纳米TiO_2光催化还原Hg~(2+)的分子动力学模拟

采用分子动力学方法模拟了Hg2+在TiO2表面上光催化还原反应中的运动过程,结果表明,在TiO2表面的水分子会形成局部有序的类冰结构,这种类冰结构限制了材料表面附近水分子的移动,也阻碍了Hg2+向TiO2表面的运动,是影响光催化效率的一个重要因素。同时,还模拟了TiO2表面光生电子密度和表面掺杂Fe3+对类冰结构的影响,结果表明,TiO2表面掺杂Fe3+抑制了类冰结构的形成,有利于提高光催化效率。     

CdS、Ag^+掺杂改性纳米TiO_2光催化降解有机物研究

在理论分析的基础上对纳米Ti02分别进行掺CdS和掺银改性实验研究。采用XRD和粒度分析技术对改性后的样品进行表征,并以掺杂CdS、Ag^＋纳米Ti02进行光催化降解甲基橙模拟实验。结果表明,掺杂CdS、Ag^＋纳米Ti02在可见光范围内降解有机物的效率有较大提高。     

纳米TiO_2光催化剂的研究与应用

本文阐述了纳米 TiO_2光催化技术的机理,纳米 TiO_2的制备技术,提高纳米 TiO_2光催化性能的途径,以及其应用现状和前景展望。     

TiO_2作为光催化剂的制备与表征研究

研究具有可见光催化活性的TiO2光催化剂的制备及表征,以探索具有可降解甲基橙的光催化剂为研究目标,利用溶胶-凝胶法合成了不同晶型的TiO2粉末,利用X-Ray衍射(XRD)实验确定其晶体结构,利用其对甲基橙的催化降解能力分析其光催化降解污染物性能。     

纳米TiO_2/偕胺肟纤维制备的研究

采用配位-水解法制备出负载于偕胺肟纤维的纳米TiO2光催化剂,并用甲基橙溶液的光催化降解反应对所制得的光催化剂进行活性评价。利用SEM,EDS,XRD等手段对该催化纤维表面的TiO2粒子的形貌、成分、晶型进行了表征。实验表明催化剂的最佳制备条件:Ti 4+溶液的浓度为0.1198mol/L,室温下配位时间60min,在温度为55℃的水浴锅中水解7h。所制得的催化剂结合牢固,易于分离。研究还发现以偕胺肟纤维为配体对TiO2的催化性能有较大的增强作用。     

TiO_2的光催化性能研究

利用第一性原理计算方法主要对非金属掺杂TiO_2可见光光催化活性进行了研究,揭示了非金属掺杂TiO_2在可见光条件下催化活性提高的本质规律。就目前为止,非金属掺杂TiO_2吸收可见光的原因主要归结为以下几点:(1)非金属掺杂引起能带变窄,从而降低光子跃迁能隙,产生可见光红移现象;(2)掺杂元素在TiO_2带隙中引入一部分间隙态,充当光子跃迁的过渡能级,减少光子吸收能量;(3)掺杂促使TiO_2产生结晶化,加大TiO_2颗粒的表面积,从而提高其催化活性。     

ZnO/TiO_2纳米管的制备及光降解性能研究

采用水热法合成TiO2纳米管,在碱性条件下与乙酸锌的无水乙醇溶液反应,得到表面负载ZnO的TiO2复合纳米管(ZnO/TNTs),并研究了复合纳米管在紫外光照射下对罗丹明B的光催化降解性能。通过透射电镜(TEM)、电子衍射能谱(EDS)、X射线衍射(XRD)、比表面积(BET)和紫外-可见光谱(UV-Vis)对所合成的材料进行了表征。结果表明,TiO2纳米管管径约5~10nm,管长约0.1~1μm;经ZnO表面修饰后,纳米管的结构没有发生明显变化,且ZnO粒子呈六方晶系纤锌矿结构均匀分散在纳米管的外表面,粒径约为6nm;光谱分析表明,ZnO/TNTs的吸收光谱有明显红移;且ZnO/TNTs的光催化活性较锐钛矿型TiO2纳米粉末、ZnO纳米粉末和TiO2纳米管有显著提高,且其光催化性能重复性好。     

电泳法制备纳米TiO_2薄膜光催化性能的研究

采用电泳法在导电玻璃上镀纳米TiO2薄膜,制得的TiO2薄膜经高温烧结后进行光降解实验。通过XRD、SEM、DTA、EDS等测试分析,确定了超细微粒TiO2的外观形貌和结构特征。实验结果表明,该法制得的TiO2薄膜具有一定的厚度、均匀平整、粗糙度好。极性溶剂种类、胶体浓度、电泳电压、电泳时间、镀膜次数及掺杂离子等影响电泳成膜质量及膜对甲基橙溶液的光降解效果。     

