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催化剂将硝酸盐转化为水和空气
来源:网络 | 作者:Bungechem | 发布时间: 1611天前 | 471 次浏览 | 分享到:
“硝酸盐主要来自农业径流,这影响到世界各地的农业群落。”该研究的科学家、水稻化学工程师Michael Wong说,“硝酸盐既是环境问题,也是健康问题,因为它们是有毒的。有一些离子交换过滤器可以将它们从水中移除,但这些过滤器每隔几个月就需要冲洗一次。当这种情况发生时,冲洗过的水就会将集中的硝酸盐返回到水供应系统中。”
"Nitrates come primarily from agricultural runoff, which affects agricultural communities around the world," said rice chemical engineer Michael Wong, a scientist on the study. "Nitrates are both an environmental and a health concern because they are toxic. There are some ions Swapping filters can remove them from the water, but these filters need to be flushed every few months. When this happens, the flushed water returns the concentrated nitrates to the water supply. "

    Rice University's Nanotechnology Enabled Water Treatment (NEWT) Center的工程师们发现了一种催化剂,它通过将饮用水转化为空气和水来净化饮用水中的有毒硝酸盐。
    这项研究已经在美国化学学会期刊《ACS Catalysis》上发表。
    “硝酸盐主要来自农业径流,这影响到世界各地的农业群落。”该研究的**科学家、水稻化学工程师Michael Wong说,“硝酸盐既是环境问题,也是健康问题,因为它们是有毒的。有一些离子交换过滤器可以将它们从水中移除,但这些过滤器每隔几个月就需要冲洗一次。当这种情况发生时,冲洗过的水就会将集中的硝酸盐返回到水供应系统中。”
    Wong的实验室专门研发纳米级的催化剂,一种可以加速化学反应的亚微观金属。2013年,他的研究小组发现,点缀着少量钯的微小金球可以分解亚硝酸盐,而亚硝酸盐是硝酸盐中毒性较大的化学同族。
“硝酸盐是由一个氮原子和三个氧原子组成的分子。”Wong*解释说。“硝酸盐如果失去了氧气,就会变成亚硝酸盐,但亚硝酸盐的毒性比硝酸盐更大,所以你不会想要停止亚硝酸盐的使用。而且,硝酸盐是更普遍的问题。”
     他说:“较终,去除硝酸盐的较好方法是催化过程,把它们完全分解成氮气和氧气,或者我们的例子中的氮和水,因为我们加入了少量的氢。”“地球上75%以上的大气都是气态氮,所以我们真的把硝酸盐变成了空气和水。”
    硝酸盐对婴儿和孕妇是有毒的,也可能致癌。硝酸盐污染在农业群落中很常见,尤其是在美国的玉米带和加州的中央谷地,那里的肥料被大量使用。一些研究表明,由于土地使用模式的改变,硝酸盐污染正在上升。
    硝酸盐和亚硝酸盐都是由环境保护局规定的,它规定了安全饮用水的允许限度。在有污染的水井和湖泊的社区,这通常意味着用离子交换树脂对饮用水进行预处理,这种树脂可以捕捉和去除硝酸盐和亚硝酸盐,而不会破坏它们。
    在他们之前的研究中,Wong的团队知道金钯纳米粒子并不是较好分解硝酸盐的催化剂。Kim Heck说,对已发表的科学文献的搜索又发现了另一种可能性:铟和钯。
   “我们能够优化这个过程,因为我们发现用铟覆盖钯球表面的大约40%,给了我们较活跃的催化剂,”Heck说,“它比我们在之前发表的研究中发现的任何方法都要**50%。我们本可以就此打住,但我们真的很想了解为什么它更好,因此我们必须探索这种反应背后的化学反应。”
    在Purdue University的化学工程同事Jeffrey Miller和University of Houston的Lars Grabow的合作下,研究小组发现,铟加速了硝酸盐的分解,而钯则明显阻止铟不被**氧化。
    “铟喜欢被氧化。”赫克说,“从我们的现场研究中,我们发现将催化剂暴露在含有硝酸盐的溶液中会使铟氧化。但是当我们加入饱和氢的水时,钯就会促使其中的一些氧与氢结合形成水,这导致铟保持在还原状态,在这种状态下,它可以自由地分解更多的硝酸盐。”
     Wong说,他的团队将与工业合作伙伴以及其他研究人员合作,将这一过程转化为一种商业上可行的水处理系统。
   “这就是NEWT来的地方。”他说。“NEWT是关于获取基础科学发现并将它们部署到现实世界的环境中。这将是NEWT中的一个例子,我们已经了解了其中的化学原理,下一步是创建一个流系统,以证明该技术可以应用于现场的概念。”
    美国国家科学基金会(National Science Foundation)于2015年建立的了一个基于Rice的多机构工程研究中心,该中心致力于开发一种紧凑、可移动、离网的水处理系统,为数百万人提供清洁的水,使美国的能源生产更加可持续和具有成本效益。预计到2025年,NEWT将在联邦和工业方面提供4000多万美元的资金支持,主要用于慈善应急、农村供水系统和远程设施发污水处理和循环利用,包括陆上和海上石油和天然气勘探钻井平台。
    共同研究的其他作者包括:Sujin Guo、 Huifeng Qian 、Zhun Zhao,以及休斯敦大学的Sashank Kasiraju。这项研究由美国国家科学基金会、能源部和中国留学基金委资助。

