Recent progress on elemental sulfur based photocatalysts for energy and environmental applications

Bioelectrochemical reactor to manage anthropogenic sulfate pollution for freshwater ecosystems: Mathematical modeling and experimental validation

Anthropogenic sulfate loading into otherwise low-sulfate freshwater systems can cause significant ecological consequences as a biogeochemical stressor. To address this challenge, in situ bioremediation technologies have been developed to leverage naturally occurring microorganisms that transform sulfate into sulfide rather than implementing resource-intensive physio-chemical processes. However, bioremediation technologies often require the supply of electron donors to facilitate biological sulfate reduction. Bioelectrochemical systems (BES) can be an alternative approach for supplying molecular hydrogen as an electron donor for sulfate-reducing bacteria through water electrolysis. Although the fundamental mechanisms behind BESs have been studied, limited research has evaluated the design and operational parameters of treatment systems when developing BESs on a scale relevant to environmental systems. This study aimed to develop an application-based mathematical model to evaluate the performance of BESs across a range of reactor configurations and operational modes. The model was based on sulfate transformation by hydrogenotrophic sulfate-reducing bacteria coupled with the recovery of solid iron sulfide species formed by the oxidative dissolution of dissolved ferrous iron from a stainless steel anode. Sulfate removal closely corresponded to the rate of electrolytic hydrogen production and hydraulic residence time but was less sensitive to specific microbial rate constants. The mathematical model results were compared to experimental data from a pilot-scale BES tested with nonacidic mine drainage as a case study. The close agreement between the mathematical model and the pilot-scale BES experiment highlights the efficacy of using a mathematical model as a tool to develop a conceptual design of a scaled-up treatment system.

Fabrication of highly luminescent and thermally stable composites of sulfur nanodots through surface modification and assembly

Sulfur nanodots (S-dots) have emerged as a promising luminescent material to excel over traditional heavy metal-based quantum dots. However, their relatively low emission efficiency and poor thermal stability in the solid state have limited their wide applications in photoelectric devices. In this work, highly luminescent, with a photoluminescence quantum yield higher than 50%, and thermally stable composites of S-dots were produced through modulating their surface states and aggregation behaviors by introducing pyromellitic dianhydride (PMDA) and benzoyleneurea (BEU), respectively. PMDA eliminated the relatively short-lived surface states and defects on the surface of S-dots and BEU regulated the aggregation states and facilitated the energy transfer from BEU to S-dots. The as-obtained composites also showed significantly improved thermal stability compared to S-dots, aided by the hydrophobic chemical groups and dense matrix of PMDA and BEU, which extended their applications in fabricating light-emitting diodes. Our presented results provide a new approach to produce highly luminescent S-dots, which widen their applications in the fields of bioimaging, sensing, photoelectric devices, and environmental science.

Development of biohybrid Ag2CrO4/rGO based nanocomposites with stable flotation properties as enhanced Photocatalyst for sewage treatment and antibiotic-conjugated for antibacterial evaluation

The proposed research outlines a facile method to synthesize Silver Chromate/reduced graphene oxide nanocomposites (Ag₂CrO₄/rGO NCs) with a narrow dissemination size for the ecological treatment of hazardous organic dyes. The photodegradation performance toward the decontamination of model artificial methylene blue dye was assessed under solar light irradiation. The crystallinity, particle size, recombination of photogenerated charge carriers, energy gap and surface morphologies of synthesized nanocomposites were determined. The experiment objective is to use rGO nanocomposites to increase Ag₂CrO₄ photocatalytic efficiency in the solar spectrum. Tauc plots of ultraviolet-visible (UV-vis) spectrum were used to calculate the optical bandgap energy of the produced nanocomposites ~1.52 eV, which resulted in a good photodegradation percentage of ~92 % after 60 min irradiation of Solar light. At the same time, pure Ag₂CrO₄ and rGO nanomaterials showed ~46 % and ~ 30 %, respectively. The ideal circumstances were discovered by investigating the effects of several parameters, including catalyst loading and different pH levels, on the degradation of dyes. However, the final composites maintain their ability to degrade for up to five cycles. According to the investigations, Ag₂CrO₄/rGO NCs are an effective photocatalyst and can be used as the ideal material to prevent water pollution. Furthermore, antibacterial efficacy for the hydrothermally synthesized nanocomposite was tested against gram-positive (+ve) bacteria viz. Staphylococcus aureus and gram-negative (-ve) bacteria viz. Escherichia coli. The maximum zone of inhibition for S. aureus and E. coli were 18.5 and 17 mm, respectively.