Preparation of Multifunctional β-hemihydrate Gypsum using Oyster Shell Powder as the Partial Replacement of Ag/TiO2 Particle

This work aimed to use oyster shell powder (OSP) as the partial replacement of Ag/TiO2 particle to obtain multifunctional β-hemihydrate gypsum.Thus,the β-hemihydrate gypsum was mixed with different contents of OSP and Ag/TiO2 particle.Antibacterial and MB removal experiments were conducted to assess the antibacterial characteristic and photocatalytic activity of β-hemihydrate gypsum with Ag/TiO2 particle and OSP.Besides,the formaldehyde degradation test was carried out to evaluate its formaldehyde removal ratio.Moreover,their setting times,compressive and flexural strengths at 1,3,and 28 days were comparatively analyzed.The experimental results prove that the composite use of OSP and Ag/TiO2 particle provide feasible multifunction for the β-hemihydrate gypsum.They can further improve the bactericidal rates and exhibit extra MB removal ratios compared with the gypsum plasters with single Ag/TiO2 particle.Besides,they can increase the formaldehyde degradation ratios,and this promotion is related to the introduction of Ag/TiO2 particle.However,OSP delays the initial setting time but promotes the final setting time of β-hemihydrate gypsum,and Ag/TiO2 particle hardly affects the setting times.Furthermore,OSP reduces the strengths of plasters at 1,3,and 28 days.But in general,the composite addition of OSP and Ag/TiO2 particle increase the compressive and flexural strengths of gypsum plasters at 1,3,and 28 days.These results provide theoretical guidance for the recycling of OSP and the preparation of gypsum-based products with antibacterial and formaldehyde degradation capabilities.

Rapid and accurate evaluation of vaporized hydrogen peroxide on the efficiency of disinfection, using a sensitive dual-channel laser scanning cytometer

Vaporized hydrogen peroxide(VHP)is a highly active disinfectant,and VHP decontamination systems have been widely applied in hospitals,microbiological laboratories,and pharmaceutical industries.However,the decomposition of VHP into non-toxic by-products is essential.Evaluation of the disinfection efficacy of VHP is crucial to ensuring the reliability of VHP disinfection and controlling microbial contamination.In this study,a rapid and sensitive strategy is proposed to evaluate the efficacy of VHP in surface disinfection by detecting the survived and killed bacteria from VHP-exposed biological indicators(BIs).A dual-channel solid-phase cytometer is designed,and fluorescent dyes are used as indicators to automatically and accurately distinguish live cells from dead cells in themixtures of bacteria.To verify the availability and effectiveness of the laser scanning cytometry,experiments on its application in estimating the efficacy of VHP disinfection practice have been carried out in this study,and its estimation effect compared with that of the traditional plate counting method.Results show that the proposed assay might distinctly identify live or killed cells labeled by green and red fluorescent dyes and examined the disinfection efficacy in 30 min by calculating the bactericidal rate.Compared with the plate counting method,the proposed approach is accurate and practical,with an average detection efficiency of 98.47%±1.55%.Moreover,an excellent correlation between the concentrations of B.subtilis var niger(ATCC 9372)measured by the proposed detection system and by the plate counting method is noticed(R2=0.9971),indicating that this approach had advantages in the detection of trace microorganisms.To summarize,the proposed strategy appears practical and significant in many fields in which microbial counting and identification are required.