| Acid mine drainage(AMD)causes pollution for a long time after entering the environment,which is very harmful to the environment and ecology.Once it causes pollution to the environment,it will be difficult to control and recover.At present,the prevention and control of acid mine wastewater has become a worldwide problem,and the effective management of AMD has become the focus of scholars at home and abroad.Among many AMD prevention and control strategies,active prevention and control can fundamentally solve the environmental problems caused by AMD.The generation of AMD is mainly caused by the oxidation of pyrite.Therefore,in this study,slowing down the oxidation rate of pyrite as the basis of AMD prevention and treatment,using hydroxyapatite(HA)to modify the organosilane passivation agent,successfully prepared hydroxyl Apatite modified silane passivation agent,and the performance and mechanism of hydroxyapatite modified silane passivation agent coating passivating pyrite are studied.The influence of compound passivation agent on the passivation performance of pyrite under different preparation conditions of hydroxyapatite was investigated,the best preparation conditions were determined,and the characterization of pyrite was analyzed by means of scanning electron microscope(SEM),X-ray diffraction(XRD)and static water contact angle test.The effects of different reaction conditions on the passivation properties of hydroxyapatite modified silane passivation agent were studied.The kinetic fitting of total iron ion leaching behavior in passivated ore was carried out by shrinkage unreacted core model,and the mechanism of passivating pyrite by HA-modified silane passivating agent was analyzed by Fourier infrared spectroscopy(FT-IR),X-ray photoelectron spectroscopy(XPS)and other characterization methods.The column leaching test of pyrite ore and HA modified silane passivated ore was carried out to simulate the inhibition of HA-modified silane passivated material on the dissolution of pyrite in real environment.The main research results are as follows:(1)The preparation conditions and characterization of HA-modified silane passivating agent were studied.Through the qualitative and quantitative analysis of pyrite ores by X-ray diffraction(XRD)and X-ray fluorescence spectrometer(XRF),the characterization results show that pyrite ores have high purity.The passivation performance of HA-modified silane passivating agent showed that the passivating ability of envelope was stronger than that of organosilane passivating mineral.By exploring the influence of reaction temperature and calcination temperature in the HA preparation system on the passivation properties of HA-modified silane passivating agent,it can be concluded that the suitable preparation conditions for HA material in the HA-modified silane passivating agent are: the reaction system temperature is 30℃ and the calcination temperature is 600℃.The pyrite before and after passivation was characterized by SEM,XRD and static water contact Angle.The SEM characterization results showed that the pyrite raw ore had a block-like structure with smooth surface and different particle size.The surface of HA-modified silane passivator was rough,and the adhesion of small sharp particles formed large block-like particles.The XRD pattern shows that HA-modified silane passivation agent interacts with pyrite,indicating that HA-modified silane passivation agent successfully loads on the surface of pyrite.Static water contact Angle test results show that the water in the pyrite surface contact Angle is less than 90 °,pyrite samples embodied in hydrophilic,when pyrite HA-modified silane passivation agent after coated,the water on the surface of pyrite contact Angle is greater than 90 °,samples of hydrophobic,illustrate the HA-modified silane passivation agent can inhibit the oxidation of pyrite(2)The effects of different reaction conditions on the film passivation properties of HA-modified silane passivating agent were studied.The effects of the dosing ratio,solution p H,reaction temperature and dissolved oxygen concentration of HA-modified silane passivating agent on the passivating properties of modified silane passivating agent were investigated by batch experiments.The results show that the passivation performance of HA-modified silane passivating agent increases first and then decreases with the increase of the proportion of HA material,and the proportion of HA-modified silane passivating agent with the best passivating performance is 16%.With the increase of p H,the total iron ion concentration and sulfate ion concentration in the reaction system generally showed a trend of decreasing,but when p H was 6 and p H was 8,the exchange occurred.With the increase of reaction temperature,the total iron ion concentration and sulfate concentration in HA-modified silane passivated ore leaching solution also increased.An increase in the concentration of dissolved oxygen also leads to an increase in the concentration of sulfate and iron ions.(3)The passivation mechanism of passivated pyrite by HA-modified silane passivating agent was explained by the model fitting of shrinkage unreacted core and the FT-IR and XPS characterization of pyrite before and after passivation.The results show that the kinetic fitting degree of the diffusion control model of passivated ore under different reaction conditions is higher than that of reaction control kinetics,which indicates that the leaching of total iron ions in passivated ore is mainly controlled by the diffusion in solid product layer.FT-IR and XPS characterization analysis results,the HA-modified silane passivation agent passivation mechanism of pyrite is mainly the HA-modified silane passivation agent by Si-O-Si key wrap pyrite in the passivator.the HA-modified silane passivation agent hydrolysis solution of silane alcohol group(Si-OH)and HA Ca-OH functional crosslinking reaction,happened in passivation agent/pyrite surface elimination of water and alcohol and covalent bond,thus forming a dense network of covalent bond "fill" organic silicide passivator passivation pyrite formation of the micro cracks,from the source to prevent pyrite exposed to the air,To prevent the production of acidic wastewater(4)The column leaching test of pyrite ore and HA modified silane passivated ore was carried out to simulate the inhibition of HA modified silane passivated material on the dissolution of pyrite in real environment.The results show that the pyrite passivated by HA modified silane passivating agent has a strong antioxidant capacity in the actual environment,and the pyrite passivated by coating can greatly slow down the production of acid wastewater. |
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