Adsorption of Basic and Acidic Dyes onto Agricultural Wastes

Abstract

Abstract. The potential of almond leaves powder, (ALP) for the removal of Crystal violet (CV) and Congo red (CR) dyes from aqueous solution was investigated. The adsorbent (ALP) was characterized by FTIR and SEM analysis. Batch adsorption studies were conducted and various parameters such as contact time, adsorbent dosage, initial dye concentration, pH and temperature were studied to observe their effects in the dyes adsorption process. The optimum conditions for the adsorption of CV and CR dyes onto the adsorbent (ALP) were found to be: contact time (100mins), pH (10.0), temperature (343K) for an initial CV dye concentration of 50 mg/L using adsorbent dose of 1.0 g and contact time (100mins), pH (2.0), temperature (333K) for an initial CR dye concentration of 50 mg/L using adsorbent dose 1.0 g respectively. The experimental equilibrium adsorption data fitted best and well to the Freundlich isotherm model for both CV and CR dyes adsorption. The maximum adsorption capacity of ALP was found to be 22.96 mg/g and 7.77 mg/g for the adsorption of CV and CR dyes respectively. The kinetic data conformed to the pseudosecond-order kinetic model. Thermodynamic quantities such as Gibbs free energy (G 0 ), enthalpy (H 0 ) and entropy (S 0 ) were evaluated and the negative values of G 0 obtained for both dyes indicate the spontaneous nature of the adsorption process while the positive values of H 0 and S 0 obtained indicated the endothermic nature of the adsorption and increased randomness during the adsorption process respectively for the adsorption of CV and CR onto ALP. Based on the results obtained such as good adsorption capacity, rapid kinetics, and its low cost, ALP appears to be a promising adsorbent material for the removal of CV and CR dye stuff from aqueous media.

Utilization of Agro-Waste in the Elimination of Dyes from Aqueous Solution: Equilibrium, Kinetic and Thermodynamic Studies

“…The plot of versus 1 � gives a linear relationship, which allows the computation of ∆ and ∆ values from the slope and intercept respectively. The negative value of ∆ 0 reveals decreased randomness at the solid/solution interfaces and suggests the adsorption MG dye adsorption onto MCP was enthalpy driven [33]. While the positive value of ∆ suggest increased randomness at the solid/solution interphase for the adsorption of CR onto MCP [34].…”