Preparation of Eco-friendly and Low-cost Activated Carbon from Gracilaria corticata Seaweeds for the Removal of Crystal Violet Dye from Aqueous Solution: Equilibrium and Modeling Studies

Abstract

In this paper, a compatible, eco-friendly and low-cost activated carbon prepared from the Gracilaria corticata seaweed materials was used for the effective removal of crystal violet dye in an aqueous solution. FTIR spectroscopy was used to detect the presence of functional groups such as hydroxyl and carboxyl and other groups. Morphological studies were carried out using SEM and EDX analysis while the physical nature of the material was analysed with XRD pattern studies. The batch mode dye adsorption properties of activated carbon as a function of dosage, solution pH, initial dye concentration, temperature, and contact time were investigated. Freundlich and Langmuir adsorption isotherms were used to calculate the uptake capacity of dye removal at equilibrium condition and also for evaluating the dimensionless separation factor (RL). The adsorption data evaluated using Freundlich and Langmuir adsorption isotherm equations confirm that Langmuir was the most fitted model as compared to Freundlich. The adsorption dynamics was predicted with Lagergren’s pseudo-first order and pseudo-second order equations and intra particle diffusion model. The adsorption dynamic results show that the adsorption process follows pseudo-second order kinetics and the adsorption process depends on both time and concentration. Thermodynamic parameters, like standard Gibbs energy (dG0), enthalpy (dH0), and entropy (dS0), were determined for assessing the feasibility of the adsorption process. Enthalpy dH0 shows a positive value, indicating that the adsorption process is endothermic in nature, while the negative value of the Gibbs free energy change dG0reveals that at different temperatures the adsorption process was spontaneous in nature and the positive value of dS0 confirms the increasing randomness between the solid-solution boundaries throughout adsorption. The experimental and correlation results revealed that the activated carbon prepared from Gracilaria corticata seaweeds, proved to be an excellent and low-cost adsorbent material for the dye removal.