• <tr id="yyy80"></tr>
  • <sup id="yyy80"></sup>
  • <tfoot id="yyy80"><noscript id="yyy80"></noscript></tfoot>
  • 99热精品在线国产_美女午夜性视频免费_国产精品国产高清国产av_av欧美777_自拍偷自拍亚洲精品老妇_亚洲熟女精品中文字幕_www日本黄色视频网_国产精品野战在线观看 ?

    A confined micro-reactor with a movable Fe3O4 core and a mesoporous TiO2 shell for a photocatalytic Fenton-like degradation of bisphenol A

    2021-10-14 00:55:26PengpengQiuToZhoXiohngZhuBinotThokchomJinpingYngWnJingLinjunWngYuchiFnXiopengLiWeiLuo
    Chinese Chemical Letters 2021年4期

    Pengpeng Qiu,To Zho,Xiohng Zhu,Binot Thokchom,Jinping Yng,Wn Jing,Linjun Wng,Yuchi Fn,Xiopeng Li,*,Wei Luo,*

    a State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Materials Science and Engineering, Institute of Functional Materials, Shanghai 201620, China

    b Indian Institute of Technology Guwahati, Guwahati 781039, India

    ABSTRACT Photocatalysis and Fenton process are two primary and promising advanced oxidation processes to degrade organic pollutants.However, the practical applications of single photocatalysis and Fenton process are still limited.Introducing one of them into another to form a combined photocatalytic Fentonlike system has shown great potential but still faces challenges in designing a well-tailored catalyst.Herein, a confined photocatalytic Fenton-like micro-reactor catalyst with a movable Fe3O4 core and a mesoporous TiO2 shell has been constructed via a successive St?ber coating strategy, followed by an ultrasound assisted etching method.The resulting micro-reactor possesses well-defined yolk-shell structures with uniform mesopores(~4 nm),a large Brunauer-Emmett-Teller(BET)surface area(~166.7 m2/g), a high pore volume (~0.56 cm3/g) and a strong magnetization (~51 emu/g), as well as tunable reactor sizes(20-90 nm).When evaluated for degrading bisphenol A under solar light in the presence of peroxymonosulfate,the micro-reactor exhibits a superior catalytic degradation performance with a high magnetic separation efficiency and an excellent recycle ability.The outstanding performance can be attributed to its unique textual structure,which leads to a great synergistic effect from the photocatalytic and Fenton-like process.This study gives an important insight into the design and synthesis of an advanced micro-reactor for a combined advanced oxidation processes (AOPs).

    Keywords:Photocatalytic Fenton-like reaction Yolk-shell Micro-reactor Magnetic Mesoporous

    Emerging organic contaminants (EOCs) are a kind of contaminants that are not regularly detected but they have high tendency to spread into the environment, which exhibit great potential to cause adverse effects to the ecology and human health.The EOCs are mainly divided into endocrine disruptors,pharmaceuticals and personal care products, surfactants, and various industrial additives as well as hormones [1-3].Bisphenol A (BPA), classified as an endocrine disruptor, is a tricky pollutant since it has been widely applied in the production of polycarbonates,epoxy resins,and other plastics over the past decade.More importantly, some traditional treatment technologies including adsorption, membrane filtration, and biological treatment are usually restricted to treat them owing to the ultralow concentration, high chemical stability and low biodegradability of BPA [4,5].As an alternative,advanced oxidation processes (AOPs) have attracted tremendous research interest for the decomposition and mineralization of them through some strong oxidative species such as·OH,·O2[6-9].

    Among various AOPs, Fenton-like process based on Fe2+and peroxymonosulfate (PMS) has recently triggered tremendous research interest because of its environmental benignity and cost effectiveness [10-12].However, the practical application of it is still limited by several drawbacks,such as the narrow operating pH range, hard to recycle the soluble metal ions and necessity for further treatment of sludge[13,14].To address these problems,the fabrication of a magnetic catalyst is desirable.Up to now,magnetite nanoparticles (NPs) have been widely investigated as one of the most efficient heterogeneous Fenton catalysts among Fe-based nanomaterials due to their higher content of structural Fe2+[15-17].However, compared with the homogenous Fenton reaction,the catalytic performance of Fe3O4NPs based one is still far from expected.Recently, the hybridization of Fenton reaction with photocatalytic process has shown great potential in this field[18-20].However,the development of a catalyst that could achieve both high Fenton-like and photocatalytic performance is still challenging.

    Herein, a unique yolk-shell structured magnetic mesoporous TiO2has been synthesized through a facile ultrasound assisted etching method and demonstrated as a highly efficient solar photocatalytic Fenton-like catalyst for degrading BPA.The resultant material exhibits a unique yolk-shell structure with uniform mesopores (~4 nm), a large Brunauer-Emmet-Teller (BET) surface area(~166.7 m2/g),a high pore volume(~0.56 cm3/g)and a strong magnetic susceptibility (~51 emu/g).More importantly, the void space can be facilely tuned from 20 nm to 90 nm by changing the thickness (10-46 nm) of SiO2middle layer, which can act as a superior micro-reactor for the confined photocatalytic Fenton-like degradation of BPA.

