The water matrix plays a complex and significant role in photocatalytic degradation by influencing several factors, including dissolved anions and cations, the presence of natural organic matter, dissolved oxygen, suspended particles, turbidity, pH, and temperature. Optimizing photocatalytic processes for practical water treatment applications necessitates understanding these relationships. The efficiency and efficacy of photocatalytic water treatment systems in degrading organic contaminants can be enhanced by carefully considering and manipulating the water matrix. Based on literature published between 2000 and 2024, this review aims to comprehend the effects of contaminants and water quality on the photocatalytic degradation of organic pollutants. Researchers have employed various water matrices and reaction conditions to understand the interactions and impacts of different water matrix pollutants on photodegradation. The literature analysis revealed that when chloride and sulfate ions interact with reactive oxygen species and photocatalysts, their effects are predominantly inhibitory, thereby reducing the photocatalytic activity of the catalysts. Conversely, nitrate ions can exhibit an inhibitory effect under certain conditions by scavenging hydroxyl radicals while promoting photodegradation in other scenarios by generating more reactive oxygen species. The degree of inhibition varies according to the concentration of these factors.
In the move away from fossil fuels, methanol is viewed as a viable alternative engine fuel and hydrogen carrier, while serving as a key component in the chemical industry. In responding to the environmental impact caused by excessive CO 2 emissions and the drive to promote green H 2 technology, CO 2 hydrogenation to produce methanol has received increasing attention, which has addressed H 2 storage and transport. The reaction is thermodynamically feasible at low temperatures with a high conversion in a single pass, but there is significant scope to enhance reaction kinetics. This article reviews the progress that has been made in engineering catalytic active sites for the heterogeneous hydrogenation of CO 2 to methanol at temperatures below 200 °C, including considerations of alloying effects, doping, defect formation, active site size and dispersion, coordination effects, and surface modification. The active site valence state and size in tandem with electron transfer, hydrogen spillover, and surface alkalinity/hydrophobicity can affect catalytic performance and the prevailing reaction pathway to varying degrees. The low-temperature reaction process is briefly discussed and future research directions required to further enhance catalytic efficiency are proposed.
This review explores the potential of gravity-driven ultrafiltration (GDU) systems as a sustainable solution to global drinking water challenges. Leveraging hydrostatic pressure instead of external energy inputs, GDU systems offer a low-maintenance, cost-effective approach well-suited for decentralized and resource-constrained settings. The paper provides a detailed analysis of the fluid dynamics and transport mechanisms that underpin GDU operation, emphasizing the influence of biofilm formation, membrane morphology, and material selectivity on system performance. Recent advancements in membrane materials have demonstrated significant improvements in antifouling performance, flux stability, and contaminant removal. Innovative membrane designs are also reviewed for their potential to enhance adaptability and multifunctionality. Real-world case studies highlight the operational feasibility and economic advantages of GDU systems, while identifying key barriers such as long-term reliability, feedwater variability, and limited community-based monitoring capacity. Socio-economic considerations, including modular design strategies and institutional engagement, are examined to support scalable implementation. This comprehensive review offers interdisciplinary insights to inform future research, technology development, and policy planning aimed at advancing sustainable water purification solutions worldwide.
