The transformation of waste plastics into value-added aromatics could incentivize better waste plastic management. The reported studies had low selectivity for monocyclic aromatics because more polycyclic aromatic hydrocarbons and carbon residues were generated. The effects of temperature, pressure, and catalyst on monocyclic aromatic selectivity were explored using a central composite design (CCD) followed by the response surface methodology (RSM) at a high ramp rate of 15 °C/min. The liquid product yield and selectivity to aromatic hydrocarbons were enhanced by regulating the acidic properties of the catalyst and processing parameters. The proportion of monocyclic aromatics in the liquid product was up to 90%, and the yield of monocyclic aromatics based on the reactant mass was 51% at the optimized condition. The carbon deposit production was low (only approximately 1%), which allowed higher liquid yields. In addition, the coupling mechanism of multiple factors on the depolymerization/aromatization reactions was proposed. This conversion of polyethylene into high-yield monocyclic aromatics provides a viable plastic recycling approach.

Conventional biochar has limited effectiveness in the adsorption of sulfonamide antibiotics, while modified biochar exhibits greater adsorption potential. Residues of sulfamethoxazole (SMX) in the aquatic environment can threaten the safety of microbial populations as well as humans. In this study, iron-nitrogen co-doped modified biochar (Fe-N-BC) was prepared from palm fibers and doped with Fe and urea via synthesis at 500 °C. Fe-N-BC has a richer surface functional group based on elemental content, X-ray photoelectron spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. The Brunauer-Emmett-Teller (BET) specific surface area test exhibited Fe-N-BC, which possessed a greater surface area (318.203 m²/g) and a better developed pore structure (0.149 cm³/g). The results of the hysteresis loop and the Raman spectrum show that Fe-N-BC has a higher degree of magnetization and graphitization. Fe-N-BC showed a remarkable adsorption capacity for SMX (42.9 mg/g), which could maintain 93.4% adsorption effect after four cycles, and 82.8% adsorption capacity in simulated piggery wastewater. The adsorption mechanism involves pore filling, surface complexation, electrostatic interactions, hydrogen bonding, and π-π EDA interactions. The results of this study show that Fe-N-BC prepared from palm fibers can be a stable, excellent adsorbent for SMX removal from wastewater and has promise in terms of practical applications.

Novel KMnO₄-modified loofah biochar loaded with nano-Fe₂O₃ (FMLB) was successfully synthesized for Cu(II) adsorption. Nitrogen adsorption method, scanning electron microscope, X-ray photoelectron spectroscopy, Fourier transform infrared spectrometer, and other characterization measurements were used to evaluate the physical and chemical properties of FMLB and nano-Fe₂O₃-loaded biochar (FLB). The results show that the adsorption behavior of Cu(II) can be best fitted by the Langmuir isotherm model and the pseudo-second-order (PSO) kinetic model, indicating that the surface of FMLB was composed of homogeneous adsorption, and chemical adsorption dominated the adsorption process under optimal reaction conditions. The adsorption capacity of FMLB is improved by 42.86% compared to FLB, and it remained over 75% after four cycles. The inner-sphere complexes with manganese oxide (MnO_x) and oxygen-containing functional groups, as well as electrostatic interaction, physical adsorption, and ion exchange, play important roles in Cu(II) adsorption. The saturation magnetization of FMLB was 10.41 emu/g, ensuring that it can be easily separated from aqueous solutions. Therefore, magnetically recyclable biochar modified by KMnO₄ is a feasible method for Cu(II) adsorption.