Study on Adsorption of Alizarin Red S and Eriochrome Black T Dyes by Untreated Typha Grass as a Low Cost Adsorbent

Abstract

The purpose of this investigation was to study the adsorptive potential of untreated typha grass (UTG) using a batch system under control conditions to decolorize Alizarin Red S (ARS) and Eriochrome Black T (EBT) anionic toxic dyes from synthetic aqueous solution. In this regard, the impact of various experimental parameters namely, contact time, adsorbent dose, initial dye concentration, pH, and temperature were assessed and optimized. The adsorbent was characterized using Fourier transformed infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and point of zero charge (PZC) analysis. The maximum adsorption rates of ARS and EBT onto UTG were determined to be 49.92 mg/g and 47.43 mg/g, respectively, at equilibrium. In comparison to previous models evaluated, removal of both ARS and EBT by the UTG demonstrated that the data had a strong fit with pseudo-second-order kinetic and Freundlich adsorption isotherms. The contact time for both dyes was optimised at 15 minutes, while the pH for ARS and EBT were attained at 8 and 2 respectively. However, based on the established results of various parameters in this study, the adsorptive removal of ARS and EBT by UTG was a favourable process. The Van't Hoff plot was used to calculate the thermodynamic quantities of the adsorption process, including ΔG, ΔH and ΔS. The outcomes showed that the process was both spontaneous and thermodynamically possible. From the parameters tested, EBT was found to be better adsorbed onto UTG than ARS. Even though both dyes are anionic in nature, but EBT has additional diazo and nitro functional groups than the hydroxyl and sulphate functional groups present in ARS. This might be the reason for the better adsorption of EBT onto UTG than ARS. Results from this investigation supported the efficiency of UTG as a low-cost and environmentally friendly solution for the adsorption of ARS and EBT from contaminated wastewater.