Julius Nsami Ndi

In this study, a Pd-Ni-MAC bimetallic catalyst was prepared by the incipient wetness impregnation method and tested for the catalytic reduction of nitrates to gaseous nitrogen in surface and groundwater using formic acid as the reducing agent. Activated carbon (AC) was modified with 2 MHNO3 and characterized by Boehm analysis, confirming successful modification. The modified activated carbon (MAC) was coated with Pd/Ni to obtain the Pd-Ni-MAC bimetallic catalyst, which was characterized using Fourier transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET) analysis, scanning electron microscopy (SEM), and X-ray diffraction (XRD) to determine its surface functional groups, surface area, surface morphology, and crystalline structure, respectively. XRD analysis revealed the presence of Pd-Ni alloys impregnated on the MAC. Catalytic tests were conducted in a semi-batch reactor at room temperature. The catalyst activity and selectivity toward N2 were found to depend on the calcination temperature and duration used during catalyst preparation. To achieve optimum activity and selectivity toward N2, calcination temperatures of 250, 350, and 450 oC and durations of 1 and 2 h were investigated. The highest nitrate conversion and N2 selectivity were obtained for the catalyst calcined at 250 oC for 1 h after 120 min of reaction, achieving 78% conversion and 97.1% selectivity. Owing to these high values of conversion and N2 selectivity, the catalytic reduction combining formic acid with Pd-Ni-MAC can be considered a promising alternative for nitrate removal from surface and groundwater.

Synthetic dyes, such as congo red (CR), are among the most hazardous pollutants released into aquatic environments due to their toxicity, persistence, and potential health risks. This study prepared and extensively characterized novel chitosan–biochar biocomposite films using SEM-EDS, N₂ adsorption–desorption, FTIR, XPS, TGA, tensile testing, water contact angle measurement, and water absorption and solubility testing to efficiently remove CR dye from aqueous solutions. These characterization techniques revealed that the films exhibited excellent mechanical strength, surfaces enriched with –OH, –NH₂, and –COOH functional groups and low porosity. Furthermore, the prepared films could be easily separated from the solution after adsorption. The CR removal percentages of the composites were ∼74%, 73%, and 85% for pristine biochar (CH₂BC), acid-modified (CH₂ABC), and base-modified (CH₂BBC), respectively, after 420 minutes with a solution pH of 6.5 at 25 °C. The adsorption data suggested that the kinetic models were those of pseudo-first-order and Elovich models, while the Freundlich model best described the adsorption isotherm. Moreover, CH₂BBC retained up to 79% of its adsorption capacity after four adsorption–desorption cycles, confirming its reusability. The CR adsorption mechanism involves electrostatic attraction, π–π stacking, H-bonding, n–π interaction, imine and sulfone bridging. The environmentally friendly preparation, low cost, and easy regeneration of the prepared chitosan–biochar biocomposite films offer a promising sustainable solution for remediating dye-contaminated water.

In this study, two biomass wastes, namely, Canarium schweinfurthii shells (CSS) and Ricinodendron heudelotii shells (RHS), were converted into activated carbons by chemical activation using phosphoric acid.

To apply the Fenton process to remove organic pollutants from an aqueous solution, catalysts are needed that can decompose hydrogen peroxide (H ₂ O ₂ ) into hydroxyl radicals and regenerate Fe ²⁺ in the system.

