English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

The black tea waste, representing an efficient natural ,bio-adsorbent has been applied for adsorption of some hazardous elements. Several batch wise experiments are conducted to determine the relevant factors affecting its adsorption characteristics especially for uranium. The studied factors are the effects of stirring, agitation time, pH, solid/ liquid ratio and initial metal concentration. The equilibrium data are found to be satisfactorily fitting to Langmuir isotherms. A maximum-metal uptake of 60.56 mg/g was observed for uranium at a solution pH range of 4.5-5.5. The studied elements include U, Th and REEs in the presences of some possible interfering elements. Elution of the studied interesting elements has been achieved and from their eluates proper concentrates have been prepared. INTRODUCTION Contamination of the environment by toxic metals from several types of both natural and industrial operations is a world wide phenomenon. Their removal by various physical, chemical or biological methods has been repeatedly attempted to overcome this problem. In the same time, the utilization of agricultural waste materials has become of vital concern as these wastes represent serious disposal problems. Numerous waste biomass sources are available and upon which several experimental adsorption studies were performed e.g. rice husk (Zulkali et al., 2006), peanut shells (Wafwoyo et al., 1999) ,corn cobs (Vaughan et al., 2001) saw dust ( Sciban et al., 2006),etc. Bio-sorption of heavy metals occur upon such biomass sources as a result of physiochemical interaction-mainly ion exchange or complex formation -between metal ions and the functional groups present on the cell surface of these sources like carboxyl, amine , amide, etc. There is a considerable potential for adopting such systems in the form of used black tea waste resulting in large quantities as a waste byproduct in cafeterias as an adsorbent for the removal of hazardous metal values from aqueous solutions. Amarasinghe and Williams (2007) reported that non treated black tea waste is a good adsorbent for the removal of Cu and Pb from waste water. Highest metal uptake attaining 48 and 65 mg/g are reported for Cu and Pb, respectively. Tan (1985) has also reported that the consumed coffee powder and black tea waste were found to be able to remove substantial amounts of Cu (II) ions from aqueous solutions. The obtained results were found to be consistent with the fact that the Cu (II) uptake mechanism was due to specific ion adsorption via chelating and to a lesser degree of ion-exchange reaction. The present work is designed to investigate the potentiality of black tea waste to adsorb some metal values from aqueous lab waste solutions as means for their recovery e.g. Cu, U, Th, REEs, etc. For this purpose several series of adsorption experiments have first been performed using proper synthetic solutions to optimize the different factors. ISSN 2314-5609 Nuclear Sciences Scientific Journal vol. 2, p 139 152 2013 140 ENASS M. EL-SHEIKH EXPERIMENTAL Materials Preparation of black tea waste The black tea is indeed prepared from the green tea being mainly produced from its vast plantations in Ceylon, India and Kenya. For this purpose, the green tea is subjected to poly phenyl oxidation through its fermentation. The black tea waste used for adsorption experiments in the present work has first been thoroughly washed with boiling water for the removal of soluble and colored components. The washed waste black tea is then washed with distilled water followed by washing with 5% HCl. Then it is dried overnight at 70 ◦C before storing in polyethylene bags. Acid washing is intended to keep the black tea waste away from its decomposition by various bacteria and fungi. Preparation of synthetic solutions Synthetic solution of uranium and other working elements have been prepared from their proper salts. Different metal solutions were thus prepared by dissolving analytical grade metal salts in distilled water or mineral acids to obtain accurate concentration as ppm (mg/l). From the latter, the working solutions were prepared by dilution to realize the required concentration. The pH of these solutions was measured and adjusted at 4.5±0.5 and all the adsorption experiments run at room temperature 25±2 ◦C. The metal salts used include the nitrate salts of U, Cu ,Ca, Pb and Th ,the chloride salts of Fe and Cd and the hydroxide salts of Ni and REEs (Y and Ce). Adsorption Experimental Procedure Batch adsorption tests are conducted by mixing of 2 g of the working black tea waste with 100 ml of the different working solutions of known metal ion concentration in proper glass beakers. The prepared mixture is shaken in a mechanical shaker and a 2ml sample solution is periodically withdrawn from the beaker at known time intervals. Preliminary experiments have shown that adsorption is adequately fast and the removal rate was actually found to be negligible after 