This study is carried out to characterize the CHU-MEL effluents discharged into the Cotonou lagoon to assess the potential hazards of these releases for this ecosystem. To achieve this goal, the effluents collected at the end of the spillways have been analyzed. The results obtained from the physicochemical and microbiological analysis made it possible to assess the quality of the effluents. The pH, temperature and conductivity measured in-situ are, on average, 6.65, 30.3 °C and 763 μS/Cm. The average contents of dissolved oxygen, nitrite, nitrate, ammonium and Nitrogen Total Kjedhal (NTK) are respectively 1.

Organic photovoltaic performance has been investigated about the fluorination effects as one part on the optoelectronic properties. The quantum chemical accuracy of the optoelectronic and structural properties based on D-A (Donor-Acceptor) conjugated copolymers as PDTPQ X -type (Poly-dithieno-pyrrol-Quinoxaline) has been tediously exposed. The Donor-Acceptor in the copolymers was in our case constitutes to the Donor part in the photovoltaic device, while the Acceptor starting is the PC 60 BM in the same device, which composed the photovoltaic solar cells. The choice of the Donor part in the copolymers was obtained by their HOMO-LUMO bandgap and UV-visible absorption. The bandgap of the Donor part must be higher than that of the Acceptor part for an untroubled charges transfer from the Donor to the Acceptor according to the photovoltaic principle. The substitution of fluorine atoms (0F, 1F, 2F) on the quinoxaline constituents is an effective way to low the HOMO and LUMO energy levels of the alternating copolymers. This fluorine effect has been explored on the optoelectronic properties such as the HOMO-LUMO band gap E gap energy, the fill factor FF, the open circuit voltage V oc , the electron transfer energy ∆E et , the excitation energy ∆E ex , the absorption wave length λ and the oscillator strength OS. The equilibrium geometry at the ground state, the electronic structures as the frontier orbital isosurface have been obtained under the caster of the density functional theory (DFT) assist by the time-dependent density functional theory (TD-DFT) with M05 as exchange-correlation functional to come with 6-311G(d,p) basis set. Calculations were performed both in vaccuum and Chlorobenzene (CB) solvent with IEFPCM quantum model. All this has been done with the aim to enhance the energy gap, the V oc values and the fill factor FF, which exposed the nanomorphology as the topology of the solar cells photoactive layers. The results of this study show that these promote compounds systems as in the fluorination order are excellent candidates to build photovoltaic device in aim to enhance the open-circuit voltage for donor-acceptor heterojunctions used in organic solar cells.

This study is conducted to characterize the heavy metal contamination of CHU-MEL effluents discharged into the Cotonou lagoon in order to assess the potential risk of these discharges for this ecosystem. To achieve this objective, the effluents collected at the end of the pipes acting as weirs in the lagoon were analyzed. The results from physico-chemical and heavy metals analyzes have made it possible to assess the quality of the effluents. The values of pH, temperature, conductivity, TDS and dissolved oxygen measured in situ are, on average, 7.95; 29.60°C; 639.60 µS/cm; 457.48 mg/l and 0.22 mg/L. The determination of heavy metals in the effluents showed low levels of contamination. The average levels of lead, cadmium, mercury and total iron are 0.1727 mg/L, 0.0261 mg/L, 0.0010 mg/L and 0.25 mg/L, respectively. This study shows that most of the parameters studied in the CHU-MEL effluent are in compliance with the standards. These effluents therefore pose a low risk for the aquatic organisms of the receiving environment, this added to the dilution effect of the effluents in the waters of the lagoon. However, the continual discharge of these effluents into the lagoon with their share of heavy metals.