A Comparative Study on the Adsorption Kinetics and Thermodynamics of Co (II) ion onto acid Modified and Activated Carbon Prepared from Groundnut Shell

Abstract

Acid modified (MGS) and activated carbon (GSAC) prepared from groundnut shell was used for the removal of Co (II) ion from aqueous solution. The effect of pH, contact time, adsorbent dose, metal ion concentration and temperature were studied. Some physico-chemical and Spectroscopic characterization of the adsorbents were carried out, such as moisture content, ash content, pH, bulk density, volatile matter, iodine number, point of zero charge (PZC), XRF, and FTIR. The moisture and ash content of MGS and GSAC adsorbents were found to be 15.36±0.09, 9.61 ±0.21% and 4.1 ±0.15, 4.85 ±0.05% respectively. The pH and PZC of the adsorbents has 6.8±0.1, 6.8±0.01 and 7.6, 7.4 respectively. The adsorbent samples has the bulk density of 0.32±0.01 g/m³ and 0.46±0.02 g/m³, iodine number of 283.10±22 mg/g and 235.36±20.3 mg/g, The XRF analysis indicate that K constitute major inorganic elements in the adsorbents while Ca, and Mg are minor element. The FTIR analysis results shows functional group such as O-H, C=O, and C=C stretching. The maximum adsorption capacity of Co (II) ions occurred at pH 7 for MGS and pH of 9 for GSAC. The experimental data were best described by Langmuir adsorption isotherm. The kinetics study revealed that the sorption of Co (II) ions could be best described by pseudo-second order kinetics models with R² value of 0.999. Thermodynamics result revealed the spontaneity and feasibility of the reaction for acid modified and activated carbon adsorbents.