碱热-酸热法合成二氧化钛-钛酸纳米管复合纳米材料对Cd(Ⅱ)和苯酚的同步去除

Simultaneous Removal of Cd( Ⅱ) and Phenol by Titanium Dioxide-Titanate Nanotubes Composite Nanomaterial Synthesized Through Alkaline-Acid Hydrothermal Method

以P25型Ti O2为原料,经碱热和酸热反应合成了Ti O2/TNTs复合纳米材料,该材料皆具钛酸纳米管(TNTs)和Ti O2晶相.Cd(Ⅱ)在Ti O2/TNTs上的吸附动力学过程很快,30 min即可达到吸附平衡,此外,Langmuir等温模型拟合所得最大吸附量达120.34 mg·g-1,其主要吸附机制为Cd2+与复合材料中TNTs层间Na+/H+的离子交换.Ti O2/TNTs对苯酚的吸附量较低(0.36 mg·g-1),因此光催化反应以实现苯酚的降解是必需的.构建的吸附-光催化系统可实现Cd(Ⅱ)和苯酚的同步有效去除,180 min时二者的去除率分别可达到99.6%和99.7%.Cd(Ⅱ)的去除源于暗室下复合材料中TNTs相的吸附,而苯酚的去除在于后续复合材料中Ti O2相的光催化.Cd(Ⅱ)的共存可提高苯酚的光催化降解效率,原因在于Cd(Ⅱ)吸附进入材料层间后有助于材料光催化性能的提升.共存Na+对Cd(Ⅱ)和苯酚在Ti O2/TNTs上的同步去除影响极小;而共存Ca2+由于竞争吸附和促进材料团聚的原因,会轻微抑制Cd(Ⅱ)在Ti O2/TNTs上的吸附,但对苯酚的光催化降解影响较小.此外,Ti O2/TNTs可有效循环利用,经HNO3解吸和Na OH再生后,3次循环后材料对Cd(Ⅱ)和苯酚的去除率依然可达91.7%和98.1%.该研究提供了一种合成皆具吸附和光催化性能的钛系材料的方法,对于应用纳米材料实现水体环境中重金属和有机物的同时去除具有一定的借鉴意义.

A composite nanomaterial,Ti O2/ TNTs,was synthesized by Ti O2( P25) through alkaline and acid hydrothermal reaction,which possessed both titanate nanotubes( TNTs) and Ti O2 phase.It was found that the adsorption kinetics of Cd( Ⅱ) onto Ti O2/ TNTs was very quick,and the adsorption could reach the equilibrium within 30 min.In addition,the maximum adsorption capacity of Cd( Ⅱ) was as large as 120.34 mg·g- 1calculated from Langmuir isotherm model.The adsorption mechanism of Cd( Ⅱ) was ionexchange between Cd2 +and Na+/ H+located in the interlayers of TNTs.However,the adsorption capacity of phenol on Ti O2/ TNTs was so small that the photocatalysis for phenol degradation was needed.In the adsorption-photocatalysis system,the removal efficiencies of Cd( Ⅱ) and phenol could reach up to 99.6% and 99.7%,respectively.Especially,removal of Cd( Ⅱ) was attributed to adsorption by TNTs of the composite nanomaterial,while removal of phenol was resulted from photocatalytic reaction by the Ti O2 phase.Moreover,the co-existing Cd( Ⅱ) enhanced the photocatalytic degradation of phenol due to the enhancement on photocatalytic activity of Ti O2/ TNTs after Cd( Ⅱ) was adsorbed.Co-existing Na+did not show obvious effect on the co-removal of Cd( Ⅱ) and phenol by Ti O2/ TNTs,but adsorption of Cd( Ⅱ) was inhibited in the presence of Ca2 +as it could compete for the adsorption sites and enhance the aggregation of the material.Furthermore,Ti O2/ TNTs could be efficiently reused after desorption via HNO3 and regeneration via Na OH,and the removal efficiencies of Cd( Ⅱ) and phenol were still as high as 91.7% and 98.1% even after three cycles.This study proposed a method to synthesize a material which had both adsorptive and photocatalytic performance,and it was of great importance for application of nanomaterials in the simultaneous removal of heavy metals and organic pollutants.