Photocatalytic inactivation of viruses using graphitic carbon nitride-based photocatalysts:Virucidal performance and mechanism

The prevalence of lethal viral infections necessitates the innovation of novel disinfection techniques for contaminated surfaces, air, and wastewater as significant transmission media of disease. The instigated research has led to the development of photocatalysis as an effective renewable solar-driven technology relying on the reactive oxidative species, mainly hydroxyl (OH●) and superoxide (O2●−) radicals, for rupturing the capsid shell of the virus and loss of pathogenicity. Metal-free graphitic carbon nitride (g-C3N4), which possesses a visible light active bandgap structure, low toxicity, and high thermal stability, has recently attracted attention for viral inactivation. In addition, g-C3N4-based photocatalysts have also experienced a renaissance in many domains, including environment, energy conversion, and biomedical applications. Herein, we discuss the three aspects of the antiviral mechanism, intending to highlight the advantages of photocatalysis over traditional viral disinfection techniques. The sole agenda of the review is to summarize the significant research on g-C3N4-based photocatalysts for viral inactivation by reactive oxidative species generation. An evaluation of the photocatalysis operational parameters affecting viral inactivation kinetics is presented. An overview of the prevailing challenges and sustainable solutions is presented to fill in the existing knowledge gaps. Given the merits of graphitic carbon nitride and the heterogeneous photocatalytic viral inactivation mechanism, we hope that further research will contribute to preventing the ongoing Coronavirus pandemic and future calamities

Hydrometallurgical processes for heavy metals recovery from industrial sludges

Hydrometallurgical approaches have been successfully employed for metal separation and recovery from various types of waste materials. Therefore, hydrometallurgy is a promising technology for metal recovery and the removal of potentially toxic heavy metals found in industrial sludge. However, a comprehensive review that focuses on the heavy metal recovery from industrial sludge using hydrometallurgical approaches has not been conducted in the recent past. The present review discusses the capacity of hydrometallurgical techniques in recovering heavy metals sourced from different types of industrial sludges, highlighting recent scientific findings. Hydrometallurgical approaches primarily consist of three process stages: metal dissolution, concentration and purification, and metal recovery. The chemical characteristics of industrial sludge, including the type, concentration and speciation of heavy metals, directly impact selection of the best recovery method. Solvent extraction, ion-exchange, and adsorption are the major techniques employed in concentration and purification, whereas electrodeposition and precipitation are the main methods used in metals recovery. Future research should focus on the development of more efficient and environmentally-friendly methods for metal dissolution from industrial sludges contaminated with multiple metals, while increasing selectivity and energy use efficiency in the concentration and purification, and recovery steps

Biochemical and physical characterization of immobilized Candida rugosa lipase on metal oxide hybrid support

Enzyme immobilization on inorganic materials is gaining more attention with the potential characteristics of high-surface-area-to-volume ratios, increasing the efficiency of enzyme loading on the support. Metal oxide hybrid support was prepared by a wetness impregnation of five metal precursors, including CaO, CuO, MgO, NiO, and ZnO, on Al2O3 and used as a support for the immobilization of Candida rugosa lipase (CRL) by adsorption. Maximum activity recovery (70.6%) and immobilization efficiency (63.2%) were obtained after optimization of five parameters using response surface methodology (RSM) by Box–Behnken design (BBD). The biochemical properties of immobilized CRL showed high thermostability up to 70 °C and a wide range in pH stability (pH 4–10). TGA-DTA and FTIR analysis were conducted, verifying thermo-decomposition of lipase and the presence of an amide bond. FESEM-EDX showed the homogeneous distribution and high dispersion of magnesium and CRL on MgO-Al2O3, while a nitrogen adsorption–desorption study confirmed MgO-Al2O3 as a mesoporous material. CRL/MgO-Al2O3 can be reused for up to 12 cycles and it demonstrated high tolerance in solvents (ethanol, isopropanol, methanol, and tert-butanol) compared to free CRL

Biotechnology for Environmental Protection

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Layered Double Hydroxides as Rising-Star Adsorbents for Water Purification: A Brief Discussion

Within the frame of this article, briefly but comprehensively, we present the existing knowledge, perspectives, and challenges for the utilization of Layered Double Hydroxides (LDHs) as adsorbents against a plethora of pollutants in aquatic matrixes. The use of LDHs as adsorbents was established by considering their significant physicochemical features, including their textural, structural, morphological, and chemical composition, as well as their method of synthesis, followed by their advantages and disadvantages as remediation media. The utilization of LDHs towards the adsorptive removal of dyes, metals, oxyanions, and emerging pollutants is critically reviewed, while all the reported kinds of interactions that gather the removal are collectively presented. Finally, future perspectives on the topic are discussed. It is expected that this discussion will encourage researchers in the area to seek new ideas for the design, development, and applications of novel LDHs-based nanomaterials as selective adsorbents, and hence to further explore the potential of their utilization also for analytic approaches to detect and monitor various pollutants

A Review on Carbon Quantum Dots Modified g-C₃N₄-Based Photocatalysts and Potential Application in Wastewater Treatment

Carbon quantum dots (CDs) are a fascinating class of carbon nanomaterials (less than 10 nm in size) with unique optical, electrical, and physicochemical properties. In addition to these properties, CQDs exhibit the desired advantages of aqueous stability, low toxicity, high surface area, economic feasibility, chemical inertness, and highly tunable photoluminescence behaviour. Recently, graphitic carbon nitride (g-C3N4) has appeared as one of the required stable carbon-based polymers due to its varied applications in several fields. In this regard, modification strategies have been made in the g-C3N4 semiconductor using CQDs to enhance the adsorptive and photocatalytic activity. In comparison to other semiconductor quantum dots, g-C3N4 shows strong fluorescent properties, such as wide excitation spectra, photostability, and tunable photo-luminescent emission spectra. The interaction inside this multicomponent photocatalyst further promotes the photocatalytic activity by improving charge transference, which plays a vital role in electrochemistry. Therefore, CQDs are auspicious nanomaterials in the field of photocatalysis, wastewater treatment and water adsorption treatment. This particular article featured the recent progression in the field of CDs/g-C3N4-based photocatalysts focusing on their luminescent mechanism and potential applications in wastewater treatment

Biochemical and Physical Characterization of Immobilized Candida rugosa Lipase on Metal Oxide Hybrid Support

Enzyme immobilization on inorganic materials is gaining more attention with the potential characteristics of high-surface-area-to-volume ratios, increasing the efficiency of enzyme loading on the support. Metal oxide hybrid support was prepared by a wetness impregnation of five metal precursors, including CaO, CuO, MgO, NiO, and ZnO, on Al2O3 and used as a support for the immobilization of Candida rugosa lipase (CRL) by adsorption. Maximum activity recovery (70.6%) and immobilization efficiency (63.2%) were obtained after optimization of five parameters using response surface methodology (RSM) by Box–Behnken design (BBD). The biochemical properties of immobilized CRL showed high thermostability up to 70 °C and a wide range in pH stability (pH 4–10). TGA-DTA and FTIR analysis were conducted, verifying thermo-decomposition of lipase and the presence of an amide bond. FESEM-EDX showed the homogeneous distribution and high dispersion of magnesium and CRL on MgO-Al2O3, while a nitrogen adsorption–desorption study confirmed MgO-Al2O3 as a mesoporous material. CRL/MgO-Al2O3 can be reused for up to 12 cycles and it demonstrated high tolerance in solvents (ethanol, isopropanol, methanol, and tert-butanol) compared to free CRL