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Mitigating Water Crossover by Crosslinked Coating of CationâExchange Membranes for Brine Concentration
Undesired water crossover through ion-exchange membranes is a significant limitation in electrically driven desalination processes. The effect of mitigating water crossover is twofold: 1) The desalination degree is less reduced due to the unwanted removal of water, and 2) the brine concentration is increased due to decreased dilution by an unwanted crossover of water molecules. Hence, water crossover limits the desalination and concentration efficiency of the processes, while the energy demand to achieve a certain level of desalination or concentration increases. This effect is especially pronounced when treating high salinity solutions, which goes hand in hand with the crossover of many ions through the ion-exchange membranes. A crosslinked coating for cation-exchange membranes (CEMs) is presented in this work, which can significantly mitigate such undesired water crossover. The efficacy is demonstrated using the flow-electrode capacitive deionization process applied for desalination and concentration of saline brines at feed concentrations of 60 and 120 g Lâ1 NaCl. With just a single coated CEM, the water crossover was reduced by up to 54%
Flow-electrode capacitive deionization enables continuous and energy-efficient brine concentration
Establishing a Fed-Batch Process for Protease Expression with Bacillus licheniformis in Polymer-Based Controlled-Release Microtiter Plates
Introducing fedâbatch mode in early stages of development projects is crucial for establishing comparable conditions to industrial fedâbatch fermentation processes. Therefore, cost efficient and easy to use smallâscale fedâbatch systems that can be integrated into existing laboratory equipment and workflows are required. Recently, a novel polymerâbased controlledârelease fedâbatch microtiter plate is described. In this work, the polymerâbased controlledârelease fedâbatch microtiter plate is used to investigate fedâbatch cultivations of a protease producing Bacillus licheniformis culture. Therefore, the oxygen transfer rate (OTR) is onlineâmonitored within each well of the polymerâbased controlledârelease fedâbatch microtiter plate using a ”RAMOS device. Cultivations in five individual polymerâbased controlledârelease fedâbatch microtiter plates of two production lots show good reproducibility with a mean coefficient of variation of 9.2%. Decreasing initial biomass concentrations prolongs batch phase while simultaneously postponing the fedâbatch phase. The initial liquid filling volume affects the volumetric release rate, which is directly translated in different OTR levels of the fedâbatch phase. An increasing initial osmotic pressure within the mineral medium decreases both glucose release and protease yield. With the volumetric glucose release rate as scaleâup criterion, microtiter plateâ and shake flaskâbased fedâbatch cultivations are highly comparable. On basis of the smallâscale fedâbatch cultivations, a mechanistic model is established and validated. Modelâbased simulations coincide well with the experimentally acquired data