纳米TiO_2对盐酸黄连素的光催化去除效果研究

采用四氯化钛水解法制备了纳米TiO_2催化剂,利用XRD和TEM对其结构进行了表征分析,并研究了其对盐酸黄连素的光催化去除效果。结果表明:纳米TiO_2催化剂为锐钛矿和金红石的混合晶型,平均粒径约25nm,并且具有良好的光催化活性;当盐酸黄连素溶液浓度为10 mg/L,催化剂用量为1.6 g/L,在300 W汞灯照射条件下反应5h时,其对盐酸黄连素的光催化去除率达80%以上。

玫瑰花状MoS_(2)对丁基黄原酸钾的吸附-光催化协同去除性能研究

利用水热法合成玫瑰花状MoS_(2),研究其对丁基黄原酸钾的吸附-光催化协同去除性能。结果表明,成功制备了具有光催化性能与吸附性能的玫瑰花状MoS_(2);在pH=7、MoS_(2)用量为25 mg、吸附时间为30 min条件下,MoS_(2)对丁基黄原酸钾的最大吸附容量达110.93 mg·g^(-1);在300 W氙灯下照射30 min时,MoS_(2)对丁基黄原酸钾的降解效率为81.99%;而通过光催化降解-吸附的协同作用,在40 min时丁基黄原酸钾去除率达99.89%;经过5次循环后,MoS_(2)对丁基黄原酸钾的协同去除率仍大于95%。此研究为MoS_(2)在含黄药废水处理方面开辟一种新方法。

钢渣粒径对光催化钢渣浮露混凝土氮氧化物去除效率及稳定性的影响

将绿色可持续的光催化技术与易接触尾气的路面混凝土材料结合,研发具备空气净化功能的新型路面材料,是特种混凝土领域的研究热点之一。研究采用钢渣负载氮化碳(PCN)后铺设在新拌混凝土表面制得光催化钢渣浮露混凝土(PSEC),并探究了钢渣粒径对PSEC光催化去除氮氧化物(NO_X)效率及其稳定性影响。结果表明,耐久性试验前,PSEC的光催化去除NO_X性能随着钢渣粒径的增大而降低;模拟老化作用后,粒径越小的PSEC拥有更高的光催化去除NO_X性能;机械磨损作用后,粒径越大的PSEC拥有更高的光催化去除NO_X性能,其光催化去除NO_X效率的损失率越小。研究成果可为PSEC的推广应用提供理论依据和技术支撑。

球状微米ZnS光催化降解法去除废水中的Cu^(2+)

以硝酸锌、乙二胺四乙酸二钠、硫磺和氢氧化钠为原料制备了球状微米ZnS,并以之作为催化剂研究了其在可见光照射下催化去除Cu^(2+)离子;结果表明,ZnS在可见光照射下有优越的光催化活性,当催化剂用量为10 mg,光照时间为2.5 h,Cu^(2+)离子浓度为50 mg/L,不加酸碱调节溶液体系pH的自然条件下,Cu^(2+)离子的去除率高达98.44%,与现有的研究方法比较,在去除废水中Cu^(2+)离子方面,显示了很高的催化活性,具有很好的研究和应用前景。

铁改性TiO2复合催化剂的制备、表征及光催化性能研究

采用等体积浸渍法制备了一系列不同铁含量的Fe/TiO2复合催化剂,利用X射线衍射、紫外-可见漫反射吸收光谱、荧光光谱等手段对催化剂的结构和光学性能进行了表征。结果表明:Fe/TiO2复合催化剂中,TiO2为锐钛矿型结构,铁以α-Fe2O3形式存在;铁元素改性不仅可使TiO2的吸收带边红移至可见光区,还可促进光生电子和空穴分离,提高其光催化效率。将其应用于光催化去除水体中盐酸小檗碱,并探讨了铁掺杂量、催化剂用量和溶液初始浓度对去除效率的影响。结果表明:当盐酸小檗碱溶液浓度为50mg/L,7%Fe/TiO2复合催化剂的用量为1.5g/L,在300W氙灯照射3h时,其对盐酸小檗碱的光催化去除率可达86%。

半导体光催化技术净化氮氧化物研究进展

氮氧化物(NO_x)是形成臭氧和二次气溶胶的重要前体物之一,开发高效的NO_x控制技术对我国大气污染防治具有重要意义。光催化技术作为一种新型的高级氧化技术,对环境浓度水平的空气污染物具有良好的去除效果,是当前研究的热点。本文总结了近年来光催化材料对污染物NO_x催化降解的研究进展,包括:(1)讨论了NO_x光催化氧化去除机理;(2)详细综述了提高光催化材料性能的三大主要措施:增强催化剂的光吸收效率,提升载流子分离和迁移效率以及构筑表面活性位;(3)阐述了半导体光催化技术在净化空气方面的应用,并指出光催化技术在去除NO_x方面的发展前景。

