Quick review of nanomaterials "regenerate" titanium dioxide photocatalysts

Titanium dioxide (TiO2), commonly known in industry, titanium dioxide, is also a typical semiconductor photocatalyst.  Calcium carbonate (CaCO3) is a common inorganic nonmetal powder, widely used filler.  The preparation of composite photocatalyst (CAT-CC) by supporting nano-tio2 with calcium carbonate particles as a carrier can improve the function of TiO2 by reducing the particle size and improving the particle dispersion, and realize the recovery and recycling of nano-tio2, and improve the utilization value of calcium carbonate.

1. Nano tio2 powder photocatalytic technology  

Photocatalytic technology is one of the ideal ways to control water pollution and environmental remediation, and it is of great significance to promote economic development and environmental protection to optimize the use conditions of photocatalysts, give full play to the function of catalysts, reduce the amount of catalysts and reduce the cost of catalysts.  

Nano TiO2 has the characteristics of non-toxic, pollution-free and stable properties, which is the most widely studied and applied semiconductor photocatalytic material.  Studies have shown that nano TiO2 can rapidly degrade more than 3000 kinds of organic compounds that are difficult to degrade in the natural environment under ultraviolet radiation, which plays an important role in water pollution control and complex ecosystem restoration.  

However, nano TiO2 also has application bottlenecks, and several important defects need to be remedied.  

For example, nanocrystalline TiO2 has high surface energy and is easy to agglomerate, which leads to the reduction of specific surface area and active site, and thus the photocatalytic activity cannot be effectively played.  The electron - hole pair of nano TiO2 has short lifetime and low recycling efficiency.  When nano TiO2 is used in water, it loses seriously and is difficult to recover.  

In order to make a breakthrough in the application of nano-tio2 in the field of photocatalysis, people have carried out a lot of research on supported TiO2 photocatalytic materials.

2. Nano tio2 powder photocatalyst support classification

Support photocatalyst support can be divided into inorganic and organic two types, among which inorganic support is the most common, including glass, metal and adsorbent support.  Glass carriers have strong chemical stability, good light transmission, and can be processed into a variety of shapes according to the needs of the reactor.  Adsorbent carriers are common carbon materials, non-metallic mineral materials, ceramics, silica gel and so on.  

The adsorbent carrier can enrich the pollutants in wastewater by adsorption and improve the photocatalytic activity of the catalyst.  Metal carriers have the characteristics of high temperature resistance and corrosion resistance. The common metal carriers are porous titanium, titanium mesh, stainless steel and so on.  Because organic matter can be photocatalytic degradation by TiO2, the application of organic carrier is limited.

3. Nano - CaCO3-TiO2 photocatalyst composite  

Nano calcium carbonate, the preparation technology is relatively mature, the product has high purity, high whiteness, large specific surface area and other characteristics, has great advantages in magnetic and catalytic aspects.  From the analysis of the internal microstructure of CAT-CC composite photocatalytic material, nano CaCO3 as the carrier of nano TiO2 is very successful.  

TiO2 can be uniformly loaded on the surface of CaCO3 to improve its dispersibility and increase the active site and light absorption area.  TiO2 and CaCO3 form chemical bond at the interface, so that TiO2 photogenerated electrons form a new transport channel, and then improve the separation efficiency of photogenerated electrons and holes.  In CAT-CC, nano TiO2 and CaCO3 are firmly bonded due to surface chemical bonding, which prevents the loss of TiO2 when degrading pollutants in water and is easy to recover and recycle from water through sedimentation, thus reducing the dosage and cost of TiO2.