Nowadays freshwater quality deterioration and quantity depletion are rapidly increasing across the globe. Especially fluoride polluted groundwater is causing a severe shortage of water supply and public health problem. Hence, this study was designed to investigate the performance of activated carbon produced from the Catha edulis stem for the removal of fluoride from aqueous solution. A C. edulis stem sample was collected from dumping sites of Addis Ababa City and its activation and carbonation processes were performed using H2SO4 and a high temperature of 600 °C. The experimental study was designed to use a full factorial approach with a 33 which were the three factors with the three levels, namely pH (2, 7 and 9), contact times (60, 90 and 120 min) and adsorbent doses (0.5 g, 1.0 g and 1.5 g in 100 mL) at the initial fluoride concentration 30 mg/L which resulted in 81 experimental runs in triplicates. The calculated maximum adsorption capacity of 18 mg/g was found under the Langmuir isotherm, whereas the Freundlich model (R2 0.98) better fitted the experimental data, which indicated that the adsorption process was multilayer and cooperative. The maximum fluoride removal of 73% was observed at the optimum condition of adsorbent dose of 1.5 g in 100 mL contact time of 60 min and pH 2, whereas the predicted value of the fluoride removal of 69% was calculated under the same experimental condition. Fluoride removal was positive and strongly influenced by the adsorbent dose, whereas the adsorption pH was negatively and weakly impacted on removal. Generally, the performance of activated carbon for the removal of fluoride from aqueous solution is promising. The study also indicated that C. edulis activated carbon is a potential candidate for water treatment technology.

False banana /Ensete ventricosum [Welw.] Cheesman/ is exploited as a food crop in Ethiopia where it represents an important staple food. The plant is harvested and large amounts of biomass residues are originated, mainly from the pseudo stem (i.e., fiber bundles obtained from the leaf sheaths after being scrapped to produce starchy food) and the inflorescence stalk. These materials were studied in relation to their summative chemical composition, composition of lignin, lipophilic and polar extracts. Moreover, their structural characteristics, in view of their valorization, were scrutinized. The analytical studies were performed with the aid of FTIR, GC/MS, Py-GC/MS and SEM. The fiber bundles are aggregates of mainly long and slender fibers with low ash, extractives and lignin contents (3.8%. 4.4% and 10.5% respectively) and high holocellulose and α-cellulose contents (87.5% and 59.6% respectively). The hemicelluloses in the fibers are mostly highly acetylated xylans and the lignin is of the H-type (H:G:S, 1:0.7:0.8). This lignin composition is in line with the FTIR peaks at 1670 cm^-1 and 1250 cm^-1.The inflorescence stalk has high ash content (12.3% in the main stalk and 24.6% in fines) with a major proportion of potassium, high extractives (25.9%), and low lignin and α-cellulose contents (5.8% and 17.9% respectively). The stalk includes numerous starch granules in the cellular structure with the predominant presence of parenchyma. The potential valorization routes for these materials are clearly different. The fiber bundles could be used as a fiber source for paper pulp production with the possibility of a prior hemicelluloses removal while the inflorescence stalk has nutritional value for food and fodder. Furthermore, it can also be used for sugar fermentation products.

Background. The demand for diesel fuel is constantly increasing, requiring its alternate that could be sustainable, technically feasible, price competitive, and ecologically acceptable. Biodiesel is one of ecologically acceptable substitute for the conventional fuels. Methods. Sufficient lime fleshing waste was collected from Addis Ababa tannery share company. The limed fleshing waste in the wet condition was delimed using boric acid, dried, chopped, and subjected to Soxhlet extraction using petroleum ether solvent. The oil was treated by orthophosphoric acid and distilled water to remove gums. The pretreated oil was subjected to homogeneous base catalyzed transesterification. Response surface was used to optimize the process variables. GC-MS was used to see composition of the biodiesel produced. Result. The oil yield of the goat, hide, and sheep delimed fleshing wastes were 23.08%, 12.05%, and 26.7%, respectively. The conversion to biodiesel by KOH-catalyzed transesterification was achieved above 96% under optimum conditions: a methanol-to-oil molar ratio of 6:1, catalyst amount of 1 % w/w, and reaction temperature of 60°C for an hour reaction time. Conclusion. It was proven that fleshing wastes from tanneries whose storage and disposal are both troublesome and costly could be transformed to a fuel with low emission values and a performance close to diesel fuel.