Membrane technology has been used in desalination and wastewater treatment due to its many advantages such as ease of operation, smaller footprint, higher efficiency, and lower chemical consumption over conventional...

Laser-induced graphene (LIG) has recently become a point of attraction globally as an environmentally friendly method to fabricate graphene foam in a single step using a CO 2 laser. The electrical properties of LIG are studied in different environmental applications, such as bacterial inactivation, antibiofouling, and pollutant sensing. Furthermore, metal or nonmetal doping of graphene enhances its catalytical performance in pollutant degradation and decontamination. Magneĺi phase (Ti n O 2n−1 ) is a substoichiometric titanium oxide known for its high electrocatalytic behavior and chemical inertness and is being explored as a membrane or electrode material for environmental decontamination. Here, we show the fabrication and characterization of LIG−Magneĺi-phase (Ti 4 O 7 ) titanium suboxide composites as electrodes and filters on poly(ether sulfone). Unlike undoped LIG electrodes, the doped Ti 4 O 7 −LIG electrodes exhibit enhanced electrochemical activity, as demonstrated in electrochemical characterization using cyclic voltammetry and electrochemical impedance spectroscopy. Due to the in situ generation of hydroxyl radicals on the surface, the doped electrodes exhibit increase in methylene blue degradation and microorganism removal. Effects of voltage and doping were examined, resulting in a clear trend of degradation and decontamination performance proportional to the doping concentration and applied voltage giving the best result at 2.5 V for 10% Ti 4 O 7 doping. The LIG−Ti 4 O 7 surfaces also showed biofilm inhibition against mixed bacterial culture. The flowthrough filtration using a LIG−Ti 4 O 7 conductive filter showed complete bacterial killing with 6 log removal in the permeate at 2.5 V, an enhancement of ∼2.5 log compared to undoped LIG filters at a flow rate of ∼500 L m −2 h −1 . The facile fabrication of Ti 4 O 7doped LIG with enhanced electrochemical properties can be effectively used for energy and environmental applications.

Interest in the pathogenesis, detection, and prevention of viral infections has increased broadly in many fields of research over the past year. The development of water treatment technology to combat viral infection by inactivation or disinfection might play a key role in infection prevention in places where drinking water sources are biologically contaminated. Laser-induced graphene (LIG) has antimicrobial and antifouling surface effects mainly because of its electrochemical properties and texture, and LIG-based water filters have been used for the inactivation of bacteria. However, the antiviral activity of LIG-based filters has not yet been explored. Here we show that LIG filters also have antiviral effects by applying electrical potential during filtration of the model prototypic poxvirus Vaccinia lister. This antiviral activity of the LIG filters was compared with its antibacterial activity, which showed that higher voltages were required for the inactivation of viruses compared to that of bacteria. The generation of reactive oxygen species, along with surface electrical effects, played a role in the mechanism of virus inactivation. This new property of LIG highlights its potential for use in water and wastewater treatment for the electrochemical disinfection of various pathogenic microorganisms, including bacteria and viruses.

Graphene research has steadily increased, and its commercialization in many applications is becoming a reality because of its superior physicochemical properties and advances in synthesis techniques. However, bulk-scale production of graphene still requires large amounts of solvents, electrochemical treatment, or sonication. Recently, a method was discovered to convert bulk quantities of carbonaceous materials to graphene using flash Joule heating (FJH) and, so named, flash graphene (FG). This method can be used to turn various solid wastes containing the prerequisite element carbon into FG. Globally, more than 2 billion tons of municipal solid waste (MSW) are generated every year and, in many municipalities, are becoming unmanageable. The most commonly used waste management methods include recycling, composting, anaerobic digestion, incineration, gasification, pyrolysis, and landfill disposal. However, around 70% of global waste ends up in landfills or open dumps, while the rest is recycled, composted, or incinerated. Even the various waste valorization techniques, such as pyrolysis and gasification, produce some waste residues that have their ultimate destination in landfills. Thus, technologies that can minimize waste volume or convert waste into valuable products are required. The thermal treatment process of FJH for FG production provides both waste volume reduction and valorization in the form of FG. In this Perspective, we provide an overview of FJH and its possible applications in various types of waste conversion/valorization. We describe the typical current MSW management system as well as the potential for creating FG at various stages and propose a schematic plan for the incorporation of FG in MSW management. We also analyze the strengths, weaknesses, opportunities, and threats of MSW as an FG precursor in terms of technical, economic, environmental, and social sustainability. This valuable waste valorization and management strategy can help achieve near-zero waste and an economy-boosting MSW management system.

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The global scenario of water shortage and pollution has necessitated the use of advanced water treatment and desalination technologies. Solar interfacial evaporation has shown promising results for clean water generation but depends on the sunlight intensity, which changes over time and climatic conditions. Furthermore, the solar-driven interfacial evaporation cannot operate in the dark and is susceptible to salt deposition. Here, we have explored the Joule heating effect in laser-induced graphene (LIG)-based Joule heaters (JHs) for interfacial water evaporation under different applied voltages. The effect of stacking of Joule heaters has been explored and found to give an enhanced evaporation rate with less spatial footprint and energy consumption. The evaporation rate in a single-layer LIG JH reached ∼5 kg·m–2·h–1 under the application of 10 V. The JH area and its stacking effect on evaporation rate, spatial footprint, and energy consumption were investigated. An increase in evaporation rate by seven times and reduction of electrical energy consumption by three times has been demonstrated by three levels of stacking compared to its equivalent triple-area LIG JH. The enhanced performance of the stacking configuration could be due to the enhanced heat transfer from the bottom JH to the upper JH, thermal concentration, and reduced thermal losses to the environment. The single-layer LIG JH also gave ∼2 kg·m–2·h–1 evaporation rate under natural sunlight and environmental conditions, showing potential for solar interfacial evaporation. The JHs also showed excellent resistance to salt deposition with self-salt-cleaning capability under the tested conditions. These compact stacked JH systems could be integrated with renewable energy, which can be operated in the presence and absence of sunlight. Such compact JH systems with a lesser spatial footprint, enhanced evaporation rate, and reduced energy requirement can help in providing constant water evaporation for various applications.

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