CI
Maître de Conférences
Scientific activity
Researcher profile
Faculty researcher at the University of Yaoundé I. Grade: Maître de Conférences.
Scientific publications
Frank Dorinel Solefack Feudjio, Cyrille Ghislain Fotsop, Donald Raoul Tchuifon Tchuifon, Julius Nsami Ndi, Rhaman Abdoul Ntieche, Horace Manga Ngomo and 1 more
Inorganic Chemistry Communications
Serge Benedoue, Julius Nsami Ndi, Min Ge, Zhihong Tian, Christian Brice Dantio Nguela, Haijian Tong and 4 more
ACS Sustainable Chemistry & Engineering
High Resolution Image Download MS PowerPoint Slide Herein, we introduce a controllable acid activation method of sulfur-doped carbon nitride (CN T ) to enhance its photodegradation efficiency for indigo carmine. We establish that the surface functionalization of sulfur-doped carbon nitride using a diluted H 2 SO 4 /H 2 O 2 aqueous solution treatment extends visible light absorption, promotes charge separation, and enables improvement in photocatalytic activity. More specifically, the optimal sample (E 1 -CN T ) exhibits a remarkable indigo carmine degradation performance of 96.27% (at 25 ppm) within 40 min under UV light irradiation, comparable to the top-performing photocatalysts reported in the literature. The apparent first-order rate constants of E 1 -CN T are 2× and 3.6× higher than those of unmodified CN T and bulk CN from melamine, respectively. This work provides new insights into designing simple, affordable, highly active, and metal-free materials toward sustainable environmental remediation.
Ernest Kentsa, Charles Fon Abi, Horace Manga Ngomo, Julius Nsami Ndi, Sary Awad, Joseph Ketcha Mbadcam
Environmental Science and Pollution Research
Aimé Victoire Abega, Horace Manga Ngomo, Isaac Nongwe, Hembe Elie Mukaya, Paul-Michel Adolphe Kouoh Sone, Xavier Yangkou Mbianda
Synthetic Metals
Christian Sadeu Ngakou, Gabche Solomon Anagho, Horace Manga Ngomo
Current Journal of Applied Science and Technology
Activated carbon obtained from ayous sawdust, Cucurbitaceae (egussi) peelings and the mixture of the two were studied for the adsorption of phenacetin. Characterisation of activated carbon by SEM and XRD analysis shows that the mixture of precursors combine the properties of activated carbon obtained separately. The well-knownbatch sorption models– Langmuir (one and two sites), Freudlich, Tempkin, Elovich, Langmuir-Freudlich, Redlich Peterson, Radke-Prausnitz, Fritz Shlunder)—were tested with experimental data for the adsorption of phenacetin to estimate adsorption equilibrium parameters—rate constantsand adsorption capacities. The model with the best fit was identified from extensive statistical analysis of the results of nonlinear regression of the experimental data. Comparison of the statistical errors in parameter estimation between linear and non-linear isotherm models shows that transformation of non-linear isotherm equations to linear forms implicitly alter their error structure. The much smaller size of the various error indicators —Determination Coefficient, R2; Sum of Square Errors, SSE; Chi Test, χ2; Average Relative Errors, ARE—, calculated for the case of non linearization when compared to linearization, indicate the greater accuracy in the application of non linearization. The Langmuir model (one site) gave the best fit and thus the values of adsorption capacity for each activated carbon were calculated from it. Kinetic models show that weak and strong interactions are involved in the adsorption process and that the controlling mechanism may not be limited to intra particle diffusion. The lower value of the boundary layer thickness in the case of activated carbon obtained from the mixture, justified the higher adsorbed quantity of this activated carbon compared to those of activated carbon from each precursor.
