The controlled oxidation of kraft lignin in mild conditions using ionic liquid as a crucial point in fabrication of antibacterial hybrid materials

Abstract

In the present study a functional lignin/ZnO material was obtained using hydrothermal treatment. As part of the research, at the outset, kraft lignin was activated by controlled oxidation in two ionic liquids: 1-butylimidazolium hydrogen sulfate and 1-butoxymethylimidazolium hydrogen sulfate. The activation with selected ionic liquids had the aim of increasing the number of active centers on the surface of the lignin, thus increasing its chemical and antibacterial activity. Lignin/ZnO hybrids were subjected physicochemical and morphological analysis, in addition to a series of bactericidal tests against Gram-positive and Gram-negative microorganisms. The lignin/ZnO material (5:1 wt./wt.), after the initial activation of the lignin using 1-butylimidazolium hydrogen sulfate, exhibited very strong action against all tested bacterial species (both Gram-positive and Gram-negative bacteria), with zones of inhibition larger than 27 mm. In all cases the antibacterial activity was superior to that of the antibiotic tetracycline.