Aluminum extraction from activated coal gangue with carbide slag

A new coal gangue(CG) activation additive was studied in this paper, carbide slag(CS) was used as an auxiliary agent on the extraction of Al2O3 from coal gangue activated by Na2CO3 through acid leaching. The dissolution rate of Al2O3 was determined by Inductively Coupled Plasma-Atomic Emission Spectrometer(ICP-AES) and calculated using industrial standard SN/T 1599–2005. The results showed that compared with the direct activation of coal gangue with Na2CO3, the addition of carbide slag could reduce the dosage of Na2CO3 by 60% and the acid leaching time by 1/3. The alumina dissolution rate reaching 94.58% when calcined at 800 °C for 120 min, m (CG:Na2CO3:CS) = 1:0.4:1.2, the liquid-solid ratio was 15 mL·g−1, and the acid leaching time was 60 min. Simultaneous thermal analyzer (TG-DSC), fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscope(SEM) analysis showed that calcination of coal gangue with Na2CO3 produces sodium aluminosilicate, sodium silicate and nepheline, making aluminum in coal gangue easier to be leached by acid. The carbide slag was involved in the activation process of coal gangue by Na2CO3 at 740–847 °C, which destroyed the Si-O structure and Al-OH structure in coal gangue, generated calcium silicate with more developed pore structure consumes part of SiO2, and reduced the consumption of Na2CO3 during the calcination process by reaction with SiO2, and shortened the reaction time between minerals and hydrochloric acid.