Highly efficient film-like nanocellulose-based adsorbents for the removal of loose reactive dye during textile laundering

Cellulose nanofibrils (CNFs) were surface functionalized with hexamethylenediamine (HMDA) and, further, integrated with native CNFs in various weight mass ratios to fabricate water-stable films by the solvent casting method, to be used for the removal of tri-chromatic and anionic black reactive dye with the highest bleeding effect in the very first minutes of textile laundering, and in a weight mass compared to a commercial color-catcher sheet (Delta Pronatura (DP)). The effects of CNF-HMDA content on film bath absorption, surface potential and contact angle properties, as well as dye removal kinetics from different laundering baths (A - without and B - with a detergent) in up to 140 min were studied at 20celcius versus 60celcius and using different dye concentrations (0.1-1 g/L). It was found that bath absorption is decreased significantly (up to 60%) by increasing the CNF-HMDA content in the films, as compared to using a DP color-catcher sheet, due to a morphologically denser structure with surface-positioned hydrophobic ethylene moieties of HMDA, as well as reducing electrostatic attraction groups of CNF and HMDA. Such a surface interacts kinetically faster with anionic and hydrophobic dye molecules already at 20celcius, reaching up to 37-80% removal of all dye colorants in the first 20 min. In contrast, the dye removal efficacy of the DP color-catcher sheet is due to it interacting with a cationic polymer being released from the surface, which is better only for a bluish color, and at 60celcius, while being between 30% and 48%, as its release is hindered and reduced by the deposition of surfactants from the detergent.