Dereje Tadesse Mekonnen

Background: This research aimed to evaluate the use of natural resin as a binder for the production of fuel briquette from solid waste biomass. Methods: Proximate analyses were made for fuel briquette prepared from solid waste biomass using natural resin as a binder in comparison with using starch as a binder. Results: The results for density, percent content of moisture, percent content of volatile matter, percent content of ash, percent content of fixed carbon, and the caloric value of solid waste biomass obtained were 158.23 kg/m3 , 18.25%, 65.99%, 4.78%, 10.98%, and 18.65 MJ/kg, respectively. Besides natural resin binder-used fuel briquette was characterized for its density, percent content of porosity weight index, percent content of shatter resistance, percent content of moisture content, percent content of volatile matter, percent content of ash content, percent content of fixed carbon content, and caloric values as 751.05 kg/m3 , 13%, 40%, 4%, 12%, 1%, 30%, and 27.05 MJ/kg, respectively. In the same way, the starch binder-used fuel briquette was characterized for its density, percent content of porosity, weight index, percent content of shatter resistance, percent content of moisture content, percent content of volatile matter, percent content of ash, percent content of fixed carbon, and caloric values as 760 kg/m3 , 10%, 42%, 4%, 11%, 2%, 31%, and 28.09 MJ/kg, respectively. Conclusion: According to the results of the study, it can be concluded that all characterized properties using natural resin as a binder indicate almost comparative properties in comparison with the use of starch as a binder.

The excessive discharge of phosphate from anthropogenic activities is a primary cause for the eutrophication of aquatic habitats. Several methodologies have been tested for the removal of phosphate from aqueous solutions, and adsorption in a flow-through reactor is an effective mechanism to reduce the nutrient loading of water. This research aimed to investigate the adsorption potential of leftover coal material to remove phosphate from a solution by using continuous flow fixed-bed column, and analyzes the obtained breakthrough curves. A series of column tests were performed to determine the phosphorus breakthrough characteristics by varying operational design parameters such as adsorbent bed height (5 to 8 cm), influent phosphate concentration (10–25 mg/L), and influent flow rate (1–2 mL/min). The amorphous and crystalline property of leftover coal material was studied using XRD technology. The FT-IR spectrum confirmed the interaction of adsorption sites with phosphate ions. Breakthrough time decreased with increasing flow rate and influent phosphate concentration, but increased with increasing adsorbent bed height. Breakthrough-curve analysis showed that phosphate adsorption onto the leftover coal material was most effective at a flow rate of 1 mL/min, influent phosphate concentration of 25 mg/L, and at a bed height of 8 cm. The maximal total phosphate adsorbed onto the coal material’s surface was 243 mg/kg adsorbent. The Adams–Bohart model depicted the experimental breakthrough curve well, and overall performed better than the Thomas and Yoon–Nelson models did, with correlation values (R²) ranging from 0.92 to 0.98. Lastly, leftover coal could be used in the purification of phosphorus-laden water, and the Adams–Bohart model can be employed to design filter units at a technical scale.

The contamination of surface and groundwater with phosphate originating from industrial and household wastewater remains a serious environmental issue in low-income countries. Herein, phosphate removal from aqueous solutions was studied using low-cost volcanic rocks such as pumice (VPum) and scoria (VSco), obtained from the Ethiopian Great Rift Valley. Batch adsorption experiments were conducted using phosphate solutions with concentrations of 0.5 to 25 mg·L⁻¹ to examine the adsorption kinetic as well as equilibrium conditions. The experimental adsorption data were tested by employing various equilibrium adsorption models, and the Freundlich and Dubinin-Radushkevich (D-R) isotherms best depicted the observations. The maximum phosphate adsorption capacities of VPum and VSco were calculated and found to be 294 mg·kg⁻¹ and 169 mg·kg⁻¹, respectively. A pseudo-second-order kinetic model best described the experimental data with a coefficient of correlation of R² > 0.99 for both VPum and VSco; however, VPum showed a slightly better selectivity for phosphate removal than VSco. The presence of competitive anions markedly reduced the removal efficiency of phosphate from the aqueous solution. The adsorptive removal of phosphate was affected by competitive anions in the order: HCO₃⁻ >F⁻ > SO₄⁻² > NO₃⁻ > Cl⁻ for VPum and HCO₃⁻ > F⁻ > Cl⁻ > SO₄⁻² > NO₃⁻ for VSco. The results indicate that the readily available volcanic rocks have a good adsorptive capacity for phosphate and shall be considered in future studies as test materials for phosphate removal from water in technical-scale experiments.

Background: Contamination of water bodies by phosphorus has caused ecological problems worldwide. Phosphate, an essential macro-nutrient for aquatic systems, causes eutrophication where industrial and household activities lead to excess amount of it to water bodies through wastewater. Modern and low-cost treatment technologies to remove phosphate from wastewater are sorely needed for developing countries. Objective: We investigated and evaluated design parameters to remove phosphate by sorption onto crushed volcanic rock common in Ethiopia where eutrophication of waters from waste streams is common. Methodology: Kinetic and equilibrium sorption experiments were conducted to evaluate removal of phosphate from aqueous solutions by crushed pumice and scoria volcanic rocks common in the main rift valley of Ethiopia. Washed and dried rocks was ground to 0.075 to 0.425mm particle size and variable amounts immersed in molal concentration of Phosphate for 240min to fully saturate the exchange sites at adjusted pH. We methodically evaluated contact time, solution pH, initial concentration of phosphate, ground rocks quantity, and particle size effects on the removal of phosphate. Phosphate was measured by molybdenum-blue ascorbic acid method using continuous flow analyzer. Zero point charges of the ground rocks were measured using solid addition method with KNO₃ as solution maker and impact of co-existing ions on the adsorption was also employed. Results: The values of point zero charge were measured to be 7.2 and 9.3 for pumice and scoria respectively at fine particle size. The maximum removal capacities of phosphate 294.30mg/Kg and 168.95mg/Kg were obtained for pumice and scoria respectively for a phosphate concentration of 10mg/L, fine particle size (0.075mm to 0.425mm), pH 6.05, crushed rock doze 40g/L and contact time of 240min. The experimental data are well described by the pseudo-second- order equation with a correlation value of R² > 0.99. Langmuir, Freundlich and Dubinin Radushkevich isotherm models were examined and fitted to the experimental data. Conclusion: kinetic and adsorption isotherm results showing it is practical to use volcanic pumice and scoria to remove phosphate from water, but additional testing in a flow-through set-up is required to reach efficiency of the approach for the practical application.

High loadings of wastewater with phosphors (P) require purification measures, which can be challenging to realize in regions where the technical and financial frame does not allow sophisticated applications. Simple percolation devices employing various kinds of adsorbents might be an alternative. Here, we investigated the application of leftover coal, which was collected from Ethiopian coal mining areas, as an adsorbent for the removal of phosphate from aqueous solutions in a classical slurry batch set-up. The combined effects of operational parameters such as contact time, initial concentration, and solution pH on P retention efficiency was studied employing the Response Surface Methodology (RSM). The maximum phosphate adsorption (79% removal and 198 mg kg−1 leftover coal) was obtained at a contact time of 200 min, an initial phosphate concentration of 5 mg/L, and a solution pH of 2.3. The Freundlich isotherm was fitted to the experimental data. The pseudo second-order equation describes the experimental data well, with a correlation value of R2 = 0.99. The effect of temperature on the adsorption reveals that the process is exothermic. The results demonstrate that leftover coal material could potentially be applied for the removal of phosphate from aqueous media, but additional testing in a flow-through set-up using real wastewater is required to draw definite conclusions.