Preparation of porous carbon from palm shell using phosphoric acid activation: process optimisation, adsorption, reagent recovery and reuseability

The objective of present work is to develop chemically activated carbons from palm shell using H3PO4 via optimisation on the process parameters such as impregnation ratio, activation temperature and activation time, with the aim of achieving high yield and well developed pore structure. The process optimisations have been conducted utilising the optimisation tool Response Surface Methodology (RSM). Various issues associated with chemical activation process such as the activation in inert media/self-generated atmosphere (SGA) and activation with reclaimed reagent were also been addressed. The kinetics of the H3PO4 activation and significance of SGA have been assessed using thermogravimetric analysis (TGA). The activated carbon have been characterised for (i) pore size distribution, average pore size and the surface area using the BET surface area analyser, (ii) the surface textures and structure of the pores using SEM, FT-IR and XRD. Based on the pore structure and the surface area, suitability of the PSAC for adsorption on specific macromolecules, Methylene Blue (MB) and dairy COD have been developed. Effectiveness of an adsorbent is assessed by the equilibrium adsorption capacity and the rate of adsorption of the adsorbent. Experiments on adsorption isotherm and kinetics of the mentioned adsorbates have been established. The recovery and reusability of H3PO4 for subsequent activation of palm shell under identical experimental conditions were also being thoroughly investigated. PSAC with BET surface area exceed 2000m /g has been developed, coupled with high carbon yield of approximately 50%. The good adsorption value on MB and dairy COD correspond with high mesopore content in PSAC, a unique character of the carbon. The significance of SGA has been demonstrated from TGA analysis. The reclaimed H3PO4 is found to have almost similar activation capability as that fresh acid in terms of yield and textural characteristics.