Department of Chemistry
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Item Comparative Evaluation of Digestion Methods for Heavy Metal Analysis in Soil, Water, and Plants from Tigray, Ethiopia(Mekelle University, 2025-08-25) Robel Dawit AregayHeavy metal contamination is a growing concern in Tigray, Ethiopia, due to mining activities, agricultural inputs, and potential risks to public health, yet no standardized local protocol exists for reliable, cost-effective, and accurate digestion methods essential for environmental monitoring. This study compared four wet digestion methods—Method A (HCl–HNO₃, 3:1), Method B (HCl–HNO₃–H₂SO₄), Method C (HCl–HNO₃–HClO₄), and Method D (HCl–HNO₃– HClO₄–HF)—for determining total concentrations of Cu, Zn, Pb, Co, Cr, Cd, Mn, Fe, and Ni in soil, plant, and water samples from Ezana Mining Development PLC, Mekelle, Ethiopia, using Flame Atomic Absorption Spectrophotometry (FAAS). Performance evaluation based on accuracy (Z-scores and spiking recovery), precision (relative standard deviation), and costeffectiveness, supported by one-way ANOVA (p < 0.05), revealed significant differences among methods, with overall recoveries ranging from 88% to 102% across matrices. Methods A and D showed superior accuracy and precision compared to Methods B and C, with Method A offering comparable performance to Method D while being simpler, safer, and more economical, making it suitable for routine monitoring. Although Method D achieved slightly higher extraction efficiencies for refractory metals, it demands specialized infrastructure, HFhandling safety, and advanced technical expertise. The findings suggest Method A is best suited for general environmental assessments in resource-limited laboratories, while Method D is recommended for targeted analyses requiring maximum recovery, thereby enhancing environmental data quality, strengthening heavy metal monitoring programs, and supporting evidence-based policy decisions in Tigray.Item Assessment of Heavy Metal Levels in Soil, Vegetables and Wastewater used for Irrigation in Wukro, Tigray, Ethiopia(Mekelle University, 2025-09-25) Nigisti GirumFresh vegetables and fruits are the most common foods of human diet all around humankind often used for balanced diet, prevention and treatment of various diseases. However, if these vegetables and fruits grow in a polluted environment they can be a major public concern due to their toxic property which leads to acute and chronic health effects. The aim of this study was to determine the level of manganese, chromium, copper, zinc and lead and to estimate their health risks associated with their daily intake in vegetables grown in Wukro town, Tigray. FAAS was used to determine concentrations of those heavy metals in selected vegetables (cabbage, onion, spinach, lettuce and tomato). 1 gm of each sample was digested by wet digestion method using a mixture of HNO3 (69%), HClO4 (70%) and H2O2 (30%) until a clear solution was prepared. After proper dilutions, the solutions were aspirated into the FAAS. The absorbance value of heavy metals was converted in to concentration using linear calibration curve equation. Finally, the concentration of each metal was expressed in mg/Kg of dry weight of each sample and health risk was estimated by using estimated daily intake (EDI), target hazard quotient (THQ), and hazard index (HI) for selected heavy metals. The validity of the method was checked by the analysis of spiked samples whose recovery was found in the range of 90.8-107.0% and %RSD value in the range of 0.03-7.7%. The average concentrations of Cr and Cu in all of the selected vegetables were lower than the maximum limit of normal values. However, concentrations (mg/kg) of Pb in cabbage (2.05), spinach (2.47), and lettuce (1.56) had exceeded the safe limit, 0.3 mg/Kg set by FAO/WHO. Hence, consuming plant products grown from contaminated water sources such as municipal wastes, industrial effluents, engine fuels, garages disposals, constructions and car washes are potentially toxic to plants, animals and humans. Therefore, people and concerned bodies should take care of the sources of water for irrigationItem EVALUATION OF AIR POLLUTION CONTROL TECHNIQUES IN MESSEBO CEMENT FACTORY, TIGRAY, ETHIOPIA(Mekelle University, 2025-09-25) Araya GebreyohannesCement production is one of the most emission-intensive industrial activities, contributing significantly