Christian Sadeu Ngakou, Horace Manga Ngomo, Solomon Gabche Anagho
Current Journal of Applied Science and Technology
Charles Melea Kede, Peter P. Ndibewu, Makonga M. Kalumba, Nikolay Panichev, Horace Manga Ngomo, Joseph Mbadcam Ketcha
South African Journal of Chemistry
Activated carbon prepared from Theobroma cacao pod husk was used as a low-costbiosorbent for the removal of mercury(II) from aqueous solutions. The influence of pH and contact time on the adsorption was investigated by conducting a series of batch adsorption experiments. The equilibrium data were fitted to the Langmuir and Freundlich isotherm models. The Langmuir isotherm was found to best describe the experimental data. The amount adsorbed increased with increasing temperature. The maximum adsorption capacity of mercury was found to be 105 ng g-1 for an initial mercury concentration of 100 ppb. The kinetics of adsorption were modelled by means of the Lagergren-first-order and pseudo-second-order models. The pseudo-second-order model was found to explain the adsorption kinetics most effectively. It was also found that pore diffusion played an important role in the adsorption, and intra-particle diffusion was the rate-limiting step during the first 30 min. A FTIR study revealed that the carbonyl and sulfur functional groups present on the surface of the adsorbing material were involved in chemical interaction with mercury(II).
J. Ketcha, David Joh Dina, Horace Manga Ngomo, N. J. Ndi
Zenodo (CERN European Organization for Nuclear Research)
Aims: To set up high adsorbent materials at lower cost from agricultural wastes in this case maize cobs and to characterize these materials. Study Design: Determination of the textural and physicochemical properties of the prepared materials. Place and Duration of Study: Technological University of Chalmers, Nuclear Chemistry Laboratory, Goteborg, Sweden, between November 2010 and January 2011. Methodology: Five activated carbon samples of maize cobs were prepared by chemical activation with zinc chloride (ZnCl2). They were characterized and the values of their textural (SEM images and XRD patterns) and physicochemical properties (specific surface area, pore volume, pore size and functional groups) were determined and compared with those of a commercial activated carbon of animal origin. Results: The results showed that the part of the cob used, the residence time, the quantity and the state of the activating agent affected the activated carbon produced. Thus, the carbon material obtained from the woody belt (hard part of the cob) showed the most significant properties with a specific surface area of 701.68 m2/g and a porous volume of about 0.39 cm3/g. On the other hand, samples obtained from the soft part of the cob mixed with small particles of woody belt, gave low specific surface area (0.43-11.62 m2/g) and porous volumes (0.00028-0.11 cm3/g). In addition, all these chars presented acidic functions at their surfaces. Conclusion: The study revealed that maize cobs particularly the hard part of the cobs, an agricultural waste, can be used as raw material for the preparation of activated carbon.
Solomon Gabche Anagho, Horace Manga Ngomo, F. Ambe
Energy Sources Part A Recovery Utilization and Environmental Effects
Raw pulverized cellulosic waste materials, fresh bituminous oils obtained from their hydrogenation, and distillates of these oils stored for one year were analyzed using infrared spectroscopy, gas chromatography, and Lasseigne's sodium fusion test, to determine the functional groups added during hydrogenation, the range of compounds present in the oils, their stability during storage, and suitability as petrochemical feedstock. The results showed that oxygen and nitrogen, which were present in the raw cellulosic materials, were no longer found in the fresh hydrogenation products. These elements reappeared during storage to show that the oils were unstable. They were also found to contain unsaturated hydrocarbons of low molecular weight, similar to products obtained from catalytic cracking and reforming of petroleum, to suggest that they can be used as feedstock for petrochemical industries.
Joseph Ketcha Mbadcam, Horace Manga Ngomo, Kouotou Daouda
The present paper reports the removal of cyanide ions from aqueous solutions using Cu/PAC, Ni/PAC, Cu/Clay and Ni/Clay adsorbents at pH=11. At this pH, the cyanide is completely dissociated into its ions. Equilibrium data fitted Langmuir and Freundlich isotherms well. The applicability of the isotherm equation to describe the adsorption process was judged by the correlation coefficients, R 2 , values. The Langmuir model yielded the best fit with R 2 values equal to or higher than 0.960, as compared to the Freundlich model. The fact that 1/n values range from 0.20 to 0.58 indicates that the adsorption of cyanide ions onto these metal supported adsorbents is also favored by the Freundlich model.
