New Attempts to Synthesize Layered Double Hydroxides Intercalated with SO42-/Cs+ Using Co-Precipitation and Exchange Reactions

Anne Sotiles,Fernando Wypych

doi:10.21577/0103-5053.20210125

Abstract

Layered double hydroxides (LDHs) with the compositions (Cs+/NH4+)0.111[M2+0.667Al0.333(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. [Mn0.667Al3+0.333(OH)2]Cl0.333.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+0.667Al0.333(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+0.667Al0.333(OH)2-y(SO4)y/2(SO4)0.222-(y/2)](M2+ = Mn, Zn), where some of the hydroxide anions were replaced with grafted SO42-.

Highlights

The removal of radioactive nuclides from contaminated waters is an important topic of research, especially after the Fukushima Daiichi nuclear power plant accident in 2011, which released large amounts of radioactive nuclides into the environment, especially the dangerous radioactive nuclide 137Cs
During exchange reactions, the layer lattice parameters remain almost constant while the basal parameter is normally dependent on the size of the intercalated cations and/or anions
(D1+ and D2+ = alkali metal cations), since the basal distance is obtained by the combination of different factors: the hydrated sulfate size in the form of a double layer; the size of the hydrated alkali metal cations with variable numbers of water molecules in the first hydration shell; and to the interactions of sulfate with the alkali metal, water molecules and both with the layers having different compositions

Summary

Introduction

The removal of radioactive nuclides from contaminated waters is an important topic of research, especially after the Fukushima Daiichi nuclear power plant accident in 2011, which released large amounts of radioactive nuclides into the environment, especially the dangerous radioactive nuclide 137Cs.

Objectives

Results

Conclusion