Solar Powered Photoreactor for Water Treatment

获得清洁水是当今世界的一个紧迫问题，在未来十年，它比气候变化、粮食危机和社会不稳定更令人担忧。在全球范围内，近十分之一的人无法获得清洁的饮用水源。热带气候的发展中国家将受到水危机的不成比例的影响，因为这些地区的人口最多，无法获得清洁的水。有不同的方法可用于水的处理，其中包括通过阶段净化水的工业水处理厂。工业处理过程中的这些步骤分为一级、二级和三级。这些水处理工艺包括慢速砂过滤、活性污泥或光催化系统等方法。对于发展中地区来说，缺乏资金和基础设施可能导致无法建立传统的水处理厂。这导致了对废水再利用的调查，因为它可以更便宜，需要最少的基础设施，并减少对主要水源的影响。来自不同来源的水会有不同的水质影响，这是理想的重复使用。该项目的目标是开发用于水处理，特别是消毒的太阳能光催化反应器。理想情况下，光催化过程将由太阳能而不是人工光源来激活，因为这将降低成本并简化系统。经过初始处理后，水将进入光催化反应器，到达反应器的光将激活催化剂，该催化剂将光降解有机化合物并光灭活病原体。光催化分解是活性氧（ROS）产生的结果，活性氧继续与水中的污染物和病原体相互作用。确定哪些活性氧负责主要污染物和病原体的分解，将允许这些活性氧被优化，以有利于降解率。所选择的催化剂要求具有惰性、稳定性和廉价性，TiO2被认为是一种理想的光催化剂。TiO2以锐钛矿、板钛矿和金红石三种不同的晶体形式存在，其中含量最多。然而，锐钛矿是最活跃的光催化形式，由于其结构中的电子-空穴对具有优越的迁移性。TiO2也可以固定在介质上，在反应器中完成光催化反应后不需要过滤。TiO2的光催化性能通常是通过在催化剂中掺杂金属颗粒来优化的。由于金属的费米能级较低，这就减少了选举孔重组的机会，从而实现了有效的分离和期望的光催化反应。为了研究光催化过程中产生的ROS对污染物和病原体的分解，最好选择在文献中得到广泛应用的模型。17- β雌二醇和大肠杆菌分别作为新型污染物和病原体在文献中被大量研究。

The access to clean water is a pressing issue across the world today, which for the decade ahead is of greater concern than climate change, food crises and social instability. Globally, close to one in ten people are without access to a clean drinking water source. Developing nations in tropical climates will be disproportionally affected by the water crisis as these regions have the largest populations without access to clean water. There are different methods available for the treatment of water which includes industrial water treatment plants that purifies water through stages. These steps in the industrial treatment process are broken into primary, secondary and tertiary stages. These water treatment processes include methods such as slow sand filtration, activated sludge or photocatalytic systems. For developing regions, a lack of funds and infrastructure can result in conventional water treatment plants not being a possibility. This has led to investigations into reusing wastewater as it can be cheaper, require minimal infrastructure and the impact on major water sources is reduced. Water from different sources will have distinct water quality that can impact which is ideal for reuse. The objective of this project is the development of a solar powered photocatalytic reactor for water treatment, specifically disinfection. The photocatalytic process would ideally be activated by solar light instead of an artificial source as this would reduce costs and simplify the system. After initial treatment, water would enter a photocatalytic reactor where light reaching the reactor would activate a catalyst that would photodegrade organic compounds and photoinactivate pathogens. The photocatalytic breakdown is a result of reactive oxygen species (ROS) being produced which go on to interact with the pollutants and pathogens present in water. Determining which ROS are responsible for the breakdown of the main pollutants and pathogens will allow for these ROS to be optimised to favour the degradation rate.The catalyst selected is required to be inert, stable and cheap, TiO2 is considered to fit these requirements as an ideal photocatalyst. TiO2 exists in three different crystalline forms, anatase, brookite and rutile which is the abundant. However, anatase is the most active form for photocatalysis due to the superior mobility of the electron-hole pairs in its structure. TiO2 can also be immobilised onto a media to remove the need for filtration after a photocatalytic reaction has been completed in the reactor. The photocatalytic capabilities of TiO2 are often optimised through doping the catalyst with metal particles. This results in less chance of election-hole recombination and therefore efficient separation and desired photocatalytic reactions due to the metal's lower Fermi levels.For research into the ROS produced in photocatalysis to breakdown pollutants and pathogens, models of each most be selected that ideally have been widely used in literature. 17-beta estradiol and Escherichia coli have been investigated heavily within literature as a model emerging pollutant and pathogen respectively.