    The schematic illustration for the synthesis of yolk-shell structured magnetic mesoporous TiO2micro-reactor are illustrated in Scheme 1.The uniform magnetite NPs are first fabricated via a facile solvothermal method,which involves the reduction of Fe(III)salts with ethylene glycol at a high temperature (200。C) in the presence of sodium citrate as a capping agent.Scanning electron microscope(SEM)images clearly show that the Fe3O4NPs exhibit uniform spherical shapes with an average size of ~130 nm(Figs.S1A and B in Supporting information).Owing to the presence of abundant citrate groups on the surface, the NPs possess outstanding dispersibility in water or ethanol, which is very favorable for the subsequent high-quality coating with SiO2and TiO2.After the first St?ber coating, the Fe3O4@SiO2nanospheres with a smooth surface and a particle size of ~200 nm can be obtained (Figs.S1C and D in Supporting information).Transmission electron microscopy(TEM)images reveal that a ~35 nm thick SiO2layer is evenly wrapped on the Fe3O4core, forming a welldefined core-shell structure.The further St?ber coating gives rise to a sandwich-like Fe3O4@SiO2@TiO2nanostructure with a uniform TiO2layer(~35 nm)coated on the Fe3O4@SiO2cores(Figs.S1E and F in Supporting information).Following an ultrasound (US)assisted etching process in a weakly basic condition, the SiO2middle layer in the Fe3O4@SiO2@TiO2nanospheres can be completely removed, thus forming the void space between Fe3O4core and TiO2shell.Note that the US can also cause the further hydrolysis of Ti-OR moiety in the TiO2shell to become complete hydrolyzed form of Ti-OH, leading to the formation of mesoporous structure.The TEM images clearly show that the welldefined yolk-shell nanostructures with a movable black core is obtained (Figs.1A and B) The overall spacing is measured to be~70 nm, that equals the thickness of double silica interlayers,indicating that the silica was completely removed in NaHCO3solution under US irradiation.No Si peak was detected in the X-ray photoelectron spectroscopy(XPS)analysis,further suggesting the complete removal of SiO2(Fig.S2 in Supporting information).After calcination at 550。C for 2 h, mesoporous TiO2micro-reactor with uniform yolk-shell structure was obtained with a highly crystalline TiO2shell.High resolution TEM (HRTEM) image of the Fe3O4@-SiO2@c-mTiO2-3 clearly shows that the TiO2shell is well crystalized with a d-spacing of 0.35 nm, which is a typical reflection of anatase TiO2(Fig.1C).Moreover, the size of the void space can be facilely tuned from 20 nm to 90 nm by adjusting the thickness of SiO2interlayer from 10 nm to 45 nm (Figs.1D-F).In previous studies[11],the collapse could occur if the etching of SiO2did prior to the calcination.However,in our study,the collapse was not observed possibly because the post-hydrolysis of TiO2shell lead to the formation of void space in the network, which could buffer the thermal expansion during calcination, thus increasing the thermal stability of TiO2shell.The yolk-shell structured sample with different void space size of 20, 40, 70, 90 nm are denoted as Fe3O4@void@c-mTiO2-1, Fe3O4@void@c-mTiO2-2, Fe3O4@void@cmTiO2-3, Fe3O4@void@c-mTiO2-4, respectively.

    Scheme 1.Schematic illustration for the synthesis of magnetic mesoporous TiO2 micro-reactor.

    Fig.1.TEM(A and B)HRTEM(C)images of Fe3O4@SiO2@c-mTiO2-3 and TEM images of Fe3O4@SiO2@c-mTiO2-1 (D), Fe3O4@SiO2@c-mTiO2-2 (E) and Fe3O4@SiO2@cmTiO2-4 (F).

    N2adsorption-desorption isotherms of the yolk-shell Fe3O4@-void@c-mTiO2-3 NPs(Fig.2A)depict an IV curve with a hysteresis loops close to H1-type, indicating that the TiO2shells contain uniform mesopores.The BET surface area and pore volume of the Fe3O4@void@c-mTiO2-3 sample are measured to be ~166.7 m2/g and ~0.56 cm3/g, respectively.Correspondingly, the pore size distribution(Fig.2B)calculated from the adsorption branch using the Barrett-Joyner-Halenda (BJH) method reveals a uniform pore size centered at ~4.2 nm.

    Fig.2.N2 sorption isothermals (A) and pore size distribution (B) of yolk-shell structured mesoporous TiO2 with a void space of 35 nm.XRD patterns(C)of Fe3O4(a),Fe3O4@SiO2(b),and Fe3O4@void@mTiO2-3(c).The magnetic hysteresis loops at 300 K of Fe3O4@void@mTiO2-3 (D).

    X-ray diffraction (XRD) pattern of the Fe3O4nanoparticles(Fig.2C) exhibits several well resolved characteristic diffraction peaks,typical for Fe3O4crystalline phase.A broad amorphous silica peak can be clearly observed in the XRD pattern of Fe3O4@SiO2compared with that of pure Fe3O4NPs, suggesting that the SiO2was coated.No amorphous SiO2peak was observed in the sample of Fe3O4@void@mTiO2-3,suggesting that the SiO2middle layer was well removed.In addition,several sharp peak attributed to anatase TiO2was detected, proving that the mesoporous TiO2shell was well crystalized.The magnetic property of the Fe3O4@void@cmTiO2-3 micro-reactor was evaluated by measuring the magnetization saturation value (Fig.2D).As a result of the high magnetization (~51 emu/g), the Fe3O4@void@c-mTiO2-3 nanospheres in their homogeneous dispersion can be quickly recycled by applying a hand-held magnetic bar(<30 s,Fig.S3 in Supporting information).

