Kopoin Adouby’s research while affiliated with Institut National Polytechnique Félix Houphouët-Boigny and other places

In this study, a new multiobjective optimization of the simultaneous removal of phosphates and nitrates by electrocoagulation was studied using the Box-Behnken design. Ten aluminium electrodes, connected in a monopolar configuration in a batch reactor, were immersed in synthetic wastewater and then in real wastewater. The optimal conditions and the effects of parameters (current intensity, electrolysis time and initial pH) on phosphate and nitrate removal, the formation of by-products, and the operating cost were assessed in the case of synthetic wastewater. This optimization allowed to eliminate 89.21 % of phos­phates, 69.06 % of nitrates with an operating cost of 3.44 USD m-3 against 13.67 mg L-1 of ammonium generated. Optimal conditions applied to real domestic wastewater made it possible to remove 93 % of phosphates and 90.3 % of nitrates with an ammonium residual of 30.9 mg L-1. The addition of sodium chloride reduced the residual ammonium content to 2.95 mg L-1. Further, XRD analysis of the sludge showed poor crystal structure and the FTIR spectrum suggested that the phosphate is removed by adsorption and co-precipitation.

This study investigated the removal and recovery of ammonium ( NH4+ ) and phosphate ( PO43− ) from anaerobically digested slaughterhouse wastewater as struvite (MgNH4PO4; 6H2O). Nutrients removal experiments were conducted by the addition of magnesium sulfate MgSO4 as a Mg2+ source to the wastewater. The effects of Mg2+: PO43− ; Mg2+: NH4+ ; Mg2+: NH4+ : PO43− molar ratios and pH on NH4+ and PO43− removal were monitored. To verify the recovery of NH4+ and PO43− as struvite, the precipitates obtained during the experiments were analyzed by X-ray diffraction. The results showed that the increase of Mg2+ concentration and raising the pH to 10 leads to a significant improvement of NH4+ and PO43− removal. The molar ratio of Mg2+: NH4+ : PO43− = 1: 19: 0.58 and a pH=9 gave optimal removal of NH4+ and PO43− . The characterization of the precipitates by X-ray diffraction showed the presence of struvite crystals, confirming the recovery of NH4+ and PO43− in struvite. Key words: Nutrient removal, Nutrient recovery, Struvite precipitation, Slaughterhouse wastewater.

This research is a case study for the search for an alternative energy to natural gas for heating the chicks of the Brin Foundation located in Yaokokro (Ivory Coast). Specifically, this study aims to reduce carbon monoxide in biogas using biochar and activated carbons prepared from plantain peels. The challenge is to use the purified biogas as an alternative energy source for heating the chicks. Three adsorbents from plantain peel were produced and characterised: 1-Biochar (BC), 2- Potassium hydroxide activated carbon (AC-K) and 3-iron oxide function- alized activated carbon (AC-Fe). Subsequently, their adsorption capacity on carbon monoxide was evaluated. The values obtained for carbonisation yield, moisture and ash content show that the raw material used is suitable for the production of activated carbon biochar. In addition, the surface morphology allows the observation of as- perities on the surface of the adsorbents which can be either macropores, mesopores or micropores. The adsorption curves showed that AC-Fe has the longest saturation time of 615 minutes compared to 191 minutes and 188 minutes for BC and AC-K respectively. Furthermore, BC, AC-K and AC-Fe have absorption capacities of 0.77, 0.84 and 3.79 mgCO/g respectively. AC-Fe has a 4.9 times higher adsorption capacity than BC and 4.5 times higher than AC-K. The same case is observed for the percentage of CO removal: 6.9%, 59.83% and 79.19% for BC, AC-K and AC-Fe respectively. According to the efficiency of the adsorbents, they can be classified in the following order: BC < AC-K < AC-Fe. Thus, among the adsorbents used, AC-Fe has the best adsorption capacity and the longest saturation time

A comparative study between anaerobic settling and anaerobic digestion was evaluated during the treatment of slaughterhouse wastewater. Anaerobic settling and anaerobic digestion were carried out using reactor capacities of 220 L and 5 L respectively under mesophilic temperature conditions. The results show that anaerobic digestion led to a stable reactor with a VFA/TA ratio<0.4. However, reactor instability is observed during anaerobic settling due to the decrease in pH to 6. For phosphate and ammonium, both treatments lead to an increase in their residual concentrations due to the biodegradation of nitrogen and phosphorus compounds. As for the organic matter, only the anaerobic settling does not allow its removal because the acid character of the treated water favors the inhibition of acetogenesis and methanogenesis. However, the solubilization of organic matter during anaerobic settling significantly improves the biodegradability of the treated wastewater. Thus, this study reveals that anaerobic settling can be used as an excellent method for wastewater pretreatment before the application of anaerobic digestion. Finally, the Comparative … Kouakou Eric ADOU et al. biological reactions during anaerobic settling deserve to be studied to further their knowledge.

