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[Display omitted] • Magnesite tailings and wastewater were resource utilization by the BMED process. • H+ for Mg leaching and OH– for struvite formation are provided by water splitting. • The P recovery ratios can reach approximately 98% under various conditions. • The nitrogen (NH 4 +-N) was recovered as struvite instead of being released. • The purity of struvite can reach as high as 97.1%. In this study, the feasibility of simultaneously recovering Mg, nitrogen (NH 4 -N) and phosphorus (P) from magnesite tailings and freshwater aquaculture have been confirmed through the bipolar membrane electrodialysis with a processing unit for the first time. The H+ required for Mg2+ leaching and OH– needed for struvite formation can be provided by the BMED system. The results indicate that adding 0.3 mol/L initial HNO 3 could enhance the Mg2+ leaching and reduce the energy consumption (EC). The recovery ratios of P and NH 4 -N reached to about 97.9 % and 52.3 %, respectively, while the EC was about 0.051 kWh/L. Increasing the tailing dosage shortened the required treatment time and reduced the EC. Increasing the current density significantly enhanced nutrient recovery rate, but accompanied by an increase in EC. A longer treatment time is necessary for treating larger volumes of wastewater, while a P recovery ratio of approximately 99 % can be achieved. Calcium is the predominant impurity. The purity of struvite was enhanced through a multi-batch process, achieving a maximum of 97.1 % at the third time. This study provides new insights into the resourceful treatment of tailings and wastewater. [ABSTRACT FROM AUTHOR]

• Concentration electrodialysis (CED) was developed by combining ED and DD. • CED was used to selectively remove NH 4 +-N from high-salinity wastewater. • CED improved 32.3% and 13.3% removal rates compared to ED and DD, respectively. • CED reduced 14 h and 10 h to achieve the same removal percentages as ED and DD. • CED increased the current efficiency by 1.84 times compared with ED. In this study, a novel method, concentration electrodialysis (CED), was developed by combining conventional electrodialysis (ED) and Donnan dialysis (DD) effectively and selectively to separate NH 4 +-N from high-salinity wastewater. A high initial concentration of Na+ was provided in the cathode compartment to impede its competitive migration with NH 4 +. After optimization, the CED process removed up to 89.1% of NH 4 +-N from simulated high-salinity wastewater with an energy consumption of 0.51 × 10−3 KWh·mol−1. The initial brine concentration was the limiting factor for the removal percentage and rate. The maximum removal percentage was 13.3% and 32.3% higher than those of conventional ED and DD, respectively. CED shortened the time required to achieve the same final removal percentages achieved by conventional ED and DD by 14 h and 10 h, respectively. In addition, the current efficiency of CED was increased by 1.84 times greater than that of conventional ED, while reduced 50.48% of energy consumption. Moreover, the Na+ concentrations in the cathode and wastewater compartments both remained relatively constant, indicating that there was no need to add additional Na+ during the experimental process, which was beneficial for prolonging the experiment and reducing cost. Finally, the performance of CED in removing NH 4 +-N from actual maricultural wastewater further supported its potential for application in the future. [ABSTRACT FROM AUTHOR]

• A BMED system was used to removal heavy metals and recycle H 2 SO 4 from a raffinate. • The optimal current density and V RC :V HMC were 3.0 mA/cm2 and 1:15, respectively. • The raffinate can be used again as leaching influent after treatment. • The energy consumption decreased in more RCs equipped BMED system. • The H 2 SO 4 with the concentration of 0.395 mol/L was obtained in a-AC. The raffinate generated during copper ore hydrometallurgical processing is difficult to be treated because it is strongly acidic, and has high concentrations of heavy metals (Iron, Zinc, Copper etc). In this study, a bipolar membrane electrodialysis (BMED) system was studied for treatment of this challenging stream because in which salts can be converted into their corresponding acids and bases, which enables resource recovery in raffinate. The target was to reuse the raffinate as a leaching influent, to achieve zero discharge of wastewater. It was found that 85.9% of SO 4 2− in the raffinate could be recovered by the formation of H 2 SO 4. The removal rates of heavy metals were 99.3% (iron), 99.1% (zinc), 99.0% (copper), 84.9% (nickel), 70.6% (chromium), 95.8% (cadmium), and 94.8% (arsenic). The heavy metal cations were mainly removed in the heavy metals chamber (HMC) and anions were mainly removed in the acid compartment. A current density of 3.0 mA/cm2, a volume ratio between the raffinate chamber (RC) and the HMC 1:15, and a duration of 40 h were the optimal experimental parameters. Increasing the RC number from one to two and three increased the current efficiency from 54.0% to 106.9% (two) and 157.9% (three), and decreased the specific energy consumption from 0.160 to 0.108 and 0.089 kWh/L of raffinate. It was concluded that the raffinate can be used as a leaching solution after treatment and the studied BMED process is an effective technique for the treatment of raffinate. [ABSTRACT FROM AUTHOR]