活性炭纤维负载二氧化钛去除挥发性有机物研究

以活性炭纤维为载体,以TiO2粉末为原料,采用浸渍涂膜法制备TiO2膜。利用TiO2膜作为光催化剂,采用功率15 W,波长253.7 nm的紫外荧光灯作为光源,在圆筒型光催化反应器中,对模拟甲苯废气的去除效果进行了实验研究。实验考察了甲苯浓度、酯醇比以及光强等因素对甲苯去除率的影响。结果表明,在光照的条件下,TiO2活性炭纤维膜对初始浓度为2920 mg/m3甲苯的去除率可达到42%。随着甲苯初始浓度的增大和反应时间的逐渐增加,TiO2活性炭纤维膜对甲苯的光催化降解效果降低,催化剂失活。

无定形TiO_2纳米颗粒的制备及紫外光降解废水中的铬(Ⅵ)

以重铬酸钾溶液为模拟废水,无定形Ti O2纳米颗粒为催化剂,用500 W高压汞灯作为光源照射样品,探讨光照时间、溶液p H、催化剂用量对铬(Ⅵ)离子去除率的影响。结果表明,在光照时间为3.0 h,催化剂用量为1.0 g/L,p H 2的条件下,催化剂有很高的光催化活性,铬(Ⅵ)离子的去除率高达98.95%。尤为值得注意的是,在中性条件下,无定形Ti O2纳米颗粒也显示了优越的光催化活性,铬(Ⅵ)离子的去除率达到了98.75%,与强酸性条件下的活性相当。这可能是光催化还原反应历程和导带、价带电位协同作用的结果。

Ternary Ag/AgCl/BiOIO_3 composites for enhanced visible-light-driven photocatalysis

Ternary Ag/AgC l/BiO IO3 composite photocatalysts are prepared by a facile method. Enhanced visible-light absorption and charge carrier separation are achieved after the introduction of Ag/AgC l particles into BiO IO3 systems,as revealed by ultraviolet-visible diffuse-reflectance spectrometry,photocurrent response and electrochemical impedance spectroscopy. The Ag/AgC l/BiO IO3 composites are applied to the visible-light photocatalytic oxidization of NO in air and exhibit an enhanced activity for NO removal in comparison with Ag/AgC l and pure BiO IO3. A possible photocatalytic mechanism for Ag/AgC l/BiO IO3 is proposed,which is related to the surface plasmon resonance effects of Ag metal and the effective carrier separation ability of BiO IO3. This work provides insight into the design and preparation of BiO IO3-based materials with enhanced visible-light photocatalysis ability.

Heterostructured BiOI@La(OH)_3 nanorods with enhanced visible light photocatalytic NO removal

Heterostructured BiOI@La（OH）3 nanorod photocatalysts were prepared by a facile chemical impregnation method.The enhanced visible light absorption and charge carrier separation can be simultaneously realized after the introduction of BiOI particles into La（OH）3 nanorods.The BiOI@La（OH）3 composites were applied for visible light photocatalytic oxidization of NO in air and exhibited an enhanced activity compared with BiOI and pure La（OH）3 nanorods.The results show that the energy levels between the La（OH）3 and BiOI phases matched well with each other,thus forming a heterojunctioned BiOI@La（OH）3 structure.This band structure matching could promote the separation and transfer of photoinduced electron-hole pairs at the interface,resulting in enhanced photocatalytic performance under visible light irradiation.The photocatalytic performance of BiOI@La（OH）3 is shown to be dependent on the mass ratio of BiOI to La（OH）3.The highest photocatalytic performance can be achieved when the mass ratio of BiOI to La（OH）3 is controlled at 1.5.A further increase of the mass ratio of BiOI weakened the redox abilities of the photogenerated charge carriers.A new photocatalytic mechanism for BiOI@La（OH）3 heterostructures is proposed,which is directly related to the efficient separation of photogenerated charge carriers by the heterojunction.Importantly,the as-prepared BiOI@La（OH）3 heterostructures exhibited a high photochemical stability after multiple reaction runs.Our findings demonstrate that BiOI is an effective component for the formation of a heterostructure with the properties of a wide bandgap semiconductor,which is of great importance for extending the light absorption and photocatalytic activity of wide bandgap semiconductors into visible light region.

