The Dynamic Experiment Study On The Treatment Of Fe²⁺ And Mn²⁺ In Acid Mine Drainage By Bentonite And Steel Slag Composite Particle

Acid mine drainage usually contains amount of acidity and heavy mental ions,such as Fe²⁺and Mn²⁺,how to cheaply,efficiently and simultaneously remove acidity and heavy mental ions has become an urgent issue to solve for harnessing mine environment.This study utilizes bentonite-steel slag composite particles as adsorbent in fixed-bed reactor,discussing dynamic adsorption feature for Fe²⁺,Mn²⁺and removal efficiency of acidity,as well as determined the best operating mode and design parameters.Adsorption dynamics model and adsorption of particles after back wash are studied.Scanning electron microscopy,X-ray diffraction,Energy disperisive spectrometer are used to reveal the adsorption mechanism of heavy metal ions on composite particles,the results are as follows:（1）Compare three columns removing effect of Fe²⁺/Mn²⁺in AMD,including composite particle,manganese and mixed adsorption column.The three adsorption capacity of Fe²⁺are 60.31 mg/g,2.62 mg/g,28.06 mg/g and Mn²⁺are 29.817 mg/g,2.194mg/g,16.935 mg/g respectively,manganese column cannot reduce acidity in waste water,while composite particle can release alkalinity to neutralize acid,indicating that it is a good water treatment material to remove acidity and heavy mental ions simultaneously.（2）Compare the removal efficiency of Fe²⁺/Mn²⁺in AMD by three kinds of operation modes of composite particle column,including upflow submerged type,downflow non-submerged type and downflow submerged type.Downflow submerged type column is easily blocked up when treating Fe²⁺.Adsorption working cycle of three are 46 d,57 d,21 d,adsorption capacity are 53.612 mg/g,60.923 mg/g,32.979 mg/g,which can still work for 15 d,13 d,30 d after backwashing and total removal amount of Fe²⁺are 68.181 mg/g,72.906 mg/g,66.856 mg/g.The adsorption capacity of Mn²⁺under three operation modes are 26.532 mg/g,28.817 mg/g,23.479 mg/g,and 4.823mg/g,4.581 mg/g,5.035 mg/g after backwashing,total removal amount of Mn²⁺are31.355 mg/g,33.398 mg/g,28.514 mg/g.The acidity in waste water can be decreased by the three.Comprehensive analysis shows that downflow non-submerged type is the best operating mode.（3）The dynamic adsorption removal characteristics and optimal design and operation parameters of downflow non-submerged type adsorption column are studied,（4）Confirming the breakthrough and exhaustible time of adsorption column increased as the flow rate and initial concentration decreased.The optimum operating parameters for dynamic adsorption process of Fe²⁺and Mn²⁺are as follows:both flow rate are 0.6 mL/min,volume hydraulic loading are 16.178 m³/（m³?d）,HRT are 90 min,the inlet of Fe²⁺and Mn²⁺concentration are 100 mg/L and 80 mg/L,when run to 73 d and 49 d,adsorption capacity of Fe²⁺and Mn²⁺are 64.762 mg/g and 35.56 mg/g,pH value are balanced by 4.5 d and 6 d.Thomas model of Fe²⁺and Mn²⁺dynamic adsorption was established.（5）Through dynamic adsorption contrast test of heavy metal ions in single and multivariate system,reveal heavy metal ions in multivariate system exist competitive adsorption inhibition effect,which competitive adsorption law is Fe²⁺>Cu²⁺>Zn²⁺>Mn²⁺when they coexist.SEM discover that sediment gathered on the surface of composite particles can remove metal ions and precipitate by coagulation.XRD and EDS further reveal the existence of ion exchange,complexation and adsorption-coagulation synergy in dynamic adsorption process.