【作者】 赵凯；

【导师】 郭华明；

【作者基本信息】 中国地质大学（北京） ， 地下水科学与工程， 2014， 博士

【摘要】 高砷地下水的治理技术已成为世界规模的全球性问题，研发经济高效的新型除砷吸附材料迫在眉睫。本文以天然菱铁矿粉末(NS)为基体通过湿法挤压造粒并灼烧改性的方法制备改性天然菱铁矿颗粒，并结合不同改性产物的除砷实验结果，确定最优改性条件为：在固液比为5g NS：1mL去离子水，添加铝溶胶的量为10mg Al/g NS条件下湿法挤压造粒，并在马弗炉中控温350℃灼烧90min。XRD、FTIR、XANES等表征分析结果一致表明，最优改性天然菱铁矿是晶格结构相对于天然矿物发生改变并活性增强的菱铁矿和赤铁矿的二元体。以最优改性天然菱铁矿(MGNS)作为除砷吸附剂，通过室内批实验系统地研究其对As(III)和As(V)的吸附性能。结果表明，改性天然菱铁矿突破了天然菱铁矿吸附平衡时间长、吸附容量低的瓶颈，对As(III)、As(V)的吸附平衡时间分别为24h、36h，等温吸附研究得到改性天然菱铁矿除砷的吸附过程为自发进行的吸热反应，25℃时其对As(III)、As(V)的最大饱和吸附量分别可达2.66、2.19mg/g。改性天然菱铁矿对溶液pH值具有良好的缓冲能力，其除砷性能基本不受溶液pH值、溶解氧、背景电解质及共存阴离子、Ca/Mg阳离子及溶解性有机物等典型高砷地下水水化学特征因素的影响，对砷表现出较高的选择吸附性。采用小型动态柱实验及现场中试对改性天然菱铁矿的动态除砷效果进行评价。柱实验结果表明，改性天然菱铁矿填充吸附柱对去离子水或自来水配制的As(III)溶液均有较好的去除效果，且不受原水中As(III)初始浓度的影响。当出水穿透浓度为50μg/L的农村地区饮用水标准限值时，填充吸附剂吸附容量均约为1.2mg/g。相比而言，改性天然菱铁矿对As(V)的动态处理效果远不如As(III)。尽管现场中试处理高砷地下水以As(III)为主，但吸附剂及原水水质因素的影响使其处理效果与室内柱实验结果相差较大。TCLP吸附剂浸出性评价结果表明，除砷后改性天然菱铁矿化学性质稳定，可进行安全填埋处置。除砷机理研究表明，改性天然菱铁矿去除As(III)的过程是一个吸附并快速Fenton氧化As(III)的过程，而As(V)则是通过与Fe(III)活性产物表面的羟基或-CO3等官能团进行配位体交换，并在吸附剂表面生成双齿双核络合物而去除的。更多还原

【Abstract】 Arsenic removal from high-As groundwater is of serious concern and hasbecome an important global problem. It is an urgent and challenging issue to developeconomic and efficient materials for As removal from As-contaminated groundwater.This study was carried out to investigate the possibility of using the fine size ofnatural siderite (NS) as the major components in fabricating modified granular naturalsiderite (MGNS) for As removal, which were synthesized by addition of alumina sol,extrusion granulation, and calcinations. The calcinated strips were manually cut intoparticles with length of1.0~2.0cm. The modification greatly improved the adsorptioncapacity of the material. Results of As removal by different modified granularadsorbents showed that the maximum removal efficiency was reached with anadhesive dosage of10mg Al/g NS and calcination temperature of350℃for90minutes. Results of XRD, FTIR, and Fe K-edge XANES analysis showed that sideritewas partially transformed into hematite in the process of modification, and MGNSwas considered as an Fe(II)/(III) hybrid system.Modified granular natural siderite was evaluated for adsorption characteristics bymeans of batch tests. Results showed that MGNS had higher adsorption rate andcapacity for As(III)/As(V) in comparison with natural siderite. Arsenic(III) and As(V)adsorption achieved equilibrium at24h and36h, respectively, with adsorptioncapacity estimated from Langmuir isotherm at25℃of2.66mg/g and2.19mg/g,respectively. Thermodynamic studies indicated that As(III)/As(V) adsorption onMGNS was spontaneous, favorable, and endothermic. In addition, MGNS adsorbedAs(III)/As(V) efficiently in a relatively wide pH. Effects of dissolved organic matter,Ca/Mg cations, background electrolyte, and coexisting anions were not significantwithin the concentration ranges observed in high As groundwater.Column study of As adsorption on MGNS demonstrated that MGNS-packedcolumn reactor removed As(III) more efficiently than As(V). A mass balancecalculation indicated that total As load in any As(III)-treated columns was around1.2mg/g before the Chinese drinking water standard in rural areas of50μg/L As was broken through. Field pilot test indicated that removal efficiency on MGNS from realhigh-As groundwater was relatively lower compared to As(III)-spiked DI water, eventhough As(III) was the dominant As species in the natural groundwater. The TCLP(toxicity characteristic leaching procedure) results suggest that the spent adsorbentsgenerated in the column filters were inert and could be landfilled.Results of studies on As removal mechanism indicated that adsorption andheterogeneous oxidation of As(III) were believed to be the main mechanism of As(III)removal by MGNS, and As(V) should be predominantly adsorbed on MGNS viainner-sphere bidendate binuclear surface complexes, as a result of the ligand exchangereactions between surface OH or CO3groups and solution arsenate anions.更多还原