The continuous increase in the number of stringent exhaust emission legislations of marine Diesel engines had led to a decrease in NO_x emissions at the required level. Selective catalyst reduction (SCR) is the most prominent and mature technology used to reduce NO_x emissions. However, to obtain maximum NO_x removal with minimum ammonia slip remains a challenge. Therefore, new mixers are designed in order to obtain the maximum SCR efficiency. This paper reports performance parameters such as uniformity of velocity, ammonia uniformity distribution, and temperature distribution. Also, a numerical model is developed to investigate the interaction of urea droplet with exhaust gas and its effects by using line (LM) and swirl (SM) type mixers alone and in combination (LSM). The urea droplet residence time and its interaction in straight pipe are also investigated. Model calculations proved the improvement in velocity uniformity, distribution of ammonia uniformity, and temperature distribution for LSM. Prominent enhancement in the evaporation rate was also achieved by using LSM, which may be due to the breaking of urea droplets into droplets of smaller diameter. Therefore, the SCR system accomplished higher urea conversion efficiency by using LSM. Lastly, the ISO 8178 standard engine test cycle E3 was used to verify the simulation results. It has been observed that the average weighted value of NO_x emission obtained at SCR outlet using LSM was 2.44 g/kWh, which strongly meets International Maritime Organization (IMO) Tier III NO_x (3.4 g/kWh) emission regulations.

Magnetic cellulose nanocrystal (MCNC) nanocomposites are promising sustainable and biocompatible platforms for magnetic hyperthermia; however, the molecular mechanisms governing Fe₃O₄ adsorption and deposition onto CNCs remain poorly understood. Here, sulfated (S-CNC) and TEMPO-oxidized CNCs (T-CNC) were used to prepare nanocomposites at 1:2 and 1:4 CNC:Fe₃O₄ mass ratios, enabling a systematic evaluation of how surface chemistry and nanoparticle loading dictate interfacial interactions and magneto-colloidal behavior. Bare magnetite nanoparticles were 21 ± 5 nm by TEM but grew to 144 ± 18 in the DLS measurement at pH 7. The S-CNC nanocomposites had hydrodynamic sizes between 144 and 210 nm, not much larger than the 140 nm long CNC rods, suggesting an enhanced dispersion stability compared to Fe₃O₄ alone. X-ray photoelectron spectroscopy combined with density functional theory revealed that −OH and −COOH groups drive electrostatic adsorption with charge transfer from Fe₃O₄ to the CNC surface, while T-CNCs showed more favorable adsorption energies and evidence of covalent Fe–O bonding. Vibrating sample magnetometry demonstrated superparamagnetic behavior for all samples, with S-CNC/Fe₃O₄ 1:4 and 1:2 displaying saturation magnetizations of 78 and 77 emu/g-Fe₃O₄, close to the 83 emu/g of bare magnetite. The T-CNC composites showed lower (60 and 66 emu/g-Fe₃O₄) saturation magnetizations. Zero-field-cooled/field-cooled measurements resulted in a blocking temperature of 112 K for all samples, except T-CNC/Fe₃O₄ 1:2 (100 K). Magnetic hyperthermia studies revealed that specific absorption rate (SAR) increased with field strength and Fe₃O₄ content; however, S-CNC/Fe₃O₄ (1:2) achieved the highest intrinsic SAR per gram of Fe₃O₄ (649 W/g-Fe₃O₄) likely due to its anisotropy and fast magnetic relaxation. Cytotoxicity assays confirmed that all nanocomposites were nontoxic toward mammalian cells. These results establish quantitative structure–property relationships between CNC surface chemistry, interfacial bonding mechanisms, and magnetic heating performance, providing a foundation for rational design of biocompatible magnetic nanocomposites for hyperthermia and related applications.

The emergence of 2D materials has significantly expanded the wide range of nanomaterials with diverse applications. Notably, their high conductivity, catalytic efficiency, and hydrophobicity have fueled heightened research interests for water treatment applications. This research aimed to investigate the synthesis and characterization of MXene and reduced graphene oxide (rGO) nanocomposites with silver nanoparticles (Ag) for enhanced catalytic activity in the decomposition of Direct Blue-24 dye. In this study, we employed well-established methods, previously documented in the literature, to prepare two distinct nanocomposites. Novel nanocomposites, namely reduced graphene oxide–silver nanoparticles (rGO–Ag) and MXene–silver nanoparticles (MXene–Ag), were synthesized using the hydrothermal and direct reduction method with an ammoniacal solution (aqueous solution). Comprehensive characterization using advanced tools revealed that the introduced Ag particles integrated seamlessly onto the parent nanofilms of the Carbon derivatives, forming a secondary phase with enhanced catalytic functionality. These nanocomposites demonstrated significant improvements in the catalytic decomposition reactions in simulated wastewater. Verification involved the reduction reaction of Direct Blue-24 dye at known nanocomposite concentrations. The results indicated that MXene–Ag exhibited a superior catalytic activity of 98% in 10 min compared to the rGO–Ag nanocomposite films, which achieved 96% in 35 min. The results indicated that MXene–Ag nanocomposites exhibited a 20–25% increase in catalytic efficiency compared to the rGO–Ag nanocomposites. The outcomes of this research hold promise for practical applications in textile wastewater management and various industrial sectors dealing with mutagenic and carcinogenic chemicals containing azo and/or phthalocyanine products.

This study presents the design and synthesis of multifunctional magnetic cellulose nanocrystal (CNC) composites engineered for targeted adsorption and broad-spectrum antimicrobial applications. The nanocomposites were fabricated by anchoring mixed-valence Fe3O4 magnetic nanoparticles on eco-friendly CNC frameworks, followed by surface functionalization with benzalkonium chloride (BC), a potent quaternary ammonium biocide. Both sulfated (S) and TEMPO-oxidized CNC (T) variants were investigated across Fe3O4:CNC mass ratios of 1:2 and 1:4. Comprehensive structural, magnetic, and morphological characterization confirmed successful surface modification, superparamagnetic responsiveness, and uniform component dispersion. Thermogravimetric analysis confirmed precise compositional tailoring, capturing up to 87 wt.% inorganic magnetite core fractions, 11−34 wt.% organic CNC matrix, and up to 11 wt.% bound BC surfactant. Density functional theory (DFT) simulations complemented these insights by mapping favorable BC binding configurations and localized electronic-structure alterations. Equilibrium adsorption isotherms followed a dominant Langmuir monolayer pathway, with saturation capacities of 178−224 mg g−1 and Langmuir correlation coefficients (R2) of 0.97−0.995. Quantum-chemical binding maps, together with robust within-variant interfacial charge inversions (e.g., from −22.1 to +8.5 mV for the 1:2 S formulation and from −20.4 to +11.2 mV for the 1:2 T formulation after BC addition), point to a cooperative physisorption−chemisorption transport mechanism. In vitro antibacterial assays showed pronounced, concentration-dependent inhibition zones of 7.9−12.8 mm against both Gram-positive (Listeria monocytogenes) and Gram-negative (Escherichia coli) foodborne pathogens, with bactericidal performance primarily correlating with BC loading and, to a lesser extent, with the underlying CNC surface chemistry. Together with the high adsorption capacity and magnetic recoverability of the CNC-Fe3O4 carrier, these results position BC@CNC-Fe3O4 nanocomposites as a promising platform for applications such as smart disinfection and active food-contact materials.