New Attempts to Synthesize Layered Double Hydroxides Intercalated with SO₄^2-/Cs⁺ Using Co-Precipitation and Exchange Reactions

Layered double hydroxides (LDHs) with the compositions (Cs⁺/NH₄⁺)_0.111[M²⁺_0.667Al_0.333(OH)_2.0 (SO₄)_0.222] (M²⁺ = Mn, Zn) and basal distance of ca. 11 Å were obtained by co-precipitating Mn/Al and Zn/Al sulfate salts with aqueous NH₃, using excess of Cs₂SO₄. [Mn_0.667Al³⁺_0.333(OH)₂]Cl_0.333^.nH₂O and [M²⁺_0.667Al³⁺_0.333(OH)₂](NO₃)_0.333^.nH₂O (M²⁺ = Mn, Zn) were also synthesized by co-precipitation, presenting respective basal distances of 8.92 and 7.92 Å. After applying exchange reactions with excess of Cs₂SO₄, materials with basal distances of ca. 11 Å were obtained, indicating the exchange of chloride and nitrate with sulfate, without incorporation of Cs⁺. When Na⁺_0.111[M²⁺_0.667Al_0.333(OH)_2.0(SO₄)_0.222](M²⁺ = Mn, Zn) obtained by co-precipitation and having basal distances of ca. 11 Å was exchanged with excess of Cs₂SO₄, the content of sulfate remained constant and Na⁺ was partially replaced with Cs⁺, but the amount was lower, indicating the probable composition (Na⁺/Cs⁺)_y[M²⁺_0.667Al_0.333(OH)_2-y(SO₄)_y/2(SO₄)_0.222-(y/2)](M²⁺ = Mn, Zn), where some of the hydroxide anions were replaced with grafted SO₄^2-.

Keywords:
layered double hydroxide; intercalation; exchange reactions; sulfate; cesium