Alfred A. Susu, Emmanuel O Ogogo, Horace Manga Ngomo
Process Safety and Environmental Protection
Alfred A. Susu, Horace Manga Ngomo, O. A. Olafadehan, Elizabeth Tador
Chemical Engineering Communications
The deactivation data obtained from the multiple regeneration of platinum-containing catalysts were utilized to explore the efficiency of reforming catalyst utilization. The data were collected in a CSTR at a total pressure of 101.325 kPa and W/F values up to 0.33 g min/cm3. The reactive system investigated was the re-forming and coking of n-octane and methylcyclopentane on the monometallic Pt/Al2O3 and the bimetallic Pt-Re/Al2O3 catalysts. The deactivation models combined the kinetic equation with the coking equation; both of these equations were derived from mechanistic models. The kinetic expressions were based on the models of Susu et al. for n-octane reaction and Dartingues et al. for methylcyclopentane reaction. The coking mechanism of Corella and Asua was used for the coking reaction. The coupling of the two models resulted in a dynamic expression, and the parameter estimates were carried out without decoupling the main reaction from the coking reaction. The model formulation affords the estimation of the level of residual activity by the incorporation of a factor, f, representing incomplete deactivation. A high value of f was obtained for all deactivation-kinetic data indicating high utilization efficiency for the catalysts for the two reactants, regardless of the large difference in the coking ability of the hydrocarbon species.
Solomon Gabche Anagho, Horace Manga Ngomo, JOHN ONO EDEWOR
Energy Sources
A kinetic study was carried out on the upgrading of cellulosic wastes to bituminous oil (synthetic oils) by hydrogenation. An autoclave, run batchwise at high temperature and pressure was used. Each pulverised cellulosic material was slurried in gas oil and the autoclave was pressurised with hydrogen. Cellulose hydrogenation was found to proceed by free radical mechanism. A rate expression derived from the postulated mechanism showed that cellulose hydrogenation was first order with respect to cellulose concentration and the reaction rate 0.128 mol m−3 s−1. This rate was found to be independent of the cellulose source and the initial hydrogen pressure in the reactor. The yield of bituminous oils was 40% by mass of the cellulose fed. This equivalent to producing 18 tonnes of oil a day, implying that by this process, it would be possible to supplement petroleum and at the same time properly disposing of cellulose wastes.
Joseph Ketcha Mbadcam, Horace Manga Ngomo, Jérôme Avom, David Daniel Dina Joh
Environnement Ingénierie & Développement
The theoretical calculation of the number of active sites of four activated carbon samples (2SAP/C, COM3, NC 35 and NCF O.5/2) during the adsorption of tartaric acid from solution has revealed that the number of accessible active sites on the surface increases with increased pH. It also appears that the number of active sites for the basic activated carbon (NC 35 and NCF 0.5/2) is greater than that of the acidic activated carbon (2 SAP/C and COM 3). The results obtained are in agreement with those obtained by Freundlich and Langmuir models such that the classification for the four samples is as follows: 2 SAP/C < COM 3 < NC 35 < NCF 0.5/2. It is also observed that the dispersion on the surface of the activated carbon increases with the total number of accessible activated sites and decreases with the total number of sites in the sample. Le calcul théorique du nombre de sites actifs lors de l'adsorption de l'acide tartrique en solution par quatre échantillons de charbons actifs commerciaux (2SAP/C, COM3, NC 35 et NCF O.5/2) révèle que le nombre de sites actifs accessibles à la surface de ces charbons croît avec le pH. Il apparaît également que vis-à-vis de l'adsorption de l'acide tartrique, les charbons actifs basiques (NC 35 et NCF 0.5/2) ont plus de sites actifs que les charbons actifs acides (2SAP/C et COM 3). Les résultats obtenus, en accord avec ceux obtenus par exploitation des modèles de Freundlich et de Langmuir, montrent que le pouvoir adsorbant varie dans l'ordre 2 SAP/C < COM 3 < NC 35 < NCF 0.5/2. On démontre également que la dispersion à la surface des charbons actifs augmente avec le nombre de sites actifs et diminue avec la grosseur des particules de charbon.
Horace Manga Ngomo, Alfred A. Susu
Petroleum Science and Technology
Experiments have been carried out to study the effects of coke composition on combustion parameters and burn-off time in the regeneration of coke-deactivated supported alumina catalyst. At high temperatures, results showed that the combustion behaviour is dependent on coke type as oxidizable and reduceable coke profiles versus time showed different trends. The curves of coke burn-off profiles were found to depend on the initial amount of coke deposited and on the oxygen concentration in the regenerating gas mixture. The higher the oxygen concentration, the shorter the time it takes to burn the same amount of coke. The high temperature combustion was assumed to follow the unreacted core model on the basis of which a model relating various parameters in coke deactivation was derived and the various dependencies demonstrated graphically for the different coke types. Oxidizable coke data fitted the linear model equation adequately while reducible coke data did not—another evidence of the difference in the kinetics of removal. Results further show a direct proportionality relationship between amount of coke accumulated under the same conditions and amount removed, confirming that the type of coke deposited is a function of accumulation conditions.
