Leaching of silica from vanadium-bearing steel slag in sodium hydroxide solution

The work aims to selectively extract silica from vanadium-bearing steel slag by a leaching process. The effects of the particle size, the ratio of solid to liquid, the concentration of sodium hydroxide solution and the leaching temperature on the leaching behavior of silica from vanadium-bearing steel slag were investigated. The leaching kinetics of silica from vanadium-bearing steel slag in 30–50% w/w NaOH solutions was studied at 240 °C and the shrinking-core model was established to express the leaching kinetics of silica. The data showed that the leaching rate was controlled by the chemical reaction on the system interface and the activation energy for the process was found to be 36.4 kJ mol− 1. By the leaching process, the majority of silica could be removed effectively from the vanadium-bearing steel slag and a residue with a low SiO2 content of 4.28% and a high V2O5 content of 11.15% was obtained. Under these conditions there was partial dissolution of Al and slight dissolution of Cr, Mn and Ti.

Research highlights
► Up to now, there has not been much research done on the removal of silica by alkali leaching, and so we attempt to find the leaching behavior of silica in the NaOH solution. The effects of the particle size, the ratio of solid to liquid, the concentration of sodium hydroxide solution and the leaching temperature on the leaching behavior of silica from vanadium-bearing steel slag were investigated and the leaching kinetics of silica from vanadium-bearing steel slag in low concentration NaOH solutions was studied. By the leaching process, the majority of silica could be removed effectively from the vanadium-bearing steel slag. The removing silica pre-treatment of vanadium-bearing steel slag in the low alkaline conditions could be available to resolve the filtration and separation difficulties. The combination of the removing silica pre-treatment with the SMS process could be a potential method, which is useful to extract vanadium from the vanadium-bearing steel slag.