Novel inorganic membrane for the percrystallization of mineral, food and pharmaceutical compounds

Abstract

This work demonstrates for the first time the phenomenon of continuous percrystallization using a carbon membrane derived from the pyrolysis of food grade sugar. In addition, it is also the first demonstration of membranes separating solute from solvent and delivering dry crystals in a single step. This is contrary to membrane crystallization, which requires two further processing steps to filter crystals from a solution followed by drying the wet crystal particles. The results indicate that carbonised sugar membranes can confer ideal conditions of super-saturation, leading to instantaneous and continuous percrystallization of compounds at the permeate side of the membrane. As a result, very high percrystallization production rates of up to 55,000 kg m−2 per year are achieved. It is proposed that the percrystallization occurs in a wet thin-film modulated by solution permeation via the mesopores of the membrane, where vapour and crystals are separated at the membrane's solid-liquid-vapour interface. The potential deployment of this novel technology is further demonstrated for a wide range of crystallization applications in chemical, hydrometallurgy, food and pharmaceutical industries.