Immobilization of chitosan-templated MnO2 nanoparticles onto filter paper by redox method as a retrievable Fenton-like dip catalyst

New insights on manganese dioxide nanoparticles loaded on cellulose-based biochar of cassava peel for the adsorption of three cationic dyes from wastewater

Herein, a cost-effective nanomaterial with excellent adsorption capacity, simply prepared, using manganese dioxide (MnO₂) nanoparticles (NP) loaded on cellulose-based biochar of an agricultural waste, which is cassava peel carbon (CPC) and denoted as MnO₂-NP-CPC. MnO₂-NP-CPC is an environmental-friendly, and efficient adsorbent analyzed using different technics such as x-ray diffraction (XRD), Fourier-transformed infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and energy dispersive x-ray spectroscopy (EDX). MnO₂-NP-CPC was used to remove three different toxic dyes; methylene blue (MB), malachite green (MG), and rhodamine b (RB) from a single (MB), (MG), (RB), binary (MB + MG), (MG + RB), (MB + RB) and ternary (MB + MG + RB) wastewater systems, the impact of pH, adsorbent dose (2-8), initial dye concentrations (10-30 mg/L), temperature (15-35 °C) were fully studied. Furthermore, all the sorption experiments were done including adsorption isotherms, kinetics, and thermodynamics to explore all the mechanisms involved in the sorption of the three ionic dyes in single, binary, and ternary systems. The equilibrium experiments data fitted well the monolayer Langmuir isotherm for the single dye system with correlation coefficients close to 1 (0.98 for MB, 0.99 for MG, and 0.86 for RB), while the extended Langmuir and extended Freundlich isotherms were investigated to study the interaction of the three dyes in their binary systems, the obtained results indicate clearly that the sorption fellows the extended Langmuir model. Besides, the kinetic study showed the applicability of the pseudo-second model for the three dyes. Finally, the thermodynamic adsorption was controlled by physisorption, endothermic, and spontaneous in nature.

Arsenite (III) removal via manganese-decoration on cellulose nanocrystal -grafted polyethyleneimine nanocomposite

The manganese is successfully induced as a "bridge joint" to fabricate a new adsorbent (CNC-Mn-PEI) connecting cellulose nanocrystal (CNC) and polyethyleneimine (PEI) respectively. It was used to remove As (III) from waste water. It has been proved that the incompact CNC and PEI were successfully connected by Mn ions, which induced the formation of O-Mn-O bonds and the removal efficiency is maintained in the broad pH range of 4-8, even with the influence of NO₃^- and CO₃^2-. The CNC-Mn-PEI was characterized by Brunauer-Emmett-Telley (BET) method and the results showed that the nanoparticle of the specific surface area was 106.5753 m²/g, it has a significant improvement, compared with CNC-Mn-DW (0.1918 m²/g). The isotherm and kinetic parameters of arsenic removal on CNC-Mn-PEI were well-fitted by the Langmuir and pseudo-second-order models. The maximum adsorption capacities toward As (III) was 78.02 mg/g. After seven regeneration cycles, the removal of As (III) by the adsorbent decreased from 80.78% to 68.2%. Additionally, the hypothetical adsorption mechanism of "bridge joint" effect was established by FTIR and XPS, which provided the three activated sites from CNC-Mn-PEI can improve the arsenic removal efficiency, and providing a new stratagem for the arsenic pollution treatment.

An environment-friendly dip-catalyst with xylan-based catalytic paper coatings

Replacing catalyst supports with sustainable and degradable materials is an urgent task. Xylan is a type of abundant natural polymers with potential applications in dispersing, anchoring, and coating materials, but its material values have always been underestimated. In this study, polyethyleneimine modified dialdehyde xylan (DAX-PEI) was used as a dispersing and anchoring agent to bind Pd nanoparticles onto paper surface to produce a DAX-PEI-Pd coated paper, which was used to catalyze Suzuki-Miyaura reactions. The catalytic coated paper exhibited a good catalytic activity with a yield of 91% and a high turnover frequency (TOF) of 3300 h^-1. Besides, it showed an excellent recyclability with the same catalytic coated paper being used 15 times and still having a yield of nearly 90%. This environment-friendly catalytic coated paper owns its great prospect in organic synthesis.

Deciphering Evolution Pathway of Supported NO3 • Enabled via Radical Transfer from •OH to Surface NO3 - Functionality for Oxidative Degradation of Aqueous Contaminants

NO₃ ^• can compete with omnipotent ^•OH/SO₄ ^•- in decomposing aqueous pollutants because of its lengthy lifespan and significant tolerance to background scavengers present in H₂O matrices, albeit with moderate oxidizing power. The generation of NO₃ ^•, however, is of grand demand due to the need of NO₂ ^•/O₃, radioactive element, or NaNO₃/HNO₃ in the presence of highly energized electron/light. This study has pioneered a singular pathway used to radicalize surface NO₃ ^- functionalities anchored on polymorphic α-/γ-MnO₂ surfaces (α-/γ-MnO₂-N), in which Lewis acidic Mn^2+/3+ and NO₃ ^- served to form ^•OH via H₂O₂ dissection and NO₃ ^• via radical transfer from ^•OH to NO₃ ^- (^•OH → NO₃ ^•), respectively. The elementary steps proposed for the ^•OH → NO₃ ^• route could be energetically favorable and marginal except for two stages such as endothermic ^•OH desorption and exothermic ^•OH-mediated NO₃ ^- radicalization, as verified by EPR spectroscopy experiments and DFT calculations. The Lewis acidic strength of the Mn^2+/3+ species innate to α-MnO₂-N was the smallest among those inherent to α-/β-/γ-MnO₂ and α-/γ-MnO₂-N. Hence, α-MnO₂-N prompted the rate-determining stage of the ^•OH → NO₃ ^• route (^•OH desorption) in the most efficient manner, as also evidenced by the analysis on the energy barrier required to proceed with the ^•OH → NO₃ ^• route. Meanwhile, XANES and in situ DRIFT spectroscopy experiments corroborated that α-MnO₂-N provided a larger concentration of surface NO₃ ^- species with bi-dentate binding arrays than γ-MnO₂-N. Hence, α-MnO₂-N could outperform γ-MnO₂-N in improving the collision frequency between ^•OH and NO₃ ^- species and in facilitating the exothermic transition of NO₃ ^- functionalities to surface NO₃ ^• analogues per unit time. These were corroborated by a greater efficiency of α-MnO₂-N in decomposing phenol, in addition to scavenging/filtration control runs and DFT calculations. Importantly, supported NO₃ ^• species provided 5-7-fold greater efficiency in degrading textile wastewater than conventional ^•OH and supported SO₄ ^•- analogues we discovered previously.