Antifouling performance of photocatalytic superhydrophobic coatings against Klebsormidium alga

Abstract

Colonization of man-made surface materials by algae and other microorganisms, i.e. biofouling, causes various aesthetical and health problems as well as deterioration of appearance and surface functioning. The present study investigated eight complex surfaces combining various TiO2, alkoxy-siloxane and hydrophobization agents that were combined to prevent growth of phototrophic filamentous alga Klebsormidium sp. Regarding photoactivity, NOx abatement at the studied surfaces has been improved by adding anti-aggregation substances such as bentonite. Surface properties were characterized by confocal microscopy, scanning electron microscopy, SEM, with the energy dispersive X-ray spectroscopy, EDX, and the contact angle measurements. Biological experiments with Klebsormidium alga were performed in a constructed flow-through system. The results indicated that superhydrophobicity, i.e. very low surface energy, was critical for efficient antifouling during the early colonization by algae. This was specifically demonstrated in two novel composite samples made of titanium dioxide and commercial hydrophobization agent UltraEverDry. Low surface energy of these materials (around 1.3 mJ/m2), high water contact angles (>140°) as well as decent photoactivity (NOx conversions by 16.7 % and 1.4 % in UV and VIS, respectively), provide a promising basis for further longer-term anti-fouling experiments. The present study introduces novel composite materials preventing the algal fouling, and it brings new evidences on the interactive effects on hydrophobic and photoactive surfaces.