Elie ACAYANKA

Inactivation of Salmonella typhi in an aquatic microcosm by plasma-actived water generated by creeping arc discharge: Importance of the cellular physiological state

Antoine Tamsa Arfao, Olive Vivien Noah Ewoti, Fils Mamert Onana, Annette Ngo Hei, Awawou Manouore Njoya, Elie Acayanka and 4 more

Cleaner Water

Conventional disinfection methods often generate toxic by-products, highlighting the need for alternative methods. The present study evaluated the antimicrobial efficacy of plasma-activated water (PAW), generated by creeping arc discharge, on Salmonella Typhi in aquatic microcosms, with a focus on the role of bacterial physiological states. Bacterial suspensions were prepared from lag, exponential, stationary, and decline phases. PAW was produced at different activation times (PAW [5 min], PAW [10 min], PAW [15 min] and PAW [20 min]). Its impact was assessed at various contact times (15, 30, 45 and 60 min) and treatment volumes (2 mL, 3 mL, 5 mL, and 10 mL). Results revealed that PAW induced significant reductions in cultivable S. Typhi cells, with complete inactivation achieved after 45 and 60 min exposure depending on the growth phase. The lag phase and decline phase exhibited the highest susceptibility. PAW [5 min] showed minimal disinfection across all time points, confirming that short activation durations are insufficient for effective microbial control during the lag phase. Increasing PAW activation time and volume positively correlated with higher inhibition rates. Physicochemical characterization indicated that bactericidal activity was driven by reactive oxygen and nitrogen species (RONS) and by progressive acidification of the medium. The Chick–Watson model and analysis of Log Removal Values confirmed the bactericidal efficacy of plasma-activated water (PAW) across all growth phases of Salmonella typhi . Overall, this work demonstrates that PAW is a promising and sustainable disinfection technology for waterborne pathogens.

• #plasma applications and diagnostics
• #microbial inactivation methods
• #listeria monocytogenes in food safety
• #salmonella typhi

Red mud neutralization by plasma for Fenton-like degradation of amoxicillin and tramadol in water

Elie Acayanka, Jean-Baptiste Tarkwa, Emilie Lucresse N. Nguetcha, Line N. Leundjeu, Franck William Tatchemo Boyom, Georges Y. Kamgang

Journal of Water Process Engineering

• #bauxite residue and utilization
• #coagulation and flocculation studies
• #molten salt chemistry and electrochemical processes
• #red mud

Self-Cleaning and Antibacterial Properties of Plasma-Elaborated Ag/AgO-TiO2-Coated Cotton Fabrics

Suzie Anne Voufouo, Jean-Baptiste Tarkwa, Elie Acayanka, Wilfrid Fokoue Fokou, Franck W. Boyom‐Tatchemo, Georges Y. Kamgang

BioNanoScience

• #nanoparticles: synthesis and applications
• #tio2 photocatalysis and solar cells
• #microplastics and plastic pollution
• #photocatalysis

Floating Amphiphilic Biomass-Based Material Obtained by Plasma Processing for Enhanced Wastewater Remediation

Nehemie Miloh, Jean-Baptiste Tarkwa, Berthelot Sop-Tamo, Claude F. G. Mbafou, Patrick M. Kouotou, Elie Acayanka and 1 more

Journal of Water Chemistry and Technology

A self-floating amphiphilic biosorbent (SFAB) was prepared by dispersing the plasma-modified water hyacinth (WH) (Eichhornia crassipes) fibers on the beeswax support. The synthesis process takes advantage of the functionalising properties of plasma with polar groups (–OH, –CO, –COOH) and the binding effect of beeswax. The characteristics of the obtained biosorbent exhibited significant changes in surface chemistry and roughness confirmed by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and energy dispersive X-ray spectroscopy (EDX). The resulting functionalised material offers appropriate anchoring sites for pollutants leading to a biomaterial with hydrophilic and lipophilic properties. The removal performance of the SFAB outperforms the natural biomass fibers taking alone, with an uptake capacity of 20.83 mg/g for merbromin (MB) (50 mg/L) and 19.90 mg/g for Green Naphthol B (GNB) (50 mg/L), based on the successfully fitted general-order kinetic model. The effects of some key adsorption parameters were optimised, and the equilibrium data (298–323 K) were best fitted by the Liu isotherm reaching 47.20 and 36.40 mg/g of uptake amounts for MB and GNB, respectively at 298 K. The removal mechanism is governed by π–π interplay, hydrophobic interaction, and hydrogen bonding effects.

