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Abstract

A method of reclaiming a well completion brine solution by using an organic chelant that is capable of discriminating between (i) iron and/or non-zinc heavy metals; and (ii) calcium and zinc. The chelant is of the formula: ##STR00001## and may be either a neutral compound, a corresponding salt, or a corresponding quaternary salt, wherein: D is F--A (Y.sup.3).sub.u(Y.sup.4).sub.v; R is independently selected from C.sub.p or C.sub.pC(O); C.sub.p is a C.sub.1 C.sub.36 hydrocarbyl group, optionally substituted with one or more substituents selected the group consisting of halogen, hydroxyl, sulfate, CH.sub.2CO.sub.2Z or --(CH.sub.2).sub.nPO(OZ).sub.2 groups; each A is independently selected from --N and --P; Y.sup.1 is independently selected from J, --[(F)--A(J)].sub.wY.sup.6 and R; J, R.sup.1, Y.sup.2, Y.sup.3, Y.sup.4, Y.sup.5 and Y.sup.6 are independently selected from the group consisting of --H, R, --(F).sub.nCO.sub.2Z and --(CH.sub.2).sub.nPO(OZ).sub.2; each F is independently selected from a C.sub.1 C.sub.12 hydrocarbyl group, optionally substituted with one or more substituents selected the group consisting of halogen, hydroxyl, sulfate, CH.sub.2CO.sub.2Z or --(CH.sub.2).sub.nPO(OZ).sub.2 groups; Z is --H or a balanced counterion of an alkali or alkaline earth metal or NH.sub.4.sup.+; m is 0 to 7; n is 1 to 7; r+s+t is 1 or 2; u+v is 1 or 2; and w is 0 to 7 provided when m is 0, no more than one of R.sup.1, Y.sup.1, Y.sup.2 and Y.sup.5 can be --H.

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