Engineers at Rice University's Nanotechnology Enabled Water Treatment (NEWT) Center have discovered a catalyst that purifies drinking water of toxic nitrates by converting it into air and water.

    The research has been published in ACS Catalysis, a journal of the American Chemical Society.

    "Nitrates come primarily from agricultural runoff, which affects agricultural communities around the world," said Rice chemical engineer Michael Wong, lead scientist on the study. "Nitrates are both an environmental and a health concern because they are toxic. Some ion exchange filters can remove them from the water, but these filters need to be flushed every few months. When this happens, the flushed water returns the concentrated nitrates to the water supply middle."

    Wong's lab specializes in nanoscale catalysts, submicroscopic metals that speed up chemical reactions. In 2013, his team found that tiny gold spheres dotted with small amounts of palladium can break down nitrite, the more toxic chemical cousin of nitrate.

"Nitrates are molecules composed of one nitrogen atom and three oxygen atoms," explains Wong*. "Nitrate becomes nitrite if it loses oxygen, but nitrite is more toxic than nitrate, so you wouldn't want to stop nitrite use. Also, nitrate is a more general problem ."

     "Ultimately, the better way to remove nitrates is a catalytic process that breaks them down completely into nitrogen and oxygen, or nitrogen and water in our case, because we add a small amount of hydrogen," he said. "75 on Earth More than % of the atmosphere is gaseous nitrogen, so we really turn nitrates into air and water."

    Nitrates are toxic to infants and pregnant women and may also cause cancer. Nitrate contamination is common in agricultural communities, especially in the U.S. Corn Belt and California's Central Valley, where fertilizers are heavily used. Some studies suggest that nitrate pollution is on the rise due to changing land use patterns.

    Both nitrates and nitrites are regulated by the Environmental Protection Agency, which sets permissible limits for safe drinking water. In communities with polluted wells and lakes, this often means pretreating drinking water with ion-exchange resins that capture and remove nitrates and nitrites without destroying them.

    In their previous research, Wong's team knew that gold and palladium nanoparticles were not good catalysts for breaking down nitrates. A search of the published scientific literature has uncovered another possibility: indium and palladium, says Kim Heck.

   "We were able to optimize the process because we found that covering about 40 percent of the surface of the palladium spheres with indium gave us a more active catalyst," Heck said, "more than anything we've found in our previously published research.* *50%. We could have stopped there, but we really wanted to understand why it was better, so we had to explore the chemistry behind this reaction.”

    In collaboration with chemical engineering colleagues Jeffrey Miller of Purdue University and Lars Grabow of the University of Houston, the team found that indium accelerates the decomposition of nitrates, while palladium significantly prevents indium from being oxidized by methionine.

    "Indium likes to be oxidized," Heck said. "From our field studies, we found that exposing the catalyst to a solution containing nitrate oxidized indium. But when we added hydrogen-saturated water, palladium promoted Some of that oxygen combines with hydrogen to form water, which causes the indium to remain in a reduced state, where it is free to break down more nitrates."

     Wong said his team will work with industrial partners as well as other researchers to translate the process into a commercially viable water treatment system.

   "That's where NEWT comes in," he said. "NEWT is about taking fundamental science discoveries and deploying them into real-world settings. This will be an example in NEWT, where we already understand the chemistry, the next step is to create a flow system to demonstrate that the technology can Concepts applied to the field.”

    The National Science Foundation established a Rice-based multi-agency engineering research center in 2015 to develop a compact, mobile, off-grid water treatment system for millions of people Provide clean water to make U.S. energy production more sustainable and cost-effective. NEWT is expected to provide more than $40 million in federal and industry funding through 2025, primarily for charitable emergencies, rural water systems, and wastewater treatment and recycling at remote facilities, including onshore and offshore oil and gas exploration drilling platform.

    Other co-authors on the study include: Sujin Guo, Huifeng Qian, Zhun Zhao, and Sashank Kasiraju of the University of Houston. The research was funded by the National Science Foundation, the Department of Energy, and the China Scholarship Council.