ABSTRACT:In this work, electrocoagulation and chemical coagulation were applied to the exit effluent of a textile factory located at Douala (Cameroon).The investigations were focused on the operational (pH, conductivity) and pollution parameters (COD, total phosphorus, turbidity). The electrolytic treatment was carried out with 0.4 A current intensity, and chemical coagulation was conducted in adding initially to the effluent the same quantities of aluminium than that electrogenerated.the elimination of pollution contents depended on the quantity of Al 3+ ions produced by the electrodissolution of the aluminium anode and that of the aluminium salt dissolved in solution. In fact, 58.86, 94.44 and 97.81% of COD, total phosphorous and turbidity were respectively removed by electrocoagulation, while hemical coagulation, the turbidity was also reduced roughly at the same level as by electrolytic treatment. Also, 56.08 and 63.64% COD and total phosphorus were respectively removed by chemical route. During electrocoagulation, highest removals were reached after 2.49x10 -3 mol of aluminum was released in solution (after 30 minutes of treatment). Thus, the final pH obtained by this process was around 9 and the conductivity varying slightly, compared to the initial value. By contrast, chemical coagulation rendered the effluent more acidic and more conducting (γ> 4 mS.cm -1 ). Electrocoagulation is the best process, by the fact that the textile effluent treated by this technique can be re-used or rejected without risk in the environment. Chemical coagulation: indeed, the corrosive nature of effluent treated by this method and the significant content of the residual phosphorus can seriously inhibit the perspective of recycling.
Phytochemical investigations on the dechlorophyllated extract of Anthocleista schweinfurthii Gilg (Loganiaceae) leaves have enabled the isolation of two xanthones derivatives: 1,8-dihydroxy-2,6-dimethoxyxanthone (1) and 1-hydroxy-3,7,8-trimethoxyxanthone (2) known, respectively, as swertiaperenin (1) and decussatin (2), but isolated here for the first time from this plant. The structures of these compounds were investigated by rigorous analysis of their one- and two-dimensional NMR spectral data. Compounds (1) and (2) were evaluated for their antioxidant activities using the 1,1-diphenyl-2-picrylhydrazyl method (DPPH°); the reducing power of iron III (FRAP) and antibacterial activity by the solid diffusion method on three bacteria strains (Escherichia coli, Staphylococcus aureus, and Bacillus cereus). The results obtained show that the two compounds have good antioxidant and antibacterial activities. Obviously, swertiaperenin and decussatin are among the active secondary’s metabolites responsible for the biological activity of A. schweinfurthii Gild recognized by the Cameroonian populations.
Water pollution by oils is more and more a preoccupation because of its increasing occurrence and the hazard to human life and environment. Depollution of oily effluents can sometimes generate a secondary pollution (with chemical coagulation / flocculation processes) or be very costly (ultracentrifugation). In this work, electrocoagulation with aluminium electrodes was applied to the treatment of a worn mineral oil effluent. For this to be achieved, the influence of the pH and the current density on the turbidity and organic matter was first investigated. A liquid-liquid extraction was then carried out on the oil samples in order to isolate hydrocarbons and study their behaviour. Finally, these hydrocarbons were analysed by gas chromatography (GC-FID) to evaluate their removal efficiency. The results obtained showed that optimal conditions were as follows: initial pH=7 and current density = 10.98 mA.cm-2. The results obtained with a supporting electrolyte concentration set at 0.5 mg.L-1 showed that optimal conditions were as follows: initial pH=7 and current density = 10.98 mA.cm-2 .) In these conditions, the turbidity was almost totally eliminated and organic matter removal efficiency was 93.30%. Analyses of the various chromatograms showed that 98.83, 99.56 and 93.02% respectively of aliphatic fraction, unsaturated hydrocarbons and polycyclic aromatic hydrocarbons (PAHs) were eliminated during electrocoagulation of the worn mineral effluent. However, the absence of regular peaks was observed on the chromatograms, and that was due to unidentified heavy PAHs. Thus, FID did not seem sensitive enough to identify and characterize PAHs compounds based only on retention.
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