Performance of Photocatalytic Cementitious Material: Influence of Substrate Surface Microstructure

Significance Statement

Researchers from Wuhan University of Technology evaluated the performance of photocatalytic cementitious material PCM and checked the influence of substrate surface microstructure. The aim is to fabricate a proper cement-based substrate, with optimal surface microstructure for TiO2 loading. The research is now published in Construction and Building Material.

According to the research team, TiO2 photocatalytic is a promising technique to improve on indoor pollution with mild reaction conditions, absolute purification and high efficiency. In the meantime, cementitious material is the most widely employed building material due to its moldability, high strength, good durability and environmental-friendly properties.

When looking at the effective incorporation between photocatalyst and cementitious, they noted admixing and loading are the main ways to prepare photocatalytic cementitious material. Cementitious substrate short comings such as low surface area, poor light transmittance and complex chemical environment limit its photocatalytic performances. ion-ion correlation could aggravate the agglomeration of TiO2 and weaken photocatalyst utilization. Moreover, the excessive concentration of catalyst on the mortar surface also results in decrease of photocatalytic efficiency.

With regard to the practical application of photocatalytic technologies, the mass transfer is one of the essential factors. When testing the influence of turbulence intensity on photocatalytic performance, the researchers realized that artificial roughness elements on catalyst surface result in increased mass transfer and hence, improved photocatalytic rate. Apart from air flow condition, prevention of gas pollutant through adsorption capability also targeted by the team.

Magnesium oxychloride cement MOC with its excellent performance such as rapid setting and hardening properties, good abrasion resistance, remarkable bonding ability and structural controllability has make it one of the potential cementitious substrate. Porus magnesium oxychloride cement PMOC was prepared by adding MgO powder into MgCl2 water solution and stirred evenly. The molar ratio of the mixture MgO: MgCl2: H2O was found to be 5: 1: 14. To improve the loading efficiency, PMOC sieved. While the preparation of photocatalytic cementitious material  involve curing PMOC substrates for 7,14 and 21 days before loading TiO2 on its surface.

Fazhou Wang the leading author said, the communicating holes was observed on most pore walls, and it can facilitate the gas permeability and light transmittance. Indeed the large surface area and pore volume of the prepared substrate is of beneficial in enhancing adsorption capability.

After 21-days curing, the research team observed a development of outward needle shape crystals to be more matured, compact and the TiO2 particles been dispersely uniform. However, substrate microstructure was covered by TiO2 film to a large extent thereby causing the surface area and pore volume not to be improved. The researchers pointed out that the adsorption of Toluene gradually stabilized after 35 min and all the specimen showed adsorption capability due to their large area and connected pores. They found out that overlapping joint effect of outward needle shape crystals would improve the specific surface area of PMOC as well as distribution proportion of mesopores and micropores. To enhance mass transfer, proper cementious substrate for photocatalytic cementitious material, appropriate microstructure for photocatalyst dispersion and good adsorption is required.

This study showed that the photocatalytic cementitious material specimen is 1.3 times better than nickel foam based photocatalytic material under same conditions. The researchers also pointed out that photocatalytic performance and loading microstructure of TiO2 photocatalyst to be significantly affected by PMOC substrate surface microstructure.

Journal Reference

Fazhou Wang1,2, Guoxin Sun1,2, Wenqin Zhang1,2, Lu Yang1,2, Peng Liu3, Performance of Photocatalytic Cementitious Material: Influence of Substrate Surface Microstructure, Construction and Building Materials 110 (2016) 175–181.

Show Affiliations
  1. State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan 430070, PR China.
  2. School of Materials Science and Engineering, Wuhan University of Technology, Wuhan 430070, PR China.
  3. School of Chemistry, Chemical Engineering and Life Science, Wuhan University of Technology, Wuhan 430070, PR China.

 

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