Use of Cu(II) catalyst assisted oxidative decolorization of dye by chlorinating species in water: A kinetic and mechanistic study with acid red1 dye

Abstract

A quick and easy decolorization method has been created in the current study to get rid of the Acid Red 1 (AR1) dye from the wastewater. At 298 K, the kinetics of oxidative decolorization of AR1 dye with Chloramine-B (CAB) in NaOH medium, catalyzed by copper(II) sulphate, have been examined spectrophotometrically (λmax = 506nm). The experimental rate laws found are as follows: d[CAB]/dt = k [CAB]0 [AR1]0 [Cu(II)]x / [OH−]y in an alkaline medium, where x and y are less than unity.Under ideal experimental conditions, 90% dye decolorization is achieved in 30 minutes using concentrations of 0.003M [CAB], 0.0003M [AR1], 0.003M [Cu(II), and 0.003M [OH−].In the current kinetic redox system, the Cu(II) catalyst showed to be an effective homogeneous catalyst. The 4-acetamido-5,6-dioxo-5,6-dihydro naphthalene-2-sulphonic acid is identified as the oxidation product using mass spectrum analysis. The FTIR spectra show the absence of N=N stretching bands at 1489 cm−1 which confirms the oxidative breakdown of the azo group, a fundamental chromophore responsible for color, which induces toxicity in the waste water. The decolorization reaction catalyzed by Cu(II) is approximately six times faster than the uncatalyzed reaction. The catalytic constant (Kc) is calculated at various temperatures, and activation parameters for copper(II) are also evaluated. The observed results are explained by plausible mechanisms, and relative rate laws has been deduced. Chemical oxygen demand (COD) has been significantly reduced by the oxidative decolorization process. Phytotoxicity tests revealed that the treated dye sample is less toxic than the untreated dye sample. An economic analysis is carried out. Notably, with appropriate modifications, the developed oxidative decolorization technique is expected to benefit in the removal of AR1 dye present from industrial wastewater.