Equilibrium Sorption Studies of Cobalt (II) Ions Removal from Aqueous Solution

Abstract

This study assessed the equilibrium sorption for Co²⁺ uptake from aqueous solutions using modified biochars from palm shells (Elaeis guineensis Jacq.) and sugarcane peels (Saccharum officinarum). KMnO₄/HNO₃ oxidation was used for modification due to their high oxidative nature, increasing biochar surface area. Unmodified and modified biochars were characterized for functional groups, morphology, elemental analysis, and surface area using Fourier transform infrared (FTIR) spectroscopy, Scanning Electron Microscopy (SEM), energy-dispersive spectroscopy (EDS), and Single/Multi-Point Brunauer-Emmett-Teller (BET/MBET). Batch equilibrium sorption for Co²⁺ uptake was analyzed using atomic absorption spectroscopy. Results showed that the KMnO₄/HNO₃-modified palm shell (AP1) and sugarcane peel (BS2) biochars had higher surface areas (MBET: 450.0 m²/g, SBET: 256.0 m²/g for AP1; MBET: 392.5 m²/g, SBET: 241.9 m²/g for BS2) compared to unmodified biochars (MBET: 356.76 m²/g, SBET: 244.2 m²/g for palm shells; MBET: 418.33 m²/g, SBET: 227.2 m²/g for sugarcane peels). Sorption data fit the Freundlich model (R²: 0.9976 for AP1, 0.9426 for BS2). AP1 showed the highest Co²⁺ adsorption with maximum adsorption capacities of 1.49×10¹⁸ mg/g and reusability of 83.1%. KMnO₄:HNO₃-modified palm shell biochar had more and better adsorption sites for Co²⁺, indicating potential for superior heavy metal adsorption compared to unmodified and modified sugarcane peel biochar.