In-line, titanium dioxide-catalysed, ultraviolet mineralization of toxic aromatic compounds in the waste stream from a flow injection-based resorcinol analyser

Abstract

A clean method was developed for the spectrophotometric determination of resorcinol. The method, based on the reaction between resorcinol and p-aminophenol (PAP), carried out in a flow system, involves an additional detoxification step based on the in-line TiO₂-catalysed photodegradation of the indophenol dye formed and the remaining unreacted PAP. For this, after the measurement step the waste stream is merged with a TiO₂ slurry (0.5 g l^–1 in 0.22 mol l^–1 HCl) and then passed through a UV photochemical reactor consisting of a PTFE tube (6 m × 0.8 mm i.d.) rolled on a UV lamp with a maximum irradiation wavelength of 254 nm. Under these conditions, the waste can be completely detoxified thus, providing a non-polluting method of analysis.