钇氮共掺杂纳米TiO_2光催化降解染料废水研究

以溶胶-凝胶法制备了钇、氮共掺杂纳米TiO2,对甲基橙染料废水进行了光催化降解实验。XRD、UV-VIS、FT-IR分析表明,500℃煅烧时得到的仍是锐钛矿型TiO2,晶粒变小;与单一的掺杂相比,共掺杂光催化活性有较大的提高,光响应范围得到很大拓展。Y3+、N的掺量分别为0.8%和0.5%时,在1.5h内甲基橙的降解率达到99.8%。     

载体形式和掺杂元素对纳米TiO_2光催化降解甲基橙的影响

通过对比不同形式玻璃载体负载TiO2紫外光催化降解甲基橙的能力以及不同元素掺杂对光催化降解的影响,探讨了提高TiO2光催化降解有机污水能力的方法。结果表明,毛细玻璃管负载的TiO2由于限域微米空间效应的作用,其光催化能力明显好于玻璃片和玻璃珠载体;同时,比较了TiO2掺杂元素Pb、N和Fe在可见光下的催化能力,得出掺杂Pb为最佳,降解率达到94.8%,以期为负载以及掺杂元素提升TiO2光催化降解污水的处理能力提供借鉴。     

Investigation on photogenerated radicals of some carboxylates in solution and in aqueous dispersions of AgBr

Abstract

The photogenerated free radicals from formate, oxalate and acetate in aqueous solutions without and with dispered AgBr grains under illuminations of 355 nm laser light, natural light and monochromatic red, green or blue light were detected by electron spin resonance with spin-trap DMPO. The results showed that: (a) ·CO₂^? radicals were produced in the formate solution by all of these illuminations; (b) the signals of ·CO₂^? radicals were greatly intensified when an AgBr dispersion was present in the formate solution; (c) the signals of ·CO₂^? radicals in the oxalate solution were also detected and intensified when an AgBr dispersion was present, but only after illumination by the 355 nm laser; (d) ·CH₃ radicals, instead of ·CO₂^?, were weakly detected in the acetate solution, but only in the presence of AgBr under illumination by the 355 nm laser. The photochemical behaviour of these carboxylates, particularly formate and oxalate, perhaps implies their capability for trapping photogenerated holes and their potential for acting as a hole converter to an effective electron carrier.     

Treatment of petroleum-hydrocarbon contaminated soils using hydrogen peroxide oxidation catalyzed by waste basic oxygen furnace slag

The contamination of subsurface soils with petroleum hydrocarbons is a widespread environmental problem. The objective of this study was to evaluate the potential of applying waste basic oxygen furnace slag (BOF slag) as the catalyst to enhance the Fenton-like oxidation to remediate fuel oil or diesel contaminated soils. The studied controlling factors that affect the removal efficiency of petroleum hydrocarbons included concentrations of H₂O₂, BOF slag dosages, types of petroleum hydrocarbons (e.g., fuel oil and diesel), and types of iron mineral. Experimental results indicate that oxidation of petroleum hydrocarbon via the Fenton-like process can be enhanced with the addition of BOF slag. Results from the X-ray powder diffraction analysis reveal that the major iron type of BOF slag/sandy loam system was iron mineral (e.g., α-Fe₂O₃ and α-FeOOH). Approximately 76% and 96% of fuel oil and diesel removal were observed (initial total petroleum hydrocarbon (TPH) concentration = 10,000 mg kg⁻¹), respectively, with the addition of 15% of H₂O₂ and 100 g kg⁻¹ of BOF slag after 40 h of reaction. Because BOF slag contains extractable irons such as amorphous iron and soluble iron, it can act as an iron sink to supply iron continuously for Fenton-like oxidation. Results demonstrate that Fenton-like oxidation catalyzed by BOF slag is a potential method to be able to remediate petroleum-hydrocarbon contaminated soils efficiently and effectively.     

纳米TiO_2-Ni基镀层的电刷镀沉积行为研究

为了使纳米颗粒均匀地悬浮在镀液中从而获得纳米颗粒均匀分布的复合镀层,研究了不同表面活性剂对纳米TiO2在镀液中的分散行为的影响,采用电刷镀方法制备纳米TiO2-Ni基复合镀层,并运用SEM、EDS和XRD研究了纳米TiO2-Ni基镀层的表面形貌和成分特点。结果表明,阳离子型表面活性剂十六烷基三甲基氯化铵(CTAB)对纳米TiO2颗粒的分散效果最好,沉降时间超过40min;CTAB分散的纳米TiO2-Ni基镀层显微硬度比不加表面活性剂的提高50%左右,镀层结合性较好,孔隙率显著降低;CTAB分散的纳米TiO2-Ni基镀层均匀细致、晶粒细小,纳米TiO2被生长着的镍晶粒夹持嵌埋,分布于镍基间隙中,镀层由纳米TiO2颗粒和镍基组成。纳米粉末与镍共沉积符合迁移、吸附、嵌埋的过程。     

