【作者】 王永忠；

【导师】 钟明强；

【作者基本信息】 浙江工业大学 ， 材料化工， 2009， 博士

【摘要】 锐钛矿型TiO₂在可见光下一般没有催化活性,只有对其进行改性,降低其禁带宽度或用光敏剂进行光敏化,才能使TiO₂具有可见光催化效果。本文首次以聚乙烯醇（PVA）和Ti（OH）₄为原料,采用水热法制备工艺,得到了对甲基橙（MO）具有优良可见光催化降解活性、对聚氯乙烯（PVC）塑料具有明显抗菌效果的降解聚乙烯醇（D-PVA）负载TiO₂可见光催化剂（TiO₂/D-PVA）。借助XRD、BET、SEM、TGA、XPS、EPR、UV-vis等分析表征手段,对TiO₂/D-PVA的晶体结构、表面组成、亲油性能和其对甲基橙的可见光催化降解性能进行了系统研究;进一步采用熔融共混法制备得到了TiO₂/D-PVA改性的抗菌PVC塑料,考察了TiO₂/D-PVA对PVC塑料的力学性能、加工流变性能和抗菌性能的影响规律。研究表明,水热法生成的TiO₂作为路易斯酸催化剂,使PVA失水降解,生成具有共轭C=C结构的D-PVA,并负载在TiO₂粒子表面;由于D-PVA和TiO₂的相互作用,使TiO₂/D-PVA具有较好的可见光催化活性,并能有效地降解甲基橙。研究还表明,TiO₂/D-PVA中TiO₂的晶型均为锐钛矿型,D-PVA负载在TiO₂的表面,没有进入TiO₂的晶格,对TiO₂的晶型无影响;此外,D-PVA能有效抑制TiO₂晶体成长和颗粒团聚,TiO₂/D-PVA比纯TiO₂具有更小的晶体尺寸和更大的BET比表面积。PVA的掺杂量、水热反应温度和水热反应时间都明显地影响TiO₂/D-PVA的晶粒大小、比表面积和光催化活性。随着PVA的掺杂量增加、水热反应温度升高和水热反应时间延长,TiO₂/D-PVA的可见光催化活性呈现先升高而后降低的变化规律;当水热反应温度为180℃、水热反应时间为6h、PVA对TiO₂的质量比为1:10时,制备得到的TiO₂/D-PVA可见光催化活性最高,在可见光连续照射40h后,其对甲基橙降解率达到84%,降解效果为P25的9.2倍。TiO₂/D-PVA对甲基橙的可见光催化降解反应符合一级反应动力学规律,动力学方程为:ln（C₀/C_t）=0.0461t。在上述研究基础上,还进一步考察了TiO₂/D-PVA对PVC塑料的加工流变性能影响,发现其使PVC塑料非牛顿指数降低;由于TiO₂/D-PVA颗粒较大,使PVC塑料的拉伸强度和断裂伸长率也下降。研究还表明,TiO₂/D-PVA改性PVC塑料具有一定的可见光催化抗菌作用,当TiO₂/D-PVA加入量为8phr时,TiO₂/D-PVA-PVC塑料对大肠杆菌和金黄色葡萄球菌的抗菌率分别达到76.3%和71.4%。论文还进一步采用硅烷偶联剂KH-560对载银纳米二氧化钛（TiO₂/Ag⁺）粒子进行表面改性,并制备得到了TiO₂/Ag⁺-PVC抗菌塑料;考察了改性TiO₂/Ag⁺粒子对PVC塑料力学性能、加工流变性能、抗紫外光老化性能和抗菌性能的影响规律。研究发现,KH-560可在TiO₂/Ag⁺粒子表面接枝,从而有效降低TiO₂/Ag⁺粒子的表面张力,提高其与PVC树脂的相容性,并抑制TiO₂/Ag⁺粒子的团聚,有利于其在PVC塑料中分散。TiO₂/Ag⁺粒子亲油化度和分散稳定性分析研究表明,KH-560加入量、反应时间和反应温度均明显影响KH-560在TiO₂/Ag⁺粒子表面接枝改性效果,当KH-560添加量为TiO₂/Ag⁺粒子质量的8%、反应时间为5h、反应温度为78.5℃时,改性效果最好。改性TiO₂/Ag⁺粒子能够同时提高PVC塑料的拉伸强度和断裂伸长率,而且随着TiO₂/Ag⁺粒子添加量增加,拉伸强度和断裂伸长率呈现先提高后降低的变化趋势。由于改性TiO₂/Ag⁺粒子的加入,削弱了PVC分子间的作用力,对PVC塑料起了内润滑作用,使其加工流动性变好。同时发现,表面改性TiO₂/Ag⁺能够吸收紫外光,使之转变为热量而散失,从而提高了PVC塑料的抗紫外光老化性能。当改性TiO₂/Ag⁺添加量为1phr时,对应的PVC塑料对大肠杆菌和金黄色葡萄球菌抗菌率都能达到90%;当添加量为4phr时,对大肠杆菌和金黄色葡萄球菌抗菌率则都能达到99%。这些研究表明,可见光催化剂TiO₂/D-PVA和纳米TiO₂/Ag⁺具有较好的应用前景。更多还原

