Synthesis and characterization of aluminium-rich layered double hydroxides intercalated with sulphate and alkali metal cations (Li+, Na+, K+)

For the first time, layered double hydroxides (LDHs) with Zn:Al in molar ratio 1:1, intercalated with sulphate and alkali metal cations (Li+, Na+, K+), were synthesized and characterized. The syntheses of Zn/Al-SO4-K was performed by precipitation with increasing pH when the KOH solution was slowly added to acid mixed solutions of ZnSO4, Al2(SO4)3 and K2SO4, with Zn:Al:K in molar ratios of 0.5:0.5:0.167, at 90°C under the dynamic flow of N2. In the exchange reactions, aqueous LDH dispersions were stirred with an excess of Li2SO4 or Na2SO4 for 96 h at room temperature under N2 flow. All the obtained materials were characterized by X-ray diffraction, Fourier transform infrared, scanning electron microscopy and energy dispersive spectroscopy and inductively coupled plasma-optical emission spectrometry analyses. After the reactions, alkali metal cations were exchanged, keeping sulphate constant, showing that this new class of LDHs can exchange cations and has the potential for new applications.