Authors:Mekuriaw Assefa Kebede, Tessera Alemneh Wubieneh, Yonas Beyene Yohannes, Kinjal J. Shah Pages: 1 - 12 Abstract: This article reports the green synthesis of ZnO nanoparticles using an endemic plant called Dovyalis abyssinica, locally known as Koshem, for the degradation of malachite green dye in photocatalytic process. An aqueous extract from the ripe fruits of the plant was incorporated into the sol-gel synthesis process to obtain ZnO NPs with the size of 17 nm. XRD data and UV-Vis absorption at 390 nm confirmed that the synthesis was successful. In addition, the FTIR result showed a characteristic absorption peak at 543 cm-1 for the presence of Zn-O stretching and additional peaks also appeared from the plant source, suggesting that the natural functionalities are present together on ZnO particles as a capping agent. The ZnO NPs produced were used as a photocatalyst to degrade the organic dye malachite green. The results showed that ZnO nanomaterials synthesized in green removed 98.5% of the dye from the aqueous solution by photo-degradation under visible light. This study contributes to efforts that try to develop efficient techniques for removing organic pollutants from wastewater treatment. PubDate: 2023-03-08 Issue No:Vol. 16, No. 1 (2023)
Authors:Tenaw Tegbar Tsega, Klaus-Dieter Thoben, D.K. Nageswara Rao, Bereket Haile Pages: 13 - 28 Abstract: Leather industries in countries with a large raw material base, such as Ethiopia, could contribute significantly to meeting future global demand for leather and leather goods. So far, Ethiopia's leather industry has begun producing leather shoes, jackets, and elegant gloves, which are sold in many developed countries through world-class branded distributors. However, shortage of raw materials has become a major constraint for the industry even if the volume of raw material production is greater than the design capacity of the industry. Therefore, the aim of this study was to investigate the complete process of raw material supply, i.e., starting from the point of production until it reaches the boundaries of tanneries and reveal how the process affects cost, quality, and availability of raw materials. Data were collected through surveys, observations, focus group discussions, and questionnaire. After modeling the existing raw material supplying process and conducting both qualitative and quantitate analysis, this study found that: (i) the existing process fails to collect about 45% of the total available raw material, (ii) the raw material price increases by five-fold when it reaches the tanneries, (iii) it takes 3 to 4 more steps than the standard of reaching raw material to the industry, and (iv) there is a lack of quality control throughout the entire process.. In conclusion, the existing process of raw material supply is a real challenge for the industry. Different interventions suggested by this study could improve the existing conditions. PubDate: 2023-03-08 DOI: 10.4314/ejst.v16i1. Issue No:Vol. 16, No. 1 (2023)
Authors:Leopord Sibomana Leonard, Elionara Gebrath Riwa Pages: 29 - 49 Abstract: Bioaccumulation of trace elements in paddy soil and rice plants was assessed from Morogoro region of Tanzania. Paddy soil, paddy plants and rice grains were sampled from 9 different sampling points within rice fields and one control sample from a separate farm and analyzed in the School of Engineering and Environmental Studies laboratory, Ardhi University, Dar es Salaam. Trace elements were analyzed using a Perkin Elmer Atomic Absorption Spectrophotometer (100-AAS). Heavy metal uptake and translocation indices including BAF, BCF, TF and EF were established. The results showed that all samples (paddy soil, paddy plant and rice grains) contained some concentration of trace elements in various levels. The uptake of trace elements in roots were in the order of Zn>Cu>Pb>Cr>Cd while in shoots the uptake was in the order of Pb>Zn>Cu>Cr>Cd and the Reiwa bio-availability of trace elements concentration in paddy grains were in the order of Zn>Pb>Cu>Cr>Cd. The trend of the total BAF, BCF, TF and EF for each metal were in the order of Cr>Pb>Cd>Zn>Cu; Cr>Pb>Cu>Zn>Cd; Pb>Cr>Cu>Zn and Cd>Pb>Zn>Cu>Cr, respectively. The concentration of Pb ranged from 1.583±0.29 mg kg-1 to 7.231±1.125 mg kg-1 above the recommended 0.2 mg kg-1 limit. Minimizing application of agrochemicals and promoting organic fertilizers in paddy farms is recommended. PubDate: 2023-03-08 Issue No:Vol. 16, No. 1 (2023)
