Synthesis of a Modified Biosorbent from Lignocellulosic Biomass: Comparative Adsorption Performance with an Activated Carbon of the Same Origin

Mango seed shells were used as a precursor for the synthesis of two adsorbent materials: an activated carbon (AC-MSS) and a modified biosorbent (MB-MSS). The AC preparation process was optimised by evaluating the specific surface area under various activation parameters, while the selection of the most effective MB-MSS was based on its paracetamol removal efficiency. Optimal conditions for AC-MSS synthesis were identified as activation with 40% phosphoric acid, an impregnation ratio of 1.5 (mass of chemical agent/mass of precursor), and carbonisation at 450˚C for 90 min. For MB-MSS, the sample prepared with a sulphuric acid impregnation ratio of 2.5 exhibited the highest adsorption capacity. Both materials were characterised using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM/EDX), and thermogravimetric analysis (TGA). Kinetic studies revealed that paracetamol adsorption onto both materials followed a pseudo-second-order model. Additionally, equilibrium data for both adsorbents fitted well to both Langmuir and Freundlich isotherm models. According to the Langmuir model, the maximum adsorption capacities were 44.84 mg/g for AC-MSS and 9.82 mg/g for MB-MSS.