Caused by pathogenic microorganisms, infectious diseases are known to cause high mortality rates, severe burdens of disability, and serious worldwide aftermaths. Drug-resistant pathogens have reduced the efficacy of available therapies against these diseases, thus accentuating the need to search for effective antimicrobials. Medicinal plants have served as starting material for the preparation of a number of antimicrobial agents. To this end, the present study highlights the green synthesis of Cocos nucifera-based nanomaterials and evaluation of the mechanistic basis of their antimicrobial action. Accordingly, Cocos nucifera extract was used for the reduction of silver nitrate solution to afford silver nanoparticles. These entities were further incorporated onto sulfuric-acid-based activated carbons to generate the nanocomposites. The antimicrobial activity of the as-prepared nanomaterials was evaluated using the broth microdilution method, while the antioxidant activity was assessed through standard methods. The cytotoxicity of potent nanomaterials was assessed on Vero cells by the spectrophotometric method. As a result, nanoparticles were successfully synthesized, as evidenced by the ultraviolet–visible spectroscopy analysis that revealed an intense absorption spectrum at 433 nm. Fourier Transform Infrared Spectroscopy presented the functional group moieties involved as a capping and reducing agent in the synthesis of the nanomaterials. The incubation of nanomaterials with selected bacterial and fungal strains has led to significant inhibitory effects of these pathogens with minimum inhibitory concentrations ranging from 7.813 to 250 μg/mL. In antioxidant assays, the nanocomposites presented scavenging activities comparable to those of ascorbic acid. Cytotoxicity experiment revealed no toxic effects on Vero cells (range of selectivity indices: from >4 to >128). These results provide evidence of the implication of Cocos nucifera-based nanomaterials in targeting bacterial or fungal systems that mediate free-radical damage or by inhibiting the oxidative damage caused by selected bacteria and fungi, the most susceptible being Escherichia coli and Candida albicans, respectively.

Caused by pathogenic microorganisms, such as bacteria, parasites, fungi, among others, infectious diseases can spread directly or from one individual to another. According to the World Health Organization, these diseases are known to cause high mortality rates, severe burdens of disability and serious worldwide aftermaths. The inappropriate use of antibiotics in humans are the main origins of the development of drug-resistant pathogens, which reduce the efficacy of these therapies, thus accentuating the need to search for effective antimicrobials. Medicinal plants have served as starting material for the preparation of a number of antimicrobial agents. To this end, the present study highlights the green synthesis of Cocos nucifera-based nanomaterials and evaluation of the mechanistic basis of their antimicrobial action. Accordingly, Cocos nucifera extract was used to reduce different concentrations (5, 10 and 20 mM) of silver nitrate solution to afford silver nanoparticles (AgNPs). These entities were further incorporated onto activated carbons (obtained by chemical activation using sulphuric acid as activation agent) to generate the nanocomposites. The antimicrobial activity of the as-prepared nanomaterials was evaluated using the broth microdilution method, while, the antioxidant activity was assessed through standard methods, such as 2,2-diphenyl-1-picrylhydrazyl (DPPH), and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) assays. Cytotoxicity of potent nanomaterials was assessed on Vero cells by spectrophotometric method. As a result, nanoparticles were successfully synthesized as evidenced by the color change of the solution from transparent to dark brown. Further characterization was carried out by UV-visible spectroscopy that showed an intense absorption spectrum at 433 nm. Fourier Transform Infrared Spectroscopy (FTIR) revealed the functional group moieties involved as a capping and reducing agent in the synthesis of AgNPs. The incubation of nanomaterials with selected bacterial and fungal strains led to significant inhibitory effects of these pathogens with minimum inhibitory concentrations ranging from 7.813 to 250 μg/ml. In antioxidant assays, the nanocomposites presented scavenging activities comparable to that of ascorbic acid. Cytotoxicity experiment revealed no toxic effects on the human mammalian cells Vero (range of selectivity indices: from >4 to >128). These results provide evidence of the implication of Cocos nucifera-based nanomaterials in targeting bacterial or fungal systems that mediate free-radical damage or by inhibiting the oxidative damage caused by selected bacteria and fungi, the most susceptible being Escherichia coli and Candida albicans, respectively.