    The photocatalytic Fenton-like degradation performance of BPA in the presence of the resultant magnetic mesoporous TiO2was tested at a neutral pH(Fig.3A).Before the irradiation of solar light,the system was mechanically stirred in dark for 1 h to achieve an adsorption-desorption equilibrium between the catalyst and BPA.As a control, the degradation performances of BPA under PMS,solar/PMS, solar/catalyst, and PMS/catalyst conditions were also examined,showing the removal efficiencies of 17.0%,44.5%,76.1%,87.1%,respectively.The larger degradation efficiency of solar/PMS process than PMS alone was due to the dissociation of PMS into sulfate radicals through light [21].When Fe3O4@void@c-mTiO2-3 micro-reactor were directly used as a Fenton-like catalyst without solar light,the efficiency was significantly improved resulted from the activation of PMS by the surface Fe2+.Interestingly, when combine solar light, PMS and Fe3O4@void@c-mTiO2catalyst together, the degradation performance of BPA can be greatly promoted, which can achieve a complete degradation within 40 min, demonstrating the priority of this combined process.To better illustrate the priority of the combined process,a synergetic factor (S) has been introduced, which can be calculated based on Eq.1 [22-24].

    Fig.3.Photocatalytic Fenton degradation performance for BPA with different processes (A) and corresponding kinetic constant value (B); in B, PMS (a), Solar+PMS (b),Solar+catalyst(c),PMS+catalyst(d),and Solar+catalyst+PMS(e).Photocatalytic Fenton degradation performance for BPA(C)and corresponding kinetic constant value(D)in the presence of different catalysts; in D, Fe3O4 (a), Hollow c-mTiO2-2 (b), and Fe3O4@void@c-mTiO2-3 (c), Fe3O4@void@c-mTiO2-4 (d) and Fe3O4@SiO2@c-mTiO2 (e).Photocatalytic Fenton degradation performance for BPA (E) and corresponding kinetic constant value (F) in the presence of catalysts with different void space; in F,Fe3O4@void@c-mTiO2-1 (a), Fe3O4@void@c-mTiO2-2 (b), Fe3O4@void@c-mTiO2-3 (c), Fe3O4@void@c-mTiO2-4 (d) and Fe3O4@SiO2@c-mTiO2 (e).

    Where, k1and k2is the kinetic constants of Fenton-like and photocatalytic process, respectively.k12is the kinetic constant of the combined photocatalytic Fenton-like process.The kinetic constants were calculated by fitting the experimental data with Langmuir-Hinshelwood model.The pseudo first order reaction equation was assumed because the concentration of BPA is very low.The correlation coefficients (R2) for all the process are above 0.95,suggesting that the assumption is reasonable(Fig.3B).The S is calculated to be 2.9, much larger than 1, suggesting that the combined process is not a simple sum of photocatalytic and Fenton-like process.The total leached iron ions concentration after the reaction was also measured at the neutral condition(Fig.S4 in Supporting information).We found that when only the catalyst was added to the system, negligible iron ions was detected,suggesting that the catalyst is stable.After the irradiation of solar light, the concentration of leached Fe ions increased, which is possibly due to that the structural Fe3+ions on the surface of Fe3O4lose their stability after scavenging the photo-excited electrons and thus get detached from the surface and then leached into the solution(Fig.S4b).The combination of PMS with the catalyst could also lead to the generation of a small amount of leached Fe ions,resulted from the mutual activation of PMS and catalyst surface.When combining these three together, the concentration of more than 20 times larger for leached Fe ions was detected,suggesting a strong synergistic interaction between these elements.This agrees well with the performance results.To demonstrate the superiority of the micro-reactor system, the degradation performances of individual Fe3O4and hollow structured mesoporous c-mTiO2(Fe3O4was etched out by a hot HCl solution)under solar light in the presence of PMS were also examined.It is clearly shown that both the photocatalytic Fenton-like degradation performances of Fe3O4and hollow structured mesoporous c-mTiO2are much smaller than that of the Fe3O4@void@c-mTiO2-3 micro-reactor, indicating that necessity to construct such a catalyst (Fig.3C).In addition, the photocatatyic performance of hollow structured mesoporous cmTiO2in the presence of PMS is larger than that without PMS,revealing that PMS also promote the photocaltyic reaction owing to the scavenge of photo-excited electrons (Fig.S5 in Supporting information).According to the calculated kinetic constant(Fig.3D), the synergistic factor is derived to be 2.5, further revealing the great enhancement after combining Fe3O4and hollow c-mTiO2together.

    The effect of void size on the degradation performance was also evaluated(Figs.3E and F).It is clear that the core-shell structured Fe3O4@SiO2@c-mTiO2without etching out the SiO2interlayer shows a much smaller photocatalytic Fenton-like degradation performance than that the samples with void space, suggesting that the void space plays an important role in promoting the catalytic performance.This is because the presence of void space can not only increase the number of exposed reactive sites of inner core, thus facilitating the Fenton-like catalytic performance, but also promote the enrichment of the organic pollutants and PMS in the void space, bringing the synergistic effects between the photocatalytic and Fenton-like catalytic process.We also found that the photocatalytic Fenton-like degradation rate of BPA increased with the increase of void space size.This result is reasonable because larger void possess more space for the confined reaction between the photocatalytic and Fenton-like reaction.However,further increasing the void space beyond 70 nm did not lead to a significant increase in the degradation reaction rate,possibly owing to that too large void space will also reduce the synergistic interaction between the two reactions.Therefore, the Fe3O4@void@c-mTiO2-3 was used for the subsequent test.

    The pH is an important factor to be considered for the practical application of Fenton based process.Thus, the degradation performance of Fe3O4@void@c-mTiO2-3 was also investigated at different pH (Fig.4A).We found that in this system, the removal efficiency in both acidic and neutral condition is similar,indicating that this catalyst can work in a neutral pH, which is favorable for the practical application.However,the removal efficiency sharply decreased when the pH was adjusted to 10 possibly owing to the change of reaction mechanism.It is speculated that on the Fe3O4nanoparticles, the mechanism could be proposed as follows (Eqs.2-4) [25-27].Where, the ≡symbol indicates the species on the surface of Fe3O4nanoparticles.

