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A highly active zinc glutarate-double metal cyanide (DMC) composite catalyst (ZnGA/Zn-CrDMC) was designed for the carbon dioxide (CO2) and propylene oxide (PO) copolymerization reaction. The composite catalyst was synthesized in a rheological phase reaction and characterized using Fourier transform infrared spectroscopy (FT-IR), powder X-ray diffraction (PXRD), and scanning electron microscopy (SEM). The synthesized composite catalysed the solvent free reactions of PO and CO2 to afford biodegradable polypropylene carbonate (PPC) copolymer. 1H NMR,13C NMR, FT-IR and ESI-TOF mass spectrometry measurements were employed to confirm the characteristics of the PPC produced. Under optimal reaction conditions (50 bar CO2, 70 °C, 24 h), the ZnGA-Zn3[Cr(CN)6]2 composite displayed higher catalytic activities in the copolymerization reactions than the individual catalysts. The ZnGA:Zn3[Cr(CN)6]2 ratio of 15:1 gave PPC yield of 47.9 g polymer/g cat compared to ZnGA that produced 42.6 g polymer/ g cat in 24 h. In addition, the PPC produced from the composite catalyst displayed higher carbonate linkage content (Fc = 85.4 %) compared to the value of Fc = 33.9 %. obtained using the Zn3[Cr(CN)6]2 catalyst. Similaly, the composite catalsyt produced PPC with molecular weight of 4200 g/mol and narrow polydispersity index of 2.2. The resultant PPC copolymer displayed good thermal stability, exhibiting a high degradation temperatures (TGA-10%) of 229 °C and complete decomposition at 350 °C.

Efficient strategies are necessary to effectively remove microplastics (MPs), which are widely present in the environment. Among various techniques, photocatalysis using visible light has emerged as a promising ap-proach to tackle the growing concerns surrounding microplastic waste. This research explored the potential of vanadium-doped titanium oxide as a photocatalyst for degrading high-density polyethylene (HDPE) micro-plastics under visible light irradiation. Vanadium-doped titanium oxide photocatalyst was synthesized using the sol-gel method, and then characterized through X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV-visible spectroscopy. The XRD analysis confirmed the formation of the anatase phase, while the SEM imaging provided valuable information on the catalyst’s morphology and elemental composition. The successful incorporation of vanadium ions into the structure was demonstrated by UV-visible spectrosco-py that revealed a redshift in the absorption edge. The vanadium-doped titanium oxide photocatalyst was em-ployed in the degradation of HDPE under visible light. The experimental results exhibited a significant reduc-tion in the mass of the plastic after 350 hours of illumination. V-TiO₂ achieved a maximum reduction of 5.7%, while TiO₂ nanoparticles showed only the 2% decrease. This study demonstrates the potential of V-TiO₂ as an efficient visible-light-driven photocatalyst for HDPE degradation, contributing to the mitigation of microplastics pollution in a sustainable manner.

Mercury (Hg) has been used for millennia in artisanal and small-scale gold mining (ASGM) to extract gold from ore as an amalgam that is heated to recover gold. Since there is hardly any sustainable technology that can be used to recover it, the vast percentage of released Hg finds its way into the environment. Currently, ASGM is the largest source of mercury pollution on Earth. Mercury (Hg) is listed among the top 10 most harmful metals by the World Health Organization (WHO), and it is known to cause several neurological disorders in humans. Thus, Hg levels in environmental systems surrounding pollution hotspots such as ASGM mines need to be monitored to ensure their proper management and protect vulnerable ecosystems and human health. This work was aimed to study the level of Hg pollution in soils and plants thriving around ASGM mines in Eastern Uganda and to evaluate the Hg phytoremediation potential of the plants. The total Hg contents were determined for soils, food crops and wild plants growing around ASGM mines. The results for the pH, organic carbon (OC) and electric conductivity (EC) of the soils in the study area were comparable to those of the control soils. The soils in the studied ASGM areas exhibited high Hg concentrations ranging between 723 and 2067 folds more than those of the control soils. All soils were moderately to heavily contaminated according to geoaccumulation (Igeo) index values that ranged between 1.16 and 3.31. The results of this study also showed that the food crops and wild plants accumulated Hg levels that were above the 20 ng/g (0.02 ppm) permissible limit. This study revealed relatively higher levels of Hg in the aerial parts of the plants compared with the underground organs, which can be attributed to Hg deposition, entry through stomata and foliar adsorption. Mercury levels in 47% of the food crop samples were above the FAO/WHO permissible mercury limit of 0.5 µg/g. Similarly, medicinal plants accumulated Hg to levels that were several folds higher than the 0.2 ppm permissible limit of mercury in herbal materials of Canada. Interestingly, this study showed that some wild plant species, especially sedges, exhibited relatively higher levels of mercury accumulation than others thriving in the same environment, an indication that such plants could be utilized in the phytoremediation of Hg-contaminated sites.

