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

Evaluation of percrystallization coupled with electrodialysis for zero liquid discharge in the pulping industry

We evaluated percrystallization at laboratory scale to determine its suitability as core technology for achieving Zero Liquid Discharge (ZLD) in a Kraft effluent desalination process. Compared with conventional evaporation/crystallization techniques, percrystallization allows to operate at room temperature and with barely pressurized fluids, using relatively unexpensive membranes and vacuum to allow evaporation of aqueous brine solutions. For further comprehension of the technology before experimentation, a computational fluid dynamics model was developed, showing how temperature affects the performance of percrystallization in terms of transmembrane flux. Additionally, we performed experiments with single and double salt solutions (NaCl and NaCl/Na₂SO₄) and concentrated industrial effluent from a Kraft pulp mill (brine from the effluent desalination with electrodialysis). Percrystallization of the concentrated industrial effluent was successfully achieved at laboratory scale, showing no signs of fouling on the membrane surface. However, high energy consumptions (above 3000 kWh/ton of evaporated water) were measured. Theoretical power consumptions of an optimized industrial percrystallization system were therefore computed. Percrystallization showed a more efficient performance compared with similar membrane systems, such as vacuum membrane distillation, but higher energy consumptions than conventional ZLD technologies (mechanical vapor compression), having an estimated energy consumption of around 110-150 kWh/ton of removed water, depending on the feed fluid temperature. Nevertheless, percrystallization could be suitable for ZLD applications where low-cost heating (e.g., solar) is available, since the vacuum energy demand is only 32-140 kWh/ton. Alternatively, it could be applied to low scale processes where the temperature of the solution must remain low (e.g., less than 40 °C).

Enhanced Specific Mechanism of Separation by Polymeric Membrane Modification-A Short Review

Membrane technologies have found a significant application in separation processes in an exceeding range of industrial fields. The crucial part that is decided regarding the efficiency and effectivity of separation is the type of membrane. The membranes deal with separation problems, working under the various mechanisms of transportation of selected species. This review compares significant types of entrapped matter (ions, compounds, and particles) within membrane technology. The ion-exchange membranes, molecularly imprinted membranes, smart membranes, and adsorptive membranes are investigated. Here, we focus on the selective separation through the above types of membranes and detect their preparation methods. Firstly, the explanation of transportation and preparation of each type of membrane evaluated is provided. Next, the working and application phenomena are evaluated. Finally, the review discusses the membrane modification methods and briefly provides differences in the properties that occurred depending on the type of materials used and the modification protocol.