Synthesis of β-SiAlON materials from blast furnace slag by acetic acid leaching combined with carbothermal reduction and nitridation

Abstract

ABSTRACT In order to optimize the utilization of blast furnace slag (BFS) and enhance the cost-effectiveness and feasibility of β-SiAlON preparation, a novel approach involving acetic acid leaching-carbothermal reduction and nitridation was proposed. The effects of acid concentration and leaching times on the leaching behavior of BFS were thoroughly investigated. The synthesis mechanism of β-SiAlON was comprehensively explored through thermodynamic analysis, X-ray diffraction, scanning electron microscope and energy dispersive spectroscopy. The results demonstrate that selective leaching of Ca and Mg elements from BFS can be achieved while effectively enriching Si and Al elements in the filter residue. Under optimized leaching conditions, the contents of CaO and MgO in the residue are reduced to below 3% and 1%, respectively. The mass ratio of alumina to silica (w(Al)/w(Si) = 0.3-0.4), the molar ratio of carbon to oxygen (n(C)/n(O) = 0.5), the roasting temperature at 1673 K and the roasting time for 4 hours should be precisely controlled in order to successfully synthesize β-SiAlON from BFS. In summary, the primary reaction pathways for β-SiAlON synthesis from BFS can be described as follows: C4H7AlO5/AlO(OH) transforms into Al2O3, which further reacts with SiO2 to form β-SiAlON; alternatively, Al2O3 reacts with SiO2 to produce mullite, which subsequently converts into β-SiAlON.