Adsorption of Organic Dyes by Carbonized and Chemically Activated Cassia Fistula Pods

Abstract

The kinetics and mechanism of methylene blue and Congo red adsorption by carbonized and chemical activated Cassia fistula was investigated for various physicochemical parameters in a batch system. The adsorbents were characterized using Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscope (SEM), and Energy Dispersive X-Ray (EDX). The results showed that the adsorbents were rich in carbon content and heterogeneous large surface area for organic dye interaction. T understand the adsorption process, the equilibrium data was tested using Langmuir, Freundlich, Temkin and Brunauer-Emmett-Teller (BET) adsorption isotherms. The good physisorption adsorption process is indicated by the Freundlich constant, n>1. Furthermore, -0.0188, 0.0007, and 0.6990 for methylene blue; -0.0692, 0.0001 and 0.3856 for Congo red were obtained for ∆G0, ∆H0 and ∆S0 thermodynamics parameters, respectively. Results from BET study revealed efficient dye adsorption and chemical activation of the adsorbent with hydrogen peroxide and potassium hydroxide. The regression coefficient (R2) of carbonized and chemical activated Cassia fistula biomass were: 0.918, 0.742, and 0.878, for methylene blue; 0.708, 0.666 and 0.527 for Congo red at 60 °C. Results from adsorption studies proved that chemical-activated adsorbent from Cassia fistula pods is a promising effective and eco-friendly alternative for the removal of organic dyes from the aqueous system.