Facile development of carbon based functional adsorbent from coconut husk for the removal of organic dyes from water

Abstract

This research work demonstrates a facile hydrothermal and functionalization process to fabricate hydrothermally functionalized carbon (HTFC) from waste coconut husk fiber and its performance in the removal of methylene blue and methyl orange as the model organic pollutant. Husk chips were used as the starting material for the preparation of porous carbon through heating with sulfuric acid and using potassium hydroxide in autoclave. Porous carbon (PC) was selectively oxidized with chloroacetic acid in presence of sodium hydroxide to synthesis of hydrothermally functionalized carbon. The prepared HTFC was characterized by Fourier Transform Infrared Spectrophotometer (FTIR), Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive X-ray Spectrophotometer (EDX) and X-ray Diffraction (XRD). Required functional groups, -COOH, -OH, C-O-C were present, proved by FTIR. Tunnel shaped enormous porosity with 3D cage-like microstructure was observed from FESEM. Layered but highly disordered structures and low crystallinity were confirmed by XRD. The synthesized HTFC was then used for adsorption study for the removal of organic toxic dyes, Methylene Blue (MB) and Methyl Orange (MO). From UV analysis HTFC showed higher affinity with methylene blue than methyl orange. In removal of MB and MO, HTFC showed higher removal percentage (93%) and adsorption capacity (16.05 mg/g) for MB than removal of MO (31.29%). From isotherm analysis, MB adsorption followed the Langmuir Isotherm equation and MO adsorption followed the Freundlich Isotherm equation. Adsorption kinetics were interpreted by pseudo first and second order kinetics, and it was best demonstrated by the later one for both MB and MO.