Mesoporous amine functionalized SiO2 supported Cu nanocatalyst and a kinetic-mechanistic degradation study of azo dyes

Abstract

The preparation of stable copper nanoparticles (CuNPs) has remained a challenge for colloid chemists. In this investigation, mesoporous amine functionalized silica (NH2-SiO2) particles have been used as platform to host copper nanoparticles (CuNPs) for preventing their agglomeration. Mesoporous NH2-SiO2 particles are first prepared in one pot by diethyl amine (DEA) catalyzed hydrolysis and condensation of tetraethyl orthosilicate (TEOS) precursor in presence of hexamethylene diamine (HMDA) and cetyltrimethylammonium bromide (CTAB). In the second step, sequential adsorption and chemical reduction of Cu ions are carried out to obtain NH2-SiO2/Cu catalyst nanocomposites. The morphology and structural composition of NH2-SiO2/Cu catalyst nanocomposite particles confirmed the anchoring of evenly distributed ~ 28 nm sized Cu particles. The catalytic activity of nanocomposite particles for reductive degradation of Congo red (CR) and Eriochrome Black-T (EBT) showed maximum degradation at pH values of 7 and 4, respectively. The degradation efficiency increased with the increase in catalyst dose and a maximum degradation of ~ 92% is achieved for CR when 2 mg of catalyst nanocomposite particles is used. Comparatively, the degradation percent for EBT is low (~ 83%). Degradation kinetics of CR preferably followed a pseudo-first-order rate model, but, for EBT degradation hardly any particular kinetic rate model could be preferentially ascertained. The improved stability and increased surface-to-volume ratio of anchored CuNPs enhanced the degradation efficiency of catalyst nanocomposite particles.