Chemical Entrapment of Pb(II) by Ettringite

This work aims to make clear whether Pb(Ⅱ) can be chemically entrapped by ettringite and under what conditions this entrapment can take place.Al2(SO4)3 and NaOH react with Pb(NO)3in synthetic liquid to produce the lead analog of ettringite,Pb6[Al(OH)6]2·3SO4·26H2O under room temperature.Furthermore,CaO,Pb(NO3)2,Al2(SO4)3 and distilled water are used to synthesize Ca-Pb ettringite,(Ca,Pb)6[Al(OH)6]2·3SO4·26H2O.The results show that Pb6[Al(OH)6]2·3SO4·26H2O can't form,while Ca-Pb ettringite can be produced.Pb(Ⅱ) can't be entrapped by ettringite when calcium is Absent during liquid phase reactions.However,Pb(Ⅱ) can be entrapped by ettringite when calcium is adequate in liquid phase.The X-ray diffraction peaks for Ca-Pb ettringite is significantly different from pure ettringite,indicating that ettringite lattice changes a little after accommodating lead.Experiments on Pb(Ⅱ)solidified by 100% cement clinker show that XRD patterns for 7-days storage period change after they doped with lead,indicating that some Pb(Ⅱ) has entered into ettringite lattice.