Materials that unlock light-controlled specific separations to enable sustainable desalination (LUCENT)

将城市废水回收为可用的清洁水是一项环境胜利。使用可再生能源为这一过程提供动力，减少了碳足迹，使这个想法变得更好。如果不使用通常会产生更多废物的化学物质，通过回收废物成分作为资源来避免这种低碳过程产生的废物呢？到2020年，全球将产生3800亿立方米的城市废水，其中每升废水中含有0.75毫克的锌，因此可以从全球城市废水中回收28.5万吨锌。这约占2021年全球锌总消费量的2%。以英国为例，每年可从城市污水中回收约4300吨锌，约占英国进口锌的5%。然而，目前我国尚未对城市污水中的重金属进行回收利用，处理后的废水排放到环境中，使这些宝贵的资源流失到环境中。这是由于废水中的金属浓度较低，并且使用传统技术从这种稀释混合物中回收金属通常会产生更多的废物。在迈向循环经济的过程中，至关重要的是，这些有价值的金属在不产生更多废物的情况下被回收。为了解决这一全球性挑战，有必要重新思考如何实现金属-金属分离，目前的重点只是从金属含量足够高的废物流中回收金属。我们还应考虑如何在现有工艺的基础上就地实现这一工艺，以及如何避免与用于分离金属或再生分离介质的化学品有关的废物产生。在本奖学金中，我建议设计和制造光响应共价有机框架，这是一类具有可定制孔径的微孔聚合物，以实现脱盐现场零废物特定金属-金属分离。我将利用光调制海水淡化的最新进展来设计一个共价有机框架库，它可以特异性地和可逆地与目标金属阳离子络合，将各种金属类型在复杂和稀释的混合物中相互分离成可重复使用的高纯度金属流。对光敏感的两性离子分子可以将阳离子和阴离子从水中分离出来，将单价阳离子从二价离子中分离出来，这是它们通过化学功能化可定制的金属相容性的功能。通过计算模拟训练，我将设计一系列化学功能化的两性离子光开关，这些光开关可以嵌入共价有机框架的孔隙中，通过一种基于尺寸选择和特定金属络合的新型分离机制将金属相互分离。我将验证光控特定金属-金属分离原位脱盐的概念，使用这些新型材料作为吸附剂和膜，在使用模型和复杂混合物以及真实城市污水样本的实验中进行实验。我将通过探索使用增材制造技术来关闭与制造和使用寿命结束的脱盐介质相关的脱盐废物循环，分别减少膜制造过程中的废物产生和解聚合技术，将废弃的脱盐介质回收为可重复使用的化合物。除了利用光控特定分离的概念来解锁脱盐作为循环经济解决方案之外，我还将与其他研究人员合作，探索在有机溶剂纳滤、药物输送、自清洁涂层等其他应用中使用这项技术。我还将进行生命周期评估研究，以评估在这里开发的从城市废水中回收金属的技术的可持续性和可行性。

Recycling urban wastewater into usable clean water is an environmental win.Using renewable energy to power this process reduces its carbon footprint and makes this idea even better.What about obviating waste generation from this low-carbon process by recovering waste components as resources without using chemicals that typically generate more waste?With 380 billion cubic metres of municipal wastewater produced globally in 2020 where every litre of this wastewater contains 0.75 mg of Zn, 285,000 metric tonnes of Zn can be recovered from global municipal wastewater. This is about 2% of the world's total Zn consumption in 2021. In a UK context, about 4300 tonnes of Zn can be recovered from UK municipal wastewater per year - about 5% of the Zn imported into the UK. However, the recovery of heavy metals from municipal wastewater is not practiced currently and these valuable resources are lost to the environment as the effluents of treated wastewater are discharged into the environment. This is due to the low metal concentrations in this wastewater and the recovery of metals from such dilute mixtures with legacy technologies typically create more waste. Moving towards a circular economy, it is crucial that these valuable metals are reclaimed without creating more wastes in its own right.To solve such a global challenge, there is a need to re-think how metal-metal separations should be achieved, where the current focus is only on recovering metals from waste streams with high enough metal content. We should also consider how this process can be achieved in-situ of existing processes as well as obviating waste generation associated with chemicals used for separating metals from each other or to regenerate separation media.In this Fellowship I propose to design and engineer photo-responsive covalent organic frameworks, a class of microporous polymers with tailorable pore sizes, to achieve zero-waste specific metal-metal separations in-situ of desalination. I will use recent advancements in photo-modulated desalination to engineer a library of covalent organic frameworks that can specifically and reversibly complex with a target metal cation, separating various metal types from each other in complex and dilute mixtures into reusable high-purity metal streams.Light-responsive, zwitterionic molecules can separate cations and anions from water, and monovalent cations from divalent ions, as a function of their tailorable metal compatibility via chemical functionalisation. With training in computational simulations , I will design a series of chemically-functionalised zwitterionic photo-switches that can be embedded within the pores of covalent organic frameworks to separate metals from each other via a novel separation mechanism underpinned by size selection and specific metal complexation. I will validate the concept of light-controlled specific metal-metal separation in-situ desalination using these novel materials as adsorbents and membranes in bench-scale experiments using model and complex mixtures and real-world municipal wastewater samples. I will close the desalination waste loop associated with fabrication and end-of-life of desalination media by exploring the use of additive manufacturing technologies that reduce waste generation during membrane fabrication and depolymerisation techniques to recycle spent desalination media into reusable chemical compounds, respectively. Beyond exploiting the concept of light-controlled specific separations to unlock desalination as a circular economy solution, I will work with other researchers to explore using this technology in other applications such as organic solvent nanofiltration, drug delivery, self-cleaning coatings. I will also perform life cycle assessment studies to evaluate the sustainability and feasibility of technologies developed here for metal recovery from municipal wastewater.