Copper nanoclusters-doped novel carrier with synergistic adsorption-catalytic active sites to enable high-performance dye removal.

Enhancing the synergistic interplay between adsorption and catalytic oxidation to amplify Fenton-like effects remains a pivotal challenge in advancing water pollution remediation strategies. In this study, a suite of novel carriers (SH) composed of silica (SiO2) and hydroxyapatite (HAp) in different ratios were synthesized through an amalgamation of the sol-gel and co-precipitation techniques. Notably, various forms of copper (Cu) species, including Cu2+ ions and Cu nanoclusters (Cu NCs), could be stably incorporated onto the SH surface via meticulous loading and doping techniques. This approach has engendered a new class of Fenton-like catalysts (Cu NCs-SH1-5) characterized by robust acid-base tolerance stability and remarkable recyclability. Compared with the previously reported Cu NCs-HAp, this catalyst with lower Cu species content could achieve better performance in adsorbing and degrading dyes under the aid of hydrogen peroxide (H2O2). The catalyst's dual action sites, specifically the adsorption sites (SiOH, POH, slit pores) and catalytic centers (multivalent Cu species), had clear division of labor and collaborate with each other. Further, reactive oxygen species (ROS) identification and astute electrochemical testing have unveiled the mechanism underpinning the cooperative degradation of dyes by three types of ROS, spawned through electron transfer between the Fenton-like catalyst (Cu NCs-SH) and H2O2. From these insights, the mechanism of synergistic adsorption-catalytic removal was proposed.

Protective composite silica/polyelectrolyte shell with enhanced tolerance to harsh acid and alkali conditions.

Here we report a facile method to fabricate composite polymeric/inorgainc shells consisting of poly(allylamine hydrochloride) (PAH)/poly-(sodium 4-styrenesulfonate) (PSS) multilayers strengthed by the in situ formed silica (SiO2) nanoparticles (NPs), achieving an enhanced stability under harsh acidic and basic conditions. While the unsiliconised PAH/PSS multilayers show a pH-dependent stability and permeability, the composite PAH/PSS/SiO2 shells display significantly higher chemical tolerance towards a variety of harsh conditions (1 ≤ pH ≤ 13, high salinity). Upon treatment with either hydrochloric acid (HCl, pH=1) or 0.2 M ethylenediaminetetraacetic acid disodium salt (EDTA, weak acid, chelator), the (PAH/PSS)6/SiO2 shells are able to maintain the integrity of most calcium carbonate (CaCO3) particles, as the shells are tickened and densified by sufficient SiO2 NPs. When treated with NaOH solution at pH=13, the (PAH/PSS)6/SiO2 shells also display an intact morphology and maintain the ability to intercept rhodamin B (Rh-B) molecules, which is quite different to that observed with the unsiliconised (PAH/PSS)6 shells. Ultrasound is proved to rapidly break the composite shells, hence can be used as a potential stimulus to trigger the release of encapsulated substances. All the results demonstrate the fact that the composite (PAH/PSS)6/SiO2 shells have a higher chemical stability, lower permeability for small molecules and a greater sensitivity to ultrasound, which is promising for many applications where protecting the activity of small molecules is required, such as the delivery of encapsulated drugs in an unhindered form to their specific destination within the human body.