Banca de QUALIFICAÇÃO: IEDA LETICIA DE SOUZA FERREIRA

Seawater softening using surfactants for application in textile chemical processes.

Water treatment, Biosurfactants, Flocculation, Seawater and Reactive dyeing

Chemical processing of textile materials requires large volumes of fresh and soft water. However, freshwater is currently considered a scarce and increasingly expensive resource. In this context, seawater can emerge as an alternative, but its high hardness is a limiting factor for its application in textile processing. Surfactants substances have proven efficiency for removing metals or contaminants in aqueous solutions, therefore, they become a real possibility for treatment in seawater. Thus, this work proposes a treatment for softening seawater using biosurfactants, in order to use it in chemical processing of cotton fabrics. Surfactants were developed from coconut and soybean vegetable oils, and an ionic flocculation and subsequent separation process was carried out to remove calcium and magnesium ions from seawater. Both proved to be effective in removing the ions responsible for hardness. At a concentration of 39 g/L, the coconut surfactant reduced the total hardness of the treated water by more than 85%, while soybean showed a reduction of 67%. The influence of seawater hardness on the dyeing capacity of cotton fabrics was evaluated, and compared to a process using fresh water. The colors of the dyed samples were evaluated using CIEL*a*b* coordinates and K/S index, in addition, structural properties, fastness and mechanical behavior of the processed samples were evaluated. In parallel, the adsorption and diffusion mechanism of the Reactive blue 222 dye on cellulosic substrate was studied using seawater as the process solvent. After softening with biosurfactants, the water will be evaluated for use in bleaching, desizing and textile dyeing processes with reactive dyes. After optimizing the seawater treatment and application process, it is expected to obtain improved samples with a quality similar to processes carried out with fresh water. In this way, we propose economically friendly processes, and we will explore an abundant natural resource in an economically active way for industrial development.