Meseret Dawit Teweldebrihan

Chromium, a prevalent heavy metal pollutant originating from various industrial processes, poses significant risks if not properly treated. In this study, batch adsorption of hexavalent chromium (Cr ⁶⁺ ) from water was performed using activated carbon derived from Cordia africana . This application represents a novel approach, as the use of this material for Cr ⁶⁺ removal has not been previously explored. The adsorbent was analyzed through Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), and the Brunauer–Emmett–Teller (BET), and Fourier Transform Infrared (FTIR) methods, revealing its structural and surface properties. Adsorption kinetics followed the pseudo-first-order model (R² = 0.99), while the Koble Corrigan isotherm (R² = 0.98) most accurately expressed the adsorption behavior. The adsorption experiments achieved a maximum Cr⁶⁺ adsorption capacity of 52.2 mg/g. Thermodynamic studies indicated that the process is spontaneous and endothermic. Reusability tests demonstrated the stability of the adsorbent over five cycles, with removal efficiencies ranging from 99.7 to 75.1%. Overall, Cordia africana leaf-based activated carbon exhibited a promising adsorption capacity, making it a cost-effective and readily available adsorbent suitable for industrial wastewater treatment.

Phenol and its derivatives in water and wastewater are highly toxic and challenging to degrade, posing serious environmental and health risks. Therefore, this research focuses on the removal of phenol from aqueous solutions using activated carbon made from Catha edulis stems. The activation process involved impregnating the Catha edulis stems with phosphoric acid followed by thermal treatment at 500 °C for 2 h. The resulting adsorbent was extensively characterized using various techniques, including Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), Brunauer–Emmett–Teller (BET) surface area analysis, and proximate analysis. Batch adsorption experiments were designed using a full factorial approach with four factors at two levels, resulting in 16 different experimental conditions. The characterization results showed that the activated carbon has a high surface area of 1323 m²/g, a porous and heterogeneous structure, and an amorphous surface with multiple functional groups. Under optimal conditions of pH 2, a contact time of 60 min, an adsorbent dosage of 0.1 g/100 mL, and an initial phenol concentration of 100 mg/L, the adsorbent achieved a phenol removal efficiency of 99.9%. Isotherm and kinetics analyses revealed that phenol adsorption fits the Langmuir model and pseudo-second-order kinetics, indicating a uniform interaction and chemisorptive process. This study highlights the effectiveness of Catha edulis stem-based activated carbon as a promising material for phenol removal in water treatment applications.

Heavy metal contamination of water sources has emerged as a major global environmental concern, affecting both aquatic ecosystems and human health. Therefore, this study aims to remove hexavalent chromium from an aqueous solution utilizing activated carbon developed from Spathodea campanulata. Chemical treatment with H₃PO₄ followed by thermal activation was employed to enhance the adsorption capability of the precursor material. On the other hand, a full factorial design of 2⁴ including pH (3 and 9), contact time (30 and 60 min), initial chromium concentration (40 and 100 mg/L), and adsorbent dosage of 0.2 and 0.6 g/100 mL was used to optimize the batch-wise adsorption of hexavalent chromium. The characterization results showed that the prepared activated carbon is composed of various functional groups (FTIR), a high specific surface area of 1054 m²/g (BET), morphological cracks (Scanning Electron Microscopy), and a pH point of zero charge of 5.8. The maximum removal efficiency of 96.5% was recorded at optimum working conditions of pH 3, contact time of 60 min, adsorbent dosage of 0.6 g/100 mL, and initial chromium concentration of 40 mg/L. Additionally, kinetics and isotherm studies revealed that the pseudo-second-order model with R² of 0.98 and the Sips model with R² of 0.99 were found to fit the adsorption data better, suggesting homogenous surface and chemisorption. Overall, this research suggests that Spathodea campanulata could be a promising natural source for the development of adsorbents with potential applications in remediating chromium-saturated wastewater at an industrial scale.

An untreated biosorbent derived from the leaves of Cordia africana was utilized in this study for the first time to remove malachite green (MG) dye from aqueous solutions via batchwise adsorption. Comprehensive characterizations of the biosorbent were conducted, including Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), and determination of the pH point of zero charge (pHpzc). The adsorption process was investigated under varying operational conditions: biosorbent dosage (0.25–0.65 g/100 mL), contact time (25–50 min), initial pollutant concentration (15–45 mg/L), and solution pH (4–9). Kinetic and isothermal models were employed to evaluate the adsorption mechanism. Characterization revealed an amorphous, heterogeneous surface. The biosorbent achieved an impressive MG removal efficiency of 98.9%, with a maximum Langmuir adsorption capacity (Q _max ) of 6.25 mg/g, indicating a monolayer chemisorption process in agreement with Langmuir and pseudo-second-order kinetics models. This study highlights the cost-effectiveness and potential of Cordia africana leaf-based biosorbent as a sustainable and efficient solution for the decolorization of MG-laden industrial effluents, providing a pathway for practical, large-scale applications.

