Enhanced removal of Pb(II) and organics by titanate in a designed simultaneous process

摘要

As a superior cation-exchanger and photocatalyst, titanate exhibited efficient ability for heavy metals decontamination and organics degradation. However, no reports about simultaneous removal of heavy metals and organics by using titanate has been found. The influence of intercalated heavy metal on the photocatalytic performances of titanate and its mechanism was poorly understood. In this work, titanate materials with different amounts of intercalated Pb(II) were prepared. Analytical TEM mapping images showed the uniform distributions of intercalated Pb(II) in titanate, excluding the formation of segregated nano-domains comprising either titanate or Pb-titanate. The crystalline and luminescent properties, which are relevant with the specific surface area and migration/recombination of the charge carriers, were considered as critical factors influencing the photocatalytic performance since the surficial charge states and derived band structures of titanate with different amounts of Pb(II) were almost identical. Steady state reaction experiments revealed that the catalytic activity of titanate after Pb(II) intercalation first sharply increased for 0.10Pb-Titanate and then decreased with further Pb(II) insertion. Better catalytic performance of 0.10Pb-Titanate was attribute to larger specific surface area, superior sorption affinity, higher excited charge carrier's quantity and satisfied luminescence lifetime. Finally, it was observed that simultaneous removal strategy by pure titanate not only enhanced the sorption of lead ions than individual removal system but also promoted the photocatalytic ability than 0.10Pb-Titanate, which provides a new idea for the utilization and optimization of titanate materials for simultaneous decontamination of heavy metals and organics.