Search

This paper is dealt with the design and experimental test on solar powered evaporative cooling system which is maintaining inside temperature lower than ambient temperature with higher level of relative humidity for the storage of fresh Agricultural products such as tomato, carrot and green chili (pepper). The experimental setup is a rectangular shaped storage space made of galvanized steel for external cover, aluminum for internal cover insulated with fiber glass. Axial fan supplies 0.78 m3/s air at a speed of 0.93 m/s to wet pad and for recycling of water through copper tube, an axial pump having flow rate of 0.054 kg/s is used to remove the heat from the commodities. The results reveal that the shelf life of the vegetables is increased 12 days when compared with ambient conditions. The temperature range of the cooling cabinet is found 16.2 to 22.1 °C during the hottest time of the day and the ambient temperature varied from 22.6 to 29.8 °C. The relative humidity is found between 75 and 90% when the outside condition is recorded between 66 and 80%. The maximum weight loss found after the sixth day for carrot, tomato and pepper are 8, 10 and 16% in cabinet conditions and 50.6, 38 and 50% in ambient conditions respectively. The commodity decay is found in an ambient condition is faster compared with the commodity stored in the present cooling system. Evaporative cooling efficiency is found 82%.

This paper deals with a locally manufactured electrical cookstove that has been modified to reduce energy losses and improve the efficiency of the cookstoves by adjusting the clay profile using switches to test small and large cookware. The system can reduce the cooking time as investigated by boiling water using different sizes. A framework made from mating parts of 4 mm thick galvanized iron sheet, steel sheet metal, a flat type clay plate weighing 2.0 kg, in which the open electric resistor was placed, the groove depth was 12 mm, and the round bar pot rest of 4 mm diameter was made in a concentric circle style for pot mounting and having a height of 10 mm above the heating element. This modification evaluates the efficiency of a modified locally manufactured electric cook stove with a 16 cm pot with a fully active switch investigated high energy loss of 0.45 kW compared with the semi-active switch of the same diameter at 0.25 kW. The efficiency of 16 cm fully active cookware is calculated based on the experiment results found 67%, and semi-active the same diameter cookware would raise to 77% efficiency, and for 22 cm cookware, the efficiency calculated is 68%.

BACKGROUND The commercial production of zeolite A mainly involves costly synthetic chemicals. However, cheaper raw materials such as clay minerals, coal ashes, natural zeolites, solid wastes and industrial sludge have been tested. Based on this, the objective of present study is synthesis of zeolite A from two sources of raw kaolins (Ansho and Bombowha) from Ethiopia and evaluation of its application in tannery wastewater treatment. RESULTS The synthesis result indicated high crystallinity (>90%) of zeolite A using Ansho kaolin. Lower grade Bombowha kaolin yielded zeolite A with crystallinity of 80%. In the tannery wastewater treatment study, a real sample having chromium concentration of 2036 mg/L was treated obtaining 99.8% removal and about 200 mg/g adsorption capacity of Cr(III) using 100 g/L and 5 g/L adsorbent dose respectively. This indicated that the synthesized zeolite A has a great potential in Cr(III) removal from tannery wastewater. CONCLUSION In this study, zeolite A has been synthesized from two sources of kaolin from Ethiopia and has been evaluated in tannery wastewater treatment. The synthesis result indicated the formation of crystals of zeolite A with optimum crystallinity of 91% and the material exhibited chromium removal efficiency of 99.8%.

Synthesis of zeolite A using low grade Bombowha kaolin from Ethiopia has been carried out by two methods: the conventional hydrothermal synthesis and alkali fusion followed by hydrothermal treatment. In the synthesis process, the metakaolinization was achieved by calcination of the kaolin at 600 °C for 3 h for the conventional method and for the alkali fusion method, the activation of the raw kaolin was done by alkali fusion for only 1 h. Zeolite A was the main product obtained using 3 M NaOH concentration, 100 °C reaction temperature and 3 h crystallization time in both methods. The molar gel composition for the best synthesis conditions for both methods was Na 2 O: Al 2 O 3 : 2SiO 2 : 37H 2 O. The main advantage of the alkali fusion method is that it allows using a low grade virgin kaolin without purification, whereas the conventional method only yields good quality zeolite A when the raw kaolin is purified. The starting raw kaolin, metakaolin and synthetic products were characterized by X-ray diffraction (XRD), ICP-OES elemental analyses, Scanning Electron Microscopy (SEM), Thermogravimetric Analysis (TGA) and Cation Exchange Capacity (CEC). Cubic crystals with rounded edges of zeolite A having crystallinity of about 85% and Cation Exchange Capacity of 300 mg CaCO 3 /g of anhydrous zeolite was achieved by the alkali fusion method of synthesis using raw, virgin Bombowha kaolin.

