜重和地下部鲜重分别增加了11.03、11.88、16.95和5.21、32.81、36.12%。钙基胡敏素能够增强小白菜对镉的抗性,降低小白菜地上部镉含量以及富集能力。钙基化后,转运系数均小于1,缓解了镉的毒害作用。通过钙基胡敏素对镉钝化稳定化的综合评价,表明钙基胡敏素具有功能性,能够降低土壤镉的活性系数、活稳比、K_RSP值和RAC,提高土壤镉的钝化效率。与CK相比,SHM、Ca-SHM、DHM、Ca-DHM、NHM和Ca-NHM对土壤镉的钝化效率分别提高了22.92、27.97、23.98、29.92、13.90和23.59%;且钙基胡敏素的生产成本（3500元/t）低于市场上现有的土壤重金属钝化剂（4000-9000元/t）,具有经济性。因此,钙基胡敏素能够作为一种新型环境材料应用于土壤镉修复。更多还原

【Abstract】 Coal-based humin is the main component of residue after extracting humic acid from lignite and weathered coals.Due to the lack of relevant utilization technologies and standards,the landfill and disorderly discharge of these waste residues have caused serious environmental pollution,and the recycling and utilization of resources have become an urgent problem to be solved in production.Additionally,cadmium（Cd）pollution has always been considered as the main pollution category of farmland soil in China.It is necessary to prepare high efficiency,environmental protection and low-cost adsorption materials to control cadmium pollution.Based on two key scientific problems of serious cadmium pollution and low utilization rate of coal-based humin in waste residue,this study mainly used the weathering coal and lignite from Shanxi（S）,Heilongjiang（D）and Inner Mongolia（N）,the main producing areas of humic acid raw materials in China,coal-based humin（HM）that after extraction of brown and fulvic acid from raw materials was used as the research object.Calcium-based humin（Ca-SHM,Ca-DHM and Ca-NHM）were prepared using Ca（OH）₂and ultrasonic-assisted hydrothermal method.The prepared calcium-based humin materials were used as heavy metal cadmium passivator,applied in aqueous solution and soil-plant system to explore its adsorption and desorption characteristics of cadmium,soil cadmium passivation stabilization effect and cadmium pollution evaluation.In addition,using SEM/EDS,BET-surface,Zeta potential,FTIR,¹³C-CPMAS-NMR and XPS to reveal the mechanism of cadmium passivation stabilization.The results provide an important reference for promoting the recycling and utilization of coal-based humin and the development of new materials for soil cadmium passivation and stabilization.The main results obtained are as following:（1）Comparison of characteristics of coal-based humin from different sources.Coal-based humin that from Shanxi,Heilongjiang and Inner Mongolia,were characterized and analyzed.The results showed that:Coal-based humin materials are environmentally friendly,the elements mainly consist of C,H,O,N and S;minerals are mainly quartz,kaolin,pearl clay,silica and other components;contains hydroxyl,aliphatic,carbonyl,carboxyl and ether oxygen and other functional groups,and are large molecular weight,high aromatic degree.Additionally,the total humic acid content and oxygen functional group content of coal-based humin in Shanxi were the highest,accounting for 11.48 and 45.39%,respectively.The organic matter content of coal-based humin of Shanxi and Inner Mongolia were 97.35 and 98.49%,respectively.The oxygen content of coal-based humin of Heilongjiang was the lowest,accounting for 16.79%.（2）Preparation and optimization of coal-based humin modified materials.Preparing the mercapto,calcium and iron-based humin,through comparing the specific surface area,pore size,infrared spectrum and cadmium adsorption performance of coal-based humin before and after modification,found that the adsorption effect of calcium-based humin on Cd²⁺was the best.The BET specific surface of calcium-based humin was 6.48 m²/g,the total pore volume was 0.025 cm²/g,and the average pore size was 15.37 nm.The optimum preparation conditions were as follows:the ratio of coal-based humin and Ca（OH）₂was 1:1,the hydrothermal temperature was 85℃,and the ultrasonic time was 3 h.After optimization,the cadmium removal rate of calcium-based humin reached 86.43%,which increased by 22.09%.