Magnesium hydroxide [MH] with porous nanoplates were synthesized from boric magnesium fertilizer (MgSO4 center dot 7H(2)O), using a large bubbling setup designed by the authors. The regular hexagonal plates of MH with a smaller specific area were formed after hydrothermal treatment. The effects of various operating variables, including the ammonia flow rate, reaction temperature, magnesium source, particle sizes, and dispersion properties of the synthesis products were investigated. X-ray diffraction, scanning electron microscopy, laser particle size analyzer, and thermogravimetric analyzer have been employed to characterize these products. The results showed that the mean particle size (D50) of the MH was about 2 mu m, and products were loose enough for filtering. The diffraction intensity of the (001) direction was higher than the (101) direction. The Mg2+ conversion in the continuous setup reached 95% and the decomposition temperature of products was 370 degrees C.