Preparation and characterization of activated carbon from pine bark biomass for malachite green removal

Using agricultural waste to prepare biomass materials to remove pollutants has become a research hotspot with the rise of the circular economy. This paper focused on the removal of Malachite Green (MG) as a cationic dye from an aqueous solution using adsorbents (ACBP1 and ACBP2) chemically activated from pine bark (PB) and phosphoric acid (H3PO4) as activated agent. Samples Characterisation was carried out by X-ray diffraction (XRD), Scanning electron microscopy-energy dispersive X-ray spectrometry (SEM-EDS), Fourier transform infrared spectroscopy (FTIR) and Zeta potential measurement. The MG adsorption study was carried out under the variation of several parameters such as pH, adsorbent dosage, contact time and medium temperature. The adsorption experimental capabilities of ACPB1 and ACPB2 for MG dye were 150.18 and 148.16 mg/g, respectively. The data fit the nonlinear equation of the Pseudo-first-order kinetic model for the two adsorbents ACBP1 and ACBP2 with correlation coefficients of 0.998 and 0.997, respectively, indicating that chemisorption controls adsorption. Temperature was found to have a slight impact on adsorption performance, with ACPB1 demonstrating a removal capacity of 184.510 mg/g at 25°C to 186.670 mg/g at 55°C. In addition, a theoretical study was performed using the Density Functional Theory (DFT) quantum calculation method to examine the interactions of reactive sites of the best adsorbent ACPB1 and the cationic dye MG. The theoretical results revealed that the – OH and – COOH groups of ACPB1 were involved in adsorption. The comparative investigation between the experimental and the theoretical results concluded that the ACPB1 adsorbent has a potential removal against the cationic MG dye.