（3）Characteristics and mechanisms of cadmium adsorption and desorption of calcium-based humin in water.The external factors such as p H value,initial concentration,adsorption time and temperature can affect the adsorption performance of coal-based humin for cadmium in water.Calcium-based humin can significantly increase the adsorption capacity of Cd²⁺.The Langmuir model was used to calculate the maximum adsorption capacity of SHM,Ca-SHM,DHM,Ca-DHM,NHM and Ca-NHM for Cd²⁺were 72.46,89.29,15.29,41.84,18.48 and 64.94 mg/g,respectively,at p H 5.5,298.15 K.The adsorption process was in accordance with Langmuir model and quasi-second-order kinetic model,which indicated that the adsorption of coal-based humin for Cd²⁺was dominated by monomolecular chemisorption,and intra-particle diffusion was the main rate-limiting step,and the liquid film had an effect on Cd²⁺adsorption rate by coal-based humin.Thermodynamic analysis showed that increasing the temperature can promote the adsorption reaction of coal-based humin to Cd²⁺.Coal-based humin adsorbed Cd²⁺mainly through ion exchange,electrostatic action,complexation reaction and physical adsorption.Calcium-based humin can improve the adsorption capacity of Cd²⁺.The first reason was increased the content of active functional groups such as Alkoxy C,Aromatic C,and Phenolic C on the surface of coal-based humin.Secondly,the corrosion of Ca（OH）₂resulted in the chemical bond rupture of oxygen-containing functional groups on the surface of coal-based humin,and Ca²⁺was successfully loaded onto the surface of coal-based humin.Thirdly,calcium hydroxide ionizes to produce OH^-,which can form hydroxide precipitation with Cd²⁺.Fourthly,the increase of pore size provided a channel for the diffusion of Cd²⁺into the coal-based humin.In addition,under different p H,temperature and ionic strength,calcium-based humin can significantly reduce the desorption capacity and desorption rate of Cd²⁺and improve the adsorption stability of Cd²⁺.（4）Soil cadmium passivation and stabilization effect and mechanism of calcium-based humin.Calcium-based humin has good passivation effect on soil cadmium.Through the adsorption isotherm fitting achieved the maximum adsorption capacity of coal-based humin for Cd²⁺was 8.62-10.23 mg/g in soil environment.Compared with coal-based humin,calcium-based humin can reduce the desorption rate of soil cadmium and enhance the stability of soil cadmium passivation.Acid leaching tests showed that compared with SHM,DHM and NHM,the leaching mass concentration of cadmium by Ca-SHM,Ca-DHM and Ca-NHM decreased by 3.85,12.90 and 2.44%,respectively,and improved the stability of soil cadmium.Combined with the analysis of soil physical and chemical properties,showed that coal-based humin can increase soil p H,conductivity,cation exchange capacity and organic matter content,and promote the passivation of soil cadmium.In addition,coal-based humin can passivate heavy metal cadmium by forming phosphate precipitation,carbonate precipitation,surface complexation of oxygen-containing functional groups,ion exchange and other functions,and the passivation effect is stable.（5）Bioavailability and comprehensive evaluation of calcium-based humin on soil heavy metal cadmium.Coal-based humin could increase chlorophyll content,photosynthesis,leaf numbers,plant height,leaf area and root length of Pakchoi under cadmium stress,and promote the growth of Pakchoi.SHM,DHM and NHM treatment groups compared with CK,aboveground fresh weight and underground fresh weight of pakchoi increased by 11.03,11.88,16.95%and 5.21,32.81,36.12%,respectively.The resistance coefficient relationship among different treatments of Pakchoi was as follows:Ca-NHM>Ca-DHM>Ca-SHM>NHM>SHM>DHM,that is,calcium-based humin could enhance the resistance of pakchoi to heavy metal cadmium,and reduce the cadmium content and enrichment ability of aboveground.The transport coefficients are all less than 1 after calcification,which alleviates the toxic effect of heavy metal cadmium.The comprehensive evaluation of calcium-based humin to cadmium passivation and stabilization showed that calcium-based humin has functionality,could reduce the activity coefficient,activity ratio,K_RSPvalue and RAC value of soil cadmium,and improved the passivation efficiency of soil cadmium.Compared with CK,soil cadmium passivation efficiency of SHM,Ca-SHM,DHM,Ca-DHM,NHM and Ca-NHM increased by 22.92,27.97,23.98,29.92,13.90 and 23.59%,respectively.Moreover,its production cost（3500 yuan/ton）is lower than the existing soil heavy metal passivator（4000-9000 yuan/ton）on the market,which is economical.Therefore,calcium-based humin can be used as a green environmental material for soil cadmium remediation.更多还原