Using pistachio shell for Remazol Red removal from aqueous solutions: equilibrium, kinetics and thermodynamics

Abstract

The pistachio shell, an agriculture waste, was studied as a no-cost and readily accessible potential dye adsorbent for the removal of the commercially important reactive azo dye, Remazol Red (C.I. 18221) from its aqueous solution. For this purpose, a series of batch adsorption tests were carried out to assess the effect of various experimental parameters such as adsorbent concentration, mixing time, initial dye concentration, pH and temperature. The experimental results indicated that the maximum dye removal could be attained at pH 2. The equilibrium between the dye and the adsorbent in the solution was established within 10 min. The maximum adsorption capacity of pistachio shell was determined around 108 mg g⁻¹ at 20°C. The pseudo-second-order model provided close fit with the experimental data (R² > 0.99) for the reactive dye. Equilibrium data also fitted well to the Freundlich isotherm model in the studied concentration range of Remazol Red at 20°C. The negative values of ΔG indicated that the adsorption process was spontaneous and thermodynamically favorable. Accordingly, the pistachio shell was shown to be a very efficient and low-cost adsorbent, and a promising alternative for eliminating dyes from industrial wastewaters.

Keywords:

• Pistachio shell
• Adsorption
• Reactive dye
• Kinetics
• Thermodynamic