The development of antimicrobial resistance has increased the prevalence of infectious diseases, causing a global health problem that accounts for over 4.95 million deaths worldwide annually. The side effects associated with current antibiotics prompt a crucial need to search for effective and safe antimicrobial agents. In this study, silver nanoparticles (AgNPs) were prepared by chemical reduction method using silver nitrates as a metallic precursor and Croton macrostachyus bark aqueous extract as a reducing and capping agent. The nanoparticles were further functionalized using C. macrostachyus-based activated carbon (CAC) to generate nanocomposites (CAC-AgNPs). The nanomaterials were characterized by ultraviolet-visible (UV–vis) absorption spectra and Fourier transform infrared (FTIR) spectra. The antibacterial activity of the as-prepared nanomaterials was evaluated against an array of bacterial strains by microdilution method, whereas their cytotoxicity profile was evaluated using Vero cells (human mammalian cells). Antibacterial mechanistic studies of active nanomaterials were carried out through bacterial growth kinetics, nucleic acid leakage tests, and catalase inhibition assays. As a result, the as-prepared nanomaterials exhibited antibacterial activity against an array of bacterial strains (minimum inhibitory concentration (MIC) range: 62.5 to 500 µg/mL), the most susceptible being Escherichia coli and Staphylococcus aureus. Cytotoxicity studies of the nanomaterials on Vero cells revealed that the nanocomposite (median cytotoxic concentration (CC₅₀): 213.6 µg/mL) was less toxic than its nanoparticle (CC₅₀ value: 164.75 µg/mL) counterpart. Antibacterial mechanistic studies revealed that the nanomaterials induced (i) bacteriostatic activity vis à vis E. coli and S. aureus and (ii) inhibition of catalase in these bacteria. This novel contribution regarding the antibacterial mechanisms of action of silver nanocomposites from C. macrostachyus-based activated carbon may contribute to our understanding of the antibacterial action of these biomaterials. Nevertheless, more chemistry and in vivo experiments as well as in depth antibacterial mechanistic studies are warranted for the successful utilization of these antibacterial biomaterials.

In this study, we report the antibacterial mechanisms of action of uniform silver nanoparticles (AgNPs) and decorated activated carbon nanocomposite (CAC-AgNPs) obtained using a green synthesis approach. The nanomaterials were characterized by ultraviolet-visible (UV-vis) absorption spectra and Fourier transform infrared (FTIR) spectra. The antibacterial activity of the as-prepared nanomaterials was evaluated against an array of bacterial strains by microdilution method, whereas their cytotoxicity profile was evaluated on Vero cells (human mammalian cells). The antibacterial mechanistic studies of active nanomaterials were carried out through bacterial growth kinetics, nucleic acid leakage test, and catalase inhibition assay. A silver nanocomposite was successfully fabricated from Croton macrostachyus-based activated carbon. The as-prepared nanomaterials exhibited antibacterial activity against an array of bacterial strains (minimum inhibitory concentration (MIC) range: 62.5 to 500 µg/mL), the most susceptible being Escherichia coli and Staphylococcus aureus. Cytotoxicity studies of the nanomaterials on Vero cells revealed that the nanocomposite (median cytotoxic concentration (CC50): 213.6 µg/mL) was less toxic than the nanoparticles (CC50 value: 164.75 µg/mL) counterpart. Antibacterial mechanistic studies unveiled that the nanomaterials induced (i) bacteriostatic activity vis-à-vis E. coli and S. aureus and (ii) inhibition of catalase in these bacteria. This novel contribution on the antibacterial mechanisms of action of silver nanocomposite from C. macrostachyus-based activated carbon might contribute to the understanding of antibacterial action of these biomaterials. Nevertheless, more chemistry and in vivo experiments, as well as in depth antibacterial mechanistic studies are warranted for the successful utilization of these antibacterial biomaterials.

Akilbenza clay (Akil) was characterized by XRD, FT-TIR, XRF, EDX, SEM, and N₂ gas adsorption. The adsorption performance for Cu(II) ions by this clay was also studied. Akil is composed mainly of kaolinite with mica illite and quartz as minor minerals. The ATR-FTIR analysis shows Si-O-Al, Si-O, Al-O, Si-OH, and Al-OH as the main functional groups. SEM indicates that the clay particles are irregular in shape and size by supported BJH. Akil has a specific surface area of 45.62 m²/g with the presence of both mesopores and micropores. The average pore diameter is 19.4196 nm. XRF and EDX reveal that the clay is mainly composed of silica, aluminum, and iron with a Si/Al ratio of 1.41. For the adsorption performance of Cu(II) ions, a maximum quantity of 76 mg/g was recorded. Freundlich isotherm models best describe the adsorption processes at equilibrium. Kinetic studies revealed that the adsorption process was well explained with pseudo-second-order kinetic model. The value of the mean energy of adsorption from Temkin isotherm and the values from Elovich kinetic model suggest that the adsorption of Copper(II) ions on Akil is a combination between ion exchange and electrostatic attraction. The results obtained can be introduced into the database of knowledge on clay minerals with emphasis on their use for the removal of Cu(II) ions.