氮-氟掺杂比例对TiO2/膨润土复合材料吸附土霉素的影响

为了探究氮(N)、氟(F)掺杂比例对TiO_2/膨润土复合材料吸附性能的影响,采用溶胶-凝胶法制备了氮-氟共掺杂TiO_2/膨润土复合材料,研究了所制备复合材料比表面积(SBET)、扫描电镜(Scanning electron microscopy,SEM)和阳离子交换量(Cation exchange capacity,CEC),分析了不同氮、氟掺杂比例对氮-氟共掺杂型TiO_2/膨润土复合材料吸附水中土霉素的影响。SEM结果证实氮-氟共掺杂TiO_2成功负载于膨润土表面;随氮掺杂比例增大,氮掺杂复合材料表面掺杂TiO_2的覆盖程度增大,氮掺杂TiO_2的粒径由50～100 nm减小到25～50 nm,氮掺杂复合材料的CEC平均减小36.24%、平均孔径减小1.74%,比表面积和孔体积增大;在氮掺杂基础上掺杂氟元素,由于氟元素对掺杂TiO_2表面的氟化作用及复合材料表面的侵蚀作用,氮-氟共掺杂复合材料的比表面积、孔径、孔体积和CEC均大于单一氮元素掺杂复合材料。吸附实验结果表明,与未掺杂复合材料相比,不同比例氮掺杂均不同程度地降低了复合材料对土霉素的吸附量(平均减少14.30 mmol·kg~(-1)),但氮掺杂比例为0.5和1时,氟掺杂可提升复合材料对土霉素的吸附能力,吸附量分别由37.98 mmol·kg~(-1)和40.90 mmol·kg~(-1)增大到42.95 mmol·kg~(-1)和43.73 mmol·kg~(-1)。研究表明,氮-氟共掺杂TiO_2/膨润土复合材料对土霉素的高吸附量是由氟掺杂提升了复合材料的负电荷数量、平均孔径及孔体积造成的。

Effect of N-F doping ratio on terramycin adsorption performance of TiO2/bentonite composites

To elucidate the effect of doping ratio on adsorption performance of TiO₂/bentonite composites, a series of nitrogen-fluoride codoped TiO₂/bentonite composites were prepared via the sol-gel method. The prepared composites were characterized by specific surface area (S_BET)and cation exchange capacity(CEC)analyses and scanning electron microscopy. The effect of doping ratios of N and F on terramycin adsorption was investigated through batch experiments. The results showed that N-F co-doped TiO₂ was successfully adhered on the surface of bentonite. With an increase in N doping ratio in the N-doped TiO₂/bentonite composites, the coverage degree of N-doped TiO₂, S_BET, and pore volume of the composites increased, while the CEC and average pore width of the composites decreased by 36.24% and 1.74%, respectively. Moreover, the particle size of N-doped TiO₂ decreased from 50~100 nm to 25~50 nm. When TiO₂ was doped with N and F, the S_BET, pore width, pore volume, and CEC of the N-F co-doped TiO₂/bentonite composites were higher than those of the N-doped TiO₂/bentonite composites. Compared with the undoped samples, N-doped TiO₂ caused a decrease in terramycin adsorption(14.30 mmol· kg^-1 on an average); however, N-F co-doped TiO₂ increased terramycin adsorption from 37.98 mmol·kg^-1 and 40.90 mmol·kg^-1 to 42.95 mmol·kg^-1 and 43.73 mmol·kg^-1 when the N doping ratio of TiO₂ was 0.5 and 1, respectively. The results demonstrated that the high adsorption of the N-F co-doped TiO₂/bentonite composites to terramycin can be attributed to the increase in negative charge, pore diameter, and pore volume of the composites due to F doping.