Conductive biomass carbon aerogel with high adsorption performance for gallium in alkaline solution

Abstract

A nitrogen-rich functional group biomass carbon aerogel (NHPA) with high specific surface area (473.5 m2/g) was synthesized by hydrothermal carbonization of urea coupled with ZnCl2 pyrolysis using discarded persimmon as biomass raw material. Thereafter, it was applied for the adsorption of gallium from alkaline solution. The results of adsorption experiments revealed that NHPA exhibited a great adsorption performance for a wide concentration range (50–300 mg/L) of gallium solution at pH = 11, T = 24 h and 1.5 g/L adsorbent dosage. Meanwhile, the adsorption capacity of NHPA for gallium in alkaline solution was 120.48 mg/g, which was 4 times higher than that of commercial resin. The adsorption mechanism performed by SEM-EDX, FTIR and XPS indicated that the adsorption of gallium in alkaline solution by NHPA was mainly caused by the reactive binding of GaO2- with oxygen-/nitrogen- containing functional groups such as, –OH, –NH2. In addition, electrochemical analysis showed that NHPA had great electrochemical properties with high reversibility and low ohmic impedance. The electrical-assisted adsorption with NHPA as the working electrode at an applied voltage of 1.3 V could significantly increase the adsorption capacity and rate between NHPA and gallium in alkaline solutions (the adsorption equilibrium time could be reduced to 2 h), which maybe an important research direction for efficient extraction of gallium from alkaline solutions.