If the wastewater produced in industrial production cannot be effectively treated, it will cause great harm to the environment. Rare earths can be prepared into water treatment materials such as adsorbents, coagulants and catalysts, and are widely used in the treatment of various industrial wastewaters.
Rare earth adsorbents are mainly prepared by impregnation-filtration-drying-calcination-sieving. It has great advantages in the treatment of wastewater containing phosphorus, ammonia nitrogen, arsenic, fluorine, and chromium. For example, La and Ce form very strong bonds together with oxyanions such as phosphates and carbonates, which make it possible to use rare earths to remove phosphates.
There are two main types of typical coagulants used in wastewater treatment: one is Fe-based coagulants, including ferric chloride, ferrous sulfate, and ferrous chloride, etc.; the other is aluminum-based coagulants, including Aluminum sulfate (alum), sodium aluminate, and polyaluminum chloride (PAC). Rare earth has gradually become a feasible phosphorus removal material.
The mechanism of rare earth removal of phosphate is to react with phosphate ions to form metal phosphate precipitation, which is then filtered. The precipitation reaction can be described by the equation: RE3+ + PO43- -> REPO4•H2O.
Rare earth elements have abundant energy levels and 4f outer electronic layer structure and have special physical and chemical properties. They not only have catalytic properties themselves but also can be used as additives and catalysts to improve the performance of other catalysts.
Printing and dyeing wastewater is a kind of refractory organic wastewater with high organic content, high chroma, and poor biochemical properties. At present, catalytic oxidation is the mainstream method to effectively degrade printing and dyeing wastewater. Adding an appropriate amount of rare earth metal compounds as catalysts in the oxidation system can effectively degrade the refractory organic compounds in wastewater. Rare earth catalysts for wastewater treatment also have the advantages of simple operation, high removal rate, low treatment cost, and stable process performance.