Going beyond Cellulose and Chitosan: Synthetic Biodegradable Membranes for Drinking Water, Wastewater, and Oil-Water Remediation.

Membrane technology is an efficient way to purify water, but it generates non-biodegradable biohazardous waste. This waste ends up in landfills, incinerators, or microplastics, threatening the environment. To address this, research is being conducted to develop compostable alternatives that are sustainable and ecofriendly. Bioplastics, which are expected to capture 40% of the market share by 2030, represent one such alternative. This review examines the feasibility of using synthetic biodegradable materials beyond cellulose and chitosan for water treatment, considering cost, carbon footprint, and stability in mechanical, thermal, and chemical environments. Although biodegradable membranes have the potential to close the recycling loop, challenges such as brittleness and water stability limit their use in membrane applications. The review suggests approaches to tackle these issues and highlights recent advances in the field of biodegradable membranes for water purification. The end-of-life perspective of these materials is also discussed, as their recyclability and compostability are critical factors in reducing the environmental impact of membrane technology. This review underscores the need to develop sustainable alternatives to conventional membrane materials and suggests that biodegradable membranes have great potential to address this challenge.

Ir(III) and Ru(II) Complexes in Photoredox Catalysis and Photodynamic Therapy: A New Paradigm towards Anticancer Applications.

Individually, photoredox catalysis (PC) and photodynamic therapy (PDT) are well-established concepts that have experienced a remarkable resurgence in recent years, leading to significant progress in organic synthesis for PC and clinical approval of anticancer drugs for PDT. But, very recently, new photoredox catalyst systems based on Ir(III) and Ru(II) complexes have garnered significant interest because they can simultaneously be used as PDT agents apart from their demonstrated PC activity. This highlight discusses the unique PC behavior of emerging Ir(III)- and Ru(II)-based systems while also examining their potential PDT activity in cancer treatment.

'Template-free' hierarchical MoS2 foam as a sustainable 'green' scavenger of heavy metals and bacteria in point of use water purification.

Molybdenum disulfide (MoS2), with its unique optical and electrical properties, has been explored for a variety of applications in the recent past. Still, its capabilities in point-of-use heavy metal ion removal remain to be explored. Herein, for the first time using a facile approach, we fabricated three-dimensional (3D) MoS2 foam from exfoliated single to few-layered MoS2 sheets for the selective exclusion of heavy metals and stringent bactericidal response. This foam was able to exclude 99.9% of Pb(ii) and 98.7% of As(iii) instantaneously and reduced more than 98% of bacteria E. coli. Moreover, the foam exhibits selective toxicity towards bacterial cells while showing no observable toxicity towards mammalian cells. The foam can be recycled and reused for at least five cycles under accelerated conditions and thus can be used for a promising non-cytotoxic, facile, and environmentally benign process for inline water remediation to remove heavy metal ions from the feed and as a potential antibacterial agent.

In situ assembly of a graphene oxide quantum dot-based thin-film nanocomposite supported on de-mixed blends for desalination through forward osmosis.

In this work, in order to enhance the desalination performance, a unique thin-film composite membrane was designed by in situ assembly of a polyamide (PA)-graphene oxide quantum dot (GQD) framework. This unique assembly was supported on a templated hierarchical porous membrane derived from the de-mixing of a classical UCST (upper critical solution temperature) system consisting of polyvinylidene fluoride (PVDF) and polymethyl methacrylate (PMMA). The de-mixing was achieved by melt processing the blend above the UCST (in the miscible state) and quenching it below UCST. The pore size was controlled by varying the composition in the blends and by etching the PMMA phase. A sandwich architecture was developed by stacking different membranes using polyacrylic acid, as an adhesive, to achieve a gradient in pore size. Pure water flux, dye removal, and desalination experiments were carried out to study the efficacy of this strategy. The stacked membrane (used here as control) showed moderate dye rejection (about 50%) and poor desalination performance. In order to improve the desalination performance, the membranes were suitably modified by depositing a layer of polyamide (PA)-GQD framework obtained using interfacial polymerization. This strategy resulted in efficient salt rejection (more than 94% and 98% for monovalent salt and divalent salt, respectively) when studied through a pressure enhanced osmosis process using a 1000 ppm draw solution, and dye rejection (more than 90% and 85% for methylene blue (MB) and Congo red (CR), respectively) was studied through a cross-flow experimental set up using a 10 ppm feed solution @ 60 psi. Moreover, the antifouling properties of the PA-GQD modified membranes were superior (80%) to those of the control stacked membrane.

Selective cleavage of the polyphosphoester in crosslinked copper based nanogels: enhanced antibacterial performance through controlled release of copper.

Polymeric architectures with controlled and well-defined structural features are required to render a sustainable antibacterial surface - a key requirement in the design of polymeric membranes for water purification. Herein, surface selective crosslinking of copper oxide-polyphosphoester (CuO-PPE) hybrid nanogels on to polyvinylidene fluoride-styrene maleic anhydride (PVDF/SMA) ultrafiltration membranes was developed. The hybrid nanogels, composed of PPE and CuO, with inherent antifouling and antibacterial properties, were crosslinked using a macroinitiator (polyethylene glycol, PEG) and subsequently grafted on to PVDF/SMA by alkyne-anhydride reaction. Partially hydrolysed SMA solubilizes membrane proteins and the phosphatase/phospholipase triggers the cleavage of PPE segments resulting in controlled release of Cu ions. This unique strategy renders the membrane surface antibacterial through sustained and controlled release of Cu ions thereby generating intracellular reactive oxygen species (ROS). In addition, the enhanced antibiofouling performance of these membranes is facilitated by the presence of the hydrophilic macroinitiator (PEG and PPE). The modified membranes designed in this study are durable and possess long-term stability due to strong covalent interaction between CuO-PPE and the PVDF/SMA membrane. Studies on the flux, porosity and protein adsorption of the membranes were performed. An enhanced flux recovery ratio was observed for the modified membrane due to the pendant PPE groups (from CuO-PPE) which prohibit irreversible protein adsorption on the PVDF surface. The cytotoxicity of CuO-PPE is greatly reduced because of an effective coverage of CuO by biocompatible PPEs. This study opens up new avenues of fabricating "smart" inorganic nanoparticles that can be confined in a soft hybrid polymeric gel network with controlled release of Cu ions thereby precluding ubiquitous bacterial treatment in water filtration systems.