【作者】 练建军；

【导师】 许士国；

【作者基本信息】 大连理工大学 ， 水文学及水资源， 2012， 博士

【摘要】 重金属钼不仅是动植物生长必需的营养元素之一,同时也是非常重要的战略资源。然而常因钼矿开采技术相对落后,尾矿管理力度不够,导致部分地区产生了相对严重的钼污染事件,如美国科罗拉多州钼矿区、加拿大哥伦比亚地区钼矿区以及辽宁省葫芦岛市钼矿区等。目前对重金属钼的研究工作主要集中在缺钼对动植物带来的影响及危害,对钼污染导致的环境问题及解决方法研究很少见,因此对重金属钼污染的治理研究是很有必要的。辽宁省葫芦岛市2005年因乌金塘水库水源地的钼污染,全市必须另找水源,虽然目前采用化学工艺法对水库钼污水进行治理,使其能够供水,但远远不能满足当地居民的需求,且该方法对入库河流的钼污染不能起到防治作用。本文以此为背景,以实现对重金属钼污染的沿程控制为目标,系统研究了人工湿地基质和植物对重金属钼的去除机理,通过静态和动态实验优选基质,作为人工湿地模型基质组成部分。考查了不同人工湿地模型除钼效果及规律,为人工湿地处理重金属钼污染技术提供理论支撑。本文主要研究内容与成果如下：(1)基质除钼的机理研究以黄棕土为对比基质,考察脱硫钢渣、转炉钢渣及煤渣对重金属钼的吸附性能。结果表明,基质对重金属钼吸附过程符合Langmuir等温吸附模型,且饱和吸附量由大到小依次为：脱硫钢渣>转炉钢渣>煤渣>土壤；各基质对重金属钼的吸附速率符合准二级动力学模型；吸附过程受体系pH影响较大,pH值为3.0-4.5时,四种基质对铝去除率最高,当pH>5.0时,去除率迅速降低,在pH为8.0时,去除率几乎为零；SO42-和P043-对基质吸附钼酸根离子影响较为显著,基质受其影响作用由大到小依次为：黄棕土>煤渣>转炉钢渣>脱硫钢渣,且P043-对基质吸附钼酸根离子的竞争作用强于S042-；四种基质对钼酸根离子的解吸作用由大到小依次为：黄棕土>煤渣>转炉钢渣>脱硫钢渣；等温吸附模型中表观能量E值及红外光谱的研究成果表明,基质去除钼酸根离子的主要机理为离子交换吸附。(2)除钼基质的筛选研究通过静态和动态两种方式,考察了改性煤渣和黄铁矿对重金属钼的去除效果,结果表明：煤渣经硫酸改性后对溶液中的M0042-产生了强烈的吸附作用,且当pH在4.0-6.0时,吸附量最大；与磁铁矿相比,黄铁矿具有较强的碱缓冲能力,在pH为中性时,去除率仍高于60%；硫酸改性煤渣与黄铁矿吸附钼酸根离子均符合准二级吸附动力学模型。由活化能状态函数E值表明,该吸附过程以物理吸附为主,吸附速率较快,且受温度的影响较小；硫酸改性煤渣与黄铁矿吸附钼酸根离子符合Langmuir等温线吸附模型。由于ΔG0<0、△S0>0、△H0>0,表明吸附都是吸热、熵增、自发的过程。改性煤渣和黄铁矿粒径分别为1-2mm及2-4mm时对钼吸附的穿透时间较长,且饱和吸附量分别为8.87g kg-1和5.0g kg-1；改性煤渣和黄铁矿与煤渣的组合比例分别为1：2和1：1时,去除效果最佳。(3)芦苇和香蒲富集钼机理研究研究了水生植物芦苇和香蒲对重金属钼的吸收特性。通过短期室内水培实验,对比考察了2种植物对重金属钼的耐毒性、动态去除率、吸收过程及富集情况,并对在不同浓度营养液中植物对重金属钼吸收的影响进行了分析。结果表明,2种植物钼中毒导致其茎叶发黄、蒸腾能力下降,在钼浓度为2-20mg L-1时,香蒲对重金属钼的耐毒性较芦苇强。香蒲对重金属钼的去除率高于芦苇,在钼浓度为2mg L-1时,香蒲和芦苇去除率分别为87%和62%。2种植物对重金属钼的吸收是一个动态平衡过程,且以被动吸收为主。香蒲对钼的富集量较芦苇高,且植物地上部分重金属积累量大于根部,符合超积累植物特征之一。营养液浓度的增加不会提高植物对重金属钼的吸收量,反而会因离子竞争等因素使去除率有所下降。(4)人工湿地除钼效果及规律考察了含有芦苇和香蒲及不同基质的垂直潜力人工湿地对重金属钼的去除性能。结果表明,在14周的运行周期,黄铁矿组合基质的人工湿地除钼效率与其他湿地相比更加稳定、高效,且在水力停留时间为2d时,去除效果基本不受影响；重金属钼主要被黄铁矿吸附,且存在形态以水溶态为主；香蒲比芦苇对重金属钼的富集能力更强,但与基质的吸附量相比,植物的生物积累量相对很小。更多还原