to global air pollution and greenhouse gas emissions. This study assesses the effectiveness, limitations, and implementation status of air pollution control techniques and their associated occupational health impacts at Messebo Cement Factory PLC (MCF) in Northern Ethiopia. A mixed-method design was employed, integrating quantitative on-site pollutant measurements (CO₂, NOₓ, SO₂, CO, and particulate matter) with qualitative surveys and clinical health data. Field results indicated that pyroprocessing and raw material handling were the dominant emission sources. CO₂ emissions increased from approximately 78,884 tonnes in 2000/01 to 990,767 tonnes in 2015/16, primarily due to production expansion, while per-tonne emissions remained above international best practice benchmarks. Particulate matter concentrations at raw milling points reached 240 mg/Nm³, exceeding Ethiopia’s national limit of 150 mg/Nm³ and the WHO/IFC guideline of 50 mg/Nm³. Despite the presence of baghouse filters and other emission control systems, frequent exceedances revealed operational inefficiencies and maintenance deficiencies. Survey data from 1,235 respondents, including factory employees and nearby residents, showed that 65% observed visible dust emissions and 76% reported receiving no environmental or safety training. Analysis of clinical records from 2013–2017 further revealed high incidences of respiratory tract infections (up to 22.4%) and dermatitis linked to particulate exposure. The findings demonstrate that current air pollution control and occupational health practices at MCF are inadequate to meet regulatory and safety standards. The study recommends upgrading filtration systems, adopting cleaner fuels, improving occupational health and safety management, and aligning operations with ISO 14001 and IFC/World Bank environmental standards to promote sustainable industrial performanceItem Quantitative Analysis of Potentially Toxic Elements (Pb, Cd, Co, Cr, Fe, Mn, and Ni) in Lipstick Brands Available in Mekelle Markets, Tigray, Ethiopia(Mekelle University, 2025-09-25) Asfaw Mulugeta GebremedhinLipsticks, widely used cosmetic products, can be a significant source of potentially toxic elements exposure through unintentional ingestion. This poses potential long-term health risks due to the bioaccumulative nature of metals like Pb, Cd, and Cr. This study aimed to quantify the concentrations of seven potentially toxic elements (Pb, Cd, Co, Cr, Fe, Mn, and Ni) in three widely available and commonly sold lipstick brands from local markets in Mekelle, Ethiopia. Samples were prepared using a wet acid digestion method with a concentrated 5:1:1 mixture of HNO3, HCl, and H2O2 and analyzed through Flame Atomic Absorption Spectrophotometer (FAAS). Cd was not detected in any sample. The concentration ranges across all samples in ppm were: Pb (0.0400–0.1000), Co (3.740–5.570), Cr (10.62–18.05), Fe (75.00–1838), Mn (0.1500–0.1600), and Ni (12.83–51.41). The levels of Pb were well below the 10 ppm guidance limit set by international bodies like Health Canada, U.S. Food and Drug Administration (FDA), their consistent presence is a concern. However, concentrations of Cr and Ni, known sensitizers, were notable. As an intentionally added pigment, Fe showed the highest and most variable concentrations. Although the detected levels of toxic metals were within international permissible limits, their consistent presence is a public health concern. Given the direct ingestion route and frequency of application, daily use may contribute to the cumulative body burden of these metals over time. This study, though limited by a small sample size, highlights the urgent need for healthy regulatory oversight and routine quality control of cosmetics in Ethiopia. Further research is essential to assess a wider range of products and evaluate the associated health risks for consumers.Item Adsorption-Based Defluoridation of Water Using Volcanic Rock Materials(Mekelle University, 2025-06-28) Tekle Brhanu GessesewFluoride (F-) contamination in water poses serious health risks, demanding effective and affordable removal methods. Therefore, this study aimed to evaluate activated pumice, which is a low-cost and ecofriendly adsorbent, for the removal of fluoride via batch adsorption. The pumice was activated by thermal treatment at 550°C followed by acid treatment with 0.1M HCl, enhancing its surface area and