Katia Grgić

The existing research deals with the process of modifying polyester knitted fabrics and polyester/cotton knitted fabrics with chitosan and the stability of functionalized surface with chitosan in the washing process according to a standard and an innovative washing procedure. The current research concept aims to evaluate the degree of progressivity and progressiveness: the modification of polyester knitted fabrics with chitosan and an innovative washing process. The polyester and polyester/cotton fabrics modified with chitosan were characterized by a staining test, microscopic analysis, zeta potential measurement, and pilling tendency of the knitted fabrics before and after five and ten washing cycles with reference detergent ECE A. The results of the zeta potential measurement of knitted fabrics functionalized with chitosan confirmed cationization of the polyester and polyester/cotton fabric with chitosan. The presence of chitosan on the washed knitted fabrics in reduced quantities is demonstrated by the staining test, the colour strength (K/S), and the zeta potential values. The staining test and surface charge of the tested knitted fabrics confirmed the research hypothesis regarding the degree of progressivity of the modification of polyester and polyester/cotton knitted fabrics with chitosan and the sustainability of the innovative washing process. The streaming potential proved to be a favorable method for monitoring the stability of chitosan in the washing process in combination with a staining test with the selected dye Remazol Red RB.

The influence of textile wastewater (TWW) secondary effluent on ultrafiltration (UF) membrane characteristics was investigated. TWW treated with a membrane bioreactor was subjected to four commercial UF membranes (2, 3, 5, and 10 kDa). Both the pristine membranes and the membranes after TWW secondary effluent treatment were characterized. Surface roughness, microscopic analysis of the membrane surface and cross-section, zeta potential, contact angle, membrane composition, and membrane flux were compared. After treatment of secondary effluent, the zeta potential decreased for 5 and 10 kDa membranes, while the contact angle and surface roughness increased for all investigated membranes. In addition, a fouling layer formed on all membranes, and new interactions with pollutants and membranes were confirmed. Membranes with larger pores (5 and 10 kDa) showed a greater decrease in permeate flux during treatment. Detailed analysis showed variations in membrane characteristics after TWW secondary effluent treatment, indicating the stability of the membranes used.