Arsenic pollution is a public health hazard in Burkina Faso due to its impact on human health and water resources. To mitigate this pollution, ferrihydrite material has been synthesized and characterized to be used as adsorbent for arsenic removal in aqueous solutions. This study aimed to contribute to improve of access to clean drinking water by removing arsenic from water using ferrihydrite. Arsenic species such as As(III) and As(V) were removed through batch adsorption. Experiments were carried out in batch mode using arsenic aqueous solutions. The characterization of ferrihydrite using Scanning Electron Microscopy (SEM) coupled with Energy Dispersive Spectroscopy (EDX), X-ray Diffraction (XRD), Infrared (IR), and Brunauer Emmett Teller (BET) showed that an amorphous and microporous 2-line ferrihydrite. The total specific surface area and pH at point of zero charge (pH_pzc) were 184.518 m²/g and 9.41, respectively. The optimal adsorbent doses were 4 g/L for As (V) and 8 g/L for As (III). The optimum pH range for the adsorption of As (V) and As (III) was between 2 and 10, The maximum adsorption capacity was 15.07 mg/g for As(V) and 13.01 mg/g for As(III) with increasing concentration between 2 and 16 mg/L. Equilibrium time for As (V) and As (III) on ferrihydrite was found to be 720 min and 960 min, respectively. The adsorption of As(V) and As(III) was consistent with the Langmuir monolayer model on ferrihydrite. Arsenic adsorption was occurred according to spontaneous chemical reaction. Arsenic removal was occurred on a monolayer following the pseudo-second order kinetic.

In Burkina Faso, water resources in mining area are sometime polluted by cyanide. To mitigate this pollution, clays have been collected in Kaya and Koro and used as adsorbents to remove cyanide in waters. Experiments have been carried out using batch adsorption with synthetic cyanide solutions. The influence of operating conditions has been evaluated on adsorption capacity. From experimental results, the particle size did not have a great impact on the cyanide removal rate up to 150 µm in diameter. The increase of initial pH from 6.5 to 11 led to a decrease in the cyanide removal capacity adsorption from 9.5 to 7.6 and the volatility rate of cyanide from 6 to 2%. When the initial concentration was increased between 5.5 and 224 mg/L, this resulted an increase in adsorption capacity from 0.8 to 23.5 mg/g and a decrease in the removal rate from 95 to 47%. The contact time increased with the temperature, it was respectively 3; 4 and 8 H for Koro and 4; 6 and 12 H for Kaya respectively at 20; 30 and 40°C. The adsorption of cyanide was described by an exothermic and spontaneous process occurred on monolayer through a chemisorption following a pseudo-second order kinetic.

This study investigated the performance of Ferromagnetic Carbon (FC) as an effective natural adsorbent for arsenic removal from groundwater in Dong Thap Province (Vietnam). To do this, leaching fixed-bed column experiments have been carried out. The influence of operating variables affecting the process was studied, under varying operating conditions and experimental data were modelled using bed depth service time (BDST) and mass transfer approaches. Speciation studies showed that the groundwater contained 48.5% of particulate arsenic and 51.5% of soluble arsenic. Indeed, As (III) and As (V) forms represented respectively 41.9% and 58.1% in the dissolved arsenic. As removal was parametric depending such as pH, flow rate, initial As and adsorbent mass, requiring an optimization for optimum conditions When the pH increased from 3 to 11, removal of As(V) decreased from 96.5% to 5% while As(III) removal increased from 40% to 69%. The increase of initial arsenic has caused an increase in removal efficiency of different forms of arsenic. The easy regeneration of FC using a molar sodium hydroxide solution suggests that is an efficient and low-cost material to reduce the contamination of arsenic in drinking groundwater.

Consumption of arsenic-contaminated water is the cause of major problems such as melanosis, hyperkeratosis and cancer. To mitigate this pollution, this study was carried out using analytical methods to prepare chemically treated laterite (TL) and chemically doped laterite with ferrihydrite (DL). The adsorbents were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), inductively coupled plasma atomic emission spectrometry (ICP-AES), X-ray fluorescence (XRF) and the Brunauer Emmett Teller (BET) method. The specific surface area, bulk density and pH at zero charge point ( pH_PZC) of TL and DL ranged from 81.306 to 40.099 m²/g, from 1.67 to 2.27 and from 5.41 to 8.02, respectively. The SiO₂/(Fe₂O₃ + Al₂O₃) ratio was 0.31 for TL and 0.20 for LD, showing that the materials prepared were still classified as laterite adsorbents. Experimental results from batch experiments on the removal of arsenic species (As (III)) and arsenic (As (V)) using two adsorbents showed the strong influence of operating conditions such as pH, initial concentration, adsorbent dose and contact time. The isotherm modelling concluded that the removal of arsenic species was occurred by multilayer adsorption on the heterogenous surfaces of laterites. For the removal of As(V), the maximum adsorption capacity was 7.36 and 9.79 mg/g for TL and DL, respectively, while for the removal of As (III), the adsorption capacity for TL and DL was 5.17 and 7.89 mg/g, respectively. The kinetic study of the adsorption of As(V) or As(III) on modified laterites concluded that the process was described by the pseudo-second-order model, with a chemisorption process to be explored.

In Burkina Faso, chemical inputs are used massively in market gardening to increase the yields. The misuse of these chemicals is responsible of contamination of market garden products, leading to the rapid rotting of vegetables. The objective of this study was to determine the pesticides in chemical inputs applied on vegetables produced in Ouagadougou City. To do this, lettuce has been sampled from producers in three sites (Tanghin, Boulmiougou and Kossodo) and pesticides amounts have been analyzed using Gas Chromatography coupled with mass spectrometry. Chemical analyses have carried out on three lettuce samples and the extraction of chemical input residues was done according to QuEChERS (Quick Easy Cheap Effective Rugged and Safe) method. Results revealed the presence of six (06) pesticide molecules (chlordimeform, quintozene, lindane, cypermethrin, α-cypermethrin, δ-deltamethrin) in Boulmiougou sample, four (04) molecules (methomyl, cypermethrin, α-cypermethrin, δ-deltamethrin) in Kossodo sample and three (03) molecules (cypermethrin, α-cypermethrin, δ-deltamethrin) in Tanghin sample. In this regard, analysis of pesticide amount revealed that the quantity of molecules was acceptable for the consumer, but these pesticides could contribute to the rapid rotting of our vegetables which generates economic and social losses for the country.