Lithium and its compounds are critical strategic resources with wide-ranging applications. This study developed a bipolar membrane precipitation coupled electrodialysis enrichment (BMp-EDe) process for extracting lithium from brines with an Mg/Li ratio of 20. The method is based on phase separation achieved through precipitation-coupled ion permeation and a synergistic mechanism for ion enrichment, resulting in significant process intensification. Key factors such as current density, molar ratio between diluate and base chambers, and base chamber concentration were optimized to control nucleation and prevent membrane fouling. Under conditions of current density ranging from 200 to 400 A·m −2 and a molar ratio of the diluate chamber to the base chamber between 13 and 16, the magnesium removal rate in the BMp-EDe process is found to exceed 99.90 %, with a separation factor greater than 20,000. The optimal separation factor is observed to reach 40,244, with a magnesium removal rate as 99.96 % and a lithium recovery rate as 95.32 %. With optimized operation conditions, the energy consumption of magnesium precipitation decreased from 11.89 kWh·kg −1 (Mg 2+ ) to 7.97 kWh·kg −1 (Mg 2+ ). Thus, an alternative method is presented that employs commercial bipolar membranes to achieve ultra-high magnesium‑lithium separation efficiency. Additionally, a mechanism for the continuous operation of the magnesium precipitation chamber is validated, which can effectively prevent membrane fouling.
A Bipolar membrane electrodialysis (BMED) was performed to achieve efficient production of N, N-dimethylglycine (DMG) from dimethylglycine hydrochloride. And the two-compartment cell configuration (BP-A) was used to avoid the amino acid macromolecules migrating through the membrane resulting in membrane fouling. Several experiment parameters including current density, initial dimethylglycine hydrochloride concentration and flow rate were discussed and compared. The results indicated that the optimal operation condition was at the current density of 50 A/m 2 , feed mole concentration of 0.3M and flow rate of 15L/h. Under the optimal condition, the energy consumption was 0.45 kWh/kg, the current efficiency was 65% and the recovery ratio for DMG reached 98% by calculation. In addition, the membrane fouling after experiments was conducted and further analyzed. It was observed that there was no appreciable change on the membrane during the BMED process by the SEM images and FTIR spectra. These results show that the harm of BMED process to membranes could be ignored. BMED method has the advantages of high purity, no by-products, low energy consumption and environmental friendliness. And this study can broaden the application of electrodialysis in the purification and preparation of macromolecular amino acids.
Electrosorption is an effective method for extracting ionic contaminants from water systems. However, weakly ionized pollutants are difficult to be efficiently removed by electrosorption due to their electrical neutrality under pH near 7. This study proposes a novel set-up of electrically driven bipolar membrane coupled with electrosorption by activated carbon fiber, specifically designed for the removal of weakly ionized antibiotics in water. The acidic and alkaline environments provided by the electrically driven bipolar membrane promote the protonation and deprotonation of weakly ionized antibiotics. Additionally, the electric field enhances the migration ability of ionized antibiotics and the formation of electric double layer on the surface of adsorbent. Under the potential of −2.0 V (ciprofloxacin) or 2.0 V (carbamazepine and tetracycline), the adsorption capacity of the target antibiotics (10 mg L -1 ) is increased by approximately 3.18 ∼ 4.65 times compared to the open-circuit adsorption in the flow mode, and the initial effluent concentration has decreased by 91.7 %. By applying a reverse potential (2.0 V), the regeneration efficiency of active carbon fiber reaches 76.5 % after four regeneration cycles. The energy consumption of the electrosorption system is 30.99 kWh kg-TC -1 and 33.79 kWh kg-CIP -1 . This coupled system broadens the application range of electrosorption in pollutants removal.
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