Comparative Study of Adsorption of Red Gram Seed Husk for the Adsorption of Congo Red, Crystal Violet, and Methylene Bluefrom Aqueous Solution

Abstract

Many industries such as paper, food, cosmetics, textiles etc. use dyes in order to color their products. The presence of Congo red, Crystal violet and Methylene blue dyes in water even at very low concentration is highly visible and undesirable. The degradation by-products of organic dyes have dangerous impacts on the environment. The ability of the low-cost materials viz. red gram seed husk (RGSH) powder to remove Methylene Blue (MB), Congo Red (CR), and Crystal Violet (CV), dyes in aqueous solution was studied by using batch adsorption process. Effect of contact time, adsorbent dosage (g/L), pH, and effect of temperature were studied in batch technique and results showed that amount of the dye adsorbed increases with increase in contact time and adsorbent dosage studied. The extent of adsorption was strongly depending on pH of solution, free energy of adsorption (∆G°), enthalpy (∆H°), and entropy (∆S°) changes were calculated. Equilibrium adsorption isotherms and kinetic were investigated. The experimental data were analyzed by the Langmuir and Freundlich models and the isotherm data fitted well to both Langmuir Freundlich isotherm. The kinetic data obtained were analyzed using a pseudo-first order and pseudo-second-order equation. The experimental data fitted very well the pseudo second-order kinetic model.