• #adsorption and biosorption for pollutant removal
• #plasma applications and diagnostics
• #electrohydrodynamics and fluid dynamics
• #wastewater

Low-temperature catalytic methane deep oxidation over sol-gel derived mesoporous hausmannite (Mn3O4) spherical particles

Patrick Ndouka Ndouka, Stéphane Kenmoe, Jacques Richard Mache, Elie Acayanka, Dick Hartmann Douma, Ralph Gebauer and 1 more

ChemPhysMater

In this study, Mn3O4 spherical particles (SPs) were synthesized by the sol-gel process, after which they were thermally annealed at 400°C, and comprehensively characterized. X-ray Diffraction (XRD) revealed that Mn3O4 exhibited a tetragonal spinel structure, and Fourier transformed infrared (FTIR) spectroscopy identified surface-adsorbed functional groups. Scanning electron microscopy (SEM) and the specific surface area analyses by Brunauer−Emmett−Teller (BET) revealed a porous, homogeneous surface composed of strongly agglomerated spherical grains with an estimated average particle size of ∼35 nm, which corresponded to a large specific surface area of ∼81.5 m2/g. X-ray photoelectron spectroscopy (XPS) analysis indicated that Mn3O4 was composed of metallic cations (Mn4+, Mn3+, and Mn2+) and oxygen species (O2−, OH− and CO32−). The optical bandgap energy is ∼2.55 eV. Assessment of the catalytic performance of the Mn3O4 SPs indicated T90 conversion of CH4 to CO2 and H2O at 398°C for gas hourly space velocity (GHSV) of 72000 mL3 g−1 h−1. This observed performance can be attributed to the cooperative effects of the smallest spherical grain size with a mesoporous structure, which is responsible for the larger specific surface area and available surface-active oxygenated species. The cooperative effect of the good reducibility, higher ratio of active species (OLat/OAds), and results of density functional theory (DFT) calculations suggested that the total oxidation of CH4 over the mesoporous Mn3O4 SPs might take place via a two-term process in which both the Langmuir−Hinshelwood and Mars−van Krevelen mechanisms are cooperatively involved.

• #catalytic processes in materials science
• #catalysis and oxidation reactions
• #advanced photocatalysis techniques
• #x-ray photoelectron spectroscopy

Low-Temperature Catalytic Methane Deep Oxidation over Sol-gel derived Mesoporous Hausmannite (Mn3O4) Spherical Particles

Patrick Ndouka Ndouka, Stéphane Kenmoe, Jacques Richard Mache, Elie Acayanka, Dick Hartmann Douma, Ralph Gebauer and 1 more

ChemRxiv

Herein, Mn3O4 spherical particles (SPs) were synthesized by the sol-gel process, followed by thermal annealing at 400 °C. The sample was analyzed by XRD, FTIR, SEM, SBET, XPS, H2-TPR and UV-vis spectroscopy. XRD and FTIR analysis show that Mn3O4 exhibits a tetragonal spinel structure. SEM and SBET analysis display a porous homogeneous surface made of strongly agglomerated spherical-like grains size with an estimated average particle size of ~35 nm, corresponding to a large specific surface area (SBET) of ~81.5 m2/g. XPS analysis indicated that, Mn3O4 were composed of metallic cations (Mn4+, Mn3+, Mn2+) and oxygen species (O2-, OH- and CO32-). The optical energy band gap energy was ~2.55eV. Moreover, Mn3O4 SPs were successfully tested as catalyst with almost 100% conversion of CH4 to CO2 and H2O at a gas hourly space velocity (GHSV) of 72 000 mL3.g-1h-1. The observed performance can be assigned to the cooperated effects of the smallest spherical-like grain size with mesoporous structure as responsible for the larger SBET, and the available surface-active oxygenated species. The cooperative effect of the good reducibility, the higher ratio of active species (OLat/OAds), as well as Density Functional Theory (DFT) calculations suggested that, CH4 total oxidation over the mesoporous Mn3O4 SPs might follow a two-term process in which both Langmuir-Hinshelwood and Mars-van Krevelen mechanisms are cooperatively involved.

