Acid Yellow 25 (AY25) is used in the textile industry for dyeing of natural fibers as well as synthetic fibers. To a lesser extent, it is also used as a coloring agent in paints, inks, plastics, and leather. Effluents from such industries are major sources of water pollution. Dyes in wastewater are difficult and costly to remove since they are stable to oxidizing agents and light. Hence, it is important to find simple, efficient, and inexpensive ways to remove the dyes from wastewater. The objective of this study is to determine the suitability of chitin extracted from waste crab legs as an adsorbent for removing AY25 dye. Purified chitin was characterized by Fourier transform infrared spectroscopy (FTIR) and X-ray powder diffraction methods. Batch adsorption experiments were performed to determine the effect of adsorbent dosage and initial dye concentration on percentage dye removal.
The adsorption kinetics were modeled using the pseudo-first order, pseudo-second order, and intra particle diffusion equations to determine the rate controlling step. Results showed that the pseudo-second order adsorption mechanism is predominant, and the overall rate of dye adsorption process is therefore controlled by adsorption reaction.
Adsorption data were analyzed using Langmuir, Freundlich, D-R and Temkin isotherm models at 23°C using various initial dye concentrations with different chitin dosages. Equilibrium data were fitted well with the Langmuir, Freundlich and D-R models giving the highest correlation with Langmuir model. This confirmed that chitin consists of both monolayer and homogeneous adsorption sites. Based on the D-R model, the adsorption of AY25 dye onto chitin was via chemisorption.
Same batch experiments were performed using unprocessed chitin and chitin extracted from red lobster shells to determine the efficiency of adsorption with different adsorbents. Results showed that unprocessed chitin is not a good adsorbent material. Chitin extracted from red lobster shell is better than that of crab legs giving the higher adsorptive capacity. In conclusion, chitin from waste crab legs is a very suitable adsorbent material that is capable of removing up to 95% of the initial concentration of AY25 dye. Also chitin is inexpensive and eco-friendly adsorbent found abundantly in nature.
|Commitee:||O'Brien, Leah C., Voss, Eric J.|
|School:||Southern Illinois University at Edwardsville|
|School Location:||United States -- Illinois|
|Source:||MAI 53/06M(E), Masters Abstracts International|
|Keywords:||Acid yellow 25, Adsorption kinetics, Adsorptive capacity, Chitin, Freundlich isotherm, Langmuir isotherm|
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