Thelong-termdumpingofcoalwastepileshascausedseriousenvironmentalproblems.Releaseoftraceelements(includingrareearthelements,REEs)fromcoalspoilsgobswasinvestigatedatYangquancoalmine,ShanxiProvince,China.X-raydiffraction(XRD)wasusedtoanalyzethemineralcompositionofthecoalspoils.Themineralsofthecoal-spoilsamplesaremainlykaoliniteandquartz,withaminorproportionofpyrite.Thebatchandcolumntestswereemployedtosimulatetheleachingbehavioroftraceelementsfromcoalspoils.ElementsV,Cr,Zn,As,Pb,andCdarehighlyenrichedinallcoalspoils.ThecoalspoilsalsohaveelevatedlevelsofGa,Ge,Se,Sn,Hf,andTh.Theleachateofcoalspoils,friedcoalspoilsandCSFGM(coalspoilsfiregasmineral)samplesareacidic,withthepHvaluesrangingbetween3.0and6.6.Thereleasedelementswithhighconcentrations(over100μg/L)includeFe,Mn,Co,NiandZn,whilemoderately-releasedelementsareCu,Se,MoandAs.Ahighcontentofheavymetalsinbatch-testleachatewithCSFGMindicatesanincreasedmobilityofheavymetalsincoalspoilcombustionbyproduct.Withinthefirsthourwashingwiththeelectrolytesolution,arapidriseofcommoncations,traceelements,andREEscontent,aswellasadropofpHvalue,ineffluentwasobserved.Anincreasedleachingvelocityfavorsthereleaseoftraceelementsfromcoalspoils.Inaddition,thepulseinputofprecipitationledtomoreelementstobereleasedthancontinuousleaching.
