China Nonferrous Metallurgy

The organic matter in sodium aluminate solution poses a significant threat to the production of alumina. Currently, the determination of humic acid concentration in sodium aluminate solution is cumbersome and the accuracy of the measurement results is low. This article innovatively proposes a method based on the humic acid concentration measured by the “extraction precipitation method”, using the “absorbance method” to quickly determine the humic acid concentration, and explores the degradation law of humic acid entering industrial sodium aluminate solution during high-temperature cycling. The main conclusions are as follows. The principle of extraction precipitation method is to add barium salt solution to the reverse extraction solution to precipitate humic acid, then calcine the precipitate, and calculate the humic acid concentration by the mass of the calcined product. The humic acid concentration in the industrial sodium aluminate solution used in the experiment is 1.80g/L; The principle of absorbance measurement is to first determine the absorbance curve equation Y=1.6298X-0.1628 through experiments, and then measure the absorbance of the solution to be tested. The absorbance measurement value should be between 0.2 and 2.0, and the concentration of humic acid in the solution to be tested can be calculated by substituting it into the equation. Temperature and time have a significant impact on the removal of humic acid. The higher the temperature, the longer the insulation time, and the higher the removal rate of humic acid. After insulation at 280℃ for 1h, the removal rate of humic acid is 68.30%; Temperature and time have little effect on the total organic carbon in sodium aluminate solution, as well as the mass concentration of small molecular acids such as malonate, formate, acetate, succinate, and oxalic acid. However, the mass concentration of oxalate increases significantly after prolonged insulation, and industrial production needs to pay attention to the changes in the mass concentration of sodium oxalate.