Engineered polymer-clay-copper oxides catalyst for the oxidation and reduction of organic molecules: synergy of degradation and instinctive interface stability by polymer self-healing function

Abstract

Although many applications of clay-polymer composites have been suggested in recent years, their potential use in water treatment processes has received relatively little attention. This study reports the synthesis, characterization, and application of supramolecular polymer-montmorillonite clay-copper oxide (MPC) as an efficient catalyst for the degradation of rhodamine B (RB), a model organic molecule (OM). MPC was synthesized by incorporating branched polyethyleneimine (PEI) into layered montmorillonite K10 (MK10) through a simple wet impregnation method, followed by the incorporation of a copper precursor and direct reduction of the metal precursor. The resulting MPC was characterized using ATR-FTIR, SEM-EDS, TEM, BJH, XRD, and SAXS. The results confirmed the incorporation of PEI and nano-copper oxides into MK10. The MPC chemically degraded RB (>99% at 5 mg L-1, pH 7) in the aqueous phase (10 mL), and the degradation followed a pseudo-second-order kinetic model with a high correlation coefficient. The synthesized MPC degraded RB (7 h) in the presence of H2O2 and adsorbed RB (>98%) without H2O2. The completeness of RB degradation was validated using liquid-liquid extraction and solid-liquid phase extraction of the aqueous phase and solid MPC after the degradation reaction, respectively. The degradation proceeded through reactive active species (hydroxide radical, center dot OH), which remained in the solution and are active for 72 h or more. This indicates that the synthesized MPC can degrade trace amounts of RB in larger aqueous volumes. PEI exhibited self-healing behavior (network remodeling) after by mechanical or chemical stress to the PEI/PEI-Cu species during RB degradation, which included the re-formation of RnN-Cu oxides as well as the synergistic effect of charge transfer/recombination between N, Cu, and other reactive species in the reaction mixtures. The post-degradation characterization of MPC confirmed that MPC could be reused for more than five cycles without the loss of copper species. The high catalytic performance of MPC towards the other four organic pollutants in the aqueous phase indicates that MPC is a promising environmental catalyst.