Polyepoxysuccinicacid(PESA),asanenvironmentalbenignbiodegradablechelant,wasusedtoremoveheavymetalsfromthesewagesludgeofShanghaiTaopuWastewaterTreatmentPlant.Theextractionofcadmium(Cd)fromsewagesludgeusingaqueoussolutionofPESAwasstudied.ItwasfoundthatPESAwascapableofextractingCdfromthesludge,andtheextractioneffciencywasdependentonbothpHandtheconcentrationofthechelatingreagent.TheextractioneffciencydecreasedgraduallywithincreasingofpH,whereasthedependencyonpHdecreasedastheconcentrationofPESAincreased.InthecaseofthehighPESAtototalmetalratio,e.g.,10:1,theextractioneffciencyreachedabove70%withinthepHrangefrom1to7.Thehighestextractioneffciencyobtainedintheexperimentwas78%.Bycomparingthecontentsoftheheavymetalsinsewagesludgebeforeandaftertheextraction,itwasfoundthattheextractedCdcamemainlyfromthefourfractions:acid-soluble,reducible,oxidizable,andwater-solublefractions.
