Synthesis and characterization of secondary doped polypyrrole/organic modified attapulgite conductive composites

Selective Adsorbent Design with Multifunctional Surfaces: Innovating Solutions for Heterogeneous Catalysis in Water

Heterogeneous catalytic systems with water as the solvent often have the disadvantage of cross-contamination, while concerns about the purification and workup of the aqueous phase after reactions are rare in the lab or industry. In this context, designing and developing the functional selective solid adsorbent and revealing the adsorption mechanism can provide a new strategy and guidelines for constructing supported heterogeneous catalysts to address these issues. Herein, we report the stable composite adsorbent (Fe/ATP@PPy: magnetic Fe3O4/attapulgite with the polypyrrole shell) that features an integrated multifunctional surface, which can effectively tune the selective adsorption processes for Cu2+, Co2+, and Ni2+ ions and nitrobenzene via the cooperative chemisorption/physisorption in an aqueous system. The adsorption experiments showed that Fe/ATP@PPy displayed significantly higher adsorption selectivity for Ni2+ than Cu2+ and Co2+ ions, especially which exhibited an approximate 100.00% removal for both Ni2+ ions and nitrobenzene in the mixture system with a low concentration. Furthermore, combined tracking adsorption of Ni2+ ions and X-ray photoelectron spectroscopy characterization confirmed that the effective adsorption occurs via ion transfer coordination; the pathway was further validated at the molecular level through theoretical modeling. In addition, the selective adsorption mechanism was proposed based on the adsorption experiment, characterization, and the corresponding density functional theory calculation.

High catalytic oxidation of As(III) by molecular oxygen over Fe-loaded silicon carbide with MW activation

The catalytic oxidation of arsenite (As(III)) to arsenate (As(V)) and the removal of arsenic (As) in an iron loaded silicon carbide (Fe/SiC) system under microwave (MW) irradiation were studied. Fe/SiC was synthesized by electro-deposition and its capability of activating molecular oxygen was also characterized. Highly efficient As(III) removal in a wide pH range of 2.5-9.5 was achieved, involving oxidation by reactive oxidation species (OH and O₂^-) induced by MW irradiation and adsorption by the generated Fe (hrdro)oxide precipitates. Significant enhancement of As(III) oxidation was achieved at acidic pH, where sequential fresh Fe(0) exposure with MW irradiation could improve the Fenton-like reactions and oxidation efficiency for As(III). As(III) removal was accelerated via adsorption at alkaline conditions, where the adsorbed Fe(II) on Fe/SiC showed significant catalytic activity for molecular oxygen and high pH further favored the formation of (hydro)oxides and the As sequestration by adsorption. Fe/SiC showed superior performance for the treatment of As in water with MW irradiation.