近日，化学化工学院（省部共建煤炭高效利用与绿色化工国家重点实验室）罗民教授负责 的能源和环境材料研究团队，在 电化学海水淡化 研究方面取得重要研究进展。研究成果在线发表在美国 ACS 数据库国际可持续化学与工程领域 Top 期刊 《 ACS Sustainable Chem. Eng 》（一区， Impact Factor 2018: 6.97 ）。论文题目： “More Ca 2+ less Na + : increase the desalination capacity and performance stability of Na x Ca y CoO 2 ” ； DOI ： 10.1021/ acssuschemeng.9b02157 . 宁夏大学罗民教授为本文的通讯作者，2018级水资源利用与化学化工博士研究生周瑞娟同学为论文第一作者。 水资源短缺和水环境的污染是困扰社会可持续发展的重大问题，而海水淡化技术则为解决水资源难题提供了有效的解决方案。反渗透、闪蒸法和电渗析等方法是目前常用的水处理技术，这些方法普遍存在高成本、高能耗和二次污染的问题。因此发展低成本，低能耗和高效率的水处理技术势在必行。 电化学去离子（electrochemical deionization，EDI）是一种从水溶液中脱除可溶性带电离子的新兴技术方法。作为一种低能耗，环境友好的脱盐技术受到关注，并在苦咸水淡化、海水脱盐、废水治理、高附加值离子的提取和有害离子的脱除等方面有潜在的应用前景。脱盐电池（FDI）是一种新型的脱盐技术，通过输入电能， 在电极表面发生氧化还原反应（法拉第反应）而提取盐溶液中的钠离子和氯离子，达到脱盐淡化之目的。然后再通过放电过程（两电极短接或反向施加电压）释放离子到浓盐水中，同时回收部分能量。 近年来，二维层状纳米科学和技术的迅猛发展为开发新型脱盐电极材料提供了契机。该课题组通过溶胶凝胶法（Sol-Gel）在层状钴酸钠脱盐电极材料的钴氧层板间化学掺杂引入Ca2+掺杂，调控Co3+/Co4+的比例和氧空位的含量。随钙掺杂含量增加，Co3+/Co4+逐渐增加，导致不稳定的Co4+ 向Co3+弛豫时产生丰富的氧空位。进而通过化学氧化法，从层间脱出Na+，同时在层间引入结构水分子，得到了掺钙脱钠的水合物电极材料。通过调控钙离子和钠离子的含量，脱盐电极的脱盐性能得到了很大的提高。Na0.27Ca0.03CoO2•0.6H2 O 的脱盐容量达到了83.5 ± 2.4 mg g-1，法拉第效率接近100%，脱盐循环50次没有明显的衰减。研究表明，由于丰富的氧空位改善了材料的导电性能，而钙离子在层间起到了稳定层板结构的作用，因而实现了高脱盐量和高循环稳定性能。本文还通过电化学石英晶体微天平原位深入研究了水合离子在层间脱嵌的微观机理。该研究成果推动了脱盐电池在高浓度盐水脱盐和水资源的重复利用中的应用。 上述研究工作得到了国家自然科学基金（Nos. 21561026, 21361020）和“化学工程与技术”一流学科“煤基储能与光电催化材料”科研创新团队项目(Grant No. NXY-LXK2017A04)项目资助。 文章链接：https://pubs.acs.org/doi/10.1021/acssuschemeng.9b02157
氧化石墨烯使海水淡化转化为饮用水 诸平 海水淡化即利用海水脱盐生产 淡水 。 现在所用的海水淡化方法有海水冻结法、 电渗析法 、蒸馏法、反渗透法、以及碳酸铵离子交换法，目前应用反渗透膜法及 蒸馏 法是市场中的主流。 世界上有十多个国家的100多个科研机构在进行着海水淡化的研究，有数百种不同结构和不同容量的海水淡化设施在工作。一座现代化的大型 海水淡化厂 ，每天可以生产几千、几万甚至近百万吨淡水。水的成本在不断地降低，有些国家已经 降低 到和自来水的价格差不多。某些地区的淡化水量达到了国家和城市的 供水 规模。但是英国 曼彻斯特 大学（ University of Manchester ）的研究人员利用氧化石墨烯可以实现海水淡化，使其转化为饮用水。 石墨烯氧化物膜作为 发展前景的 过滤新技术的候选 者， 已经引起了 世人备受 关注。现在的更受欢迎的 是开发出能够 实现 使 常见的盐 分离的石墨烯氧化膜。英国曼彻斯特大学的研究结果显示，利用氧化石墨烯膜可以有望解决目前全世界面临的饮用水源短缺问题，为那些生活在海边确没有或缺少淡水资源，难以得到 清洁的饮用水 资源的 数百万人 解决饮用水危机，提供 足够的清洁水源。曼彻斯特大学 科研人员 的新发现 ， 2017 年 4 月 3 日已经 在《 自然纳米技术 》（ Nature Nanotechnology ）杂志上发表 —— Jijo Abraham , Kalangi S. Vasu , Christopher D. Williams , Kalon Gopinadhan , Yang Su , Christie T. Cherian , James Dix , Eric Prestat , Sarah J. Haigh , Irina V. Grigorieva , Paola Carbone , Andre K. Geim , Rahul R. Nair . Tunable sieving of ions using graphene oxide membranes . Nature Nanotechnology , (2017) doi: 10.1038/nnano.2017.21 . Published online : 03 April 2017 . 联合国预计 , 到 2025 年世界 将会有 14% 的人口将面临缺水 问题 。 而英国曼彻斯特大学的此项 技术有可能在全世界范围内彻底改变 海水淡化，是海水中的盐份过滤问题得到解决，这对于那些 担不起大规模的海水淡化厂 的国家来说 特别 重要 。更多信息请注意浏览原文： Graphene sieve turns seawater into drinking water April 3, 2017 A graphene membrane. Credit: The University of Manchester Graphene-oxide membranes have attracted considerable attention as promising candidates for new filtration technologies. Now the much sought-after development of making membranes capable of sieving common salts has been achieved. New research demonstrates the real-world potential of providing clean drinking water for millions of people who struggle to access adequate clean water sources. The new findings from a group of scientists at The University of Manchester were published today in the journal Nature Nanotechnology . Previously graphene-oxide membranes have shown exciting potential for gas separation and water filtration. Graphene-oxide membranes developed at the National Graphene Institute have already demonstrated the potential of filtering out small nanoparticles, organic molecules, and even large salts. Until now, however, they couldn't be used for sieving common salts used in desalination technologies, which require even smaller sieves. Previous research at The University of Manchester found that if immersed in water, graphene-oxide membranes become slightly swollen and smaller salts flow through the membrane along with water, but larger ions or molecules are blocked. The Manchester-based group have now further developed these graphene