Water treatment with CoZnAl-LDH and its mixed metal oxide

Abstract

CoZnAl-layered double hydroxide (LDH) was synthesized by homogeneous co-precipitation. CoZnAl-Mixed Metal Oxide (MMO) was prepared by calcining the LDH. The samples' structure and morphology were studied by analytical techniques including X-ray diffraction, N2 adsorption-desorption isotherm, scanning electron microscopy and UV–visible spectroscopy. Acid orange 7 (AO7) adsorption by as-prepared samples was studied. CoZnAl-MMO showed 526.32 mg/g adsorption capacity, higher than that of CoZnAl-LDH, 243.9 mg/g. Kinetic studies confirmed the pseudo-second-order and pseudo-first-order AO7 adsorption kinetics of the LDH and MMO, respectively. AO7 adsorption onto both LDH and MMO fitted the Langmuir isotherm model well. Band gap calculation confirmed the ability of this nano-MMO to operate in the visible light region. It displayed synergetic adsorption-photocatalytic performance under visible light and the removal efficiency was about 97%. HIGHLIGHTS The CoZnAl-LDH with high surface area was synthesized.; The LDH adsorbed acid orange 7 from aqueous solution effectively.; The CoZnAl-MMO was prepared via calcination of the CoZnAl-LDH.; The MMO showed photocatalytic activity in visible light and high adsorption capacity towards AO7.;

Keywords

• adsorption
• layered double hydroxide
• mixed metal oxide
• photocatalysis