• #catalytic processes in materials science
• #catalysis and oxidation reactions
• #mesoporous materials and catalysis
• #mesoporous material

Low-Temperature Catalytic Methane Deep Oxidation over Sol-gel derived Mesoporous Hausmannite (Mn3O4) Spherical Particles

Patrick Ndouka Ndouka, Stéphane Kenmoe, Jacques Richard Mache, Elie Acayanka, Dick Hartmann Douma, Ralph Gebauer and 1 more

ChemRxiv

Herein, Mn3O4 spherical particles (SPs) were synthesized by the sol-gel process, followed by thermal annealing at 400 °C. The sample was analyzed by XRD, FTIR, SEM, SBET, XPS, H2-TPR and UV-vis spectroscopy. XRD and FTIR analysis show that Mn3O4 exhibits a tetragonal spinel structure. SEM and SBET analysis display a porous homogeneous surface made of strongly agglomerated spherical-like grains size with an estimated average particle size of ~35 nm, corresponding to a large specific surface area (SBET) of ~81.5 m2/g. XPS analysis indicated that, Mn3O4 were composed of metallic cations (Mn4+, Mn3+, Mn2+) and oxygen species (O2-, OH- and CO32-). The optical energy band gap energy was ~2.55eV. Moreover, Mn3O4 SPs were successfully tested as catalyst with almost 100% conversion of CH4 to CO2 and H2O at a gas hourly space velocity (GHSV) of 72 000 mL3.g-1h-1. The observed performance can be assigned to the cooperated effects of the smallest spherical-like grain size with mesoporous structure as responsible for the larger SBET, and the available surface-active oxygenated species. The cooperative effect of the good reducibility, the higher ratio of active species (OLat/OAds), as well as Density Functional Theory (DFT) calculations suggested that, CH4 total oxidation over the mesoporous Mn3O4 SPs might follow a two-term process in which both Langmuir-Hinshelwood and Mars-van Krevelen mechanisms are cooperatively involved.

• #catalytic processes in materials science
• #catalysis and oxidation reactions
• #mesoporous materials and catalysis
• #mesoporous material

Plasma-assisted Synthesis of Supported Superparamagnetic Oxides for Enhanced Fenton Reactions

Nehemie Miloh, Verdiane K. Kengne, Elie Acayanka, Patrick M. Kouotou, Georges Y. Kamgang

Water Air & Soil Pollution

• #advanced oxidation water treatment
• #iron oxide chemistry and applications
• #advanced photocatalysis techniques
• #chemical engineering

Plasma-Synthesized Combined Nitrogen and Cationic Species Doped-MnO2: Impact on Texture, Optical Properties, and Photocatalytic Activity

Franck W. Boyom‐Tatchemo, Albert Poupi, François Devred, Elie Acayanka, Georges Kamgang‐Youbi, Carmela Aprile and 2 more

Catalysis Letters

• #catalytic processes in materials science
• #advanced photocatalysis techniques
• #nanomaterials for catalytic reactions
• #chemistry

Plasma synthesis of various polymorphs of tungsten trioxide nanoparticles using gliding electric discharge in humid air: characterization and photocatalytic properties

Romaric L. Seutcha, Georges Kamgang‐Youbi, Elie Acayanka, Valeria Vermile, François Devred, Éric M. Gaigneaux and 1 more

