DefinePK

Abstract

A new way of decomposing and recycling ammonium bicarbonate (AB) in aqueous solution has been achieved using a membrane transport process with both dense and porous hollow fibre membranes, which offer efficient heat and mass transfer coefficients. It has been established that the decomposition of AB solutions occurs via contact through a permeable membrane, of AB solutions pre-heated to 80 °C, with a continuous counter-flow of dehumidified air at room temperature. In this process, ammonia (NH3) and carbon dioxide (CO2) gases permeate through the membrane and are thereby separated from the feed solution and they can then be collected into aqueous solution, for recycling purposes. The new process could, for example, be applied to the treatment of concentrated AB solutions used as draw solutions in forward osmosis (FO) or in the regeneration of depleted ion exchange resins. The results also show that AB recovery depends largely on the membrane surface area. The membrane can be used and optimised to achieve a high decomposition rate for AB with a single pass system to avoid additional pumping of the solution.