reactivity. The material was characterized using Scanning Electron Microscope, X-ray diffraction, and Fourier-Transform Infrared Spectroscopy. SEM images showed fractured, porous, and rough surface morphology favorable for adsorption. XRD analysis revealed a broad hump, indicating an amorphous structure, the FTIR spectra also showed peaks around 3740 cm-1, corresponding to O-H stretching, confirming the presence of hydroxyl groups and surface-bound water molecule; while peaks at 1001 cm-1 and 779 cm-1 confirming the presence of a silicate, aluminosilicate framework. Key parameters, including contact time (15–90 min), pH (3–11), dose (0.5–2.5 g), and initial fluoride concentration (2– 14 mg/L), were optimized at a constant shaking rate (250 rpm) at room temperature. Maximum Fremoval occurred at a contact time of 60 min, a dose of 0.5 g, and an initial F- concentration of 10 mg/L. A UV-visible spectrophotometer was utilized to measure F- using the SPADNS reagent (2- parasulfophenylazo)-1,8-dihydroxy-3,6-naphthalene disulfate. Adsorption kinetics followed the pseudosecond-order model (R2=0.99), described by the Freundlich isotherm model (R2 =0.99), indicating multilayer adsorption on a heterogeneous surface. A field study using a real water sample from Semema, Tigray, Ethiopia, demonstrated a maximum adsorption capacity of 1.59 mg/g. These findings indicated that activated pumice is a promising locally available material for F- removal, offering an effective and sustainable option for community water treatment.Item Green Synthesis of Copper Oxide Nanoparticles (CuONPs) using Clematis simensis, Characterization and their Antibacterial Activity against MultiDrug Resistant Bacteria(Mekelle University, 2025-06-28) Alem Gebrehawerya RetaRecent advancements in material science and green nanotechnology have led to the development of bioinspired nanoparticles, which offer promising alternatives for combating multidrugresistant bacteria, a major public health concern. The unique, antibactericidal properties of CuONPs offer invaluable possibilities for combating multidrug-resistant bacterial infections. In the present study, copper oxide nanoparticles were synthesized by a cost-effective, eco-friendly, and single-step method using ethanolic leaf (ET) extract of clematis simensis (CS) acting as a reducing agent. CS-CuONPs and ethanolic leaf extract were characterized by UV-Vis, FT-IR, GC-MS, XRD, DLS, SEM, and TEM. UV-Vis spectrum showed a characteristic peak at 286 nm, indicates the formation of CS-CuONPs. Phytochemical, GC-MS, and FTIR analysis of ethanolic leaf extract of C. simensis revealed the presence of polyphenolic compounds, flavonoids, and their related bioactive compounds like Eugenol and methyl eugenol, with the broad peak 3599.77 cm-1 indicating the OH functional group responsible for reducing, capping, and stabilizing agents in the synthesis of CS-CuONPs. The XRD diffractogram proved the existence of a crystalline structure of CS-CuONPs with an average size of 22.7 nm, and the DLS analysis of CS-CuONPs was -28.3 mV, which confirms moderate stability and high surface negative charge. SEM and TEM analysis revealed that the CS-CuONPs were predominantly pseudo-spherical with some irregular shapes, and had an average particle size of 22.65 nm.The CS-CuONPs have shown strong antibacterial activities against the tested Gram-positive bacteria B. subtilis, with the highest zone of inhibition of 30±0.4 mm and minimum inhibitory concentration of 100µg/mL. In addition, E. faecalis and K. pneumoniae showed moderate susceptibility with the zone of inhibition of 20±0.2 mm for both bacteria in comparison with Positive controls (Ciprofloxacin). The results suggest that clematis simensis, with its rich phytochemical profile, enhances nanoparticle stability and antibacterial efficacy. Therefore, CSCuONPs show potential as an effective alternative for combating MDR bacteria.Item Investigating the Impact of Laboratory and Practical Activities on Chemistry teaching and Learning: A Case Study of Grade 10 Students at Weldu Negus Secondary and Preparatory School(Mekelle University, 2024-11-25) Geberemariam Fissha AbebeChemistry laboratory activities play a crucial role in enhancing students’ understanding by providing hands-on experience that reinforces theoretical knowledge. This study examines the impact of laboratory-based teaching on student performance and attitudes