    Fig.4.Photocatalytic Fenton degradation performance for BPA with at different pH(A)and in the presence of different scavengers(B).Schematically illustrate the mechanism for photocatalytic Fenton degradation of BPA in the presence of yolk-shell structured mesoporous TiO2 as the micro-reactor (C).

    According to these equations,the reaction mechanism could be different at acidic and basic condition.At an acidic/neutral condition,the ferric ions could directly react with PMS to generate·OH(Eq.2).While in a basic condition,the system is abundant with negatively charged OH groups, which could be adsorbed on ≡Fe(II) ions to form ≡Fe(II)--OH complex.After addition of PMS,≡Fe(II)--OH on the catalysts could first react with HSO5-to generate ≡Fe(II)(HO)OSO3-(Eq.3) that subsequently decomposed to SO4·-(Eq.4).Consequently, Fe(II) would transform to Fe(III).Owing to the lower oxidation potential of SO4·-than·OH,thus the performance of this catalyst in basic condition is less effective than that in acidic condition.The recycling test of the Fe3O4@void@c-mTiO2-3 micro-reactor at pH 7 was also tested(Fig.S6 in Supporting information).After five recycles,no apparent decrease in the degradation kinetic constant was observed,indicating the excellent reusability of the catalyst.Both the SEM and TEM images of the recycled samples have shown that the welldefined core-shell structure were well retained, suggesting the excellent stability of the micro-reactor.However,the particle size of the inner magnetite cores slightly decreased,which is due to the iron leaching during the reaction.There is no clear change in the XRD pattern,revealing that the crystal structure of the catalyst was well maintained (Fig.S7 in Supporting information).To further clarify the reactive species involved in the reaction system, the scavenging tests were carried out in neutral condition(Fig.4B).The addition of a scavenger for·OH (tert-butyl alcohol) dramatically suppressed the combined photocatalytic Fenton-like reaction,suggesting that the·OH was the dominate species [28].A slight decrease of the degradation performance in the presence of pbenzoquinone (BQ) for·O2-, indicating that·O2-degradation was not significant [18].Besides, the introduction of AgNO3, as a scavenger for photo generated electrons(e-),had a strong effect on the performance for degrading BPA,suggesting that e-was also the dominate species.This is possibly because the addition of AgNO3scavenged the photo-generated electrons, thus inhibiting the recombination of photo-generated charges [29].This result is different from that occurs in photocatalytic process, holding the fact that if the Ag+consumed the electrons, more holes would survive and thus could generate more·OH.However, in this combined system, the Fenton-like reaction was also involved,which constructs the relationship with the photocatalytic process by scavenging the electrons with the Fe3+.The Ag+would capture most electrons because it has a higher oxidation potential than Fe3+and thus the interactions between the Fenton-like and photocatalytic process could be inhibited.While from the synergistic factor calculation, we can see that the performance enhancement from the synergy is much larger than that by the individual process.As a final result, the overall reaction rates are reduced upon the addition of Ag+.In the PMS involved Fenton reaction,the generation of SO4·-usually occurs.Therefore, the methanol(MeOH) was added to examine the effect of SO4·-.However, very little decrease in the degradation performance was found suggesting that SO4·-is not the directly reactive species responsible for BPA degradation [10,30].

    Based on the results above,the mechanism can be explained by Fig.4C that BPA molecules are mainly degraded by·OH,which are produced by several pathways.The irradiation of solar light could excite the outer TiO2shell to generate photo-excited electrons and holes at the conduction band (CB) and valance band (VB),respectively.Then, the holes can react with the water molecules or OH-to generate·OH.At the same time,the ferric ion can activate the PMS to generate sulfate radicals and ferrous ions.At this moment, the ferrous ions plays an important role in keeping the interaction between the TiO2shell based photocatalytic and Fe3O4based Fenton process because on one hand,the Fe3+can scavenge the photo-excited electrons, thus greatly inhibiting the recombination of electrons and holes.Note that the PMS could also scavenge the photo-excited electrons, but from the experiment result(Fig.S5),the scavenge effect is not significant;on the other hand,the Fe3+can be recovered quickly to generate Fe2+to promote the Fenton-like reaction.It is well known that the lifetime of these radicals is very short,which can be easily recombined to form H2O2or SO42-, exhibiting a much smaller oxidation potential.The presence of void spaces can effectively reduce this effect because they can provide enough space to enrich the BPA modules to get close to the radicals, thus achieving an excellent degradation performance.Finally, the radicals can oxide the BPA molecules to small intermediates and then partially be mineralized into CO2and H2O, which has been proved by the total organic carbon (TOC)degradation test.

    In summary, we have successfully prepared the yolk-shell structured Fe3O4@void@c-mTiO2micro-reactor through a combined St?ber coating method and an ultrasound assisted etching process.The Fe3O4@void@c-mTiO2NPs with a high specific surface area and a well-defined yolk-shell structure exhibit a remarkable performance for degrading BPA due to the synergic effect between the TiO2shells based photocatalytic process and the Fe3O4cores based Fenton-like reaction.More importantly, the void space can act as a micro-reactor, providing a special place for the catalytic reaction.Furthermore, the catalyst can work efficiently in both acidic and neutral condition.Owing to the high magnetization,the catalyst can be conveniently recovered by a hand-held magnet and be recycled for 5 times without significant loss of activity.This study provides a novel way for the design of unique micro-reactor catalyst for the photocatalytic Fenton-like reaction.