Corbula trigona shell powder (CTSP) was modified by a hydrothermal method using phosphoric acid to remove fluoride ions from groundwater. This method was performed by keeping the Ca/P molar ratio constant at 1.67. Fourier Transform Infrared Spectroscopy (FT-IR), X-Ray Diffraction (XRD) and scanning electronic microscopy (SEM) analysis confirmed the formation of hydroxyapatite (HAP) after CTSP pre-treatment. Batch adsorption experiments were conducted in beakers containing modified-CTSP. Moreover, the modified-CTSP dose variated from 0.1 to 0.8 g, in the presence of 100 mL of groundwater. This groundwater was contaminated by 2.20 mg/L of fluoride. Adsorption kinetics indicated that the adsorption process was governed by pseudo-second-order kinetics. Furthermore, the reaction rate constant for fluoride removal was 0.161 g mg⁻¹ min⁻¹. Also, adsorption isotherms showed that fluoride removal was mainly controlled by physical adsorption with 4.517 mg g⁻¹ maximum adsorption capacity. But the relatively low enthalpy value (∆adH⁰ < 200 kJ.mol⁻¹) indicated that during the adsorption process, very low interactions occurred between fluoride and modified-CTSP. The adsorption process was spontaneous, endothermic, and irreversible in nature. The best results with 89 % fluoride removal were recorded at pH 7.5 ± 0.1 in 175 min with 5 g/L modified-CTSP. These results showed that HAP derived from Corbula trigona shell waste can be a promising sorbent for groundwater fluoride removal in developing countries.

The Tongon mine, the largest gold mine in Côte d'Ivoire, has been in operation since April 2010. However, to our knowledge to date, no study has been conducted on metallic contamination in suspended particulate matter (PM10 and PM2.5) where there is a lack of information on the carcinogenic and non-carcinogenic risk to human health associated with the exposure of populations in the Tongon area to these pollutants. The general objective of this study is to evaluate the level of contamination of PM10; PM2.5 by heavy metals and their impact on the health of populations exposed Application… Koné et al.2022 to these pollutants in the Tongon gold mine area. The sampling and measurement of suspended particulate matter (PM10 and PM2.5) was done using a MiniVol TAS passive air sampler. Heavy metal concentrations were determined by inductively coupled plasma mass spectroscopy (Nex ION 2000 ICP-MS, USA). The results indicate that the average concentrations of suspended particles (PM10 and PM2.5) obtained are all above the recommended exposure limits. In addition, among the heavy metals contained in the suspended particles, the concentrations of arsenic and nickel are high and all above the standard limit values. The assessment of the health risks related to the inhalation of PM10 particles reveals that their inhalation over a long period could cause a carcinogenic risk.

This study aimed at understanding the influence of the generation of oxidants in a heterogeneous way at boron-doped diamond (BDD) anode (anodic oxidation (AO)) or homogeneously in the bulk (electro-Fenton (EF)) during treatment of a textile industry wastewater. Both processes achieved high TOC removal. A yield of 95% was obtained by combining EF with BDD anode during 6 h of treatment. The EF process was found to be faster and more efficient for discoloration of the effluent, whereas AO was more effective to limit the formation of degradation by-products in the bulk. An advantage of AO was to treat this alkaline effluent without any pH adjustment. Operating these processes under current limitation allowed optimizing energy consumption in both cases. However, using BDD anode led to the formation of very high concentration of ClO3⁻/ClO4⁻ from Cl⁻ oxidation (even at low current density), which appears as a key challenge for treatment of such effluent by AO. By comparison, EF with Pt anode strongly reduced the formation of ClO3⁻/ClO4⁻. Operating EF at low current density even maintained these concentrations below 0.5% of the initial Cl⁻ concentration. A trade-off should be considered between TOC removal and formation of toxic chlorinated by-products.

The performance of a two-stage process combining anaerobic digestion (AD) and electrocoagulation (EC) was studied for the treatment of slaughterhouse wastewater (SWW). Anaerobic digestion was used as primary treatment, whereas electrocoagulation process was used as secondary treatment. After anaerobic digestion, the optimal current density and the treatment time for Chemical Oxygen Demand (COD) and P-PO43− removal by electrocoagulation using Fe and Al electrodes were determined. These optimal conditions were finally used for the secondary treatment of slaughterhouse wastewater by electrocoagulation. The primary treatment by anaerobic digestion removed of 49.93 ± 0.37% COD. However, this led to an increase in residual concentration of P-PO43−. The optimal conditions for COD and P-PO43− removal by electrocoagulation were obtained with a current density of 18.18 mA/cm² and a treatment time of 40 min for both types of electrodes. The secondary treatment by electrocoagulation respectively resulted from a total removal of 79.73±0.75% and 80.12±0.85% COD, 95.90±0.03% and 95.42±0.11% NO3−, and 92.48±0.20% and 90.66±0.36% of turbidity, respectively, with Fe and Al electrodes. This study reveals the complementarity of anaerobic digestion and electrocoagulation could be the basis of a process able to simultaneously remove organic and inorganic pollutants for various applications (municipal and industrial wastewater treatment, etc.).

Persulfate activation by heterogeneous catalysts based on transition metals is of interest in textile effluent treatment processes. Thus, iron-rich electrocoagulation sludge has been thermally treated to obtain new catalysts. The characterization of this catalyst by X-ray diffraction revealed the presence of FeAl2O4 nanoparticles active in the decomposition of persulfate into sulfate radicals (SO4•-). The efficiency of catalyst/persulfate was monitored during the methylene blue (MB) solution discoloration. The effects of temperature, pH, initial MB concentration, catalyst dose and persulfate dose were also studied. MB removal catalytic activity showed around 94% discoloration and 45.7% TOC reduction after 180 minutes batch reaction at pH = 4.0 (catalyst dose: 0.5 g/L, persulfate dose: 1 g/L; initial MB concentration: 20 mg/L). This catalyst reuse further confirmed its catalytic potential as a discoloration rate of about 82.45% was obtained after five cycles. The biodegradability monitoring measured by the carbon oxidation state (COS) has revealed a remarkable and continuous degradation of organic compounds. The EPR tests revealed that this catalytic reaction generates the radical species responsible for the degradation of MB. Finally, these results show that this catalyst from the thermal activation of electrocoagulation sludge is capable of decomposing persulfate to degrade bioresistant compounds such as textile dyes.