Pineapple peel–derived carbon for adsorptive removal of dyes

The pineapple peel activated carbon (PiPAC) showed remarkable adsorption capacities for methylene blue (MB) and methyl red (MR) dyes as a result of its high porosity. Characterization techniques, including Thermogravimetric analysis (TGA), Brunauer–Emmett–Teller (BET), X–ray diffraction analysis (XRD), Fourier Transform Infrared (FTIR), Energy–dispersive X–ray spectroscopy (EDX), and Scanning Electron Microscopy (SEM) were employed to analyze the PiPAC's performance. The EDX examination revealed that the PiPAC (BET surface area: 1160 m2/g) contained 67.18% of the carbon supported by PiPAC's functional group and XRD crystallization. Results showed the highest maximum adsorption capacity (qmax) for PiPAC–MB dye at 165.17 mg/g (pH 8) and PiPAC–MR dye at 94.87 mg/g (pH 6) at 60 °C. The Langmuir, Freundlich and Tempkin isotherm for PiPAC–MB and PiPAC–MR dyes fitted the equilibrium isotherm studies. The PiPAC–MB dyes were found to suit the PSO kinetic model, whilst the PiPAC–MR dyes fitted the PFO kinetic model and were in excellent agreement with the experimental findings. The thermodynamic behaviour showed endothermic, physisorption–mediated, and spontaneous adsorption of PiPAC–MB and PiPAC–MR dyes. The regeneration efficiency of PiPAC showed higher in the third cycle, 75.6% for the MB dye supported with FTIR spectra, EDX spectra and SEM. Molecular docking studies also revealed that van der Waals, π–π stacking, and hydrogen bonding interactions were involved in the adsorption of PiPAC–MB and PiPAC–MR dyes. Thus, pineapple waste, a conventional environmental liability, can be transformed into valuable adsorbents for wastewater treatment.