60 min. Therefore, 60 min is used as the contact time for almost batch tests except in the experiments of the effect of the initial uranium concentration. At the end of each experiment, the black tea waste sample is filtered and washed to remove any fine particles before being analyzed for the adsorbed metal ions. Several series of experiments are thus conducted to determine the optimum values of the relevant factors controlling the adsorption process. As previously mentioned , The solution pH all the time is fixed at 4.5±0.5 and all the experiments are conducted at room temperature (25±2 ◦C). On the other hand , for the determination of uranium equilibrium isotherm, the corresponding experiments are conducted by mixing 1 g of the working black tea waste with 50 ml of uranium of initial concentrations ranging from 10 to 2000 mg/l. In these experiments, each batch mixture is shaken for a contact time of up to 3 h to reach equilibrium . For each adsorption experiment the adsorptive capacity (qe) is determined according to the following equation; qe= V (C0-Ce)/M where V is the total volume of the solute solution ( in L), M is the weight of adsorbent used (gm), C0 is the initial concentration of the solute (mg/l), and Ce is the residual equilibrium concentration of the solute (mg/l). After studying the adsorption character of agitation solution containing U and possible interferers an application experiment is conducted upon the actual working lab waste solution . For the latter, both a loading test is achieved followed by elution and precipitation of REEs ,U and Th . Concerning the application studies upon a working laboratories waste solution , a recovery test of U, Th and REEs have been performed by proper elution and precipitation. 141 POTENTIALITY OF URANIUM ADSORPTION AND ITS ASSOCIATED ELEMENTS Analytical Procedures The various metal ions are determined using atomic absorption spectrometer (A AS) (Unicam 969, England). Meanwhile, thorium and REEs are spectrophotometerically determined by the chromogenic reagent Arsenazo-III (Merczenko, 1986), while uranium analysis in different processing stream solutions is performed by an oxidimetric titration method using ammonium metavanadate. On the other hand, the obtained REEs ,U and Th final products have been subjected to proper analysis using both the ESEM-EDX and XRD techniques. RESULTS AND DISCUSSION Structure of the Working Black Tea Waste According to Harler (1963), the ethanol insoluble black tea waste is mainly composed of cellulose, lignin and some structural proteins in different ratios . To assess the working black tea waste, a proper sample is subjected to a chemical analyses of these major components for the determination of their relative amounts. For this purpose , the procedures adopted by Tappi(1957) for cellulose lignin and carbohydrate and by Bradford, (1976) for protein have been applied. The obtained results (Table1) have indicated an almost complete similarity to that given by Harler (1963) . As a matter of fact , the fresh green tea leaves contain indeed nine main compounds, namely: polyphenols (sometimes called tannins), alkaloids, protids, organic acids, glucids, lipids, cholorphylls, mineral salts and volatile substances. Each of these can be further divided into subcategories. Yang and Wang( 1996) have reported that the manufacture of the black tea from the green tea would cause changes in the chemical formulae of these components (Fig. 1). Results of Uranium Adsorption Upon Black Tea Waste Effect of stirring state In order to study the effect of stirring state upon uranium adsorption efficiency, two adsorption experiments have been performed using mechanical shaking in one of them. In these experiments, 2g weight of black tea waste sample is used in a S/l ratio of 1/50 using a uranium solution assaying 100 ppm and its pH was fixed at 4-5. After 1hour, the black tea waste sample is filtered and the obtained filtrate is analyzed for uranium. From the obtained results, it is clear that stirring is quite important for attaining a high uranium adsorption efficiency. Thus, the latter has reached up to 95.67 %. while under the same conditions, the mere soaking has attained a much lower efficiency reaching only 51.13% (Fig. 2). Effect of agitation time For studying the effect of agitation time upon uranium adsorption efficiency, three series of experiments have been performed in which the uranium concentration was varied between 25 and 100 ppm . In these experiments, about 2g of black tea waste were allowed for stirring within the uranium solution having different concentrations at a fixed pH of 4-5. The applied agitation time periods involved 15, 30, 60, 90, 120 and 180 min. The obtained results are shown in Table (2) and plotted on Fig (3). From the latter results, it is noticed that by increasing the agitation time, the adsorption efficiency increases during the

POTENTIALITY OF URANIUM ADSORPTION AND ITS ASSOCIATED ELEMENTS FROM WASTE LABORATORY LIQUIDS USING BLACK TEA WASTE