Enhancing a novel Al2O3–Chitosan@activated carbon nanocomposite for indoor air quality: Examination of vapor-phase phenanthrene adsorption efficiency of air cleaner material

Abstract

Herein, we report the chemical activation of Triticum monococcum (einkorn wheat) waste biomass (TRM) with ZnCl₂ to obtain a tailored activated carbon (TAC) and modified TAC (MTAC). Chitosan and aluminum oxide nanoparticles (CS–Al₂O₃@TAC) were incorporated to prepare MTAC. Both TAC and MTAC were exploited for the removal of non-polar phenanthrene (PHE) from the controlled gas steam. The effectiveness of the resulting MTAC was systematically investigated in the gas to solid-phase removal of PHE. Also, the physicochemical properties were evaluated by the Brunauer-Emmett-Teller specific surface area (583 m²g^-1 for TAC and 729 m²g^-1 for MTAC), Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, and powder X-ray diffraction. The findings revealed that the MTAC composite is a promising adsorbent for developing cost-effective filters to remove polycyclic aromatic hydrocarbons from indoor environments. The PHE adsorption on MTAC (85 mg g^-1) was higher than on TAC (60 mg g^-1) during the first 50 min, attributed to the oxygenated functional groups. The adsorption capacity of MTAC increased sharply at concentration of 300 ng m^-3 and then slowly increased up to 131 mg g^-1 at 500 ng m^-3. The adsorption isotherms at different temperatures were determined by thermodynamic parameters such as free energy (ΔG° = −2.59 kJ mol^-1 to −5.03 kJ mol^-1 for TAC; ΔG° = −5.69 kJ mol^-1 to −8.95 kJ mol^-1 for MTAC), enthalpy (ΔH° = 30.49 kJ mol^-1 for TAC; ΔH° = 36.53 kJ mol^-1 for MTAC), entropy (ΔS° = 0.14 kJ mol^-1 K for TAC; ΔS° = 0.15 kJ mol^-1 K for MTAC) and, overall, PHE adsorption was feasible, spontaneous, and endothermic. This work showed that incorporation of CS–NPs and Al₂O₃–NPs into TAC brings about better adsorption properties , compared to pristine TAC, which can be attributed to the modification of major functional groups. The desorption efficiency of TAC (73 %) and MTAC (86 %) decreased over five cycles of multiple reuse. Moreover, the adsorption capacity of MTAC remained noticeably higher than that of TAC, suggesting that chemical modification can enhance the removal of gas flow PHE.