    Declaration of competing interest

    The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

    Acknowledgments

    This work is supported by the National Natural Science Foundation of China (Nos.5182220221972163 and 51772050),the Fundamental Research Funds for the Central Universities (No.2232020D-02), Shanghai Sailing Program (No.20YF1400500),Shanghai Natural Science Foundation (No.20ZR1401500), Shanghai Rising-Star Program (No.18QA1400100), Youth Top-notch Talent Support Program of Shanghai, Science and Technology Commission of Shanghai Municipality(No.19520713200),Shanghai Scientific and Technological Innovation Project (No.19JC1410400), Key Basic Research Program of Science and Technology Commission of Shanghai Municipality (No.20JC1415300), DHU Distinguished Young Professor Program and Fundamental Research Funds for the Central Universities.

    Appendix A.Supplementary data

    Supplementary material related to this article can be found,in the online version, at doi:https://doi.org/10.1016/j.cclet.2020.09.061.

    高清毛片免费观看视频网站| 身体一侧抽搐| 国产成+人综合+亚洲专区| 日韩欧美国产在线观看| 制服人妻中文乱码| 91大片在线观看| 日本在线视频免费播放| 亚洲黑人精品在线| 天堂√8在线中文| 搡老岳熟女国产| 国产在线观看jvid| www.自偷自拍.com| 身体一侧抽搐| 国产黄片美女视频| 观看免费一级毛片| 中文字幕最新亚洲高清| 国内久久婷婷六月综合欲色啪| 色尼玛亚洲综合影院| 国产精品永久免费网站| 老司机福利观看| 亚洲avbb在线观看| 国产97色在线日韩免费| 十八禁人妻一区二区| 成在线人永久免费视频| 男女床上黄色一级片免费看| 国产精品一及| 在线视频色国产色| 欧美在线黄色| 亚洲片人在线观看| 少妇被粗大的猛进出69影院| 国产精品香港三级国产av潘金莲| 男人舔奶头视频| 欧美高清成人免费视频www| 国产av又大| 国产伦人伦偷精品视频| 亚洲欧美一区二区三区黑人| videosex国产| 婷婷六月久久综合丁香| 亚洲自拍偷在线| 精华霜和精华液先用哪个| 亚洲成人中文字幕在线播放| 日韩欧美精品v在线| 最好的美女福利视频网| 欧美av亚洲av综合av国产av| 亚洲国产精品999在线| 亚洲国产精品sss在线观看| 人人妻,人人澡人人爽秒播| 此物有八面人人有两片| 97碰自拍视频| 成人国产一区最新在线观看| 日韩欧美国产一区二区入口| 午夜福利18| 国产不卡一卡二| 国产一区在线观看成人免费| 欧美在线黄色| 亚洲成人精品中文字幕电影| 美女午夜性视频免费| 久久中文看片网| 99在线人妻在线中文字幕| 中文字幕人妻丝袜一区二区| 日韩欧美三级三区| 久久久国产精品麻豆| 国产亚洲精品久久久久5区| 亚洲aⅴ乱码一区二区在线播放 | 一进一出抽搐动态| 国产精品美女特级片免费视频播放器 | 亚洲熟女毛片儿| 午夜福利高清视频| 精品久久久久久,| 国产av一区二区精品久久| 国产91精品成人一区二区三区| 亚洲精品美女久久av网站| 免费观看人在逋| 最近最新免费中文字幕在线| 丝袜人妻中文字幕| 欧美成狂野欧美在线观看| 非洲黑人性xxxx精品又粗又长| 免费看十八禁软件| 日本精品一区二区三区蜜桃| 天天躁夜夜躁狠狠躁躁| 一本综合久久免费| 亚洲国产精品久久男人天堂| 成年人黄色毛片网站| 亚洲国产欧美人成| 亚洲国产精品sss在线观看| 三级男女做爰猛烈吃奶摸视频| 亚洲天堂国产精品一区在线| 麻豆国产av国片精品| 亚洲无线在线观看| 国产一区二区在线观看日韩 | 国产在线精品亚洲第一网站| 香蕉国产在线看| 香蕉丝袜av| 久久久水蜜桃国产精品网| 日韩成人在线观看一区二区三区| 