Comparison between catalytic activities of two zinc layered hydroxide salts in brilliant green organic dye bleaching

Murilo Gonçalves da Rocha; Shirley Nakagaki; Geani Maria Ucoski; Fernando Wypych; Guilherme Sippel Machado

doi:10.1016/j.jcis.2019.01.111

Comparison between catalytic activities of two zinc layered hydroxide salts in brilliant green organic dye bleaching

J Colloid Interface Sci. 2019 Apr 1:541:425-433. doi: 10.1016/j.jcis.2019.01.111. Epub 2019 Jan 28.

Authors

Murilo Gonçalves da Rocha¹, Shirley Nakagaki², Geani Maria Ucoski², Fernando Wypych², Guilherme Sippel Machado³

Affiliations

¹ Laboratório de Bioinorgânica e Catálise, Departamento de Química - Centro Politécnico, PO Box 19032, 81531-980 Curitiba/PR, Brazil; Centro de Estudos do Mar, Pontal do Paraná/PR - Universidade Federal do Paraná (UFPR), Brazil.
² Laboratório de Bioinorgânica e Catálise, Departamento de Química - Centro Politécnico, PO Box 19032, 81531-980 Curitiba/PR, Brazil.
³ Centro de Estudos do Mar, Pontal do Paraná/PR - Universidade Federal do Paraná (UFPR), Brazil. Electronic address: guimachado@ufpr.br.

PMID: 30711636
DOI: 10.1016/j.jcis.2019.01.111

Abstract

This paper reports the use of two layered hydroxide salts (LHS) (zinc hydroxide nitrate - ZHN - Zn₅(OH)₈(NO₃)₂·2H₂O, and zinc hydroxide chloride - ZHC - Zn₅(OH)₈Cl₂·H₂O) as catalysts for brilliant green (BG) organic dye bleaching, using hydrogen peroxide as oxidant. The LHS were prepared by precipitation reaction between an aqueous solution of zinc salts and an aqueous ammonia solution. The solids were characterized by powder X-ray diffraction (XRD), electron paramagnetic resonance (EPR), ultraviolet-visible electronic spectroscopy (UV-Vis) and Fourier-transform infrared spectroscopy (FTIR). The catalytic activity of the solids was investigated at temperatures of 25, 35 and 45 °C, using different molar ratios of oxidant:dye:Zn²⁺ ions (present in the catalyst), in the absence and presence of ambient light. The kinetic aspect of the reaction was investigated considering that the reaction showed pseudo-first order behavior in relation to BG dye concentration. We propose a mechanism where superoxide radicals account for most of the bleaching taking place. The catalytic results obtained, along with the low cost and low toxicity of zinc compounds, establish ZHN and ZHC as novel catalysts for dye wastewater treatment, an area with constant demand for new methods and materials given its relationship with environmental equilibrium and human health.

Keywords: Dye bleaching; Heterogeneous catalysis; Layered hydroxide salt.