The Study Of Passivation And Self-Healing Properties Of Organosilane /Halloysite-Benzotriazole Composite Active Passivator For Pyrite And Its Mechanism

In the process of mining,huge amounts of metal sulfide minerals are usually produced,which stored as tailings,and pyrite is the most common mineral in tailings.Under natural conditions,these sulfide mine tailings are oxidized due to exposure to oxygen and water to produce acid mine drainage?AMD?.The pollution caused by AMD is serious and lasting,and it is one of the environmental problems to be solved urgently.In order to control the generation of AMD from the source,?-mercaptopropyltrimethoxysilane?Prop S-SH?was selected as the matrix passivating agent,the hollow cavity structure of halloysite?HNT?is used to load benzotriazole?BTA?into the halloysite lumen by creating a vacuum,and the encapsulated HNT-BTA composite is prepared,which is used as the performance"strengthening agent"of the silane passivator.Electrochemical test,chemical leaching method and scratch experiment were used to detect the passivation and self-repair performance of the composite active passivating agent on pyrite.Also,the passivation mechanism of the studied composite acive passivtor on pyrite was studied.First,comparing the data of the electrochemical experiment and the chemical leaching experiment,the optimal addition amount of HNT in the 100m L Prop S-SH passivator solution is 2.0g,that is the PSHT-2.0 coated pyrite.The PSHT-2.0 coated pyrite has a largest static water contact angle,indicating that this sample has the most hydrophobic and pyrite is difficult to be oxidized.At the same time,the HNT encapsulated with BTA was also prepared as HNT-BTA.Using FT-IR and TGA to test its'chemical properties and the dosage of BTA in HNT,results show that the dosage is5.2wt%.The experiment of slow-release effect in solutions of different p H values shows that it has acidic stress release function,and the release rate is inversely proportional to the p H value of the acidic solution.Using the Ritger-Peppas model to fit the obtained data,the slow release mechanism of encapsulated HNT-BTA under different acidic p H conditions was deduced.Secondly,passivating pyrite by preparing Prop S-SH/HNT-BTA?PSHB-2.0?composite active passivation agent,using electrochemical and chemical leaching experiments to detect its antioxidant properties.The data of the PSHB-2.0 coated pyrite in the electrochemical test shows that its antioxidant capacity has been improved again on the basis of the PSHT-2.0 coated pyrite.After 60 days of chemical leaching,the total iron and SO₄^2-leaching concentrations of PSHB-2.0 coated pyrite were reduced by66.1%and 61.9%respectively,achieving a long-term breakthrough in passivation.The mechanical properties of the passivation film were tested by scratch test.The critical load value of the PSHB-2.0 passivation film was 7.12N,which was improved by 113.8%and 20.4%compared to Prop S-SH and PSHT-2.0 passivation film,respectively.Finally,²⁹Si NMR,XPS and FT-IR detection methods were used to study the mechanism of PSHB-2.0 composite active passivation agent for the passivation of pyrite.Derivation of the passivation mechanism:In the mixed solution of ethanol/water,silane generates silanol solution due to hydrolysis,and the silanol solution will continuously generate Si-O-Si bonds due to dehydration condensation,and then it reacts with the silicon hydroxyl group on the surface of halloysite,so that halloysite is bound inside the silanol solution.Next,the PSHB-2.0 composite active passivation agent forms Fe-O-Si bonds and combines with the pyrite surface to form a dense passivation film.The BTA encapsulated in HNT is released after the composite active passivation film is destroyed,and reacts with pyrite to form Fe-BTA complex,which plays a secondary active repair role for pyrite.