Herein is reported an efficient catalytic system for the direct synthesis of styrene carbonate from styrene and CO2. The preparation and characterization of the catalyst using FTIR, TEM, EDX, XPS, and PXRD is presented. The catalyst comprised of nano-silver modified polyoxometalates (Agx/POM) and n-tetra butyl ammonium bromide (TBAB) was employed in the oxidative carboxylation of styrene with CO2 in water as the solvent using H2O2 oxidant. The catalysed reaction was performed in a stainless steel autoclave reactor and the products were analysed using GC-MS and GC-FID. The oxidative carboxylation process was carried out in a one pot set up without need for subsequent work-up and isolation of the styrene oxide formed from the epoxidation process. The process led to 64.6% styrene conversion in 6 h with 96.9% selectivity towards styrene carbonate at 50 ⁰C and 25 bar CO2. The Agx/POM catalyst and TBAB co-catalyst were both beneficial for the reaction and no cyclic carbonate was formed without the catalyst system. When tested on selected styrene derivatives, the catalyst system showed> 90% conversion and> 90% selectivity to the desired cyclic carbonates. The Agx/POM catalyst could be recovered at the end of the reaction and reused with a fresh amount of TBAB without significant loss in activity.

ABSTRACTPoly(ethylene terephthalate) (PET) has a wide range of applications that generate a lot of waste globally; thus, upcycling PET is important because it offers several industrial and economic advantages. This study describes a sustainable, emissions-free process for converting PET plastics into carbon nanomaterials (CNMs) named PT-nano powder. The thermal-hydrothermal method has employed the production of PT-nano powder above the glass transition temperature (Tg) of PET plastics. Under optimal conditions, PET plastics were efficiently converted into PT-nano powder with 86.6% crystallinity and an average particle size of 6.5 nm. The PT-nano powder was characterized for physical and chemical properties using different techniques, including UV-Vis, FTIR, Raman spectroscopy, XRD, FESEM, TEM, and proton NMR analysis. The characterization confirms the complete conversion of PET to solid fractions of carbon nanomaterial. The PT-nano powder was tested in supercapacitor performance application with electrochemical characterization. The symmetric fabrication showed a specific capacitance of 250.8 F/g, energy density of 34.83Wh/kg, and power density of 999.9W/kg with a current density of 0.5A/g. The device fabrication exhibited high cycle stability and high capacitance retention of 96.8% with a current density of 1.5A/g after 10000 cycles.

Abstract Naturally occurring phyllosilicate minerals such as talc and vermiculite in conjunction with n-tetra butyl ammonium bromide (TBAB) co-catalyst were found to be efficient in the coupling of CO2 with epoxides to form cyclic carbonates. The reaction was carried out in a pressurized autoclave reactor at moderate pressures of 10–35 bars and temperatures of 100–150 °C. The optimized catalyst system exhibited > 90% conversion of the epoxides and > 90% selectivity for the desired cyclic carbonates, in the presence or absence of a solvent. The selectivity of the catalytic system could be improved with heat pre-treatment of the phyllosilicates albeit this resulted in slightly lower epoxide conversion. The results obtained using the heat treated phyllosilicates strongly support the hydrogen bond assisted mechanism for the cycloaddition of epoxides and CO2. The cycloaddition reaction could also be carried out in the absence of TBAB, although lower cyclic carbonate yields were observed. The phyllosilicate part of the catalyst system is heterogeneous, easy to separate after completion of reactions and reusable a number of runs without loss of activity.

Abstract The study carried out a primary validation of Charm II tests for the detection of antimicrobial residues in aquaculture fish. The validation was performed according to European Commission Decision 2002/657/EC and the parameters determined included: detection capability, repeatability, reproducibility, specificity and robustness for the detection of antimicrobial residues in fish. Fish materials from different species including cat fish, trout, salmon, sea bass, tilapia, lingue and pangasius, were spiked with varying concentrations of selected antimicrobials including sulfonamides, β-lactams, macrolides, tetracyclines and aminoglycosides to determine the detection capabilities and other validation parameters of the Charm II tests. Results of the validation showed that the detection capabilities for the tetracyclines ranged from 25 to 100 µg/kg, while the sulfonamides and aminoglycosides were detected at 25 µg/kg for all species under study. The detection capabilities for the beta-lactams ranged from 25 to 300 µg/kg; and was 100 µg/kg for the tested macrolides. Results of the study showed that there was no significant difference between counts for samples read immediately after addition of the scintillation liquid and those read 14 h after addition of the scintillation liquid, provided that there was good vortexing before analysis. There was also no significant difference between counts for the same samples analyzed in different runs under repeatability and reproducibility conditions at the same spiking concentrations for the different fish species analyzed. The relative standard deviation for both repeatability and reproducibility ranged from 1.2 to 15.1%. The Charm II tests were found to be 100% group specific, as none of the antimicrobials kits, gave false positive results when testing non-target antimicrobial drugs. Results of this study demonstrate the suitability of the Charm II technique as a rapid screening tool for detection of antimicrobial residues in a variety of fish species at maximum residue limits (MRL) established in the EU guidelines, with the exception of tilmicosin which was detected at 2 MRL. The results also prove the robustness, specificity, reliability and precision of the Charm II assay in the detection of various antimicrobial residuals in fish and its applicability for the rapid evaluation of the quality of aquaculture fish for safety and trade purposes.

