Chitosan silver nanoparticles assisted oxidation of textile dyes with H2O2 aqueous solution: Kinetic studies with pH and mass effect

Abstract

The effluents of textile dyes act as hazardous aqueous pollutants. Acid blue15 (AB), acid green 1 (AG), acid orange 52 (AO), acid red 88 (AR), acid red 28 or direct red (DR), basic blue 6 (BB), basic blue N (BBN), basic green 4 (BG), reactive brilliant red X-5B (RBR) are the dyes chosen and studied in the present work. Silver nanoparticles (Agnp) were prepared by wet chemical reduction method using chitosan bio-stabiliser having 90% deacetylation and sodium borohydride as the reducing agent. FTIR, FESEM, HRTEM, UV-Visible, SPR spectroscopy measurements were used for the nanoparticles characterization. Nearly monodisperse particles were obtained. The catalytic efficiency of the Agnp was investigated for the oxidative degradations of nine different intensely coloured dyes. Kinetic parameters were obtained from the time variance UV-Visible spectra, under pseudo first order conditions. The rate coefficient value for DR was found to be 4.29 x 10-4 /sec.The dyes used are categorized under azo, quinonoid and anthracene based class of dyes with many aromatic rings. In all, azo dyes oxidation rate coefficients were higher than the quinionoid and the other dyes. Among the azo class of dyes, the trend in the oxidation rate coefficients are found to be DR>AR>RBR>AO while that of quinonoid and other dye show the trend as AG>AB>BG>BB>BBN. Optimum pH and catalyst mass effects are also studied. Chitosan Agnp incorporated advanced oxidation process (AOP) exhibited much significant results, that these may be used in the bleaching processes of organic pollutants and colourants in aqueous system.