壳聚糖-银/二氧化钛核壳型复合小球的制备及其对布洛芬的降解性能

针对目前污水中布洛芬等典型PPCPs类污染物光催化降解效率低、催化剂回收难度大等难题,以壳聚糖为载体,通过负载银掺杂TiO₂,制备有机核-无机壳结构的CTS-Ag/TiO₂复合小球,开展了光催化降解布洛芬性能研究。结果表明:壳聚糖紧密团聚成核,银掺杂TiO₂分布在壳聚糖表面,共同形成了有机核-无机壳结构。在紫外光作用下,复合小球对布洛芬展现出良好的去除效能,在最佳条件下(CAT投加量为4 g/L,布洛芬初始浓度为1 mg/L,pH值为6),处理60 min后布洛芬去除率达到96.1%,经过5次回收利用,去除率仍可达到85.0%。新型有机核-无机壳复合结构以及壳聚糖中含碳基团和含氮物质在价带上形成的附加带,使CAT复合小球在强化吸附、光催化和稳定性的同时,提高了材料可重复使用性。Ag在TiO₂表面掺杂形成的无机壳包裹在壳聚糖形成的有机核表面,使光生电子更易从TiO₂转移到Ag上并积累,减少电子-空穴对的复合,提高了CAT的光催化效率。活性组分淬灭实验表明,·O₂-和空穴氧化是引起布洛芬降解的主要活性成分。

SYNTHESIS OF CORE-SHELL CHITOSAN-Ag/TiO2 COMPOSITE BEADS FOR DEGRADATION OF IBUPROFEN

For the current obstacles of low photocatalytic degradation efficiency of typical PPCPs such as ibuprofen and the limited reusability restricts,the organic core-inorganic shell structured chitosan-Ag/TiO₂(CAT) composite beads were successfully synthesized using chitosan as the carrier and silver-doped TiO₂ as the photocatalyst,and used for the degradation of ibuprofen.The results illustrated that chitosan agglomerated tightly to form a core,and the silver-doped TiO₂ was distributed on the surface of the chitosan,eventually forming an organic core-inorganic shell structure.The composite beads showed a good removal efficiency on ibuprofen under UV irradiation.The ibuprofen removal efficiency of 96.1% was achievable in 60 min under optimal operational condition (catalyst load=4 mg/L,initial IBP concentration=1 mg/L,initial pH=6).The results showed that even after the fifth photocatalytic cycle,the removal efficiency after 60 min was still as high as 85.0%.Novel core (organic)-shell (inorganic) composite structure and the additional band above the valence band was created by the carbon-contain groups and the doped N species of chitosan,which could enhance the absorption,photocatalysis,stability and reusability of the CAT composite beads.The inorganic shell formed by doping Ag on the surface of TiO₂ was wrapped on the surface of the organic core formed by chitosan.So photogenerated electrons transfer readily from TiO₂ to Ag with heavy accumulation due to doping Ag on TiO₂ surfaces,which may reduce the recombination of electron-hole pairs and thus enhance the photocatalytic efficiency.The reactive species scavenging experiments showed that·O₂- mediated reactions and direct-hole oxidation were the major degradation reactions.