Environmental Protection Lever Pries the Development of New Snow-Thawing Agents  
By Zhou Zhonghai and Guo Huiming, the Sciences School of Nanjing University of Technology   

1. Chloride varieties

Chlorides snow-thawing agents mainly include sodium chloride, calcium chloride and magnesium chloride, as well as their blends with anti-corrosion and anti-rust agents.
   Sodium chloride is a road snow-thawing agent in popular use today. It has the features of quick snow thawing and low cost. Its heat absorption in dissolution and its corrosion are however strong and the application produces serious negative impacts on soil, water and vegetation.
   Calcium chloride is also called hot salt and is usually used at extremely low temperatures. Its advantage is heat liberation in dissolution. Anhydrous calcium chloride, in particular, has great dissolved heat and remarkable snow thawing effect. Application results prove that calcium chloride also has corrosion and its negative impact on environment is only slightly smaller than sodium chloride.
   Researchers from Zhengzhou University headed by Wang Xiaoguang have developed PSA snow-thawing agent with calcium chloride and magnesium chloride as main ingredients. Test results show that such snow-thawing agent conforms to the standard for environmental protection snow-thawing agents in Beijing and also has a considerable advantage in price.

2. Non-chlorides varieties

Mr. Zhang Tiande has used liquid methyl glucoside, a byproduct in the wine production, as major raw material and developed an environment-friendly snow-thawing agent with no toxicity and no corrosion through the blending of alcoholic dreg or dreg liquor, waste paper pulp, natural calcium carbonate ore powder and ganister powder. Its active ingredients are soluble matters precipitated in fermentation.
   Researchers in China have used methyl glucoside as major raw material, conducted alcohol removal, color removal and refining to it, added diethylene glycol or triethylene glycol and developed an environment-friendly snow-thawing agent through blending and agitating.
   CAS Institute of Oceanology and the Qingdao Municipal Maintenance and Management Division have jointly developed a new snow-thawing agent called sanitary and color-changing Huaxuejing. Its main ingredients are extracts of some marine and land plants.
   Hebei University of Technology and Hebei Xuanhua-Datong Expressway Management Division have jointly developed a non-corrosive compound snow-thawing agent. The production and application have no hazards, the process is innovative and the property/price ratio is high.

3. Mixed varieties

Li Zhen and others from Tianjin Changhao Chemical Co Ltd have developed a compound anti-rust snow-thawing agent composed of two substances including magnesium chloride and sodium chloride or three substances including magnesium chloride, sodium chloride and magnesium sulfate. Raw materials are from waste liquor in the bromine production, byproduct industrial salt or high/low-temperature salt in chemical plants. Sodium metasilicate with anti-rust effect is also added to reduce damages to roads and buildings in application. Wang Guoqiang and others from Lanzhou Jinling Petrochemical Co Ltd have developed a mixed snow-thawing agent with calcium chloride as major raw material and urea, sodium nitrite and potassium sulfate as auxiliary raw materials. Such snow-thawing agent has small environmental impact and high snow-thawing effect and also contains nutrients needed in plant growth. It therefore has a bright prospect for application dissemination.