Research on ClO2 as a Fluorescence-Reducing Agent: A Simple Method to Evaluate the Treatment Effect Based on Color Measurement

Abstract

Fluorescent whitening agents (FWAs) are often used as a means of enhancing the overall whiteness of fabrics, papers, and plastics. It is a kind of fluorescent dye which absorbs the light strongly in the near-ultraviolet region (generally 340-400 nm) and emits in the 430-460 nm region, generally peaking around 440-450 nm to enhance the whiteness and brightness of objects. FWAs act by adding a blue component to counteract the yellowness found in paper or textiles, taking non-visible UV radiation and converting it to blue [1,2]. In textile mills, there can sometimes be mistakes and FWA can be applied onto the fabric that will be dyed. In this situation, because the FWA blocks the dye sites, the fluorescence-reducing agent is needed to destroy the fluorescence on textiles.ClO 2 is stable and soluble in an aqueous solution. ClO 2 is a powerful oxidizing agent and is widely used to bleach flour and wood pulp. It is also a highly effective, eco-friendly micro biocide for high quality water [3][4][5]. It is known to all that common fluorescent whitening agents include diaminostilbene compounds. ClO 2 can destroy the stilbene dyes that make up most FWAs, rendering them non-fluorescent.Several papers and patents have been published about ClO 2 as a fluorescence-reducing agent for recycling paper [6,7]. However, there is no report on its use on fabrics. 1 In the case of reducing fluorescence, colorists need to know the effect of the agent. But with the advent of fluorescent whitening agents, the general idea of whiteness has changed. Numerous whiteness formulas (including the CIE [Commission Internationale de l'Eclairage] whiteness formula) were found not to correlate well with visual estimation [1]. Thus, the measurement of fluorescence is important.The measurement of fluorescent samples has focused on two methods: the two-monochromator method [1,8] and the two-mode method [9, 10]. We have reported the difference between these two methods and introduced the twomode method in detail [11]. The two-monochromator method requires the use of research instrumentation having two monochromators, in the irradiating and the viewing Abstract The reducing effects of fluorescent whitening agent-treated cotton under the action of chlorine dioxide were studied. Various factors were studied, including pH value, temperature, ClO 2 concentration, and treating time. Furthermore, a simple method to evaluate the effect of fluorescence-reducing agent (ClO 2 ) was proposed. By measuring the spectral radiance factor of the samples, the total absorption energy, total emission energy, and fluorescence quantum efficiency were calculated. It is demonstrated that fluorescence quantum efficiency could be used as a criterion to judge the fluorescence-reducing effect of ClO 2 .