membranes and found a strategy to avoid the swelling of the membrane when exposed to water. The pore size in the membrane can be precisely controlled which can sieve common salts out of salty water and make it safe to drink. As the effects of climate change continue to reduce modern city's water supplies, wealthy modern countries are also investing in desalination technologies. Following the severe floods in California major wealthy cities are also looking increasingly to alternative water solutions. When the common salts are dissolved in water, they always form a 'shell' of water molecules around the salts molecules. This allows the tiny capillaries of the graphene-oxide membranes to block the salt from flowing along with the water. Water molecules are able to pass through the membrane barrier and flow anomalously fast which is ideal for application of these membranes for desalination. Professor Rahul Nair, at The University of Manchester said: Realisation of scalable membranes with uniform pore size down to atomic scale is a significant step forward and will open new possibilities for improving the efficiency of desalination technology . This is the first clear-cut experiment in this regime. We also demonstrate that there are realistic possibilities to scale up the described approach and mass produce graphene-based membranes with required sieve sizes. Mr. Jijo Abraham and Dr. Vasu Siddeswara Kalangi were the joint-lead authors on the research paper: The developed membranes are not only useful for desalination, but the atomic scale tunability of the pore size also opens new opportunity to fabricate membranes with on-demand filtration capable of filtering out ions according to their sizes. said Mr. Abraham. By 2025 the UN expects that 14% of the world's population will encounter water scarcity. This technology has the potential to revolutionise water filtration across the world, in particular in countries which cannot afford large scale desalination plants. It is hoped that graphene-oxide membrane systems can be built on smaller scales making this technology accessible to countries which do not have the financial infrastructure to fund large plants without compromising the yield of fresh water produced. Explore further: Researchers develop hybrid nuclear desalination technique with improved efficiency More information: Tunable sieving of ions using graphene oxide membranes, Nature Nanotechnology , nature.com/articles/doi:10.1038/nnano.2017.21 Abstract Graphene oxide membranes show exceptional molecular permeation properties, with promise for many applications 1 , 2 , 3 , 4 , 5 . However, their use in ion sieving and desalination technologies is limited by a permeation cutoff of ～9 Å (ref. 4 ), which is larger than the diameters of hydrated ions of common salts 4 , 6 . The cutoff is determined by the interlayer spacing ( d ) of ～13.5 Å, typical for graphene oxide laminates that swell in water 2 , 4 . Achieving smaller d for the laminates immersed in water has proved to be a challenge. Here, we describe how to control d by physical confinement and achieve accurate and tunable ion sieving. Membranes with d from ～9.8 Å to 6.4 Å are demonstrated, providing a sieve size smaller than the diameters of hydrated ions. In this regime, ion permeation is found to be thermally activated with energy barriers of ～10–100 kJ mol –1 depending on d . Importantly, permeation rates decrease exponentially with decreasing sieve size but water transport is weakly affected (by a factor of 2). The latter is attributed to a low barrier for the entry of water molecules and large slip lengths inside graphene capillaries. Building on these findings, we demonstrate a simple scalable method to obtain graphene-based membranes with limited swelling, which exhibit 97% rejection for NaCl.
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标签: 海水淡化
