Rapid surfactant-free synthesis of Mg(OH)₂ nanoplates and pseudomorphic dehydration to MgO

Abstract

Mg(OH)2 nanoplates are synthesised from MgO and water without surfactants in <3 min using microwaves; MgO is recycled pseudomorphically by either microwave or conventional heating.

Investigation of the properties of MgO recovered from reject brine obtained from desalination plants

“…Furthermore, the pore volumes of both samples were recorded as 0.055 and 0.029 cm 3 /g, respectively. This morphological difference could be related to the pH and cations present in each solution (Hanlon et al, 2015;Henrist et al, 2003). The introduction of the strong base, NaOH, set the pH of solution beyond the IEP of Mg(OH)2 (~12) (Hanlon et al, 2015).…”

“…This morphological difference could be related to the pH and cations present in each solution (Hanlon et al, 2015;Henrist et al, 2003). The introduction of the strong base, NaOH, set the pH of solution beyond the IEP of Mg(OH)2 (~12) (Hanlon et al, 2015). Furthermore, the high supersaturation generated by NaOH enhanced the nucleation of tiny crystals, which agglomerated together and generated a much denser structure with a lower porosity, therefore resulting in a lower SSA.…”

Recent progress in the synthesis of nanostructured magnesium hydroxide

“…In 2015, a surfactant-free hydrothermal MW synthesis inside a multimode cavity MW reactor was proposed, which could yield gram-quantities of single-phase nano-MgIJOH) 2 from only MgO and without the use of additives. 6 The synthesis was performed hydrothermally in a Teflon-lined autoclave and the reaction time could be decreased from 6 to 2 minutes by increasing the incident power from 750 to 800 W. The hexagonal nanoplates so-produced were 100-600 nm across and with a typical thickness of 10-60 nm (Fig. 8).…”

“…When heated to temperatures above 350°C, bulk MgIJOH) 2 undergoes a dehydration process resulting in the formation of MgO (cubic, Fm3m) 5 and the evolution of water (eqn (1)). 6,7 Mg(OH) 2 → MgO + H 2 O ΔH°(298 K) = 98.4 kJ mol −1 H 2 O 1The ability of the hydroxide to decompose endothermically releasing water and forming MgO without the production of corrosive or toxic by-products, accounts for its major importance as a commercial non-toxic flame retardant. Magnesium hydroxide also finds application as an acidic waste neutraliser, as a pharmaceutical excipient, in paper conservation, as a component in ethanol chemical sensors and as the most important precursor for the preparation of (nanostructured) magnesium oxide which, in turn, finds application in catalysis.…”

“…Magnesium hydroxide also finds application as an acidic waste neutraliser, as a pharmaceutical excipient, in paper conservation, as a component in ethanol chemical sensors and as the most important precursor for the preparation of (nanostructured) magnesium oxide which, in turn, finds application in catalysis. 6,[8][9][10][11][12][13][14][15][16] A variety of methods for yielding nanostructured MgIJOH) 2 have been reported. These include hydrothermal/ solvothermal techniques, precipitation routes and microwave-assisted methods.…”