Horace Manga Ngomo, Alfred A. Susu
Petroleum Science and Technology
The various types of coke found deposited on a deactivated Pt/Al2O3 reforming catalyst are described. They are claSsified into major types: oxidiZable (primary) coke, reducible (secondary) coke and non oxidizable and non reducible (tertiary) coke. Primary coke is generally non toxic to catalytic hydrocarbon conversion as its removal restores initial catalyst activity. The secondary and tertiary forms are, however, toxic to this reaction. A methodology for the prolongation of reforming catalyst life is evident from these results. In the new method, secondary coke is also removed from the catalyst surface subsequent to primary coke removal. Results of the application of this methodology using accelerated aging of Pt/Al2O3 catalyst is presented. The overall catalyst life was extended for up to 52 deactivation-regeneration cycles from the 23 previously reported. Catalyst life was not correlated with the oxidizable and reducible coke content. These profiles were found to be aperiodic and exhibited a nonlinear dynamic behavior. In contrast, catalyst life per cycle of deactivation-regeneration correlate with the rate of oxidizable coke deposition. The model coking reaction investigated was the dehydrogenation of cyclohexane to benzene in nitrogen carrier at 430°C on a commercial Pt/Al2O3 catalyst using a Berty CSTR.
Dominic O. Onukwuli, Horace Manga Ngomo, Alfred A. Susu
Petroleum Science and Technology
The conversion of n-octane on Pt/Al2O3 catalyst to hydrocracked products, isooctane, ethylbenzene, o-,p-,m-xylene and toluene was investigated in hydrogen in a Berty CSTR at three different partial pressures of n-octane, 101·325 KPa total pressure, temperatures between 400°C-460°C and W/F values up to 0·33gmincm-3. The hydrocracked products were the most predominant. Of the other products, isooctane was present in the highest yield. A sequence of elementary steps based on the suggested reaction network of Ako and Susu (1986) was found to predict the experimental conversion-W/F data with the conversion of adsorbed isooctane to adsorbed o-xylene as the rate determining step. The activation energies for the forward and backward reactions of this step were determined to be 21·2 and 14·3 Kcal/gmol, respectively.
Horace Manga Ngomo, Alfred A. Susu
Chemical Engineering Communications
Two reaction deactivation kinetic models of the deactivation of cyclohexane on platinum/alumina catalyst have been proposed based on the coking mechanism of Corella and Asua and the reaction mechanism of Susu el al. The difference in the models was in the number of active sites participating in the coking reaction represented by h with h = 1 in model 1 and h ≠ 1 in model 2. The models were dynamic models and parameter estimates were carried out by a method that did not require decoupling of the main from the coking reaction. The model formulation has made possible the estimation of the level of residual activity by the incorporation of a factor, ƒ, that represents incomplete deactivation. For the deactivation kinetic data studied, a high value of ƒ; was obtained indicating a low residual activity. The models were found to give a good fit with the data. The standard deviation of the models from experimental were 10.21 % for model 1 (h ≠ 1) and 12.63% for model 2 (h ≠ 1), None of the models is superior to the other, though for having a lower standard deviation model I is better. It is therefore appropriate to propose that deactivation by coking in this work occurred preferably by a single site mechanism of the rate controlling step of the coking reaction.
Horace Manga Ngomo, Charles Fon Abi, Gaëlle Tatiana Ngnie Tuemgnie, Patrice Kenfack Tsobnang, Joseph Ketcha Mbadcam
Asian Journal of Water Environment and Pollution
The removal of Co(II) ions by two Cameroon clays&mdash;kaolinite and smectite as adsorbents&mdash;was investigated in a batch system. The effect of Co(II) ions initial concentration, Co, pH and contact time, t, has been studied in terms of kinetic models. The experimental data fitted well the pseudo-second order kinetic model allowing the rate constant to be evaluated. This study shows that these clays could be used as important efficient adsorbent materials for the uptake of Co(II) ions from aqueous solution at low initial concentrations. This study is important for the treatment of Co(II) ions effluent where continuous removal can be achieved on a large scale.
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