No abstract

The intensification of agricultural, domestic and industrial activities leads to the increasing contamination of groundwater and surface water by nitrates. Indeed, agricultural runoff, septic tank effluents, landfill leachates or wastewater treatment plant effluents contribute to this nitrification, yet drinking water containing high nitrate content can cause health problems. The study examines the improvement of nitrate removal in synthetic water solution by adsorption on banana peel's activated carbon (BPAC). Different effects of physicochemical parameters, such as the optimal contact time of BPAC in solution, the pH of the nitrate solution, the initial concentration of nitrate solution, the BPAC mass, and the temperature were evaluated. The study revealed that BPAC has a low nitrate adsorption capacity under normal laboratory conditions. However, this adsorption capacity of BPAC increases with increasing of temperature and initial content of nitrate, while it decreases with increasing BPAC mass. For a content of 100 mg/L nitrate solution, the maximum adsorption capacity was 0, 687 mg/g for an equilibrium time of 180 min. Nitrate adsorption is optimal in acidic media (pH=3). The application of kinetic models to the experimental data showed that the mechanism of nitrate adsorption on BPAC obeys pseudo-first order kinetics. The Freundlich isotherm perfectly describes the mechanism of nitrate adsorption on BPAC.

Aims: Pollution by wastewaters from various urban activities such as artisanal dyeing plants is a real problem for developing countries. The treatment of wastewater by the adsorption method is carried out by means of less expensive and available adsorbent media. Two techniques of the adsorption method are possible: adsorption in continuous mode (column adsorption) and adsorption in discontinuous mode (batch adsorption). The choice of the continuous adsorption technique is justified by its ability to process large volumes of solutions. In this study, dyes contained in wastewater from artisanal dyeing plants were removed by continuous adsorption in a fixed-bed column of deactivated lichen biomass (Parmotrema dilatatum). Study Design: Random design Place and Duration of Study: Laboratory of Thermodynamics and Environmental Physico-Chemistry (University Nangui Abrogoua, Ivory Coast) between May 2020 and October 2020. Methodology: Four (4) categories of wastewater were collected in artisanal cotton and leather dyeing plants through two municipalities of the city of Abidjan, economic capital of Ivory Coast. Two (2) wastewaters colored in blue from dyeing of cotton boubous and jeans and two (2) wastewaters colored in red from dyeing of leather jackets and bags. These wastewaters were treated through the fixed bed column of deactivated lichens. The column feed rate was set at 0, 07 L.min-1 and the adsorbent bed mass at 100 g. Results: The study showed that, regardless of the nature of the dyed object and regardless of the target dye, the amount of dye adsorbed was better with waters of higher initial concentration. Thus the best amount of adsorbed dye is 44.444 mg.g-1 and the best removal rate is 97.9%. These values are obtained with the red wastewater of bags (RWB) treatment which was the most concentrated wastewater. Conclusion: Good efficiency of deactivated lichen bed as adsorbent for the in situ removal of dyes from wastewater by continuous adsorption.