at Weldu Negus Secondary and Preparatory School. A quasi-experimental research design was employed, where 263 Grade 10 students were divided into experimental and control groups. The experimental group engaged in hands-on laboratory activities, while the control group received only theoretical instruction. Data were collected through questionnaires, interviews, and post-test assessments, and statistical analysis was conducted using SPSS. The findings revealed that students in the experimental group demonstrated a significant improvement in their post-test scores, with 88.65% scoring above 50, compared to 54.54% in the control group. This highlights the effectiveness of laboratory-based instruction in improving student comprehension and engagement. Despite these benefits, several challenges were identified, including a lack of laboratory equipment and chemicals, insufficient trained personnel, time constraints, and limited teacher preparedness. Additionally, 61.9% of students expressed disinterest in laboratory activities, indicating the need for more engaging and student-centered approaches. Based on these findings, the study recommends improving laboratory facilities, providing professional development for teachers, integrating student-centered teaching methods, and increasing student motivation through real world applications of chemistry. Collaboration with external institutions and regular monitoring of laboratory practices are also suggested to sustain improvements in practical chemistry education. Future research should explore the long-term impact of laboratory-based learning on student career choices and the effectiveness of digital and virtual labs as supplementary tools. Implementing these recommendations will create a more effective learning environment and foster deeper scientific understanding among students.Item EFFECT OF COOPERATIVE LEARNING ON STUDENTS’ ACADEMIC ACHIEVEMEN IN CHEMISTRY ON THE TOPICS OF CHEMICAL EQUILIBRIUM AND PHASE EQUILIBRIUM: THE CASE OF KELLEM PREPARATORY SCHOOL, KELLEMWOLLEGA ZONE, OROMIA REGIONAL STATE, ETHIOPIA(Mekelle University, 2025-01-25) GUTA DEGU DISASAThe study investigate effects of cooperative learning on students’ academic achievement in chemistry on the topics of chemical equilibrium and phase equilibrium: The case of Kellem preparatory school, Kellem Wollega zone, Oromia regional state, Ethiopia. The study sampled 120 students from two sections one taken as experimental group and the other as control group which are purposively selected from six sections of Kellem Preparatory School grade 11 natural science because of relatively low score in chemistry. The data obtained from 60 students (M=29 and F=31) participated in cooperative learning instruction methods and 60 students (M=30 and F=30) participated in instruction based on regular learning methods, 2 School administrators and 2 Chemistry teachers. The research was used experimental methods, questionnaire and interview for data collection. Data analysis was done descriptively using mean, frequencies, percentages and t-test. A pre-test was administered before the study to identify students’ prior knowledge. Sample students score an average academically achievements 60.12% of control group (M=30.06% and F=30.06%) and 60.4% of experimental group (M=29.20% and F=31. 20%) before the treatment. A post- test was administered after cooperative learning instruction methods in order to examine the difference in achievements. In the comparison of the post –test of the two groups, the experimental groups were an average of 81.44 % (M=39.36% and F=42.08%) of academic achievements and 62.52% of control group (M=31.26% and F=31.26%) academic achievements in selected topic. The result of study show that cooperative learning instructional methods was better than the regular method of instructional methods in increasing students’ academic achievements and promote face to face interaction, creating positive dependence and insuring the active participation of all students in activities.Item Comparative Assessment of Heavy Metal Levels in the Soil and Some selected Edible Fruits (Orange and Papaya) Grown in the Addiha Irrigational site, Kola Tembien-Woreda Tigray, Ethiopia(2025-03-25) Gebremeskel Welegebrial HagosEdible fruits (orange and papaya) are source of vitamins, minerals and organic acids which provide an excellent health promoting nutrients. Heavy metals are