The simultaneous reduction and adsorption for V(V) and Cr(VI) anionic species in aqueous solution by polyethyleneimine cross-linked titanate nanotubes

Treating water containing hazardous V(V) and Cr(VI) by using a efficient and simple method is an urgent need, but still a challenge. Novel binary composites (PEI-TNTs) were successfully synthesized by introducing polyethyleneimine (PEI) onto titanate nanotubes (TNTs) in a cost-effective and facile route, where TNTs and PEI existed as an interior core and an exterior shell. The removal efficiency of PEI-TNTs was highly reliant on the initial solution pH according to the batch adsorption experiments, and the maximum adsorption capacity for V(V) reached 1280.36 mg g−1 at pH 3.0 and for Cr(VI) reached 980.39 mg g−1 at pH 2.0 calculated by the Langmuir model. And PEI-TNTs effectively resisted the interference of various coexisting anions and cations. In simulated mining wastewater experiments, PEI-TNTs still remained fine V(V) and Cr(VI) adsorption capability; and PEI-TNTs could be regenerated and reused for 5 cycles without significantly reducing its removal efficiency. The excellent removal performance mainly owned to the high stability of inorganic skeleton and high surface activity from polymer modification. A comprehensive mechanism was proposed for the adsorption process associating with electrostatic attraction, redox reaction, and chelation. This work provides the theoretical and practical information for the novel inorganic–organic nanomaterials based on titanate nanotubes and polymers for the efficient reduction and adsorption of heavy metal anionic pollutants in water.