Evaluation of nano-scale zero-valent iron for removal of organo-selenium species from industrial wastewater

硒是一种令人担忧的污染物，存在于加拿大许多行业的工业废水中，包括煤炭开采、油砂开采、石油精炼和燃煤发电厂。在废水中，硒通常以无机形式存在，包括亚硒酸盐(SeO4)2-和亚硒酸盐(SeO3)2-氧阴离子。应用于处理工业废水的生物处理工艺已显示出将无机硒氧阴离子还原为元素硒。然而，在生物处理过程中，也注意到有机硒化合物的形成，如硒蛋氨酸，具有较高的毒性和生物积累的趋势。最近的法规针对的是鱼类组织中硒的生物累积量，而不是管道末端流出物中的硒浓度。环境影响、毒性和严格的法规要求从工业废水中去除有机硒物种。斯坦泰克热衷于开发一种技术，可以有效地从工业废水中去除有机硒，因为目前还没有针对这些化合物的技术证明。*这项研究工作建议评估纳米零价铁(NZVI)复合材料吸附去除工业废水中有机硒物种的效果。NZVI复合材料的应用前景看好，因为这种材料在去除废水中各种无机金属和类金属方面表现出了很高的潜力。NZVI对有机硒物种的吸附能力将通过实验室批量和连续实验进行评估。实验将以硒蛋氨酸、硒氰酸酯和S-(甲基)硒半胱氨酸作为有机硒化合物的参照物。将对这些参考化合物的吸附等温线和各种工艺参数的影响进行评估，如废水pH、离子强度、温度和其他竞争阴离子。在这个项目下开发的这些新的理解将被用于从工业废水中去除有机硒化合物。

Selenium is a contaminant of concern that is present in industrial wastewaters from many Canadian industries, including coal mining, oilsands mining, petroleum refining, and coal-fired powerplants. In wastewater, selenium is typically present in inorganic form which include selenate (SeO4)2- and selenite (SeO3)2- oxyanion species. Biological treatment processes applied to treat industrial wastewaters have shown to reduce inorganic selenium oxyanions to elemental selenium. However, formation of organic selenium compounds such as selenomethionine with higher toxicity and tendency to bioaccumulate have been noted during biological treatment. Recent regulations target magnitude of bioaccumulation of selenium in fish tissues rather than selenium concentrations in end-of-pipe effluents. The environmental effects, toxicity and stringent regulations demand removal of organoselenium species from industrial wastewater. Stantec is keen in developing a technology that will effectively remove organoselenium from industrial wastewaters as there are no technologies that has been demonstrated for these compounds. ****This research work proposes to evaluate removal of organoselenium species from industrial wastewaters by adsorption using nano zerovalent iron (nZVI) composites. Use of nZVI composites is promising as the material has demonstrated high potential for removal of wide range of inorganic metals and metalloids from wastewaters. The ability of nZVI to adsorb organoselenium species will be evaluated through laboratory batch and continuous experiments. Experiments will be conducted with selenomethionine, selenocyanate, and S-(methyl)selenocystine as references for organoselenium compounds. Adsorption isotherms and the effect of various process parameters such as wastewater pH, ionic strength, temperature and other competing anions will be evaluated for these reference compounds. These new understanding developed under this project will be employed for the removal of organoselenium compounds from industrial wastewaters.****************