Solvent-assisted synthesis of porous g-C_3N_4 with efficient visible-light photocatalvtic performance for NO removal

Graphitic carbon nitride（g-C3N4） with efficient photocatalytic activity was synthesized through thermal polymerization of thiourea with the addition of water（CN-W） or ethanol（CN-E） at 550 ℃for 2 h.The physicochemical properties of the g-C3N4 were investigated by X-ray diffraction,transmission electron microscopy,ultraviolet-visible spectroscopy,photoluminescence spectroscopy,diffuse-reflection spectroscopy,BET and BJH surface area characterization,and elemental analysis.The carbon content was found to have self-doped into the g-C3N4 matrix during the thermal polymerization of thiourea and ethanol.CN-W and CN-E showed considerably enhanced visible-light photocatalytic activity,with NO removal percentages of 37.2%and 48.3%,respectively.Compared with pure g-C3N4,both the short and long lifetimes of the charge carriers in CN-W and CN-E were found to be prolonged.The mechanism of improved visible-light photocatalytic activity was deduced.The present work may provide a facile route to optimize the microstructure of g-C3N4photocatalysts for high-performance environmental and energy applications.

Enhanced plasmonic photocatalysis by SiO_2@Bi microspheres with hot-electron transportation channels via Bi–O–Si linkages

The semimetal Bi has received increasing interest as an alternative to noble metals for use in plasmonic photocatalysis. To enhance the photocatalytic efficiency of metallic Bi, Bi microspheres modified by SiO2 nanoparticles were fabricated by a facile method. Bi-O-Si bonds were formed between Bi and SiO2, and acted as a transportation channel for hot electrons. The SiO2@Bi microspheres exhibited an enhanced plasmon-mediated photocatalytic activity for the removal of NO in air under 280 nm light irradiation, as a result of the enlarged specific surface areas and the promotion of electron transfer via the Bi-O-Si bonds. The reaction mechanism of photocatalytic oxidation of NO by SiO2@Bi was revealed with electron spin resonance and in situ diffuse reflectance infrared Fourier transform spectroscopy experiments, and involved the chain reaction NO -> NO2 -> NO3- with center dot OH and center dot O-2(-) radicals as the main reactive species. The present work could provide new insights into the in-depth mechanistic understanding of Bi plasmonic photocatalysis and the design of high-performance Bi-based photocatalysts. (C) 2017, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

S-scheme Sb2WO6/g-C3N4 photocatalysts with enhanced visible-light-induced photocatalytic NO oxidation performance

Normal photocatalysts cannot effectively remove low-concentration NO because of the high recombination rate of the photogenerated carriers.To overcome this problem,S-scheme composites have been developed to fabricate photocatalysts.Herein,a novel S-scheme Sb2WO6/g-C3N4 nanocomposite was fabricated by an ultrasound-assisted method,which exhibited excellent performance for photocatalytic ppb-level NO removal.Compared with the pure constituents of the nanocomposite,the as-prepared 15%-Sb2WO6/g-C3N4 photocatalyst could remove more than 68%continuous-flowing NO(initial concentration:400 ppb)under visible-light irradiation in 30 min.The findings of the trapping experiments confirmed that•O2^–and h+were the important active species in the NO oxidation reaction.Meanwhile,the transient photocurrent response and PL spectroscopy analyses proved that the unique S-scheme structure of the samples could enhance the charge separation efficiency.In situ DRIFTS revealed that the photocatalytic reaction pathway of NO removal over the Sb2WO6/g-C3N4 nanocomposite occurred via an oxygen-induced route.The present work proposes a new concept for fabricating efficient photocatalysts for photocatalytic ppb-level NO oxidation and provides deeper insights into the mechanism of photocatalytic NO oxidation.

Enhanced photocatalytic NO removal and toxic NO2 production inhibition over ZIF‐8‐derived ZnO nanoparticles with controllable amount of oxygen vacancies

The controlled introduction of oxygen vacancies(OVs)in photocatalysts has been demonstrated to be an efficient approach for improving the separation of photogenerated charge carriers,and thus,for enhancing the photocatalytic performance of photocatalysts.In this study,a two‐step calcination method where ZIF‐8 was used as the precursor was explored for the synthesis of ZIF‐8‐derived ZnO nanoparticles with gradient distribution of OVs.Electron paramagnetic resonance measurements indicated that the concentration of OVs in the samples depended on the temperature treatment process.Ultraviolet–visible spectra supported that the two‐step calcined samples presented excellent light‐harvesting ability in the ultraviolet‐to‐visible light range.Moreover,it was determined that the two‐step calcined samples presented superior photocatalytic performance for the removal of NO,and inhibited the generation of NO2.These properties could be attributed to the contribution of the OVs present in the two‐step calcined samples to their photocatalytic performance.The electrons confined by the OVs could be transferred to O2 to generate superoxide radicals,which could oxidize NO to the final product,nitrate.In particular,the NO removal efficiency of Z 350‐400(which was a sample first calcined at 350℃ for 2 h,then at 400℃ for 1 h)was 1.5 and 4.6 times higher than that of Z 400(which was one‐step directly calcined at 400℃)and commercial ZnO,respectively.These findings suggested that OV‐containing metal oxides that derived from metal‐organic framework materials hold great promise as highly efficient photocatalysts for the removal of NO.

