Almond Shell As an Adsorbent for Removal of Acid Blue 129

AB129 is an anthraquinone acid dye commonly used for dyeing cotton, wool and silk fabric. However, due to its ecotoxic potential posed by its genotoxicity, mutagenicity and carcinogenicity properties. Furthermore, this dye may cause eye and skin irritation in humans as well as block light penetration into water bodies, inhibit the growth of microorganisms and disrupt natural biological processes within aquatic organisms.

Thus, the removal of AB129 from aqueous solutions has become a crucial issue in textile industries. Recently, studies were undertaken to study decolorization using poly(allyl (triethylammonium chloride)) and chitosan as adsorbents; batch mode experiments were run to observe their influence on pH values, initial adsorbate concentration levels, dosage rates, contact times and temperatures as they relate to adsorption effectiveness of various adsorbents.

In this work, almond shell (AS) was evaluated as an adsorbent for the removal of AB129 through batch tests. First, AS was dried and crushed using a ball mill into particle sizes ranging from 0-177, 210-297 and 350-500 microns before being immersed into an AB129 solution with 40 mg/L concentration for 30 minutes in water before analyzing its color index index, water absorbency index (WAI), TDS concentration, total dissolved solids concentration (TDS), TDS concentration and total dissolved solids concentration using Shimadzu UV-vis spectrophotometer.

Results demonstrated that AS was an excellent adsorbent for the removal of AB129 dye at pH 2.00 with an optimal removal efficiency of 96% at concentration of 0.4 g/25 ml and concentration of 0.4 g/25 ml, where correlations were established between dye concentration and dye uptake; when more sorbate concentration is used more dye is absorbed; this result was verified through various analyses such as FTIR and elemental analysis of AS.

Adsorption of AB129 by AS was determined to occur via a chemisorption process characterized by formation of sulfate radicals generated through photocatalytic activation of peroxydisulfate at wavelength 260nm, the kinetics of which was studied, and a pseudo-first order model proposed. Furthermore, decolorization by the AS was further confirmed through in vivo toxicological testing using Daphnia magna and Lemna minor as verification agents.

Chitosan was tested as another possible means for the adsorption of AB129 in batch experiments and it was discovered that its rate was much greater than on PTS-modified AS. Chitosan modified with AS showed significantly greater adsorption capacity for AB129 than AS-modified chitosan, with 96% showing up on an adsorption capacity test. This result was supported by various analyses including FTIR, elemental analysis, and porous structure parameters. Regenerative tests on both adsorbents show that they can retain the AB129 molecule after regeneration, an encouraging result as it shows great promise for future organic dye treatments.

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