煤矸石焙烧活化-酸浸提取氧化铝的实验研究

Extracting valuable metal elements from coal gangue is one of the essential ways to realize the comprehensive utilization of coal gangue. Focused on Al2O3 from high-iron and low-aluminum coal gangue, the activated roasting method was employed using hydrochloric acid as the leaching medium. The effects of roasting temperature, roasting time, acid leaching temperature, hydrochloric acid concentration, acid leaching time and liquid-solid ratio (volume of hydrochloric acid used for leaching 1 g coal gangue) on the leaching of Al2O3 from activated coal gangue were investigated, and the leaching kinetics of Al2O3 in coal gangue was also discussed. The experimental conditions encompassed five groups for each parameter: roasting temperature (550 ℃, 650 ℃, 750 ℃, 850 ℃, 950 ℃), roasting time (0.5 h, 1.5 h, 2.5 h, 3.5 h, 4.5 h), acid leaching temperature (60 ℃, 80 ℃, 100 ℃, 109 ℃, 120 ℃), concentration of hydrochloric acid (36%, 43%, 49%, 57%, 64%), acid leaching time (0.5 h, 1.5 h, 2, 5 h, 3. 5 h, 4.5 h), and the liquid-solid ratio (2 mL/g, 3 mL/g, 4 mL/g, 5 mL/g, 6 mL/g). The morphology and mineral composition of raw coal gangue, activated material and acid-leaching slag were character-ized by scanning electron microscopy (SEM) and X-ray diffractometer (XRD), respectively. The leaching mechanism was further discussed, The results show that the optimum experimental con-ditions are as follows: the roasting temperature is 650 ℃, the roasting time is 1.5 h, the volume fraction of hydrochloric acid is 49%, the ratio of liquid volume to solid mass is 4mL/g, the leac-hing time is 2 h , and the leaching temperature is 109 ℃. In these conditions, the leaching ratio of alumina can reach 94.9%. The unreacted shrinking core model can preferably describe the leaching process. The reaction rate is controlled by the mixture of solid product layer and interfa-cial chemical reaction, and the apparent activation energy is 39.93 kJ/mol. SEM analysis mani-festes that the roasting activation can effectively destroy the stable structure of coal gangue, re-sulting in a porous structure; XRD analysis suggestes that the Al2O3 in the roasted coal gangue is composed of amorphous meta kaolinite and boehmite in the activated state, and the leaching char-acteristics of Al2O3 in the coal gangue have conspicuously improved through acid leaching.