Surface hydrophobic modification of sulfur-containing waste rock for the source control acid mine drainage

Hydrophobic modification of sulfur-containing waste rock is a promising strategy for reducing acid mine drainage (AMD) generation. This study investigated the use of sodium oleate and nano silca to modify sulfur-containing waste rock and evaluated the acid-suppressive properties of the sodium oleate and nano silca treatment through static and dynamic leaching tests. Results from these tests indicated that the pH of the leachate from the modified waste rock remained stable above 6.0. The results of 30-day dynamic tests also showed that the inhibition rate of acid generation could be more than 65 % and the reduction rate of total Fe can be more than 85 %. Furthermore, a protective film was formed on the surface of the modified waste rock, and the contact angle was increased to 84.3° compared with the original waste rock (17.9°). Sodium oleate interacted with Fe2+ and Fe3+ to form iron oleate complexes, which were encapsulated on the surface of the waste rock, thus effectively preventing the oxidation of the waste rock and thus inhibiting the generation of acidic water. X-ray photoelectron spectroscopy (XPS) results showed that the C 1 s signal of the modified waste rock sample was enhanced and the characteristic COO-Fe peaks appeared. Additionally, the ratio of the C–C/C–H to O-C = O characteristic peaks increased with the presence of nano silca powder. These findings indicated that ferric oleate complexes facilitated the attachment of nano silca to the surface via van der Waals forces, which filled the pores of the hydrophobic film layer.This study provides a viable solution to the ability of sulphur-containing waste rock to resist oxidation and inhibit acid production.