Self-healing coatings based on PropS-SH and pH-responsive HNT-BTA nanoparticles for inhibition of pyrite oxidation to control acid mine drainage

Aiming at the prevention and control of acid mine drainage (AMD) at the source for a long-term period, herein, we report for the first time an active passivation coating with self-healing function to protect metal sulfide minerals from oxidation. Benzotriazole (BTA) inhibitor was loaded into halloysite nanotube (HNT) under vacuum condition and encapsulated by Cu-BTA complexes stoppers, and then the PropS-SH/HNT-BTA (PSHB) coating was prepared by mixing HNT-BTA nanoparticles with gamma-mercaptopropyltrimethoxysilane (PropS-SH) to inhibit pyrite oxidation. The morphology and composition of HNT nanocontainers were characterized by SEM, TEM, EDS and FTIR methods. The loading capacity of BTA in HNT-BTA lumen was determined by TGA measurements. The releasing behavior of BTA under different pH conditions was investigated by UV-vis spectrophotometer and the release mechanism of BTA from HNT-BTA lumen was validated using Ritger-Peppas model. It was found that HNT-BTA could achieve stimulus-responsive release of BTA under acidic conditions. The passivation and self-healing properties of PSHB coating were studied by electrochemical measurements, chemical leaching tests and scratch tests. The experimental results showed that the novel PSHB coating had long-term oxidation resistance and active self-repair function after damage. Meanwhile, the passivation and self-healing mechanism of the PSHB coating is also introduced. It is thought that this study is helpful to bring new ideas in the field of metal sulfide mineral passivation.