超碰成人久久| 99国产精品一区二区三区| 亚洲欧美精品综合一区二区三区| 动漫黄色视频在线观看| 久久久久久人人人人人| 999久久久国产精品视频| 亚洲真实伦在线观看| 国产不卡一卡二| 欧美黑人欧美精品刺激| 国产精品精品国产色婷婷| 亚洲精华国产精华精| 欧美日韩福利视频一区二区| 蜜桃久久精品国产亚洲av| 男女那种视频在线观看| 国产激情偷乱视频一区二区| 国产亚洲精品av在线| 成人高潮视频无遮挡免费网站| 一边摸一边做爽爽视频免费| 黄色 视频免费看| 老熟妇仑乱视频hdxx| 波多野结衣高清无吗| 男女下面进入的视频免费午夜| 免费在线观看完整版高清| 亚洲av日韩精品久久久久久密| а√天堂www在线а√下载| 桃红色精品国产亚洲av| 两人在一起打扑克的视频| 国产高清videossex| 亚洲av片天天在线观看| 日本熟妇午夜| 麻豆av在线久日| 亚洲五月婷婷丁香| 99精品久久久久人妻精品| 99久久综合精品五月天人人| 中文字幕最新亚洲高清| 亚洲国产日韩欧美精品在线观看 | 久久天躁狠狠躁夜夜2o2o| 在线观看午夜福利视频| 午夜老司机福利片| 亚洲第一欧美日韩一区二区三区| 精品久久久久久久久久久久久| 亚洲精品av麻豆狂野| www日本在线高清视频| 全区人妻精品视频| 人人妻人人澡欧美一区二区| 91麻豆精品激情在线观看国产| 久久精品综合一区二区三区| 久久天躁狠狠躁夜夜2o2o| 美女 人体艺术 gogo| 亚洲avbb在线观看| 黄色毛片三级朝国网站| 欧美精品亚洲一区二区| 久久久久久人人人人人| 欧美黑人精品巨大| 国产精品日韩av在线免费观看| 欧美在线一区亚洲| 在线观看免费日韩欧美大片| 久久久久性生活片| 国产人伦9x9x在线观看| 搞女人的毛片| 久久婷婷成人综合色麻豆| 日韩成人在线观看一区二区三区| 亚洲,欧美精品.| 成在线人永久免费视频| 亚洲五月婷婷丁香| 首页视频小说图片口味搜索| 黄色a级毛片大全视频| 亚洲成av人片在线播放无| 亚洲av五月六月丁香网| 久久久久久九九精品二区国产 | 好男人在线观看高清免费视频| 亚洲欧美精品综合久久99| 50天的宝宝边吃奶边哭怎么回事| 少妇熟女aⅴ在线视频| 国内少妇人妻偷人精品xxx网站 | 亚洲国产精品999在线| 亚洲精品美女久久av网站| av超薄肉色丝袜交足视频| 国产日本99.免费观看| 国产精品一区二区免费欧美| 亚洲一区二区三区不卡视频| 动漫黄色视频在线观看| 日韩精品免费视频一区二区三区| 成在线人永久免费视频| 99riav亚洲国产免费| 久久精品国产99精品国产亚洲性色| 男女那种视频在线观看| 亚洲自偷自拍图片 自拍| 国产亚洲av高清不卡| 97人妻精品一区二区三区麻豆| 亚洲国产欧洲综合997久久,| 亚洲一码二码三码区别大吗| 女警被强在线播放| 午夜久久久久精精品| 韩国av一区二区三区四区| 日本黄色视频三级网站网址| 日本五十路高清| 美女高潮喷水抽搐中文字幕| 欧美成人性av电影在线观看| 久久久国产成人免费| 欧洲精品卡2卡3卡4卡5卡区| 亚洲成av人片在线播放无| 在线观看www视频免费| 美女午夜性视频免费| 免费高清视频大片| 啪啪无遮挡十八禁网站| 久久久国产成人精品二区| 99精品在免费线老司机午夜| 精品不卡国产一区二区三区| 国产又色又爽无遮挡免费看| 色综合站精品国产| 午夜福利视频1000在线观看| 91麻豆av在线| 丁香六月欧美| 在线观看免费视频日本深夜| 国产一区二区在线观看日韩 | 很黄的视频免费| 一级毛片女人18水好多| 国产精品98久久久久久宅男小说| 亚洲欧美日韩无卡精品| 露出奶头的视频| 俺也久久电影网| 精品久久久久久成人av| 久久久久免费精品人妻一区二区| 熟女电影av网| 久久香蕉精品热| 老熟妇乱子伦视频在线观看| 亚洲国产高清在线一区二区三| 欧美日本视频| 午夜精品一区二区三区免费看| 制服人妻中文乱码| 美女扒开内裤让男人捅视频| 日本撒尿小便嘘嘘汇集6| 国产日本99.免费观看| xxxwww97欧美| 欧美3d第一页| 日韩有码中文字幕| 亚洲欧美日韩高清专用| 国产视频内射| 国产真实乱freesex| 亚洲人成电影免费在线| 久99久视频精品免费| 日本撒尿小便嘘嘘汇集6| 亚洲人成网站高清观看| 精品福利观看| 美女大奶头视频| 精品国产乱码久久久久久男人| 日韩有码中文字幕| 精品国内亚洲2022精品成人| 亚洲熟女毛片儿| 日韩欧美一区二区三区在线观看| 亚洲av日韩精品久久久久久密| 国产精品美女特级片免费视频播放器 | 91av网站免费观看| 国产成人一区二区三区免费视频网站| 啦啦啦韩国在线观看视频| 国产精品1区2区在线观看.