【Abstract】 The anatase TiO₂ does not show photocatalytic activity under visible light irradiation.In order that TiO₂ can show the visible light photocatalytic activity,TiO₂ must be modified through decreasing its E_bg or doping photosensitizer.A novel visible light active photocatalyst（TiO₂/D-PVA） was prepared in one portion of PVA（polyvinyl alcohol） and Ti（OH）₄ by means of hydrothermal method.The structure,surface composition,lipophilic nature and photocatalytic activity of TiO₂/D-PVA were investigated by XRD,BET,SEM,TGA,XPS,EPR,UV-vis and the degradation of methyl orange（MO）.TiO₂/D-PVA-PVC plastics was prepared by mixing and melting of TiO₂/D-PVA,PVC and other necessary additives,and its mechanical properties,rheological behavior and antibacterial properties were studied in detail.PVA was degraded to produce the D-PVA of conjugated C=C accelerated by the synthesized TiO₂ as a Lewis acid under hydrothermal process,and the D-PVA was doped onto the surface of TiO₂.Due to the interaction between D-PVA and TiO₂, TiO₂/D-PVA showed significant visible light photocatalytic activity and could effectively degrade methyl orange under visible light.All the synthesized TiO₂/D-PVA samples consisted of anatase structure with high crystallinity and D-PVA was doped on the surface of TiO₂ particles,which indicated that D-PVA did not exist in the crystal lattice and hardly influenced the crystalline phase of TiO₂.The feed ratio of PVA to TiO₂,hydrothermal reaction temperature and reaction time obviously influenced the crystal size,BET surface area and photocatalytic activity.TiO₂/D-PVA showed less crystal size and bigger BET surface area than pure TiO₂,because D-PVA prohibited TiO₂ from crystallizing and agglomerating.TiO₂ showed the tendency of visible light photocatalytic activity from increasing to decreasing with the increased feed ratio of PVA to TiO₂.The visible light photocatalytic activity also showed the tendency from increasing to decreasing with the increased hydrothermal reaction temperature and reaction time.TiO₂/D-PVA,synthesized at 180℃with the reaction time for 6h and the 1: 10 feed ratio of PVA to TiO₂,exhibited a higher visible light photocatalytic activity. When the suspension system of TiO₂/D-PVA and methyl orange was irradiated under visible light for 40 h,the degradation percentage of methyl orange reached 84.0%, which was 9.2 times than P25.The rate of methyl orange degradation fit the first-order reaction kinetics equition in the form of（[MO]₀ /[MO]_t） =0.0461t).The influence of TiO₂/D-PVA on the rheological behavior of PVC plastics was also investigated.The results showed that TiO₂/D-PVA could obviously improve the rheological behavior and decrease the Non-Newtonian parameters.Due to the big particle size,the tensile strength and elongation at break of PVC plastics were all obviously decreased,compared to the PVC plastics without TiO₂/D-PVA particles.The antibacterial rates to Colibacillus and Staphylococcus were 76.3%and 71.4%with the addition of 8 phr TiO₂/D-PVA,respectively.The surface modification of TiO₂/Ag⁺ nanoparticles by grafting the coupling agent of KH-560 and preparation of modified nano-TiO₂/Ag⁺-PVC plastics were performed, and the effect of the modified nano-TiO₂/Ag⁺ content on the mechanical properties, rheological behavior,ageing resistance and antibacterial properties of PVC plastics were investigated.The KH-560 grafted onto the surface of nano-TiO₂/Ag⁺ particles decreased the surface tension of TiO₂/Ag⁺ nanoparticles and prohibited the TiO₂/Ag⁺ nanoparticles from agglomeration,which improved the compatibility of TiO₂/Ag⁺,nanoparticles with PVC plastics and had the TiO₂/Ag⁺ particles be dispersed in plastics with nanometer scale.The content of TiO₂/Ag⁺ nanoparticles,reaction time and reaction temperature all influenced the modified effect of KH-560.The results showed that the optimal modified conditions were 8%contents of KH-560,78.5℃reaction temperature and 5h reaction time.The tensile strength and elongation at break of PVC plastics could all been improved and showed the tendency from increasing to decreasing with the increased content of TiO₂/Ag⁺ nanoparticles.The rheological behavior was also improved because the TiO₂/Ag⁺ nanoparticles reduced the interaction force of PVC molecules,which acted as an internal lubricant.TiO₂/Ag⁺ nanoparticles could absorb the ultraviolet radiation and improve the uvioresistant ageing resistance.The antibacterial rates to Colibacillus and Staphylococcus were exceeded 90%and 99%with the additions of 1 phr（0.63%） and 4 phr（2.5%） modified TiO₂/Ag⁺ nanoparticles,respectively.All the results show that the good application perspective of these new kinds of TiO₂/D-PVA and TiO₂/Ag⁺ additives.更多还原