A porous activated carbon supported Pt catalyst for the oxidative degradation of poly[(naphthaleneformaldehyde)sulfonate

Abstract

Abstract Wet catalytic oxidation of sodium poly[(naphthaleneformaldehyde)sulfonate], a hazardous contaminant of wastewater streams from the textiles industry, by hydrogen peroxide under ambient conditions was explored over platinum supported on a porous activated carbon (PAC). Bulk and surface properties of the Pt/PAC catalyst were investigated by XRD, XPS, SEM, TEM, FTIR, EPR and thermogravimetric analysis. The parent PAC, derived from pyrolysis and subsequent activation of rice husks, exhibited significant micro- and mesoporosity, and a high degree of surface oxidation. Incorporation of 1.7 wt% Pt resulted in mesopore blockage, and a corresponding drop in surface area, associated with the formation of large ∼8 nm metallic nanoparticles. Poly[(naphthaleneformaldehyde)sulfonate] oxidative degradation was studied as a function of reactant concentration and solution pH, revealing first order decomposition kinetics and good activity over pH 3–9 at ambient temperature. Electron Paramagnetic Resonance (EPR)-DMPO spin trapping experiments confirm that oxidation of the organic pollutant proceeded via hydroxyl radical generation. The 1.7 wt% Pt/PAC catalyst showed excellent catalyst stability for five consecutive runs over 25 h in a fluidised bed reactor, delivering > 85% removal of 100 mg/L sulfonate with negligible Pt leaching or activity loss, and comparable performance for treatment of a real tannery effluent stream with a COD equivalent of 1860 mg/L.