| 日韩欧美精品v在线| videosex国产| 欧美日韩福利视频一区二区| 脱女人内裤的视频| 麻豆久久精品国产亚洲av| 美女黄网站色视频| 俺也久久电影网| 淫妇啪啪啪对白视频| 国产午夜福利久久久久久| 国产精品,欧美在线| 久久久久九九精品影院| 中文字幕最新亚洲高清| 一二三四在线观看免费中文在| 日韩 欧美 亚洲 中文字幕| av视频在线观看入口| 国产单亲对白刺激| 久久精品国产综合久久久| 久久欧美精品欧美久久欧美| 国产精品日韩av在线免费观看| 很黄的视频免费| 国产亚洲精品综合一区在线观看 | 欧美人与性动交α欧美精品济南到| 精品国产乱子伦一区二区三区| 亚洲电影在线观看av| www.999成人在线观看| 成人手机av| 亚洲人成网站高清观看| 成人特级黄色片久久久久久久| 99热只有精品国产| 麻豆成人午夜福利视频| 国产激情欧美一区二区| 亚洲专区中文字幕在线| 久久久国产精品麻豆| 夜夜夜夜夜久久久久| 香蕉久久夜色| 亚洲成人中文字幕在线播放| 日韩av在线大香蕉| 亚洲精品国产一区二区精华液| 精品福利观看| 免费av毛片视频| 在线观看免费日韩欧美大片| 亚洲在线自拍视频| 每晚都被弄得嗷嗷叫到高潮| 亚洲18禁久久av| 亚洲人成电影免费在线| 亚洲精品av麻豆狂野| 日本五十路高清| 日韩欧美免费精品| www国产在线视频色| 欧美日韩精品网址| 亚洲片人在线观看| АⅤ资源中文在线天堂| 在线观看午夜福利视频| 国产人伦9x9x在线观看| 久久精品91蜜桃| 午夜视频精品福利| 亚洲,欧美精品.| 国产伦人伦偷精品视频| 亚洲一卡2卡3卡4卡5卡精品中文| 国产精品野战在线观看| 97碰自拍视频| 久久中文字幕人妻熟女| 久久久久性生活片| 欧美 亚洲 国产 日韩一| 国产一区二区在线观看日韩 | 91大片在线观看| 国产午夜福利久久久久久| 麻豆国产97在线/欧美 | 一级毛片高清免费大全| 国产爱豆传媒在线观看 | 国产激情欧美一区二区| 国产野战对白在线观看| 欧美成人一区二区免费高清观看 | 国产99久久九九免费精品| 好男人电影高清在线观看| 亚洲性夜色夜夜综合| 两人在一起打扑克的视频| 两性午夜刺激爽爽歪歪视频在线观看 | videosex国产| 桃色一区二区三区在线观看| 中文资源天堂在线| 国产真人三级小视频在线观看| 1024视频免费在线观看| 黄色a级毛片大全视频| 亚洲 国产 在线| 成在线人永久免费视频| 精品欧美一区二区三区在线| av免费在线观看网站| 一二三四社区在线视频社区8| 十八禁人妻一区二区| 中文字幕久久专区| 精品电影一区二区在线| 欧美日韩乱码在线| 亚洲第一欧美日韩一区二区三区| 免费在线观看视频国产中文字幕亚洲| 国产不卡一卡二| 99riav亚洲国产免费| 啦啦啦观看免费观看视频高清| 久久精品人妻少妇| 国产一区二区三区在线臀色熟女| 国产v大片淫在线免费观看| 中文亚洲av片在线观看爽| 女生性感内裤真人,穿戴方法视频| 狂野欧美白嫩少妇大欣赏| 亚洲国产看品久久| 日韩欧美免费精品| www.精华液| 欧美日韩黄片免| 欧美性猛交黑人性爽| av片东京热男人的天堂| 色老头精品视频在线观看| 男女床上黄色一级片免费看| 黄色片一级片一级黄色片| 欧美精品啪啪一区二区三区| 国产av一区二区精品久久| av福利片在线| 国产精品乱码一区二三区的特点| av欧美777| 国产欧美日韩一区二区精品| 好看av亚洲va欧美ⅴa在| 黄色女人牲交| 亚洲成人久久爱视频| 熟妇人妻久久中文字幕3abv| 色噜噜av男人的天堂激情| 最近在线观看免费完整版| 免费在线观看视频国产中文字幕亚洲| 国产欧美日韩一区二区三| 女警被强在线播放| 两性午夜刺激爽爽歪歪视频在线观看 | 久久中文看片网| 无人区码免费观看不卡| 久久久久国产精品人妻aⅴ院| 亚洲精品色激情综合| 性欧美人与动物交配| 亚洲中文字幕日韩| 久久久久久久午夜电影| 亚洲av电影不卡..在线观看| 人妻夜夜爽99麻豆av| 黄频高清免费视频| 久久久久国产一级毛片高清牌| 变态另类成人亚洲欧美熟女| 亚洲精品色激情综合| 国产成人一区二区三区免费视频网站| 国产黄片美女视频| 欧美黑人欧美精品刺激| 国产精品久久视频播放| 亚洲成a人片在线一区二区| 淫妇啪啪啪对白视频| 国产精品免费视频内射| 美女免费视频网站| 欧美一区二区国产精品久久精品 | 好男人在线观看高清免费视频| 日本在线视频免费播放| 免费无遮挡裸体视频| avwww免费| 99国产精品一区二区蜜桃av| 成人国语在线视频| 国产亚洲精品一区二区www| 欧美+亚洲+日韩+国产| 19禁男女啪啪无遮挡网站| 给我免费播放毛片高清在线观看| 成人永久免费在线观看视频| 精品国产美女av久久久久小说| bbb黄色大片| 精品一区二区三区视频在线观看免费| 男女之事视频高清在线观看| 窝窝影院91人妻| 欧美午夜高清在线| 国产视频内射| 一区二区三区高清视频在线| 51午夜福利影视在线观看| 中文字幕高清在线视频| 日韩欧美一区二区三区在线观看| 国产日本99.