Efficient elimination of U(vi) by polyethyleneimine-decorated fly ash

Abstract

The toxicity and radioactivity of uranium [235,238U(vi)] has resulted in serious environmental issues in recent years. Polyethyleneimine-decorated waste fly ash (FA@PEI) from thermal power plants has been fabricated via a novel and cost-efficient method and applied to the U(vi) elimination from aqueous solutions by batch experiments. The U(vi) removal was found to be dramatically influenced by pH whilst being ionic strength-independent, which indicated that the interaction was primarily controlled by inner-sphere surface complexation. Kinetic studies showed that the FA@PEI had an ultrafast removal rate (1.5 h to achieve adsorption equilibration) for U(vi) and a pseudo-second-order model fitted the adsorption process. The maximum removal capacity of U(vi) by FA@PEI was 70.3 mg g-1 at 298 K and pH 5.0. Based on the thermodynamics data (ΔH° > 0, ΔS° > 0 and ΔG° < 0), the U(vi) removal process is typically spontaneous and endothermic. According to the XPS analysis, the enhanced U(vi) adsorption was mainly attributed to the abundant metal-oxide bonds and amine groups (-NH2, -NH-). Furthermore, the FA@PEI material also demonstrated an outstanding regeneration ability. This paper highlights FA@PEI as an environmentally-friendly and economical alternative for U(vi) elimination from waste water.