Mixed hydroxide carbonates containing Bi3+ and divalent metals were synthesized by hydrolyzing mixed solutions of M(NO3)(2) (M = Mg, Zn) and Bi(NO3)(2) with Na2CO3 solution at room temperature. The materials were studied using powder X-ray diffraction (XRD), IR spectra, N-2 adsorption/desorption and thermogravimetric and differential thermal analyses (TG/DTA). Simultaneous substitution of a divalent metal ion (Mg2+ or Zn2+) and hydroxyl group for the Bi2O22+ layer in the bismutite structure occurred, forming hydroxide carbonates. Their chemical composition and the lattice parameters were represented by (Bi-0.910, Mg-0.090)(2)(O-0.910, (OH)(0.090))(2)CO3.0.51H(2)O with a(0) = 0.3862(2) nm and c(0) = 1.3673(6) nm, and (Bi-0.233, Zn-0.767)(2)(O-0.233, (OH)(0.767))(2)CO3.0.38H(2)O with a(0) = 0.3864(2) nm and c(0) = 1.3657(9) nm. The BET surface area of the bismutite, 6 m(2)/g, increased to 35-40 m(2)/g with the former and to 16-18 m(2)/g with the latter. Both hydroxide carbonates showed an excellent ion-exchange selectivity for SeO32-. These materials are promising for selective removal of SeO32- ion from selenite-contaminated aqueous effluents.