免费观看| 色哟哟哟哟哟哟| 国产精品久久视频播放| 亚洲在线自拍视频| 国产精品亚洲一级av第二区| 国产午夜福利久久久久久| 欧美精品亚洲一区二区| 国产麻豆成人av免费视频| 亚洲av电影在线进入| 亚洲美女视频黄频| 国产不卡一卡二| 亚洲国产欧美一区二区综合| 国产在线精品亚洲第一网站| 亚洲精品一区av在线观看| 欧美成人一区二区免费高清观看 | 又黄又粗又硬又大视频| 哪里可以看免费的av片| 国产av一区在线观看免费| 亚洲自拍偷在线| 在线观看日韩欧美| 在线a可以看的网站| 俄罗斯特黄特色一大片| 精品国产乱子伦一区二区三区| 亚洲美女视频黄频| 最新在线观看一区二区三区| 激情在线观看视频在线高清| 欧美 亚洲 国产 日韩一| 变态另类丝袜制服| 国产人伦9x9x在线观看| 97人妻精品一区二区三区麻豆| bbb黄色大片| 精品国产亚洲在线| 69av精品久久久久久| 韩国av一区二区三区四区| 久久精品综合一区二区三区| 两个人看的免费小视频| 成人三级黄色视频| 免费在线观看亚洲国产| 亚洲国产高清在线一区二区三| 老鸭窝网址在线观看| 亚洲专区字幕在线| 国产精品日韩av在线免费观看| 男女那种视频在线观看| 亚洲美女视频黄频| 99久久综合精品五月天人人| 亚洲成人精品中文字幕电影| 久久这里只有精品19| 欧美日韩黄片免| 母亲3免费完整高清在线观看| 成人永久免费在线观看视频| 90打野战视频偷拍视频| 国产成人av激情在线播放| 在线永久观看黄色视频| 精品久久久久久成人av| 在线视频色国产色| xxxwww97欧美| 天天躁夜夜躁狠狠躁躁| 亚洲五月婷婷丁香| 精品少妇一区二区三区视频日本电影| 欧美在线一区亚洲| 白带黄色成豆腐渣| av视频在线观看入口| 免费在线观看视频国产中文字幕亚洲| 亚洲人成77777在线视频| 中文在线观看免费www的网站 | 日韩av在线大香蕉| 99久久99久久久精品蜜桃| 久久香蕉国产精品| 欧美久久黑人一区二区| 在线永久观看黄色视频| 国产精品久久电影中文字幕| 国产男靠女视频免费网站| 一进一出抽搐动态| 免费在线观看影片大全网站| 亚洲精品久久国产高清桃花| 国产精品一区二区精品视频观看| 两个人视频免费观看高清| 中文资源天堂在线| 久久久久久大精品| 成人一区二区视频在线观看| 国产成年人精品一区二区| 制服人妻中文乱码| 在线永久观看黄色视频| 国产av一区在线观看免费| 在线永久观看黄色视频| 国产精品 欧美亚洲| 久久精品夜夜夜夜夜久久蜜豆 | 岛国在线观看网站| 国产高清有码在线观看视频 | 国产在线观看jvid| 首页视频小说图片口味搜索| 婷婷精品国产亚洲av在线| 免费在线观看黄色视频的| 不卡一级毛片| 午夜福利视频1000在线观看| 婷婷精品国产亚洲av| 亚洲七黄色美女视频| 亚洲va日本ⅴa欧美va伊人久久| 91av网站免费观看| 欧美日韩国产亚洲二区| 久久中文字幕人妻熟女| 欧美乱码精品一区二区三区| 一个人免费在线观看的高清视频| 99国产精品99久久久久| 琪琪午夜伦伦电影理论片6080| 看片在线看免费视频| 色综合站精品国产| 啦啦啦观看免费观看视频高清| 天堂动漫精品| 午夜精品一区二区三区免费看| 免费在线观看完整版高清| 观看免费一级毛片| 精品乱码久久久久久99久播| 国产又黄又爽又无遮挡在线| 欧美午夜高清在线| 久久午夜综合久久蜜桃| 国产精品一及| 天堂影院成人在线观看| 宅男免费午夜| 一本精品99久久精品77| 18禁国产床啪视频网站| 亚洲在线自拍视频| 长腿黑丝高跟| 亚洲 欧美一区二区三区| 久久香蕉国产精品| 真人做人爱边吃奶动态| 久久久国产精品麻豆| 看黄色毛片网站| 精品久久久久久久毛片微露脸| 久久精品国产综合久久久| 黄色视频,在线免费观看| 国产伦在线观看视频一区| 久久久精品欧美日韩精品| 韩国av一区二区三区四区| 精品国产乱码久久久久久男人| 免费在线观看视频国产中文字幕亚洲| 成人午夜高清在线视频| 午夜激情av网站| 丝袜人妻中文字幕| 国产99白浆流出| 麻豆国产av国片精品| 国内少妇人妻偷人精品xxx网站 | 中文字幕精品亚洲无线码一区| 人人妻,人人澡人人爽秒播| bbb黄色大片| av天堂在线播放| 国产单亲对白刺激| 男女下面进入的视频免费午夜| 国产高清videossex| 美女高潮喷水抽搐中文字幕| 亚洲 欧美一区二区三区| 九九热线精品视视频播放| 亚洲成av人片在线播放无| 欧美性猛交╳xxx乱大交人| 757午夜福利合集在线观看| 99久久无色码亚洲精品果冻| av福利片在线观看| 18禁裸乳无遮挡免费网站照片| 动漫黄色视频在线观看| 欧美色视频一区免费| 18禁观看日本| 欧美丝袜亚洲另类 | 一本综合久久免费| 成人午夜高清在线视频| 三级男女做爰猛烈吃奶摸视频| 久久性视频一级片| 黄色 视频免费看| 老司机午夜十八禁免费视频| 搡老岳熟女国产| 高清在线国产一区| 亚洲精品色激情综合| 波多野结衣巨乳人妻| 日韩欧美免费精品| www日本在线高清视频| 色精品久久人妻99蜜桃| 日本黄色视频三级网站网址| 欧美日韩一级在线毛片| 亚洲自拍偷在线| 成人亚洲精品av一区二区| 香蕉av资源在线| 窝窝影院91人妻| 最近视频中文字幕2019在线8| 亚洲自偷自拍图片 自拍| 人成视频在线观看免费观看| 欧美成人午夜精品| 别揉我奶头~嗯~啊~动态视频| 国产精品影院久久| 婷婷丁香在线五月| 色综合亚洲欧美另类图片| 91老司机精品|