Authors:Tilahun Dagnew, Zenamarkos Bantie Pages: 51 - 75 Abstract: The oxidation of trivalent chromium (Cr(III)) to more toxic hexavalent chromium (Cr(VI)) in wastewater causes several problems in aquatic environments and downstream users. The aim of this research was to optimize Cr(VI) removal from an aqueous solution using activated orange peel adsorbent for treating tannery wastewater by analyzing the effects of adsorbent dose, pH, and contact time. The design expert software was used. Raw and activated orange adsorbents were characterized by FT-IR spectroscopy, scanning electron microscope (SEM), and Brunauer-Emmett -Teller (BET). Batch adsorption experiments were carried out at room temperature and the residual concentration of Cr(VI) was analyzed by UV-VIS spectrometer. Bio-sorbent desorption was also conducted to regenerate the bio-adsorbent and recover the metal. The removal efficiency was maximum (94.74%) at pH of 2, dosage 2.5 g/L, and contact time of 90 minutes. FTIR results confirm that hydroxyl functional groups, which have high affinity towards heavy metals, are responsible for the removal of Cr(VI). Methoxy groups, which undergo demethylation to generate new hydroxyl groups after carbonization confirming oxidation, also play significant role in the adsorption process. SEM results indicate that activated orange peel adsorbent has highly porous surface created due to the removal of viscous compounds during activation. The Langmuir isotherm model shows a better fit and the reaction kinetics is described by a pseudo-second-order kinetic model (R2=0.99). The Cr(VI) removal efficiency in real effluents is lower than in stock solution due to the scavenging effects of competitors. In summary, results of this research indicate that the use of activated orange peel adsorbent is promising to treat wastewater effluents for removal of Cr(VI). PubDate: 2023-03-08 Issue No:Vol. 16, No. 1 (2023)
Authors:Zelalem Getu, Muluken Aklilu Pages: 77 - 97 Abstract: Nowadays, the applications of metal nanoparticles are growing rapidly in different fields due to their unique properties such as size and shape. Among the different metal nanoparticles, silver nanoparticles (Ag NPs) have attracted considerable attention. In recent years, biosynthesis of Ag NPs has gained much interest from researchers. Ethiopian flora has a potential to provide cost-effective non-hazardous reducing and stabilizing compounds in preparing Ag NPs. In this study, leaf extracts of endod (Phytolacca dodecandra) were used as a reducing and stabilizing agent for the synthesis of Ag NPs because it is cost effective, eco-friendly and has medicinal property. During the synthesis of the nanoparticles, we used 8 % (w/v) of 25 mL P. dodecandra leaf extract and 5 mM of 50 mL silver nitrate solution. The synthesised Ag NPs were characterized by using UV–Vis absorption, FTIR and XRD spectroscopy. Antibacterial susceptibility of green-produced Ag nanoparticles was examined against Gram-positive and Gram-negative microorganisms. The UV-Visible spectrum of the colloidal solutions has a maximum absorbance observed at 424 nm. FTIR spectrum analysis revealed the presence of functional groups in the leaf extract which are responsible for the reduction of Ag+ to Ago. XRD spectrum showed the crystallinity and face-centered cubic (FCC) structure of the synthesized Ag nanoparticles. The particle size of silver nanoparticles calculated using the Debye-Scherrer formula was found to be equal to 22 nm. The antibacterial susceptibility test showed an inhibition zone of 22 mm against S. aureus and an inhibition zone of 21 mm against S. typhi. PubDate: 2023-03-08 Issue No:Vol. 16, No. 1 (2023)
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