Direct recycling of discarded reverse osmosis membranes for domestic wastewater treatment with a focus on water reuse

Sustainability in Membrane Technology: Membrane Recycling and Fabrication Using Recycled Waste

Membrane technology has shown a promising role in combating water scarcity, a globally faced challenge. However, the disposal of end-of-life membrane modules is problematic as the current practices include incineration and landfills as their final fate. In addition, the increase in population and lifestyle advancement have significantly enhanced waste generation, thus overwhelming landfills and exacerbating environmental repercussions and resource scarcity. These practices are neither economically nor environmentally sustainable. Recycling membranes and utilizing recycled material for their manufacturing is seen as a potential approach to address the aforementioned challenges. Depending on physiochemical conditions, the end-of-life membrane could be reutilized for similar, upgraded, and downgraded operations, thus extending the membrane lifespan while mitigating the environmental impact that occurred due to their disposal and new membrane preparation for similar purposes. Likewise, using recycled waste such as polystyrene, polyethylene terephthalate, polyvinyl chloride, tire rubber, keratin, and cellulose and their derivates for fabricating the membranes can significantly enhance environmental sustainability. This study advocates for and supports the integration of sustainability concepts into membrane technology by presenting the research carried out in this area and rigorously assessing the achieved progress. The membranes' recycling and their fabrication utilizing recycled waste materials are of special interest in this work. Furthermore, this study offers guidance for future research endeavors aimed at promoting environmental sustainability.

Effect of hydrophobized PET TeMs membrane pore-size on saline water treatment by direct contact membrane distillation

This paper describes the desalination process by membrane distillation (MD) using track-etched membranes (TeMs). Hydrophobic track-etched membranes based on poly(ethylene terephthalate) (PET TeMs) with pore diameters from 700 to 1300 nm were prepared by UV-initiated graft polymerization of lauryl methacrylate (LMA) inside the nanochannels. Modified PET TeMs were investigated by Fourier transform infrared (FTIR) spectroscopy, atomic force microscopy (AFM), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and contact wetting angle (CA) measurements. Hydrophobic PET TeMs were tested for treating saline solutions of different concentrations by the direct contact membrane distillation (DCMD) method. The influence of membrane pore diameter and salt solution concentration on the water flux and rejection degree were investigated. Membranes with CA 94 ± 4° were tested in the direct contact membrane distillation (DCMD) of 7.5-30 g L-1 saline solution. Hydrophobic membranes with large pore sizes showed water fluxes in the range of 1.88 to 11.70 kg m-2 h-1 with salt rejection values of up to 91.4%.

Recent progress in semiconductor/graphene photocatalysts: synthesis, photocatalytic applications, and challenges

The presence of an increasing number of organic pollutants in water now poses serious risks to both human health and ecological systems. Many of these pollutants are persistent and non-biodegradable. The contamination of fresh water by harmful substances has compelled researchers to develop innovative, efficient, and cost-effective water remediation techniques and materials. Thus, photocatalysis has long been recognized as a promising approach to tackle both environmental remediation and the energy crisis. However, semiconductor photocatalysts frequently suffer from defects such as photo-generated charge carrier recombination, poor visible light response, and slow surface reaction kinetics, which can be remedied by modifications with appropriate co-catalysts. Therefore, graphene and its derivatives have widely been used as supports for semiconductors and photocatalysts due to their distinctive optical, physicochemical, and electrical features. This critical review addresses the current progress in the design and synthesis of graphene/semiconductor photocatalysts, as well as their use in photocatalytic degradation of organic pollutants and hydrogen production. Several influencing parameters are addressed, including pH, photocatalyst loading, initial pollutant concentration, light wavelength, and oxidizing species, all of which could have a significant impact on the rate of organic pollutant's degradation. Furthermore, the recyclability of the catalyst and its photocatalytic activity mechanisms are thoroughly discussed. Numerous case studies are systematically presented. Moreover, future prospects and major challenges are highlighted.

Study for Recycling Water Treatment Membranes and Compnents towards a Circular Economy-Case of Macaronesia Area

Desalination is an opportunity to get fresh water for irrigation and for drinking. Reverse Osmosis (RO) for sea water desalination is a solution for the high demand for water in Atlantic islands. The most efficient process to get desalinated water is RO; however, it is necessary to study what to do with the RO membranes used at the end of their life. This paper confirms the possibility to recycle them. The main categories of recycling by thermal processing commonly used in the industry include incineration and pyrolysis to produce energy, gas and fuel. These processes can be applied to mixed plastic waste, such as the combination of materials used in the manufacture of RO membranes. Recycling RO elements from desalination plants is shown to be an opportunity and pioneering initiatives are already underway in Europe. Energy recovery, via incineration, is feasible nowadays and it is a possibility to recycle RO membranes. On the other hand, the recycling of RO elements, via the pyrolytic industry, for fuel production could be centralized in a new industry already planned in the Macaronesia area and all obsolete osmosis membranes could be sent there for recycling. Recycling RO membranes is a very important opportunity for the environment and economy of the zone. This is a new business in water treatments with membranes, very interesting for decreasing the residues and the carbon footprint. The importance of this work is applied to sea water membranes, brackish water ones, and also wastewater tertiaries RO elements at the end of their life.