The use of lithium-intercalated transition metal dichalcogenides, Li
xES
2, asredox-recyclable ion-exchangematerials for the extraction of the aqueous heavy metalions Hg
2+, Pb
2+, Cd
2+, andZn
2+ was investigated (0.25
x 1.9; E = Mo, W, Ti, Ta). ForLi
xTiS
2 andLi
xTaS
2,hydrolysisproduced S
2-(aq) ions, whichprecipitated Hg(II) asHgS(s). In contrast, the materialsLi
xMoS
2 andLi
xWS
2 didnot undergo hydrolysis to form S
2- ions.Instead, ion-exchanged materials such as Hg
0.50MoS
2 andPb
0.15MoS
2were isolated. The selectivity ofLi
xMoS
2 for theheavymetal ions was Hg
2+ > Pb
2+ >Cd
2+ > Zn
2+. Theaffinitiesfor the latter three ions but not for Hg
2+ increasedwhenthe extractions were performed under anaerobicconditions. When Hg
yMoS
2was heated under vacuum at425
C, an entropy-driven internal redox reactionresultedin deactivation of the extractant, producing essentiallymercury-free MoS
2 and a near-quantitative amountofmercury vapor (collected in a cold trap). The ratio ofthevolume of metallic mercury (secondary waste) to thevolume of 10.0 mM Hg
2+(aq) (primary waste) was 1.5×10
-4. Samples of MoS
2produced by heating Hg
yMoS
2werereactivated to Li
xMoS
2 bytreatment with
n-butyllithium.Some samples were used for three cycles ofextraction,deactivation/recovery, and reactivation with a primarywaste simulant consisting of 10 mM Hg
2+(aq) in 0.1 MHNO
3with no loss in ion-exchange capacity. When theMo/Hg molar ratio was 5.0 and the initial[Hg
2+(aq)] = 1mM, only 0.033(2)
M mercury (6.5 ppb) was detectedin the filtrate after the extraction step. The highestobservedcapacity of Li
xMoS
2 forHg
2+(aq) was 580 mg of mercury/gof Li
1.9MoS
2.