Hexadecyltrimethylammonium-silver-kaolinite as a marine anti-biofouling paint additive

Abstract

Copper-based anti-biofouling paint coating has been used to combat biofouling on man-made artificial marine structures for several decades. Despite its widespread use, the massive accumulation of copper and its compounds causes a serious threat to marine ecosystems. Thus, the search for efficient and environmentally friendly anti-biofouling coating has become more significant. Therefore, this current study focused on developing an anti-biofouling paint additive employing the active compounds, silver ion (Ag+) and surfactant hexadecyltrimethylammonium (HDTMA) embedded in the kaolinite clay structure which is designated as Organo-silver-kaolinite (Or-Ag-Kao). The developed paint additive is intended for applications in marine artificial structures. The Or-Ag-Kao was prepared by adding Ag-kaolinite with HDTMA via a cation exchange process. The prepared samples; Ag-Kao, HDTMA-Kao and Or-Ag-Kao were characterized using ATR-FTIR and EDX. In this study, these analyses confirmed that the Ag+ and HDTMA were successfully intercalated into the kaolinite without affecting their original structure. The samples were then incorporated into the commercial paint matrix to test for their anti-bacterial adhesion and anti-biofilm efficiency as an anti-biofouling coating additive against isolated marine biofouling bacteria, Bacillus niabensis and Alteromonas litorea. It was observed Or-Ag-Kao paint coating efficiently reduced the bacterial adhesion of B. niabensis (91.51%) and A. litorea (87.53%), as compared to commercial paint without additive. The Or-Ag-Kao paint coating also showed excellent anti-biofilm on B. niabensis and A. litorea with EPS mean volume of 0.219 ± 0.129 × 105 µm3 and 0.151 ± 0.052 × 105 µm3, respectively. A weak interaction was observed between the model bacteria and Or-Ag-Kao with commercial paint coated surface with the mean lateral detachment force 139.4004 nN (B. niabensis) and 146.2251 nN (A. litorea). Major contact surface area reduction was also observed in Or-Ag-Kao paint coating (0.275 µm2 in B. niabensis and 0.391 µm2 in A. litorea) indicated that Or-Ag-Kao paint coating successfully minimized surface bacterial attachment. As a conclusion, the broad-spectrum effectiveness of Or-Ag-Kao paint coating minimized bacterial adhesion and biofilm formation may provide an environmental-friendly solution for marine biofouling. It is envisaged that the newly developed Or-Ag-Kao has high potential to be commercialized as an alternative marine anti-biofouling coating replacing the present traditional antifouling paints.