Plasma Science and Technology

Abstract A gliding electric arc (glidarc) discharge generates a low-temperature plasma at atmospheric pressure. When the discharge occurs in humid air as the feed gas, the chemistry of a glidarc plasma consists of in situ formation of HO° and NO° as the primary chemical species. Tungsten trioxide (WO 3 ) nanoparticles were successfully prepared by exposure of a liquid precursor to glidarc plasma. The WO 3 samples were calcined at three different temperatures (300 °C, 500 °C and 800 °C), resulting in different pure polymorphs: γ -WO 3 (at 300 °C), β -WO 3 (at 500 °C) and α -WO 3 (at 800 °C) according to x-ray diffraction analysis. The identification of WO 3 compounds was also confirmed by attenuated total reflection Fourier transform infrared spectroscopy analysis. Increase in the calcination temperature of WO 3 induced a decrease in its specific surface area according to Brunauer–Emmett–Teller nitrogen physisorption analysis. The UV-visible results showed that the absorption bands of plasma-WO 3 samples were more intense than those of WO 3 samples obtained by a precipitation route, a classical method used for comparison. Consequently, this parameter can improve the photocatalytic properties of WO 3 under visible light. The photodegradation (in sunlight conditions) of gentian violet, chosen as a model pollutant, confirmed the photocatalytic properties of plasma-WO 3 samples. This novel synthesis method has great potential to improve the efficiency of advanced tungsten trioxide-based functional material preparation, as well as in pollution-reducing and energy-saving tungsten extractive metallurgy.

• #transition metal oxide nanomaterials
• #gas sensing nanomaterials and sensors
• #advanced photocatalysis techniques
• #tungsten trioxide

Removal of Various Pollutants from Wastewater Using Plasma-Modified Lignocellulose-Derived as a Low-Cost Adsorbent: An Overview

Elie Acayanka, Jean-Baptiste Tarkwa, Brice Takam, Daouda Abia, Serge Nzali, Georges Y. Kamgang and 1 more

Mini-Reviews in Organic Chemistry

In their search for an alternative to commercial adsorbents, much research is turned to the local biomass-based materials such as agricultural residues and assimilated derivatives. However, natural biomass due to its low specific surface area must first undergo several pre-treatments. Among the newly emerging electric techniques for environmental applications, those who operate at atmospheric pressure (Non-thermal plasma) have recently found many breakthrough applications arising from their easy use with no extra additional reagents and their high reactivity. The Non-thermal plasma treatment of biomass is one of the promising developed approaches mainly due to significant effects including the formation of micro and macrospores, the increase of surface roughness, and surface functionalization. The most used plasma is non-thermal, so as not to denature the biomass, likewise the hot plasma can burn and/or destroy high contains carbon biomaterials. Especially, the gliding arc plasma obtained using moisten air as feeding gas, which is known to induce acidifying and oxidizing effects in an aqueous target. The primary species HO• radicals [E° (HO•/H 2 O) = 2.85 V/SHE] mainly formed in the arc will be with the dimer H 2 O 2 [E°(H 2 O 2 /H 2 O) = 1.76 V/SHE] the determining agents for the chemical reactions induced. Exposure of a target to this kind of environment is likely to promote great surface transformations. This approach has some advantages: (i) the merit of not using commercial chemical reagents, the reactive species being in situ generated; (ii) the risks related to the manipulation of the products, the plasma reactor is robust and can be modulated to treat large quantity; (iii) the efficiency of the bi-functionality of the plasma (acidifier and oxidative). In this review, we will highlight the main changes induced by exposure of biomass to plasma treatment and also make a comparative study between chemically and plasma-activated materials in the removal of various pollutants from aqueous solution; and finally, we summarize the findings in the existing literature.

