Membrane Separation of Ammonium Bisulfate from Ammonium Sulfate in Aqueous Solutions for CO2 Mineralisation

Abstract

The separation of ammonium bisulfate (ABS) from ammonium sulfate (AS) in aqueous solutions by monovalent ion selective membranes was studied. Optimised usage of these chemicals is both an important and challenging step towards a more efficient CO 2 mineralisation process route developed at Åbo Akademi University (ÅA). The membranes were placed in a three or five-compartment electrodialysis stack. Silver, stainless steel and platinum electrodes were tested, of which a combination of Pt (anode) and stainless steel (cathode) electrodes were found to be most suitable. Separation efficiencies close to 100% were reached based on ABS concentrations in the feed solution. The tests were performed with an initial voltage of either 10 V-20 V, but limitations in the electrical power supply equipment eventually resulted in a voltage drop as separation proceeded. Exergy calculations for energy efficiency assessment show that the input exergy (electrical power) is many times higher than the reversible mixing exergy, which indicates that design modifications must be made. Further work will focus on the possibilities to make the separation even more efficient and to develop the analysis methods, besides the use of another anode material.

Energy Use of Flux Salt Recovery Using Bipolar Membrane Electrodialysis for a CO2 Mineralisation Process

“…This article presents work done in order to separate and produce AS, ABS and aqueous ammonia, respectively, by different setups of a bipolar membrane electro dialysis (BPMED) setup. Initial work using monovalent cationic and monovalent anionic membranes in order to separate ABS from AS was reported recently [16]. This study is a continuation of that work.…”

“…The calculated exergy for intervals in a test was summed to a total cumulative exergy input at any time and is presented as figures in the results section. This way of calculating input exergy was also used in [16]. The energy needs for separating 1 kg of NH 4 + from the process stream were also calculated for four different test approaches in this study and compared between each other.…”

“…The cumulative exergy consumption as presented in Section 2.1 was calculated in the same manner as in the previous study [16], where electric energy could be directly calculated as exergy input.…”

Metals Production, CO2 Mineralization and LCA

“…Mineral sequestration offers a large-scale CCS option for Finland and many other countries, where the underground storage of CO2 is not possible [10]. While a significant volume of the literature using ÅA routes for CO2containing exhaust gases from heat and power production exists, metal production or mineral processing [11][12][13][14][15][16][17][18] a special opportunity arises for the processing of a BF top gas with Mg(OH)2 that can be obtaineded from thevast(more than needed) natural resources of magnesium silicate rock Figure 2 summarizes the slag2PCC concept that may operate on CO 2 -containing gas directly (if the target PCC quality allows for it) without a need for a separate CO 2 capture step. This opportunity is one of the main strengths of CO 2 mineralization as a CO 2 capture and storage (CCS) technology, since the capture step gives a very significant energy penalty (see [10]).…”

Enhancing the Sustainability of Phosphogypsum Recycling by Integrating Electrodialysis with Bipolar Membranes

“…Recently, researchers have addressed this issue by proposing sustainable process routes for eliminating the PG piles, while generating different chemical products with increased market value and at the same time sequestrating CO 2 . Zevenhoven and co-workers − used carbonated aqueous ammonia to convert PG into ammonium sulfate, which is marketed as fertilizer. In a previous work, Cardenas-Escudero et al used NaOH to convert PG to Na 2 SO 4 solution and Ca­(OH) 2 .…”