This study dives into the essential issue of sustainable water management techniques in East Africa. Recognizing water as a key component of sustainable agricultural development, the study highlights the importance of a complete approach that takes into account technological, socio-economic, and environmental issues. A detailed, comprehensive review of 109 scientific research articles published between 1993 and 2024 was conducted to acquire a thorough grasp of current sustainable water resource management techniques in East Africa. This in-depth investigation sought to uncover major regional trends, challenges, and opportunities in water resource management. Furthermore, the evaluation aimed to identify specific knowledge gaps impeding the region’s implementation of sustainable water management techniques. As East Africa faces rising problems from climatic variability and change, which have a direct impact on water availability and agricultural output, the need for comprehensive policies becomes clear. The review reveals significant gaps in previous research, including a lack of focus on the socio-economic consequences of water management methods, gender dynamics, long-term assessments, indigenous knowledge integration, and climate change adaptation. By highlighting these areas, the study emphasizes the necessity of future research in addressing these gaps and developing more effective and sustainable water management solutions for East Africa.

This study dives into the essential issue of sustainable water management techniques in East Af-rica. Recognizing water as a key component of sustainable agricultural development, the study highlights the importance of a complete approach that takes into account technological, socio-economic, and environmental issues. As East Africa faces rising problems from climatic variability and change, which have a direct impact on water availability and agricultural output, the need for comprehensive policies becomes clear. The review reveals significant gaps in previous research, including a lack of focus on the socioeconomic consequences of water management methods, gender dynamics, long-term assessments, indigenous knowledge integration, and climate change adaptation. By highlighting these areas, the study emphasizes the necessity of future research in addressing these gaps and developing more effective and sustainable water management solutions for East Africa.

Freshwater scarcity is becoming more of a concern as populations grow and economic demands increase. The Dhidhessa River, a critical source for the Abbay River basin, is under pressure. This study looked at how water resource development projects and changes in water flow impact the basin. Water flow was simulated using WEAP model (software), which took into account various water sources and needs. The study also looked at crop water requirements and the level of flow alteration. Future water demand scenarios were created. The first, scenario considered population growth, with projections indicating that unmet water demand would increase significantly by 2050. The second scenario focused on irrigation expansion, which resulted in a significant increase in unmet water demand. These findings demonstrate the impact of both population growth and water resource development for irrigation activities. The study further investigated how flow alterations affect the river. While most months saw little change, a particular section near Dembi was discovered to be more vulnerable. Remarkably, allocating water specifically for environmental needs, in addition to human demands, resulted in a decrease in unmet water demand. This suggests that prioritizing environmental flow management is critical for long-term water use in the Dhidhessa River basin.

This work focused on the decolorization of methyl red (MR) from an aqueous solution utilizing Rumex abyssinicus-derived biochar (RAB). RAB was prepared to involve unit operations such as size reduction, drying, and carbonization. The pyrolysis of the precursor material was carried out at a temperature of 500 °C for two hours. After that, the prepared RAB was characterized by the pH point of zero charge (pHpzc), the Brunauer–Emmett–Teller (BET) method, Scanning Electron Microscopy (SEM) and Fourier-Transform Infrared (FTIR) spectroscopy. On the other hand, a batch adsorption experiment of MR removal onto RAB was conducted, considering four operating parameters: pH, contact time, adsorbent dose, and initial dye concentration. The characterization of the adsorbent material revealed a porous and heterogeneous surface morphology during SEM, a specific surface area of 45.8 m²/g during the BET method, the presence of various functional groups during FTIR, and a pHpzc of 6.2. The batch adsorption experiment analysis results revealed that a maximum removal efficiency of 99.2% was attained at an optimum working condition of pH 6, contact time of 40 min, initial dye concentration of 70 mg/L and adsorbent dosage of 0.2 g/100 mL. Furthermore, Freundlich isotherm (R² = 0.99) and pseudo-second-order kinetics (R² = 0.99) models confirmed the heterogeneous surface interaction and chemisorption nature. Generally, this study highlighted that RAB could be a potential adsorbent for the detoxification of MR-containing industrial effluents.