natural constituents of the Earth's crust and their excessive consumption levels can be damaging to the organisms. The objective this study was compartive assessement of heavy metals (Fe, Zn, Cu, Cr and Mn) in the soil and selected edible fruits (Orange and Papaya). The sampling methods of this study were randomly and targeted methods.The chemicals used in this study were HNO3, HClO4, HCl and distilled water and the materials used inthis study were cutters, sample containers (plastic bags), gloves, hot plates, beakers, test tubs, electrical balance, spoon, stirrer, sample cells, oven, sample holder, volumetric flask and digester. The study was assessed heavy metal (Zn, Cu, Cr, Mn, and Fe) in both soil and selected edible fruits (orange and papaya) grown in the Addiha irrigation site Kola Tembien woreda central zone of Tigray, Ethiopia. Soil analysis revealed that Zn, Cu, and Mn were below established WHO (2011) safe limits, while Cr and Fe exceeded them. In contrast, all heavy metal levels in the selected edible fruits (orange and papaya) were below the established WHO (2012) safe limits. T-tests showed statistically significant differences (p<0.05) for the concentration level of heavy metals Zn, Cr, Mn, and Fe, but the heavy metal Cu is not statistically significant (p>0.05), while the analysis using ANOVA showed significance for all elements when comparing soil to fruit which between soil and orange and between soil and papaya were statistically significant differences (p<0.05). Transfer factors between soil and edible fruits (orange and papaya) varied, with Zn being highest in both. Strong positive correlations were also observed between heavy metal levels in soil and those in the selected edible fruits. The correlation coefficients of soil and orange are (0.9877) and soil and papaya is (0.99932). ANOVA revealed statistically significant differences (p<0.05) between orange and papaya fruits for the mean concentration of heavy metals except Cu at (p<0.05) for Zn, Cu, and Fe, but not for Cr and Mn (p>0.05). Furthermore, ANOVA comparisons between orange and soil, as well as papaya and soil, showed statistically significant differences for all heavy metals (Zn, Cu. Cr. Mn and Fe) (p<0.05). Keywords: Heavy metals, Edible Fruits, Soils, Permissible levelsItem THE CHALLENGES OF CHEMISTRY LABORATORY PRACTICES AND THEIR SOLUTIONS IN THE CASE OF CISTERCIAN MONASTERY MARIAM TSION SECONDARY SCHOOL, BOLE SUB CITY, ADDIS ABABA, ETHIOPIA(Mekelle University, 2025-01-25) Zeray WelegerimaChemistry laboratory practices are essential for reinforcing students' understanding of scientific concepts and developing critical practical skills. However, educational institutions in developing countries often encounter significant challenges in maintaining well-equipped and functional chemistry laboratories. This study investigates the challenges faced in chemistry laboratory practices at Cistercian Monastery Mariam Tsion Secondary School in Bole Sub City, Addis Ababa, Ethiopia, and explores feasible solutions to address these issues. A mixed-methods research approach was employed, incorporating both quantitative and qualitative data collection techniques. Surveys were conducted among chemistry teachers and students to assess their perceptions of the prevalent challenges. The findings indicate several key issues, including inadequate laboratory equipment and supplies, outdated or malfunctioning apparatus, limited laboratory space, and insufficient safety protocols. Additionally, challenges related to teacher training, student engagement, and overall laboratory management were identified. Based on these findings, the study proposes a multifaceted strategy to address these obstacles. Recommendations include securing funding for laboratory upgrades, implementing systematic equipment maintenance and replacement plans, providing extensive training for teachers and laboratory technicians, and improving student safety awareness and hands-on participation in laboratory activities. This study contributes to a broader understanding of the difficulties faced by secondary schools in developing countries in implementing effective chemistry laboratory practices. The proposed solutions offer valuable insights for policymakers, school administrators, and educational stakeholders in formulating strategies to enhance the quality of chemistry education and laboratory experiences for students.