【Abstract】 Molybdenum (Mo) is an essential trace element for plants and animals, as well as an important stratagic resource. However, some Mo pollution incidents have been produced in partial area, such as Colorado in the USA, British Columbia Province in Canada and Liaoning Province, due to the backwardness of Mo mining exploitation technology and the poor management. Rencently, the research on Mo was mainly focused on the effect and harm on animal for lacking Mo. Little research has been done on controlling Mo pollution, so treating this pollution is necessary.People of Huludao City had to find another riverhead for the Mo pollution of Wujintang reservoir in2005. Although the reservoir have supplied certain water for the local inhabitants now, the water supply is not enough. Therefore, based on Mo tailings pollution in Liaoning province and the aim of on-way control for Mo pollution, the removal mechanism of Mo was studied by the substrates and plants of constructed wetlands. The substrates were tested in static and dynamic experiments for further applied in wetlands. Moreover, the removal effect, mechanism and influence factor for mo by different constructed wetlands was studied. So it could provide some valuable reference to practice application of constructed wetlands for mo removal. The main contents are as follows:(1) Study on the adsorption mechanism of Mo(VI) by the substrates.In this study, the removal efficiencies of Mo(VI) from aqueous solutions by desulfurization steel slag (DSS), converter steel slag (CSS) and cinder (CI) were investigated and compared against that of loessial soil (LS). The results showed that the sorption isotherms fitted the Langmuir model well, and the Langmuir adsorption capacity (Qo) of the four sorption media generally complied with the following order:DSS>CSS>CI>LS. Adsorption reaction was found to follow the pseudo second-order rate,and the adsorption of Mo(Ⅵ) was sensitive to pH values.The four adsorbents exhibited a significant Mo(Ⅵ) removal at low pH values (e.g.,3<pH<4.5), but such adsorption decreased rapidly when pH was greater than5.Only little adsorption occurred when pH value was greater than8.The competitive effect of PO43-and SO42-with Mo(Ⅵ) for adsorption associated with the four sorption media followed the order: LS>CI>CSS>DSS,and moreover,the effect of PO43-on the adsorption of Mo(Ⅵ) was observed stronger than that of SO42-. The desorption capacity of the four sorption media generally complied with the following order:LS>CI>CSS>DSS.The value of E calculated by the isotherm model and the results of FTIR indicated that the iron exchange adsorption was the main mechanism.(2) The screening experiment of substrates for Mo(Ⅵ) removalMo(Ⅵ) removal by modified cinder and pyrite was investigated in static and dynamic experiments.The results showed that the surface pore of cinder was enhanced by the modification of sulphuric acid, and the adsorption amount of Mo(Ⅵ) was increased. Maximum adsorption of Mo(Ⅵ) by modified cinder occurred at pHs between4.0and6.0. Compared to magnetite,the pyrite was with large buffer capacity on alkali.When the pH was7.0,the removal rate was higher than60%.Kinetic studies showed that the adsorption generally obeyed a pseudo second-order model.The values of activation energy indicated the adsorption processes were governed by interactions of physical nature.Furthermore,Langmuir and Freundlich isotherms were used to model the adsorption equilibrium data and the adsorption behavior obeyed the Langmuir model.Finally, thermodynamic parameters such as△H0,△S0and△G0for the adsorption were also evaluated, which showed the adsorption of Mo(VI) on treated cinder and pyrite was endothermic,entropy increasing and spontaneous. The time of break-through was longer, when the particle size was1-2mm and2-4mm for modified cinder and pyrite, respectively. The maximum adsorption amount of Mo(Ⅵ) by modified cinder and pyrite in dynamic experiments was8.87g kg-1and5.0g kg-1,respectively. Moreover, the perfectly combination proportion of modified cinder/cinder and pyrite/cinder was1:2and1:1.(3) Study on the enrichment mechanism of Mo(Ⅵ) by reed and cattailThe adsorption characteristics of reed and cattail to Mo(Ⅵ) were studied. The Mo(Ⅵ) toxicity, removal rate, adsorption process and accumulation of Mo (Ⅵ) were investigated in the short-term indoor-culture experiment.The effects of Mo(Ⅵ) adsorbed by two plants in nutrition solution of different concentration were also studied. Due to the Mo(Ⅵ) toxicity, the color of stems and leafs of the two plants had become scorch and the transpiration was declined. The tolerance to Mo(Ⅵ) toxicity of cattail was better than reed at Mo(Ⅵ) concentration of2-20mg·L-1. The removal rate of Mo(Ⅵ) by cattail was87%, which was higher than reed (62%) at Mo(Ⅵ) concentration of2mg·L-1. The absorption process of Mo(Ⅵ) by two plants was homeostasis, and the passivity absorption was the main absorption mechanism. Mo(Ⅵ) enrichment ammount in cattail was higher than that in reed, and Mo concentrations in shoot were higher than that in roots. The results displayed that the two plants were with Mo(Ⅵ) hyperaccumulative characteristics. The absorption of Mo(Ⅵ) was not enhanced with the increase of nutrition solution concentration, owing to the competition of other ions.(4) Study on the removal of Mo(VI) by simulated constructed wetlandsThe efficacy and capacity of using vertical subsurface water constructed wetlands to removal Mo(VI) was examined, employing reeds and cattail as well as granular media of different adsorption capacities.Results showed that the performance of wetland V (combined with pyrite) was found to be more stable and excellent than that of other wetlands during14-week of intermittent influent,and2-d HRT is sufficient for Mo(VI) removal in wetland V. Most Mo(VI) was adsorbed by the pyrite,which retained primarily in water-soluble fraction. Cattail was more suitable for Mo(VI) absorption than reeds, but the bioaccumulation accounted for a very small portion of the total removal.更多还原