O and S co-doping induced N-vacancy in graphitic carbon nitride towards photocatalytic peroxymonosulfate activation for sulfamethoxazole degradation.

Doping-induced vacancy engineering of graphitic carbon nitride (GCN) is beneficial for bandgap modulation, efficient electronic excitation, and facilitated charge carrier migration. In this study, synthesis of oxygen and sulphur co-doped induced N vacancies (OSGCN) by the hydrothermal method was performed to activate peroxymonosulfate (PMS) for sulfamethoxazole (SMX) antibiotic degradation and H2 production. The results from experimental and DFT simulation studies validate the synergistic effects of co-dopants and N-vacancies, i.e., bandgap lowering, electron-hole pairs separation, and high solar energy utilization. The substitution of sp2 N atom by O and S co-dopants causes strong delocalization of HOMO-LUMO distribution, enhancing carrier mobility, increasing reactive sites, and facilitating charge-carrier separation. Remarkably, OSGCN/PMS photocatalytic system achieved 99.4% SMX degradation efficiency and a high H2 generation rate of 548.23 µ mol g-1 h-1 within 60 min and 36 h, respectively under visible light irradiations. The SMX degradation kinetics was pseudo-first-order with retained recycling efficiency up to 4 catalytic cycles. The results of EPR and chemical scavenging experiments revealed the redox action of reactive oxidative species, wherein 1O2 was the dominant reactive species in SMX degradation. The identification of formed intermediates and the SMX stepwise degradation pathway was investigated via LC-MS analysis and DFT studies, respectively. The results from this work anticipated deepening the understanding of PMS activation by substitutional co-doping favoring N-vacancy formation in GCN lattice for improved photocatalytic activity.

Environmental impact of COVID-19 Vaccine waste: A perspective on potential role of natural and biodegradable materials.

The mass immunization is the prioritised post-pandemic phase offering preventive countermeasure for COVID-19 pandemic. However, it is crucial to tackle the environmental impact of COVID-19 vaccine waste for sustainable vaccination management because a prolonged immunisation campaign is expected. As the pace of vaccine production, distribution and mass vaccination has been expedited, there is a simultaneous rise in plastic derived vaccine waste including syringes, needles, used/unused vaccine vials, vaccine packaging, and protective gear (surgical facemasks, gloves, face shields, etc). Henceforth, in view of the repercussions of heaping plastic waste in the environment, this article provides a perspective on the usage of synthetic and natural materials as potential substituents for vaccination tools. The biodegradable polymeric gums such as cellulose, gellan, pectin, etc. have been successfully applied for the fabrication of surgical facemasks. The highly suggestive practice is replacement of conventional polypropylene based plastics with bioplastics or paper for vaccine packaging. The usage of biodegradable bio-plastics as packaging material along with environmentally friendly face masks can help to achieve the zero waste approach. The discussion in the article significantly highlights the necessity of opting sustainable solutions of disinfecting and substituting vaccination tools for an environment friendly ongoing vaccination campaign.

The practicality and prospects for disinfection control by photocatalysis during and post-pandemic: A critical review.

The prevalence of global health implications from the COVID-19 pandemic necessitates the innovation and large-scale application of disinfection technologies for contaminated surfaces, air, and wastewater as the significant transmission media of disease. To date, primarily recommended disinfection practices are energy exhausting, chemical driven, and cause severe impact on the environment. The research on advanced oxidation processes has been recognized as promising strategies for disinfection purposes. In particular, semiconductor-based photocatalysis is an effective renewable solar-driven technology that relies on the reactive oxidative species, mainly hydroxyl (•OH) and superoxide (•O2-) radicals, for rupturing the capsid shell of the virus and loss of pathogenicity. However, the limited understanding of critical aspects such as viral photo-inactivation mechanism, rapid virus mutagenicity, and virus viability for a prolonged time restricts the large-scale application of photocatalytic disinfection technology. In this work, fundamentals of photocatalysis disinfection phenomena are addressed with a reviewed remark on the reported literature of semiconductor photocatalysts efficacies against SARS-CoV-2. Furthermore, to validate the photocatalysis process on an industrial scale, we provide updated data on available commercial modalities for an effective virus photo-inactivation process. An elaborative discussion on the long-term challenges and sustainable solutions is suggested to fill in the existing knowledge gaps. We anticipate this review will ignite interest among researchers to pave the way to the photocatalysis process for disinfecting virus-contaminated environments and surfaces for current and future pandemics.

The environmental impact of mass coronavirus vaccinations: A point of view on huge COVID-19 vaccine waste across the globe during ongoing vaccine campaigns.

The vaccine innovation is a ubiquitous preventive measure to the transmission of highly infectious SARS-COV-2. The ongoing mass coronavirus vaccination programmes have inadvertently become the bulk producers of biomedical and plastic waste triggering severe impact on the environment. The sustainable management of bio hazardous vaccine waste in particular; syringes, needles, used/un-used vials and single-use plastic equipment is of utmost importance. This perspective presents a critical point of view in terms of the generated vaccine waste and the subsequent knock-on effect on all aspects of ecosystem. The discussion includes dire consequences due to the release of huge amount of plastic-based personal protective equipment into marine environment. The pivotal crisis of CO2 emission during the manufacture and storage of different vaccines has contributed to global warming. The unavoidable generation of microfibers upon incineration, autoclaving, pyrolysis and open dumping of vaccine waste has further jeopardized the environment. In this vein, exploration of biodegradable materials for vaccine inoculation and development of green technologies for sound waste management is suggested to mitigate the environment pollution.

Advanced activation of persulfate by polymeric g-C3N4 based photocatalysts for environmental remediation: A review.

Photocatalytic materials for photocatalysis is recently proposed as a promising strategy to address environmental remediation. Metal-free graphitic carbon nitride (g-C3N4), is an emerging photocatalyst in sulfate radical based advanced oxidation processes. The solar-driven electronic excitations in g-C3N4 are capable of peroxo (O‒O) bond dissociation in peroxymonosulfate/peroxydisulfate (PMS/PDS) and oxidants to generate reactive free radicals, namely SO4•- and OH• in addition to O2•- radical. The synergistic mechanism of g-C3N4 mediated PMS/PDS photocatalytic activation, could ensure the generation of OH• radicals to overcome the low reductive potential of g-C3N4 and fastens the degradation reaction rate. This article reviews recent work on heterojunction formation (type-II heterojunction and direct Z-scheme) to achieve the bandgap for extended visible light absorption and improved charge carrier separation for efficient photocatalytic efficiency. Focus is placed on the fundamental mechanistic routes followed for PMS/PDS photocatalytic activation over g-C3N4-based photocatalysts. A particular emphasis is given to the factors influencing the PMS/PDS photocatalytic activation mechanism and the contribution of SO4•- and OH• radicals that are not thoroughly investigated and require further studies. Concluding perspectives on the challenges and opportunities to design highly efficient persulfate-activated g-C3N4 based photocatalysts toward environmental remediation are also intensively highlighted.