Electrochemically selective ammonium recovery from wastewater via coupling hydrogen bonding and charge storage.

Electrochemical ammonium (NH) storage (EAS) has been established as an efficient technology for NH recovery from wastewater. However, there are scientific difficulties unsolved regarding low storage capacity and selectivity, restricting its extensive engineering applications. In this work, electrochemically selective NH recovery from wastewater was achieved by coupling hydrogen bonding and charge storage with self-assembled bi-layer composite electrode (GO/VO). The NH storage was as high as 234.7 mg N g (> 10 times higher than conventional activated carbon). Three chains of proof were furnished to elucidate the intrinsic mechanisms for such superior performance. Density functional theory (DFT) showed that an excellent electron-donating ability for NH (0.08) and decrease of diffusion barrier (22.3 %) facilitated NH diffusion onto electrode interface. Physio- and electro-chemical results indicated that an increase of interlamellar spacing (14.3 %) and electrochemical active surface area (ECSA, 388.9 %) after the introduction of GO were responsible for providing greater channels and sites toward NH insertion. Both non-ionic chemical-bonding (V=O‧‧‧H, hydrogen-bonding) and charge storage were contributed to the higher capacity and selectivity for NH. This work offers underlying guideline for exploitation a storage manner for NH recovery from wastewater.