Recovery of Germanium from Coal Fly Ash Leachate by Precipitation

摘要

The valorization of coal gasification fly ash is studied by leaching the fly ash with waterand a subsequent precipitation of trace amounts of germanium from the leachates.Experimental investigations were focused on the optimization of the precipitation of agermanium?catechol(CAT)complex with cetyl trimethyl ammonium bromide(CTAB).The influences of pH and the amounts of CTAB and CAT on the precipitation yield wereinvestigated.For a appropriate set of experiments,a statistical technique such as theresponse surface methodology(RSM)has been used.A central composite rotatabledesign was employed for experimental design and analysis of the results.Theindependent and combined effects of pH,CAT/Ge and CTAB/Ge molar ratios wereinvestigated and optimized using a quadratic mathematical model.The optimum valuesof these factors were found to be 10,12 and 4 respectively.In this case,the germaniumprecipitation yield was 98.8%.The analysis of variance was performed to validate theregression model.Also,the response surface plots were drawn for spatialrepresentation of the regression equations.The precipitation of germanium as a complex compound with catechol and CTAB canbe selective towards germanium and this element can be effectively separated from As,Mo,Sb,V or Zn.Thermo-gravimetric analysis has been applied to the germanium-complex solids and asa result of which 600oC was determined as the minimum temperature to completelyremove the organic content of the precipitate.