Ammonia Recovery from Wastewater as a Fuel: Effects of Supporting Electrolyte on Ammonium Permeation through a Cation-Exchange Membrane

Linji Xu; Dingyang Liu; Wenzong Liu; Jixiang Yang; Jiansheng Huang; Xinzhu Wang; Qiang He

doi:10.1021/acsomega.2c00700

Ammonia Recovery from Wastewater as a Fuel: Effects of Supporting Electrolyte on Ammonium Permeation through a Cation-Exchange Membrane

ACS Omega. 2022 Jun 7;7(24):20634-20643. doi: 10.1021/acsomega.2c00700. eCollection 2022 Jun 21.

Authors

Linji Xu¹, Dingyang Liu², Wenzong Liu³, Jixiang Yang⁴, Jiansheng Huang⁵, Xinzhu Wang², Qiang He¹

Affiliations

¹ Faculty of Environment and Ecology, Chongqing University, Chongqing 400044, People's Republic of China.
² Chongqing Key Laboratory of Heterogeneous Material Mechanics, College of Aerospace Engineering, Chongqing University, Chongqing 400040, People's Republic of China.
³ School of Civil and Environmental Engineering, Harbin Institute of Technology Shenzhen, Shenzhen 518055, People's Republic of China.
⁴ Key Laboratory of Reservoir Aquatic Environment, Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing, 401174, People's Republic of China.
⁵ School of Chemistry and Chemical Engineering, Chongqing University of Science and Technology, Chongqing 401331, People's Republic of China.

Abstract

Electrodeionization (EDI) is used to recover ammonia from wastewater as a fuel, but how its performance for ammonia recovery is affected by the supporting electrolyte is not very clear. This study involved experimental tests and theoretical calculations on NH₃ recovery, NH₄ ⁺ permeation, and NH₄ ⁺ and Na⁺ interacting with the functional groups in a cation exchange membrane (CEM) using Na₂SO₄ as the supporting electrolyte. The results demonstrated that a low concentration (≤0.250 mol L^-1 of Na₂SO₄) was conducive to NH₄ ⁺ permeation, while the a concentration (0.750 mol L^-1 of Na₂SO₄) hindered NH₄ ⁺ permeation. A maximum recovery efficiency of ammonia of 80.00%, a current efficiency of 70.10%, and an energy balance ratio of 0.66 were obtained at 0.250 mol L^-1 of Na₂SO₄. Numerical results indicated that an increase in Na₂SO₄ concentration caused severe concentration polarization that resisted NH₄ ⁺ migration in the CEM. The DFT results demonstrated that competitive adsorption of Na⁺ to the CEM hindered NH₄ ⁺ migration. The weaker interacting force between NH₄ ⁺ and the sulfonate functional group (-SOH₃) in comparison to that between Na⁺ and -SOH₃ might be related to the geometric and orientation effects, which generated an additional energy barrier for NH₄ ⁺ transport. Therefore, this study suggests that the supporting electrolyte concentration should be matched with that of the desalted ions.