Chemical conversion of carbon dioxide (CO2) into value-added products is an attractive industrial process because it offers several economic and environmental advantages. This review presents advances and challenges in the CO2 and propylene oxide (PO) co-polymerization using heterogeneous catalysts to form poly (propylene carbonate) (PPC), an environmentally friendly polymer with several applications. In the co-polymerization process, CO2 is employed as a green carbon source, an alternative to the toxic phosgene which has numerous negative environmental impacts. However, this route of polycarbonate production, is hindered by the chemical inertness of CO2, and to overcome this, various catalysts have been developed. A number of heterogeneous catalysts including carboxylates, double metal cyanides and composites, have achieved varying success in activating CO2 in the production of polycarbonates. The effect of different reaction conditions including pressure, temperature and solvent has been explored. The limitations faced by various heterogeneous catalysts and improvements made over the past decades have been highlighted. Mechanistic insights for the production of PPC from CO2 and PO have been presented and the differences in both the regioselectivity and stereochemistry of the resultant polymers discussed.

Honey has multifaceted nutritional and medicinal values; however, its quality is hinged on the floral origin of the nectar. Taking advantage of the large areas that they cover; honeybees are often used as bioindicators of environmental contamination. The focus of the present paper was to examine the quality of honey from within the vicinity of an abandoned pesticide store in Masindi District in western Uganda. Surficial soils (

The utilization of CO2 as a feedstock to produce valuable chemical products is an important area of research in the field of sustainable chemistry and climate change. It addresses the challenge of rising CO2 atmospheric levels and also the concern that the fossil fuels which are the major source of carbon-based raw materials used in the chemical industry are predicted to be depleted in the near future. This review examines the advances and challenges in the glycerol carbonylation with CO2 to produce glycerol carbonate. Glycerol is the main by-product of the biodiesel industry and its surplus is creating a lot of disposal challenges to this budding industry. Thus, its reaction with CO2 is very attractive because the process converts two wastes into a high value-added product. In this review, the nature and performance of different homogeneous and heterogeneous catalysts are discussed with respect to the attendant process conditions and their effects on conversion and selectivity in the reaction of CO2 and glycerol. Metal free catalyst systems for the same process have also been explored and their efficiency discussed. The presence of dehydrating agents has been found to play a key role in improving selectivity of glycerol carbonate formation when using a variety of catalyst systems. The role of other key reaction parameters such as solvent, pressure and temperature have also been highlighted. Mechanistic insights for the production of glycerol carbonate from CO2 and glycerol have been presented.

We report an efficient process for the oxidation of benzyl alcohols using molecular oxygen as the oxidant catalyzed by Ag-Cu catalysts supported on polyoxometalates (Ag-Cu/POM). The Ag-Cu/POM catalyst was prepared by galvanic displacement in the presence of polyvinyl pyrrolidone and polyethylene glycol. The catalysts were characterized using Fourier transform infrared spectroscopy (FTIR), ultraviolet–visible spectroscopy (UV–Vis), powder X-ray diffraction (PXRD), X-ray fluorescence (XRF), Brunauer-Emmett-Teller (BET) surface analysis, transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS) and thermogravimetric analysis (TGA). The oxidation reaction was carried out using a Schlenk– line setup, under ambient atmospheric pressure. Reaction products were identified by GC–MS and quantified with GC using an internal standard method. The Ag-Cu/POM catalyst gave close to 100% benzyl alcohol conversion in 5 h with >99% selectivity to benzaldehyde. When tested on various benzyl alcohol derivatives the Ag-Cu catalysts showed good conversions and >99% selectivity to the corresponding aldehydes. The Ag-Cu catalysts supported on the POM are highly stable, and don’t show tendency to leach or deactivate. The catalysts are heterogeneous in nature and easy to recover after reactions, and could be reused at least 5 times without significant loss in activity and selectivity.

Graphite is a mineral mined from different parts of the world which including Africa. It can be used or converted into different carbon materials such as exfoliated graphite, graphene, Graphene Oxide (GO), graphene nano platelets, carbon nano tubes, carbon onions among others by chemical or mechanical methods. The locally mined graphite flakes was converted to GO using chemical methods known as Hummer’s oxidation method (HM). This method was also compared with other modified Hummer’s methods by altering the conditions and the materials used. In the modified Hummer’s method 1 (MHM1) a ratio of 9:1 of H2SO4/H3PO4 was used. While the modified Hummer’s method 2 (MHM2) a reflux process was employed. The synthesized GO materials were characterized by different techniques such as UV–Vis spectroscopy, FTIR, SEM-EDX, XRD and electrochemical analysis. The morphology, functional groups, different bonds, elemental composition, crystallographic structure and energy storage applicability of the GO were examined. The techniques confirmed formation of functional groups like C–O, CO and the C/O ratio in the materials. The electrochemical characterization performance of materials produced the highest specific capacitance of 211.2 ​F/g with a current density of 0.5 ​A/g and the specific energy of 7.33 ​Wh/kg.