• #plasma applications and diagnostics
• #oxidizing agent
• #surface modification
• #biomass (ecology)

Highly efficient degradation of azo dye Orange G using laterite soil as catalyst under irradiation of non-thermal plasma

Jean-Baptiste Tarkwa, Elie Acayanka, Bo Jiang, Nihal Oturan, Georges Y. Kamgang, Samuel Laminsi and 1 more

Applied Catalysis B: Environmental

• #advanced oxidation water treatment
• #plasma applications and diagnostics
• #environmental remediation with nanomaterials
• #laterite

Producing oxide catalysts by exploiting the chemistry of gliding arc atmospheric plasma in humid air

Antoine Tiya-Djowe, Elie Acayanka, Albert Poupi Mbouopda, William Boyom-Tatchemo, Samuel Laminsi, Éric M. Gaigneaux

Catalysis Today

• #advanced photocatalysis techniques
• #copper-based nanomaterials and applications
• #tio2 photocatalysis and solar cells
• #catalysis

Gliding arc plasma pre-treatment of kaolin in spatial post-discharge mode for removal of Reactive Red 2 dye from aqueous solution

Berthelot Sop-Tamo, Elie Acayanka, Franck W. Boyom‐Tatchemo, Serge Nzali, Georges Kamgang‐Youbi, Samuel Laminsi

Water Science & Technology

This study investigates the ability of spatial post-discharge mode functionalized kaolin to remove textile dye Reactive Red 2 from aqueous solution compared to that of the raw kaolinite. To fulfill the aim, the removal conditions, including plasma exposure time, processed mode (direct and post-discharge), pH of the aqueous dye solution, initial dye concentration and adsorbent dosage, were investigated. The changes that occur on clay surfaces before and after gliding arc plasma treatment were followed by Fourier transform infrared spectroscopy, scanning electron microscopy and nitrogen physisorption. The point of zero charge and the changes of the textural properties after gliding arc plasma treatment were also examined. The experimental data were analyzed using pseudo-first-order, pseudo-second-order and empirical Elovich models. The diffusion phenomenon was also studied. The results obtained indicate that spatial post-discharge pre-treatment of kaolin deeply influences the functional groups of some of its minerals as well as the morphology and texture of its particles. Consequently, at room temperature (∼30 °C), the maximum adsorption capacities of natural raw kaolin clay were tripled after treatment with gliding arc plasma in spatial post-discharge mode and were almost doubled after the direct treatment mode.

• #adsorption and biosorption for pollutant removal
• #landfill environmental impact studies
• #recycling and utilization of industrial and municipal waste in materials production
• #aqueous solution

Photo-Fenton oxidation of Orange G azo dye: process optimization and mineralization mechanism

Jean-Baptiste Tarkwa, Nihal Oturan, Elie Acayanka, Samuel Laminsi, Mehmet A. Oturan

Environmental Chemistry Letters

• #advanced oxidation water treatment
• #advanced photocatalysis techniques
• #tio2 photocatalysis and solar cells
• #chemistry

Reduction of sludge formed during a coagulation treatment of Ridomil Gold by means of non-thermal quenched plasma pre-treatment

Doringar Tadom, Georges Kamgang‐Youbi, Elie Acayanka, Njoyim Estella Buleng Tamungang, Samuel Laminsi

Environmental Monitoring and Assessment

• #analytical chemistry methods development
• #recycling and waste management techniques
• #environmental remediation with nanomaterials
• #coagulation

Gliding Arc Plasma Synthesis of MnO2 Nanorods for the Plasma-Catalytic Bleaching of Azoïc Amaranth Red Dye

Franck W. Boyom‐Tatchemo, Serge Nzali, Georges Kamgang‐Youbi, Antoine Tiya-Djowe, Duclair Kuete Saa, Elie Acayanka and 2 more

Topics in Catalysis

• #plasma applications and diagnostics
• #laser-ablation synthesis of nanoparticles
• #mercury impact and mitigation studies
• #catalysis

New-route synthesis of N-doped TiO2 via exposing the TiCl3 precursor to non-thermal quenched plasma at various times

Albert Poupi Mbouopda, Elie Acayanka, Franck W. Boyom‐Tatchemo, Georges Y. Kamgang, A.M. Nzeufa, Samuel Laminsi and 1 more