Preparation of CuxO/C composite derived from Cu-MOFs as Fenton-like catalyst by two-step calcination strategy

Cu_xO/C composites were successfully prepared using Cu-MOFs as the template and precursor by a two-step calcination strategy. SEM and TEM observations indicated that the composites had a microstructural prototype of porous cubic frameworks with the attachment of graphitic nanosheets on the surfaces, where the co-existence of CuO and Cu₂O nanoparticles were uniformly encapsulated. The Fenton-like activities of the Cu_xO/C composites were studied by the degradation of Rhodamine B. The sample calcinated firstly at 500?°C in N₂ followed at 300?°C in air achieved the optimal catalytic properties. Approximate 90% contaminant could be degraded within 40?min and the performances was maintained stable after five cycling runs. The superior Fenton-like activities of as-prepared Cu_xO/C composites were attributed to the high specific surface area, good adsorption and enhanced electron transport of well crystallized microstructures.     

Novel synthesis of Cu-HAP/SiO2@carbon nanocomposites as heterogeneous catalysts for Fenton-like oxidation of 2,4-DCP

Hydroxyapatite (HAP) has stable ion exchange capacity and is a potential environmental catalyst carrier. In this paper, a novel metal–carbon nanocomposite (Cu-HAP/SiO₂@carbon) was synthesized as a catalyst to remove 2,4-DCP. The SEM, XRD, FT-IR, XPS and BET were used to characterize the synthesized catalyst materials, the results showed that Cu-HAP/SiO₂@carbon has a rich pore structure and a high specific surface area, and the copper element is well dispersed on the surface of the carrier. The results of 2,4-DCP removal effect showed that almost 100 % of 2,4-DCP was removed under the optimal reaction conditions. In addition, the Cu-HAP/SiO₂@carbon broaden the applicable pH range and has excellent performance in terms of reusability (93.73 % of removal rate after 5 cycles). Finally, based on the intermediate products identify by HPLC, the degradation mechanism and possible degradation pathway of 2,4-DCP was investigated, EPR was employed to confirm the effects of ·OH.     

以D2EHPA为载体的中空纤维丝液膜提取镧

本文以液膜法提取稀土获得基础知识为目的,以二(2-乙基己基)磷酸(D2EHPA)为载体,用中空纤维丝液膜提取稀土金属镧。测定了流量随时间的变化以及外水相的酸浓度、镧浓度、载体浓度对膜传质速度的影响,并利用传质速度方程式对实验结果给予定量解释。     

纳米TiO2稀土元素掺杂改性光催化还原CO2制甲醇研究

讨论采用改良的溶胶-凝胶法，以钛酸丁酯为前驱体，以冰醋酸为鳌合剂，通过水解缩聚作用制备纳米TiO2，掺杂稀土金属进行改性，进行CO2光催化还原制甲醇研究；利用X射线衍射（XRD）、高分辨透射电镜（HRTEM）、BET比表面积、光致发光光谱（PL）技术来分析制得的光催化材料结构、吸光性能、化学吸附等特性，期待能弄清楚纳米TiO2结构与催化效果之间的关系，从而确定主导CO2光催化还原反应效率的因素。     

模板法制备介孔TiO2及其光催化性能研究

以十六烷基三甲基溴化铵(CTAB)作为模板剂,钛酸正四丁酯(TBOT)为钛源,异丙醇为溶剂,通过溶胶-凝胶过程合成出介孔TiO2前驱体凝胶后,经老化、焙烧得到了TiO2介孔材料.利用XRD、HR-TEM、TGA、N2的吸附-脱附、BET等方法对材料的结构、形貌、比表面积、孔径分布进行表征.以亚甲基蓝的降解为模型反应,对其催化性能进行评价并与商品DegussaP-25进行比较.实验结果表明,比表面积为137.5m2/g、孔径为8.62nm的锐钛型介孔TiO2具有很高的催化活性.     

超声-醇盐水解法制备TiO_2及其光催化性能研究

以四异丙醇钛为前驱体,通过超声-醇盐水解法一步合成锐钛矿相TiO2,利用傅里叶红外光谱、X射线衍射、扫描电镜测试对样品性能进行表征。结果表明,在醇盐水解过程中加入超声辅助作用,能得到光催化活性高且粒径均匀的锐钛矿相TiO2;当紫外光照180 min后,经超声处理制备的TiO2对甲基橙的降解率能达到90%以上,锐钛矿相的TiO2在紫外光照下具有很好的光催化活性。