| dc.description.abstract | Luffa cylindrica, a lignocellulosic material that grows in tropical climates as found in Kenya, was bought from Gikomba, Kangemi, Kawangware markets and kiosks within parklands areas of Nairobi. A total of 287 pieces of luffa cylindrica was procured and found to be sufficient for this work. Both batch and continuous mode of operation were employed in this study. All the procured pieces were mixed and subjected to the same treatment.
In the batch mode the effects of contact time, initial dye concentration, adsorbate weight, solution media ionic strength, pH and treatment of luffa cylindrica with both nitric acid and hydrogen peroxide (as possible regeneration agents) were investigated. Luffa-derived activated carbon was prepared and investigated.
Twenty minutes contact time was found to be adequate producing up to 95.1% adsorption. The % adsorption of methylene blue dye onto the luffa cylindrica was found to increase with increase in the ratio of weight of luffa to initial dye concentration. Ionic strength of the solution did not have any effect on the % adsorption signifying a possible non-ionic type of interaction between the adsorbate and the adsorbent. A highly acidic condition (i.e. pH below 3.0) was found to be unfavourable for adsorption and higher % adsorptions only occurred in the initial mixture pH 3.9 - 11 range. The near-buffering effect of luffa cylindrica produced a final
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solution pH that indicated % adsorption was optimal between pH 4.3-5.6 range. Nitric acid instantaneously regenerated the spent luffa without any deleterious effect while the hydrogen peroxide-regenerated spent luffa had a slightly reduced adsorption capacity (from 96.4% to 94.9%) and took a minimum of 8hours to regenerate under sonication.
Adsorption Isotherm studies showed that the uptake of methylene blue dye by luffa cylindrica occurred by monolayer sorption while Freundlich adsorption isotherm yielded values for adsorption intensity, n, greater than 1, indicating favourable adsorption.
The continuous flow mode of operation showed the practical utility of luffa cylindrica in the removal of methylene blue dye from aqueous solution. Breakthrough studies indicated that breakthrough point was attained with less dye solution volume when a higher concentration dye solution was used in a fixed weight of luffa cylindrica and takes more dye solution for increased weight of luffa cylindrica. For instance, with a 1.695 a.u. methylene blue dye solution, lOg of luffa material involved use of 34,000ml of the dye solution to reach the breakthrough point. Alternatively for 1.595 a.u. methylene blue dye solution, a total volume of 130,000ml of the dye solution was required with 40g luffa to reach the breakthrough point signifying a 3.8% increase in solution volume.
Luffa cylindrica was applied to a real textile dye effluent (direct red dye) with quite good results. 4.5g of luffa cylindrica removed 58.2% of the dye
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while 6g removed 77.9%, confirming that luffa cylindrica, in its natural form, has the potential to be used in stripping textile dye off effluents before discharge into water bodies.
Luffa-derived activated carbon resulted in 77.5% weight loss and therefore it was found unnecessary to produce activated carbon from luffa cylindrica considering its already proven effectiveness in the removal of methylene blue dye in its raw form.
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