Efficient removal of ammonia with a novel graphene-supported BiFeO_3 as a reusable photocatalyst under visible light

Graphene‐supported BiFeO3 (rG‐BiFeO3) was synthesized by the hydrothermal method and used for the efficient removal of ammonia under visible light. X‐ray diffraction, transmission electron microscopy,Fourier transform infrared spectroscopy, Raman spectroscopy, and ultraviolet‐visiblediffuse reflectance spectroscopy were conducted to characterize the rG‐BiFeO3. The specific surfacearea of the rG‐BiFeO3 catalyst was 48.6 m2/g, larger than that of BiFeO3 (21.0 m2/g). When used as aheterogeneous photocatalyst, rG‐BiFeO3 achieved 91.20% degradation of a NH3‐N solution (50mg/L) at pH = 11 under visible‐light irradiation in the absence of hydrogen peroxide. The degradationof ammonia followed pseudo‐first‐order kinetics, and the catalyst retained high photocatalyticactivity after seven reaction cycles. Study of the mechanism showed that the holes, superoxide anion radicals, and hydroxyl radicals, arising from the synergy between graphene and BiFeO3, oxidized NH3 directly to N2.

Polyoxometalates‐doped Bi_(2)O_(3–x)/Bi photocatalyst for highly efficient visible‐light photodegradation of tetrabromobisphenol A and removal of NO

Bismuth‐based photocatalysts are a class of excellent visible‐light photocatalysts;however,their redox activity is relatively poor and the efficiency of photogenerated carrier separation is low,limiting their development and application in the field of photocatalysis.To address these issues,a series of polyoxometalate PW_(12)O_(40)^(3–)‐doped Bi_(2)O_(3–x)/Bi Schottky photocatalysts PW_(12)@Bi_(2)O_(3–x)/Bi‐n(PBOB‐n,where n is the amount of NaBH4,i.e.,6,12,18,24,and 48 mg)were prepared by a simple electrospinning/calcination/in‐situ NaBH4 reduction method.In this composite photocatalyst,the doping of PW_(12) could effectively adjust the electronic structure of Bi_(2)O_(3–x) and improve its redox properties.As a shallow electron trap,PW_(12) promoted the separation of the photogenerated carriers.Furthermore,desirable Schottky junction between the metal Bi nanoparticles and PW_(12)@Bi_(2)O_(3–x) further accelerated the separation of the photogenerated carriers.The synergistic effect of the aforementioned factors endowed PBOB‐n with excellent photocatalytic activity.Among the samples,PBOB‐18 exhibited superior photocatalytic activity.Under visible‐light irradiation,93.7%(20 mg catalyst)of 20 ppm tetrabromobisphenol A(TBBPA,20 mL)was degraded in 60 min.Its activity was 4.4 times higher than that of Bi_(2)O_(3).PBOB‐18 also exhibited an ultrahigh photocatalytic performance for the removal of NO.Its removal rate(600 ppb)reached 83.3%in 30 min,making it one of the most active Bi‐based photocatalysts.Furthermore,the photocatalytic mechanisms of PBOB‐18 for TBBPA and NO have been proposed.This work provides a new direction and reference for the design of low‐cost,efficient,stable,and versatile photocatalysts.

The photocatalytic performance and active sites of g-C3N4 effected by the coordination doping of Fe(Ⅲ)

Element doping is a simple and effective method to improve photocatalytic activity of g-C3N4. However, the doping model and mechanism of metal elements are still uncharacterized. In this study, we found that Fe(Ⅲ) can be doped into g-C3N4 through the coordination between amidogen and Fe(Ⅲ). After activity tests, it was found that this coordination doping of Fe(Ⅲ) could enhance the Rh B oxidation and Cr(Ⅵ) reduction activities of g-C3N4 in interesting ways, but it is not helpful for the NO-removal performance of g-C3N4. Characterization and calculation results show that the coordination of Fe(Ⅲ) can not only improve the transfer of photogenerated electrons, but it also can passivate the carbon site of triazine rings, which is the active site of NO-removal. This study revealed some doping mechanisms and effect mechanisms of elemental metal in photocatalysis.