The purpose of adding aluminum sulfate for defluoridation treatment is to make the fluorine content in the wastewater meet the standard and avoid fluorine pollution or fluorosis caused by excessive fluorine intake by the human body. Fluorosis can form deposits on teeth and bones and can cause loss of appetite, dizziness, headaches, and memory loss. Defluorination of aluminum sulfate is carried out through its adsorption, precipitation, and complex precipitation. Through pH adjustment, aluminum sulfate treats fluorine-containing wastewater by using the principle of neutralization and symbiotic precipitation. Arsenic, fluorine, etc., precipitate at their suitable pH value and are thus separated from the water.
On the other hand, the aluminum hydroxide colloid generated by dissolving aluminum sulfate in water has an adsorption and precipitation effect on solid suspended small particles in the water, and aluminum ions can undergo an electrical neutralization reaction with it. The first is the treatment of fluoride-polluted wastewater. In the traditional treatment method, we put calcium salt into the sewage, but the precipitation rate will be very slow, and using it alone will increase the cost of treatment. But adding iron-free aluminum sulfate makes a big difference. Its main function is chemical precipitation, adsorption, or flocculant treatment of pollutants, and it greatly reduces the fluorine content in sewage. The precipitation method is only suitable for the treatment of sewage with high fluorine content; while for the treatment of drinking water with low fluorine content, we have to use the adsorption method. The commonly used method is to use the chemical precipitation method first, and then treat aluminum sulfate with an adsorbent or flocculant to reduce the fluorine content to less than 10 mg/L.
The second is the treatment of heavy metal wastewater. Heavy metal wastewater treatment methods include neutralization, precipitation, the sulfide soda method, the ferrite method, the resin method, etc. Iron-free aluminum sulfate precipitation is also the most commonly used one. Iron-free aluminum sulfate also has the effect of adsorbing and settling heavy metal wastewater, and is also a method used by many companies for sewage treatment. In order to improve the fluoride removal effect, some coagulants and regulators can be added to the wastewater, such as commonly used lime, polyacrylamide, etc.