Nature-inspired self-powered reverse osmosis membranes for sustainable water purification

由于快速城市化、人口增长、严重滥用和气候变化，对清洁饮用水的需求增加和短缺已成为本世纪前所未有的紧迫问题。在全球范围内，每10人中就有近2人无法获得清洁饮用水，根据世界卫生组织的数据，每天有3 900名儿童死于不安全的水/卫生条件差传播的各种疾病。根据联合国《世界水资源开发报告》，到2050年，这一令人不安的困境预计将大幅恶化，届时地球上至少四分之一的人口将生活在长期或经常性淡水短缺的国家。现有的淡水水体需要得到保护，必须通过成本较低、能源较少的净水新方法来产生新的清洁水源，以满足日益增长的需求。这需要更好的创新水处理技术。基于膜的水过滤上级于消毒、蒸馏或介质过滤方法，因为其过程更清洁，并且不需要热输入和废介质的再生。迄今为止，大多数分离和水过滤膜是基于常规的聚合物材料，例如纤维素、聚酰胺、聚砜、聚偏二氟乙烯、聚丙烯腈等。这些基于膜的过滤技术的限制因素包括例如：高能耗、低通量、截留折衷、高有机和生物污染;对高温、氧化剂、酸性/碱性介质和有机溶剂的耐受性差，为新型水处理工艺的新研究提供了重要的动力。在过去的十年里，纳米技术已经完全从学术研究转化为商业现实。已经尝试使用纳米材料、微凝胶、交联蛋白质等来构建膜。然而，使用先进材料的新材料或基于设计的创新仍然不足以解决传统膜过滤中的基本瓶颈之一-需要多余的外部压力来克服盐溶液的渗透压以驱动纯水穿过半透膜。在没有外部驱动力的情况下，水分子抵抗渗透压的运输似乎打破了基本的热力学定律，但这种自然现象确实存在。耐盐树木是自然界中最简单的例子之一，它利用红树林叶片中蒸发毛细力产生的高度负压，有效地将其环境中的咸水转化为淡水。在该提议中，申请人旨在设计一种新型膜，其模仿天然膜，使得可以实现自驱动水输送。

Increasing demand for and shortage of clean drinking water as a result of rapid urbanization, population growth, gross misuse, and climate change have become an unprecedented urgent issue in this century. Globally nearly 2 in every 10 people lack access to clean drinking water, and according to World Health Organization, 3,900 children die every day due to various diseases transmitted by unsafe water/poor hygiene. According to the U.N. World Water Development Report, this troubling predicament is projected to worsen substantially by 2050, when at least a quarter of the people on Earth will live in a country suffering from chronic or recurring freshwater shortages. The existing freshwater bodies need to be protected and new sources of clean water must be generated through new methods of purifying water at lower cost and with less energy to meet the growing demand. This requires better and innovative water treatment technology. Membrane-based water filtration is superior to the disinfection, distillation, or media filtration methods because of the cleaner process and requires no thermal inputs and regeneration of spent media. So far, the majority of separation and water filtration membranes are based on conventional polymeric materials, such as cellulose, polyamide, polysulfone, polyvinylidene fluoride, polyacrylonitrile, etc. The limiting factors for these membrane-based filtration technologies include, for example: high energy consumption, low flux, rejection compromise, high organic and biological fouling; poor tolerance to high temperature, oxidizing agents, acidic/alkaline medium, and organic solvents, impart significant impetus to deliver new research for novel water treatment process. Over the past decade, nanotechnology has totally transformed from academic research to commercial reality. Attempts have been made to construct membranes using nanomaterials, microgels, cross-linked proteins etc. The new materials or design-based innovations using advanced materials, however, are still deficient in tackling one of the fundamental bottlenecks in conventional membrane filtration - the requirement of surplus external pressure to overcome the osmotic pressure of the salt solution to drive pure water across a semipermeable membrane. Transport of water molecules against the osmotic pressure in the absence of an external driving force seems to break the fundamental thermodynamic laws, but such natural phenomena exist. Salt-tolerant trees are one of the simplest examples in nature that efficiently convert the salty water of its environment into freshwater by using highly negative pressure that is generated by evaporative capillary forces in mangrove leaves. In this proposal, the applicant aims to design a new type of membrane which mimics the natural membranes such that self-driven water transport can be achieved.