Experimental study on treatment of acid mine water in closed pit coal mine by dispersing alkaline matrix method

In recent years,most of the coal mines have been closed to produce a large amount of acid mine drainage,causing serious water environmental pollution in the Yudong River area,Kaili,Guizhou.In order to explore the effect of the dispersed alkaline matrix system composed of limestone and wood chips on the treatment of acid mine water in closed pit coal mines,a total of 50 days of acid mine water treatment simulation experiments were carried out.The experiment used inductively coupled plasma mass spectrometry (ICP-MS) to measure the concentration of Fe,Al,Mn,Zn,Cd metal ions in the water in and out of the reaction at different times,the titration method to determine the acidity and alkalinity,and the portable analyzer to measure pH,redox potential ORP and temperature,etc.The results show that at the end of the experiment,the dispersed alkaline matrix treatment column can effectively increase the pH of the acidic mine water and keep the effluent above 6.With the passage of time,the reaction section of the system continues to move down.At the end of the reaction,the section that can effectively release alkalinity has moved to the deepest layer of the system.At this time,the removal efficiency of each element corresponding to Al,Fe,and Zn can reach up to 98.58%,51.51%,35.45%,but no obvious removal effect on Mn and Cd.The solid precipitate in the reaction column can be analyzed by X-ray diffractometer (XRD) mineral composition analysis,scanning electron microscope (SEM) micro-morphology analysis and energy dispersive X-ray spectroscopy (EDX) micro-chemical composition analysis.Fe2+ is oxidized to form Fe3+,and then hydrated or precipitated to form iron hydroxide,but iron hydroxide is unstable,so part of it will be converted into its hydrolysate (goethite,wurtzite,etc.),and part of it will pass through with Swidth=26,height=17,dpi=110.The complexation forms fibrous iron alum and other paths to be removed from the solution.It can be obtained by calculating the saturation of each metal ion mineral form at different depths.There may also be precipitation of Al related minerals in the system surface layer 0～8 cm,such as hydroxyapatite,boehmite,diaspore,etc.