MnO2 loaded soybean stem activated carbon for capacitive removal of phenolphthalein in simulated laboratory wastewater: A new strategy for sustainable water treatment

The primary objective of this work is to remove the phenolphthalein (PhIn) from wastewater using a simple and highly effective adsorption methodology based on manganese oxide (MnO₂)-modified activated carbon (AC) nanocomposites. MnO₂-AC nanocomposites were synthesized using the mechano-chemical preparation process. In order to witness the physico-chemical properties, the synthesized manganese oxides-modified activated carbon have been evaluated using the several analytical techniques such as FT-IR, Raman spectroscopy, SEM with EDX, optical profilometer, XRD, particle size and zeta potential analyser. Manganese oxides-modified activated carbon was successfully prepared, as evidenced by the results. The soyabean stem activated carbon- manganese oxide (SyTAC-MnO₂) nanocomposite zeta potential is 10.1 mV indicating the stability of nanocomposite. The MnO₂ metal oxide particles were effectively incorporated into the activated carbon void area of soybean stems. The adsorption of PhIn on the SyTAC-MnO₂ was best characterized by the Freundlich isotherm model. Batch adsorption study revealed that, the maximum PhIn removal from the aqueous solution was 92.2 % at 298 K. The adsorption process was believed to involve the electrostatic contact. The PhIn adsorption on SyTAC-MnO₂ was further shown to be spontaneously exothermic and to reduce disorder by calculating the thermodynamic parameters (ΔG, ΔH, and ΔS). The pseudo-second-order kinetic model may be able to capture the kinetic process, according to the R² values (= 0.958). High removal efficiency was observed in the pH range of 2–6, and there was a direct correlation between pH and SyTAC-MnO₂'s adsorption capability for PhIn. Monte Carlo (MC) simulations and density functional theory (DFT) provided support for the experimental results. SyTAC-MnO₂ may therefore be a useful adsorbent for the adsorptive removal of PhIn from the wastewater. For thorough water filtration, the synthetic SyTAC-MnO₂ nanocomposite provided an economical and sustainable source of materials.