http://ir.haramaya.edu.et//hru/handle/123456789/219 2026-05-22T19:26:53Z http://ir.haramaya.edu.et//hru/handle/123456789/8414 THE EFFECT OF USING CONTEXT BASED-APPROACH ON THE CONCEPT OF GAS LAWS ON STUDENTS’ ACHIEVEMENT AND ATTITUDE Eliyas Burqa Usman; Ayalew Temesgen (PhD); Yiheyis Bogale (PhD) The study was aimed to evaluate the effect of using a Context-Based Approach (CBA) on the concept of gas laws on students' understanding and attitude. The study conducted at Ejersa Goro secondary school in Oromia region, Ethiopia. The research focused on the physical state of matter, specifically Boyle's, Charles', and Gay-Lussac's gas laws, which are fundamental concepts in secondary school chemistry with applications in various sciencerelated fields. The study employed quasi-experimental research approach, which contains experimental, control groups, and involved 72 grade 9 students selected by convenience sampling techniques. The experimental group received CBA instruction, while the control group received traditional instruction. The data were collected using pretests, posttests, retention tests, questionnaires, interviews, and observations. The study found that CBA significantly improved students' understanding and retention of gas law at each conceptual level (macro, micro, symbolic and graphical representation). The experimental group also showed a positive attitude toward CBA. The study concluded that CBA is a more effective instructional method than traditional teaching for enhancing students' understanding and retention of gas laws. The findings suggested that CBA is effective instructional approach and better if integrated into chemistry instructions to improve students' academic achievement and attitudes toward learning gas-law. 104p. 2025-01-01T00:00:00Z http://ir.haramaya.edu.et//hru/handle/123456789/8146 Salvia tilifolia LEAF EXTRACT-BASED SILVER NANOPARTICLES FOR COLORIMETRIC DETECTION OF Hg(II) IN SELECTED FOOD, COSMETICS, AND ENVIRONMENTAL SAMPLES Lencho Mume Ahmed; (PhD) Meseret Amde; (PhD) Deribachew Bekana In the present research, we report easy, quick, ultrasensitive, inexpensive, and eco-friendly colorimetric sensor using green synthesized silver nanoparticles (AgNPs). The AgNPs were biosynthesized utilizing Salvia tilifolia leaf extract and well characterized by various techniques, and then employed to design a colorimetric assay for Hg(II) sensing in food, cosmetics, and environmental samples. The developed colorimetric sensor found very sensitive and specific for Hg(II) detecction with limits of detection down to 5.0 nM and 0.27 nM through the naked eye and UV-vis spectrometer detection, respectively. In addition, the method showed good precision (intra- and inter-day RSD values of 2.4% and 4.9%, respectively) with linearity of R2 = 0.9984 over the 0.1–100 μM interval. Furthermore, the proposed AgNPs-based colorimetric sensors has been succesfully tested for sensing Hg(II) in a variety of real samples, including wastewater effluent, lake water, drinking water, soft drinks, mineral water, beauty cream, and canned light tuna. The percent recovery of the tested samples varied from 86.9 to 110%, demonstrating the method's real world application. In summary, the proposed method is greener, selective and highly sensitive, and recommended for detecting Hg(II) in food, cosmetics, and environmental samples 72p. 2024-06-01T00:00:00Z http://ir.haramaya.edu.et//hru/handle/123456789/7381 Synthesis and Characterization of Zeolite-A from Kombolcha Kaolin by Hydrothermal Method for the Removal of Mg2+and Ca2+ from Aqueous Solution Yohannes Dassie Eshete; Ephirem Taddesse (PhD); Endale Teju (PhD) Zeolite-A is one of the most important synthetic Zeolites especially in water softening with high ion exchange ability due to its low Si/Al ratio. In this study, Zeolite-A was synthesized using a hydrothermal method from Kombolcha kaolin, and its adsorptive removal efficiency for Ca2+ and Mg2+ was investigated. The material prepared as such was characterized using different instruments including XRD, SEM, FTIR, and TGA. The Powder X-ray diffraction (XRD) patterns clearly show the presence of the characteristic 2�� peaks (12.32 and 24.92°) of kaolin. X-ray diffraction measurements 2�� peaks (7.18, 10.16, 12.44, 16.12, 21.68, 24.02, 26.14, 27.16, 30.00, 32.56, and 34.22°) and scanning electron micrographs clearly show the morphology of Zeolite-A. Characteristic OH, Al-OH, Si-OH, and Si-O-Al bands were confirmed in samples with Infrared spectroscopy studies. The thermal analysis indicated that the kaolin sample undergo de-hydroxylation from 563.73℃ to about 700 ℃ and converted to metakaolin. The potential of the material to remove Ca2+ and Mg2+ ions from water sample was evaluated using EDTA titration. Batch adsorption experiments demonstrated that solution pH, the adsorbent dose, contact time, initial concentration, and temperature have significant effects on Ca2+ and Mg2+ ions removal. Using the optimized experimental parameters, removal percentages 98.27 for Ca2+ and 97.12 for Mg2+ were obtained at pH 10, contact time 30 min, initial concentration 250 mg/L, and adsorbent dose of 0.5 g. In the Freundlich isotherm model, R2 values for Ca2+ and Mg2+ adsorption were found to be 0.9992 and 0.9985, respectively. The obtained highest R2 values for the Freundlich isotherm are approximately equal to unity that confirms the experimental data is well-fitted to the model and pseudo-second-order kinetic model, which suggests that the applicability of the model to the adsorption of Ca2+ and Mg2+ by Zeolite-A. Based on this study, it can be concluded that zeolite-A was successfully synthesized from Kombolcha kaolin by using a hydrothermal method and the results obtained showed that it can be used as an effective adsorbent for the removal of Ca2+ and Mg2+ ions from aqueous solution 82 2023-11-01T00:00:00Z http://ir.haramaya.edu.et//hru/handle/123456789/7380 SYNTHESIS AND CHARACTERIZATION OF ZEOLITE-A FROM KOMBOLCHA KAOLIN BY HYDROTHERMAL METHOD FOR THE REMOVAL OF Mg2+AND Ca2+ FROM AQUEOUS SOLUTION Yohannes Dassie Eshete; Ephirem Taddesse (PhD); Endale Teju (PhD) Zeolite-A is one of the most important synthetic Zeolites especially in water softening with high ion exchange ability due to its low Si/Al ratio. In this study, Zeolite-A was synthesized using a hydrothermal method from Kombolcha kaolin, and its adsorptive removal efficiency for Ca2+ and Mg2+ was investigated. The material prepared as such was characterized using different instruments including XRD, SEM, FTIR, and TGA. The Powder X-ray diffraction (XRD) patterns clearly show the presence of the characteristic 2�� peaks (12.32 and 24.92°) of kaolin. X-ray diffraction measurements 2�� peaks (7.18, 10.16, 12.44, 16.12, 21.68, 24.02, 26.14, 27.16, 30.00, 32.56, and 34.22°) and scanning electron micrographs clearly show the morphology of Zeolite-A. Characteristic OH, Al-OH, Si-OH, and Si-O-Al bands were confirmed in samples with Infrared spectroscopy studies. The thermal analysis indicated that the kaolin sample undergo de-hydroxylation from 563.73℃ to about 700 ℃ and converted to metakaolin. The potential of the material to remove Ca2+ and Mg2+ ions from water sample was evaluated using EDTA titration. Batch adsorption experiments demonstrated that solution pH, the adsorbent dose, contact time, initial concentration, and temperature have significant effects on Ca2+ and Mg2+ ions removal. Using the optimized experimental parameters, removal percentages 98.27 for Ca2+ and 97.12 for Mg2+ were obtained at pH 10, contact time 30 min, initial concentration 250 mg/L, and adsorbent dose of 0.5 g. In the Freundlich isotherm model, R2 values for Ca2+ and Mg2+ adsorption were found to be 0.9992 and 0.9985, respectively. The obtained highest R2 values for the Freundlich isotherm are approximately equal to unity that confirms the experimental data is well-fitted to the model and pseudo-second-order kinetic model, which suggests that the applicability of the model to the adsorption of Ca2+ and Mg2+ by Zeolite-A. Based on this study, it can be concluded that zeolite-A was successfully synthesized from Kombolcha kaolin by using a hydrothermal method and the results obtained showed that it can be used as an effective adsorbent for the removal of Ca2+ and Mg2+ ions from aqueous solution. 82 2023-11-01T00:00:00Z