Dissolution behavior of DTPA-promoted barium slag and synthesis of submicron BaSO4 particles

Abstract

Barium slag (BS) is a kind of industrial solid waste generated in barium salt production. Barium in BS can be considered as a secondary source as the content of BaO is as high as 34.80%. The main existent forms of barium in BS are BaSO4, BaCO3 and BaSiO3. It is challenging to dissolve BaSO4 using conventional acids and alkalis due to the low solubility. In this study, diethylenetriaminepentaacetic acid (DTPA) was introduced to investigate the dissolution behavior of barium in BS, and the DTPA complex solution was acidified to release barium for submicron BaSO4 products preparation. Leaching tests were carried out at DTPA concentrations of 0.025–0.30 mol/L, liquid solid ratio of 10–100 mL/g, pH of 8.0–13.0, and reaction temperature of 20–80 °C. The leaching efficiency of barium was 78.64% under the conditions of using 0.10 mol/L DTPA solution (pH of 12.0) at 80 °C for 300 min with the liquid solid ratio of 50 mL/g. BaSO4 products were obtained by the addition of H2SO4 to acidify the leachate at pH ranges of 9.0–7.5. Characterization results from X-ray diffraction, scanning electron microscopy, transmission electron microscopy and dynamic light scattering indicated that the BaSO4 products were nearly sphere particles with the average diameter of 300–500 nm. This work demonstrates that DTPA can dissolve barium in BS and acidifying Ba-DTPA leachate can dissociate barium ions. Furthermore, barium source in BS can be recovered in the form of submicron BaSO4 products through DTPA complexation and decomplexation process.