Due to the usual resistance of textile dyes to conventional biological treatment processes, the color removal of dyeing wastewaters remains a challenge for the textile industry. This work evaluates the capacity of advanced oxidation processes based on thermally-activated persulfate concerning textile dyes’ degradation in aqueous solution and the reuse of dyeing baths. Preliminary studies were carried out in a bench-scale jacketed reactor, using Reactive Black 5 (40 mg L−1) as a model dye. Almost complete dye degradation was observed in 60 min in this stage, using 300 mg L−1 of persulfate and activation temperatures of 80 ºC, basically due to the action of radical sulfate. The use of high concentrations of persulfate (1000 mg L−1) allowed efficient color removal of dyeing baths containing remazol dyes in processes activated at 80 and 90 ºC. However, the wastewaters treated under these conditions did not lead to high dyeing efficiency in reuse studies, probably due to residual persulfate presence. In contrast, low concentrations of persulfate (250 mg L−1) lead to partial color removal and a better dyeing quality. The results suggest a good potential for treating high-temperature dyeing baths, saving water and auxiliary agents used in textile dyeing processes.

ENVIRONMENTAL APPLICATIONS OF PERSULFATE: REMEDIATION OF CONTAMINATED GROUNDWATER AND SOILS. Environmental remediation represents a major technological challenge due to the complexity of the environmental matrices and the high treatment cost. In recent years, in situ chemical oxidation technologies (ISCO) have shown a good cost/benefit ratio, which has favored their use in the degradation of several relevant environmental pollutants. In this context, persulfate-mediated processes are of relevant importance once persulfate can be activated in situ, promoting the formation of highly oxidative radical species. Persulfate-based treatments have been frequently reported in environmental remediation studies because they guarantee the effective degradation of pollutants without producing significant changes in the remediated matrix. Given these statements, this study aims to discuss the main ways of activating persulfate and the relevant applications in the remediation of groundwater and soils contaminated with resistant organic pollutants.