Materials Chemistry and Physics

• #tio2 photocatalysis and solar cells
• #advanced photocatalysis techniques
• #advanced nanomaterials in catalysis
• #x-ray photoelectron spectroscopy

Synergetic effect of gliding arc discharge treatment and biosorption for removal of nitrophene and glycine from aqueous solution

Daouda Abia, Serge Nzali, Elie Acayanka, Georges Y. Kamgang, Samuel Laminsi, P.M. Ghogomu

Journal of Industrial and Engineering Chemistry

• #adsorption and biosorption for pollutant removal
• #plasma applications and diagnostics
• #graphene research and applications
• #chemistry

Degradation of Dithizone by Non Thermal Quenched Plasma of Gliding Arc Type

Elie Acayanka, Samuel Laminsi, Peter T. Ndifon, Sop Tamo Berthelot, Jean‐Louis Brisset

Journal of Advanced Oxidation Technologies

Abstract Dithizone is an extracting agent largely used for metallurgical processes and has been found in waste waters. Its degradation is studied by exposing basic solutions to a gliding arc discharge burning in various gases (i.e., humid and dry air, humid air and tert-butanol) to underline the role of the formed °OH radicals and H

• #plasma applications and diagnostics
• #catalytic processes in materials science
• #analytical chemistry methods development
• #dithizone

Plasma-Assisted Synthesis of TiO2 Nanorods by Gliding Arc Discharge Processing at Atmospheric Pressure for Photocatalytic Applications

Elie Acayanka, Antoine Tiya-Djowe, Samuel Laminsi, C. C. Tchoumkwé, Serge Nzali, Albert Poupi Mbouopda and 2 more

Plasma Chemistry and Plasma Processing

• #electrohydrodynamics and fluid dynamics
• #gas sensing nanomaterials and sensors
• #catalytic processes in materials science
• #anatase

Surface Modification of Smectite Clay Induced by Non-thermal Gliding Arc Plasma at Atmospheric Pressure

Antoine Tiya-Djowe, Samuel Laminsi, Daniel Njopwouo, Elie Acayanka, Éric M. Gaigneaux

Plasma Chemistry and Plasma Processing

• #clay minerals and soil interactions
• #iron oxide chemistry and applications
• #recycling and utilization of industrial and municipal waste in materials production
• #clay minerals

Direct impact and delayed post-discharge chemical reactions of Fe II complexes induced by non-thermal plasma

Samuel Laminsi, Elie Acayanka, Serge Nzali, Peter T. Ndifon, Jean‐Louis Brisset

Desalination and Water Treatment

• #molecular junctions and nanostructures
• #mass spectrometry techniques and applications
• #graphene research and applications
• #ferrocene

PLASMACHEMICAL DISSOCIATION AND DEGRADATION OF NAPHTOL GREEN B COMPLEX

Jean‐Louis Brisset, Samuel Laminsi, Elie Acayanka, Peter T. Ndifon, Antoine Tiya-Djowe

Environmental Engineering and Management Journal

Exposure of a diluted solution of naphtol green B (50 mg L -1 ) complex to non-thermal plasma in humid air induced a rapid dissociation of the complex after 5 min of treatment.This dissociation of the complex is not only due to the acidifying species created by the discharge but also to the oxidizing species.The main properties of non-equilibrium plasma processes at atmospheric pressure (gliding arc plasma) are related to the high values of the oxidation potentials of the reactive species.Organic ligand once released in solution is gradually degraded to approximately 50.66% after 30 min of treatment.The relevant controlling kinetics are first zero order (for up to 5 min, with k 0 = 22.35 mgL -1 min -1 ) then pseudo-first order (k 1 = 0.05 min -1 ).This study established that exposing complex substrates to cold-plasma species can be used in recovering/recycling extraction solvents.

• #agricultural economics and practices
• #rice cultivation and yield improvement
• #dissociation (chemistry)
• #degradation (telecommunications)