Common treatment methods of fluorinated wastewater

Common treatment methods of fluorinated wastewater

The main source of fluorine-containing wastewater is the "three wastes" containing fluorine discharged from industrial production, which are mainly involved in aluminum electrolysis, steel, cement, brick, ceramics, phosphate fertilizer, glass, semiconductor, pharmaceutical and so on. The common feature of these industries is that fluorine-containing minerals are the main raw materials or auxiliary raw materials. In the process of smelting and production, fluorine-containing wastewater is generated from the decomposition of fluorine from minerals.

At present, there are many studies on the treatment of fluorinated wastewater at home and abroad. The main treatment methods are: chemical precipitation, flocculation precipitation, adsorption, crystal seed addition, ion exchange, reverse osmosis, activated carbon defluorination, electrodialysis and electrocoagulation. There are many fluorine-containing treatment methods, but most of them have problems such as unstable effluent quality, excessive use of agents, or secondary pollution, which makes these methods have certain limitations. In view of the above methods, ion exchange has high requirements on water quality. The treatment cost of activated carbon defluorination is high. The process of reverse osmosis and electrocoagulation is complex, power consumption is high, and cost is high. At present, the goal of industrial treatment of fluorine-containing wastewater is only to reach the effluent discharge standard. On this basis, the widely used treatment methods are mainly chemical precipitation and flocculation precipitation.

Chemical precipitation method, adding calcium salt, using the chemical reaction of calcium ions and fluoride ions to generate calcium fluoride precipitation to remove fluoride ions in fluoride wastewater. The price of calcium salt is cheaper and the operation cost is low, but the amount of slag produced is large, and if the water contains some other salts, the solubility of calcium fluoride will increase, resulting in the reduction of fluorine removal efficiency in fluorine-containing wastewater;

Flocculation precipitation method, the method is to use alum produced by aluminum salt in water on fluorine ion adsorption, ion exchange, complex settlement and other effects to remove fluorine ions, using flocculation precipitation method for fluoride wastewater treatment dosage is small, large, obvious effect, can achieve disposable fluoride industrial wastewater treatment treatment standard discharge; The adsorption method is the most suitable, although the effect is better, the operation costs will be higher because the adsorption carriers need to be replaced first.

Chemical precipitation method can treat high-concentration fluorine-containing wastewater, reducing the final COD concentration of wastewater to 20-30mg/l, while flocculation precipitation method can further treat low-concentration fluorine-containing wastewater, and can also adopt the combination of chemical precipitation and flocculation precipitation, so that the treated wastewater can meet the discharge standards.