Synthesis And Characterization Of Zeolite A From Kaolin Of Ethiopia Studies Of Its Application As Detergent Builder And In Tannery Wastewater Treatment

Zeolite A is a synthetic sodium aluminium silicate often also referred to as Zeolite NaArnor Zeolite 4A with LTA framework type. It is the universal type of synthetic zeolite usedrnfor detergent manufacturing and water softening to substitute the environmentallyrnunfriendly material sodium tripolyphosphate (STPP). Despite its remarkable potential,rnthe high cost of zeolite A has restricted its effective use in detergents. Based on this, inrnthis work detergent-grade zeolite A has been synthesized using kaolins of Ethiopia;rnAnsho and Bombowha kaolins. The synthesis was done by two different methods: thernconventional hydrothermal and alkali fusion methods. The process parameters for thernsynthesis of detergent-grade zeolite A, like the metakaolination temperature, alkalinernconcentration, crystallization time crystallization temperature and gel formationrnconditions have been systematically studied. The characterization of the synthesizedrnzeolite was carried out by X-ray diffraction (XRD), Scanning electron microscopyrn(SEM), Thermogravimetric analysis (TGA) and Inductively coupled plasma opticalrnemission spectroscopy (ICP-OES) study confirms its formation. By the conventionalrnhydrothermal synthesis, cation exchange capacity (CEC) exceeding 290 mg of CaCO3/grnand average particle size of 3.0 μm, whereas by the alkali fusion method, cation exchange capacity (CEC) greater than 300 mg of CaCO3 and average particle size of 4.0 μm arernachieved, which make the zeolite A obtained as promising detergent builder. The studyrnalso included evaluating the detergency action of the powder detergent formulated withrnthe synthetic zeolite A by analyzing some physicochemical properties like foam height,rnpH value, moisture content and alcohol and water insolubility test. The results show thatrnthis detergent has comparable detergency with a known commercial powder detergent.rnWastewater treatment from tanneries is another environmental issue that needs greatrnattention in Ethiopia. In this work we have investigated the removal of Cr(III) fromrntannery wastewater with Cr(III) > 2000 ppm collected from various tannneries inrnEthiopia. This was done using the synthetic zeolite A prepared using kaolin fromrnEthiopia and other natural adsorbents for comparison. The results indicate that 99.8%rnremoval and about 200 mg/g adsorption capacity of Cr(III) with 100 g/L and 5 g/Lrnadsorbent dosage, respectively. The adsorbent dosage was varied systematically from 2rng/L to 100 g/L. Kinetic and adsorption isotherm studies have been conducted usingrnzeolite A as adsorbent. The removal efficiency of the synthetic material for Cr(VI) wasrnalso evaluated incomparison with other natural adsorbents from Ethiopia. In this aspectrnthe natural adsorbents bentonites and synthetic clay materials hydrotalcite ans nanohydrotalcatiternhave been found to be efficient. The natural bentonite exihibited thernmaximum removal of 90% and the hydrotalcite exhibited 100% removal of Cr(VI).

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