Most commercial manufacturers of soap and detergents in developing countries and few developed countries are still using environmentally unfriendly phosphate based materials like sodium tripolyphosphate as detergent builders. Detergents that contain phosphorus contribute to the eutrophication of fresh water bodies. To surmount this problem, many detergent manufacturers are currently using zeolite A as the builder material which has proved to be a better substitute for phosphorus containing additives. Despite its remarkable potential, the high cost of zeolite A has limited its effective use in detergents. In this work detergent-grade zeolite A has been synthesized from the Ethiopian kaolin collected from the southern part of the country with the molar gel composition of Na2O:Al2O3:2SiO2:37H2O. Two routes are surveyed for the synthesis of zeolite A: alkali fusion using raw kaolin and conventional hydrothermal synthesis. The resulting zeolite A samples are studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), chemical analysis (ICP) and thermogravimetry (TGA). Moreover, the cation exchange capacity (CEC) of >310 mg CaCO3 per g as well as the average particle size of 3 μm of zeolite A is found to be satisfactory to be used as a detergent builder. This study also focused on evaluating its potential use as a detergent by analyzing some physicochemical properties like foam height, pH value, moisture content and alcohol and water insolubility of the formulated detergent using our synthetic zeolite A. The result showed that the synthesized detergent has comparable detergency to commercial brands of powder detergents.

Zeolite A is synthesized using natural kaolin from Ethiopia. Raw kaolin and mechanically purified kaolin from Ansho, southern part of Ethiopia, have been surveyed. The starting kaolin and the final zeolite A samples were characterized by X- Ray Diffraction (XRD), elemental analysis (ICP), Scanning Electron Microscopy (SEM), Thermogravimetric Analysis (TGA) and Cation Exchange Capacity (CEC). Metakaolinization was achieved by calcining the kaolin in air at 600 °C within 3 h, much lower than the temperatures previously reported in the literature. The optimization of the hydrothermal synthesis includes various NaOH concentrations at 100 °C, for different reaction time. Zeolite A with molar ratio SiO2/Al2O3 = 2.04 and Na2O/SiO2 = 0.44 was obtained with 90% crystallinity using solid/liquid (1.25 g/25 ml) and reaction time of 3 h which is significantly lower than the literature value that can reach up to 24 h. In this study, cubic crystal with rounded edge of zeolite A having cation exchange capacity of 295 mg CaCO3/g (4.6 meq Ca2+/g) of anhydrous zeolite is obtained that can be a good candidate for detergent formulation., ID is grateful to CSIC for her research leave at AAU. The authors acknowledge Spanish Government, MINECO MAT2012-31127 project and the Spanish Research Council CSIC I-COOP-H2O (2013CD0009), for funding. The Chemistry Department, Addis Ababa University is also acknowledged for financial support.

Nano-hydrotalcite (nano-HT), particles have been supported on silica and tested for chromium(VI) retention through anion exchange mechanism. Ultra high resolution has been achieved in the structural characterization of the nano-hydrotalcite particles allowing identification of the Cr within few layers of the nanoparticles. Compared to a reference hydrotalcite (HT), in which the Cr(VI) retention takes place via memory effect, nano-HT/SiO2 exhibits better adsorption capacity, for 4 mg/L Cr(VI) solutions, even when the adsorption mechanism of the later is anion exchange. This higher adsorption capacity can be attributed to the considerable smaller size of the crystals, which would favor adsorption kinetics and would minimize possible hindrances between the layers of hydrotalcite. The adsorption behavior of nano-HT/SiO2 can be described by a Freundlich isotherm suggesting a non-uniform surface, which is consistent to their arrangement in nanocrystallites observed by TEM., The financial support from the Spanish Government MINECO (project MAT2012-31127) and Mexican Government CONACYT is acknowledged. A.M. acknowledges the European Union Seventh Framework Programme under grant agreement 312483—ESTEEM2 (Integrated Infrastructure Initiative—I3).

The conversion of glucose into platform chemicals such as 5-hydroxymethylfurfural, levulinic acid and formic acid has been investigated using two aluminophosphate based zeotypes (SAPO-5 and MeAPO-5) catalysts in 1-butyl-3-methylimidazolium chloride [BMIM]Cl ionic liquid as a reaction medium. The silico aluminophosphates (SAPO-5) and metal aluminophosphates (MeAPO-5) were designed and chosen for their tunable amount and strength of acid sites. The dehydration of glucose using each catalyst gave more than 90% glucose conversion. Among all the catalysts tested, the most hydrophilic SAPO-5 (1.5T) results in a better 5-HMF yield of 8% at 100 deg;C and 6 h reaction time. Contrary to this, the more hydrophobic SAPO-5 gives higher yield of levulinic acid and formic acid and no 5-HMF yield at this particular reaction time. In general, despite the higher glucose conversion attained by these aluminophosphate based catalysts, the lower yield obtained by these materials can be attributed to the type of acidity and the incompatibility of the pore diameter of the AFI channels of the catalysts and the desired products., The authors also thank the Spanish Research Council (CSIC) for funds through the programme CSIC for development, project number i-COOP014. The Chemistry Department, Addis Ababa University is also acknowledged for financial support.