Catalytic removal of malachite green from aqueous solution by a peroxidase-mimicking Cu-Al layered double hydroxide nanoparticle: Synthesis, characterization, and application

Abstract

Nanozymes are nanomaterials with inherent enzyme-like activities that have recently received much attention due to their high catalytic activity, low cost, and high stability. This research aimed to investigate the applicability of copper-aluminum layered double hydroxide (CuAl-LDH) for the catalytic decolorization of malachite green (MG). The enzyme-mimic activity of the prepared particles was tested using a colorimetric approach based on the oxidation of 3,3', 5,5'-tetramethylbenzidine (TMB) with hydrogen peroxide (H2O2), which results in the production of a blue-colored product with maximum absorption at 652 nm. The impact of different factors, including pH, temperature, TMB, and H2O2 concentrations, on the catalytic performance of CuAl-LDH was assessed. The kinetic parameters (Km and Vmax) were obtained to be 14.3 × 10−3 mM and 96.1 × 10−8 M/s (for TMB), and 0.05 × 10−3 mM, and 71.9 × 10−8 M/s (for H2O2), respectively. Compared to natural horseradish peroxidase (HRP), CuAl-LDH showed a high affinity for H2O2 and TMB. In addition, the results showed that CuAl-LDH could decolorize MG by 100% under optimum conditions of pH 4, 3.42 µM MG, and 4 mg/mL CuAl-LDH at 50 °C and within 13 min. These findings demonstrate the potential of CuAl-LDH, with intrinsic peroxidase-mimic activity, to decolorize and detoxify MG from industrial wastewater.