| Boron bearing tailings are the remaining substances after iron separation from paigeite,which can be used instead of borosite to prepare borax and boric acid.There was a large amount of boron bearing tailings in the Dandong area of Liaoning province,China,which was caused by the policy "separate iron and dispose boron" in the area.In order to solve the problem of wasting land and wasting resources due to the stacking of large amounts of boron bearing tailings,this paper used low grade boron bearing tailings to prepare boraxThis paper used boron bearing tailings from the Kuandian area of Liaoning province as the raw material,and used the sodium roasting and pressure leaching method to prepare the borax.The effects of three factors on the quality of borax and the recovery of boron in the sodium calcining process were studied,and the three factors were roasting temperature,the amount of sodium carbonate and roasting time.Meanwhile,the effects of three parameters,liquid to solid ratio,water temperature and time,on borax and boron recovery were also analyzed.The samples were characterized by scanning electron microscopy(SEM),X-ray diffractometer(XRD),Fu Liye transform infrared spectrometer(FT-IR),X-ray photoelectron spectroscopy(XPS)and integrated thermal analyzer(TG-DTA).The mechanism of borax preparation by sodium roasting and pressure leaching process was preliminarily discussed and analyzed.The analysis results showed the conditions of sodium roasting and pressure leaching process had a certain effect on boron recovery.But different conditions of sodium roasting process exerted different impacts on boron recovery.Sodium roasting temperature mainly affected the pyrolysis of sodium carbonate and the reaction degree of each phase in the mixture.The amount of sodium carbonate mainly affected the species involved in the whole roasting process.Roasting time mainly affected the degree of sodium reaction,and then affected the subsequent leaching and recycling of boron.The liquid-solid ratio of the water immersion mainly affected the fluidity of the slurry in the system;the increase of the water immersion temperature could provide more energy to destroy the network structure,thus affecting the intensity of the water molecules’ movement;and the water immersion time mainly affected the adequate contact of the roasted products with deionized water.Comprehensive analysis of the experimental results showed that the boron recovery reaches its maximum of 75.03%under the optimal condition where the sodium roasting temperature was 950 ℃,the amount of Na2CO3 was 5 times the theoretical amount,the roasting time was 2h,the water-solid ratio was 5:1,the water immersion temperature was 180℃,and the immersion time reached 6.5h.The prepared crystals had a smooth surface,a complete cubic structure,and good development.Through the mechanism analysis of sodium roasting and pressure leaching process,the main reason for the increase of boron recovery was that the Na2O produced by the pyrolysis of Na2CO3 reacted with the boron bearing phase in the boron bearing tailings to form a soluble sodium borate salt,which provided a good basis for the subsequent water immersion reaction to prepare borax. |
