Abstract
Acid Yellow 25 (AY25) is used in the textile industry for dyeing of natural and synthetic fibers, and is also used as a coloring agent in paints, inks, plastics, and leathers. Effluents from such industries are major sources of water pollution. Hence, it is important to find simple, efficient, and inexpensive ways to remove these dyes from wastewater. Here, we determined the suitability of chitin extracted from waste crab legs as an adsorbent for removing AY25 dye. The adsorption kinetics was modeled using pseudo-first order, pseudo-second order, and intraparticle diffusion equations to determine the rate controlling step. Results showed that the pseudo-second order adsorption mechanism is predominant, and the overall rate of the dye adsorption process is therefore controlled by an adsorption reaction. Adsorption isotherms were analyzed by utilizing the Langmuir, Freundlich, Dubinin-Radushkevich (D-R) and Temkin isotherm models at 23℃, with data collected by using various initial dye concentrations with different chitin dosages. Our results show the highest correlation with the Langmuir model, consistent with the fact that chitin contains both a monolayer and homogeneous adsorption sites. Based on the D-R model, the adsorption of AY25 dye onto chitin is via chemisorption. Furthermore, we have concluded that the rate constants of both pseudo-second order adsorption and film diffusion are correlated to the initial dye concentrations and chitin dosages. In conclusion, chitin from waste crab legs is a very suitable adsorbent material that is capable of rapidly removing up to 95% of the initial concentration of AY25 dye at a pH of 2 and room temperature.
Highlights
Dyes are widely used by textile, food, paper, paint, and pharmaceutical industries [1], producing tremendous amounts of wastewater
Adsorption isotherms were analyzed by utilizing the Langmuir, Freundlich, Dubinin-Radushkevich (D-R) and Temkin isotherm models at 23 ̊C, with data collected by using various initial dye concentrations with different chitin dosages
Though the basis of the correlation is not known, our results indicate that the mass transfer process of Acid Yellow 25 (AY25) adsorption onto the chitin surface from the onset of the process is very quick, followed by a slower intraparticle diffusion, and both processes are controlled by the “availability” of dye to the surface of chitin
Summary
Dyes are widely used by textile, food, paper, paint, and pharmaceutical industries [1], producing tremendous amounts of wastewater. Precipitation, electrochemical destruction, electro-flocculation, irradiation, and oxidation, are used to treat wastewater dyes [5]. Physical methods like membrane filtration and ion-exchangers have their own drawbacks in dye wastewater removal. We used chitin prepared from waste snow crab legs as a sorbent for the removal of AY25 dye from an aqueous solution. Chitin associates with proteins, organic pigments, and minerals [9] This crab-waste recycling method will benefit both the food industry and the textile industry by saving on their waste management expenses and their effluent treatment cost, respectively. The objective of this research is to study the suitability of using chitin prepared from waste snow crab legs to remove AY25 dye from aqueous solutions
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