Decomposition and removal of hydrazine by Mn/MgAl-layered double hydroxides.

The layered double hydroxide (MgAl-LDH) was modified by manganese for obtaining Mn/MgAl- LDH. The obtained material was characterized by inductively coupled plasma, X-ray powder diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy and X-ray photoelectron spectroscopy. The as-synthesized Mn/MgAl-LDH was investigated for the decomposition and removal of hydrazine in a batch system. Factors affecting the decomposition and removal of hydrazine such as pH, time, initial hydrazine concentration and temperature were optimized. At the optimal pH 8, Mn/MgAl-LDH dose (100 mg), time of 90 min and temperature of 293 K, the hydrazine decomposition and removal percentage was 100% for initial concentrations of 5, 10 and 15 mg L-1. Where, the pure MgAl-LDH showed 14% removal at 90 min for 10 mg L-1 of hydrazine compared to Mn/MgAl-LDH. The decomposition of hydrazine increased when the temperature was increased from 293 to 318 K and the time of complete decomposition reduced from 90 to 45 min, respectively. The decomposition process of hydrazine on Mn/MgAl-LDH depended on the formed ions of manganese(II) and (III) as well as Mn3O4 on the surface. The existence of Mn3+ as a strong oxidant could decompose hydrazine to nitrogen and hydrogen. The catalytic decomposition of hydrazine was best followed by the first-order rate law and the calculated Ea value was found to be 24.841 kJ mol-1. The simple methodology regarding the material preparation and the method used as well as its effectiveness may provide a promising future for the decomposition and removal of hydrazine. [ABSTRACT FROM AUTHOR]