Toxicity of the Cementitious Coatings Containing Nano-TiO2 Towards Thiobacillus Thioparus Bacterium

Most studies on antimicrobial properties of nano-TiO2 in deionized water deal with its photocatalytic properties. Few studies have shown that the presence of nano-TiO2 can inhibit the growth of the bacteria and it ultimately kills them in a culture medium in the dark. In this study, the antibacterial effects of suspended in a culture medium and immobilized nano-TiO2 systems in cement bed (0.1-1%) were investigated on Thiobacillus thioparus as a bacterium involved in cement biodegradation. The pH and turbidity tests were carried out in order to monitor the viability of the bacteria in the culture medium. The results showed that T. thioparus did not grow in the presence of cements containing nano-TiO2 and at longer contact time the bacterial death occurred. The optimum concentration of nano-TiO2 has been found to be 1% to maintain antibacterial properties. Thus, with evaluation of the toxicity effects, the cementitious antimicrobial coatings could be produced by immobilized nano-TiO2 for self-protected against biodegradation.