Sustainable recovery of strategic element gallium from wastewater carries great significance for economic development and environmental conservation. In this study, nitrogen-doped and vacancy-engineered synergistically modified molybdenum oxide nanowires (α-MoOx/N) were rationally designed for efficiently adsorbing gallium ions in the range of 1–200 mg L-1 under acidic conditions. The introduction of moderate amount of ethylenediamine induced the transition of α-MoOx to the amorphous state. Mixed-valence α-MoOx/N-0.53 (Mo(V) and Mo(VI)) with abundant active sites notably enhanced the adsorption kinetics of gallium ions, accompanied by 98.9 %25 of gallium ions being adsorbed within 60 min. Advantageously over most gallium adsorbents, α-MoOx/N-0.53 exhibited the maximum adsorption capacity of 464.8 mg g-1 (298 K), mainly attributed to the synergistic effect of electrostatic adsorption, ion exchange with H as well as surface complexation with Mo-O and pyridinic N. Self-enhanced adsorption mechanism and oxygen vacancies as gallium ion adsorption traps in α-MoOx/N-0.53 augmented the opportunities for capturing gallium ions. Excellent selective adsorption of gallium ions from binary and multivariate systems containing Zn2 , Al3 , Cu2 , Ni2 and robust cyclic stability further endorse α-MoOx/N as the promising candidate for recovering gallium ions from complex wastewater.
