In June 14th, China State Council Information Office announced the "<National Human Rights Action Plan (2012-2015)> Implement assessment report", in the section of "environmental rights" it pointed out that:

1. China modified the Environmental Protection Act, which strengthen citizen's right to know, and perfect public interest litigation system, strengthen the system of accountability;

2. In the period of 6 years from 2010 to 2015, the central finance allocated 17.2 billion RMB to support the governing of heavy metal pollution, and achieved good results. Compared to 2007, in 2014, the national emissions of the focused five heavy metals which are lead, mercury, cadmium, chromium and metalloid of arsenic decreased by 20%; besides, heavy metal pollution incidents decreased from more than 10 cases per year of 2010 - 2011 on average to less than 3 cases of 2012-2015 the annual average;

3. The capacity of the water pollution treatment has been enhanced;

4. Air pollution governing intensified.

 

The original meaning of heavy metal refers to the metal which the specific weight is greater than 5 (The metal with density greater than 4.5 grams per cubic centimeter), including gold, silver, copper, iron and lead ect.. Heavy metal pollution refers to the environmental pollution caused by the heavy metals or their compounds, mainly caused by human factors mining, emissions, waste water for irrigation and use of heavy metals exceeded products. The heavy metal discharged with wastewater, although the concentration is very small, it can accumulate in sediments and algae, adsorbed on the surface of fish and shellfish, thus to generate food chain concentrated and become a public disaster.

 

Photocatalyst can well solve the problem of chromium, mercury, lead, cadmium and other metal ions pollution. Its photocatalytic reduction can be divided into three types:

1. Photocatalytic reduction to remove toxic metal ions;

2. Photocatalytic deposition to recover precious metals;

3. Photocatalytic deposition to load metal, thus to improve activity of photocatalyst.

 

Tungsten trioxide is a photocatalyst with excellent performance, which responses to visible light, rather than only rely on ultraviolet light. Tungsten trioxide photocatalyst has a strong adsorption for metal ions, furthermore, with the light intensity increasing, the precipitation of metal ions accelerated noticeably. In addition, the outstanding advantage of photocatalytic reaction like tungsten trioxide photocatalyst is that it can be applied into a very dilute solution, to play a role of potently concentrating metal ions. Meanwhile, as a catalyst, it does not consume itself, and can be put into use after the separation of metal through an appropriate process.