• <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 ?

    Hydroxyl radical induced from hydrogen peroxide by cobalt manganese oxides for ciprofloxacin degradation

    2023-01-30 06:49:18ShundiWngXiodongZhngGuozhuChenBoLiuHongmeiLiJunhuHuJunweiFuMinLiu
    Chinese Chemical Letters 2022年12期

    Shundi Wng ,Xiodong Zhng ,Guozhu Chen,Bo Liu,Hongmei Li ,Junhu Hu,Junwei Fu,*,Min Liu,*

    a Hunan Joint International Research Center for Carbon Dioxide Resource Utilization,School of Physics and Electronics,State Key Laboratory of Powder Metallurgy,Hunan Provincial Key Laboratory of Chemical Power Sources,Central South University,Changsha 410083,China

    b School of Materials Science and Engineering,Zhengzhou University,Zhengzhou 450 002,China

    Keywords:Catalytic decomposition Hydrogen peroxide Advanced oxidation processes Ciprofloxacin Pollutant degradation

    ABSTRACT Advanced oxidation processes(AOPs)are promising technology to remove organic pollutant in water.However,the main problem in the AOPs is the low generation of hydroxyl radical(?OH)owing to the low decomposition efficiency of hydrogen peroxide(H2O2).Herein,the spinel type cobalt acid manganese(MnCo2O4)with flower morphology was fabricated through a co-precipitation method.In situ Fourier transform infrared spectroscopy confirms that the MnCo2O4 with the optimal molar ratio of Co and Mn precursors(CM3,Co:Mn=3)has more Lewis acid sites compared with single metal oxide catalysts(Co3O4 and Mn2O3),leading to the excellent performances for H2O2 decomposition rate constant on CM3,which is about 15.03 and 4.21 times higher than those of Co3O4 and Mn2O3,respectively.As a result,the obtained CM3 shows a higher ciprofloxacin degradation ratio than that of Co3O4 and Mn2O3.Furthermore,CM3 shows an excellent stability during several cycles.This work proposes effective catalysts for ciprofloxacin decomposition and provides feasible route for treating practical environmental problems.

    Ciprofloxacin(CIP),with a total use of 5340 tons in China,has been considered as one of the most commonly used fluoroquinolones[1,2].CIP has been detected in surface water,municipal wastewater,pharmaceutical wastewater and groundwater.These highest concentrations were 2500μg/L,14 mg/L,31 mg/L and 14μg/L,respectively[3–5].The fluoroquinolones may have adverse effect on aquatic ecology by inducing the proliferation of bacterial resistance[6–9].However,because high concentrations of organic pollutants are toxic to biochemical reactions,microorganisms and conventional physical and chemical treatments cannot effectively remove these pollutants[10,11].Advanced oxidation processes(AOPs)with hydrogen peroxide(H2O2)are considered as a promising environmentally friendly strategy for the removal of organic pollutants[12–14].AOPs can be effectively applied to organics degradation by improving the biodegradability or directly mineralizing of pollutants by oxidation,including Fenton/Fenton-like oxidation[15–18],ozonation[19–21],photocatalytic oxidation and peroxymonosulfate oxidation[22–25].Among these technologies,the Fenton-like catalytic system is a promising choice for AOPs on account of the easy separation and recovery of solid catalyst,the wide working pH range and the high organic removal efficiency[26,27].However,this system suffers from low content of free radicals and poor removal efficiency of organic pollutants,which is originated from slow decomposition of H2O2.This inspires us to design and develop efficient catalysts to produce more free radicals during AOPs.

    H2O2is a Lewis base that is readily absorbed by the Lewis acid sites and produces a large number of?OH[28].However,catalytic performance of single metal oxide is limited by the insufficient Lewis acid sites and the slow redox cycles of metal valence[29,30].In order to produce more oxygen-containing free radicals,previous studies reported that doping MnOxwith other metal to form mixed metal oxides tended to produce more oxygen-containing free radicals[26].For examples,the chemical states and properties of Mn can be substantially tuned in the perovskite-and spineltype oxides[31–34].Composite metal oxides possess the sufficient Lewis acid sites and fast redox cycles of metal valence due to the interactions between different metal atoms[35–37].Miet al.have investigated the electron communication between the different metal sites in composite metal oxides[38].The result indicated that the composite metal oxides have synergistic effect Co and Mn sites,which is beneficial for generating?OH abundantly.Therefore,we considered that composite metal oxides can greatly improve the catalytic oxidation efficiency.

    Fig.1.(a)XRD patterns of CM3,Mn2 O3,Co3O4 candidates.(b)SEM and(c)TEM images of CM3.(d)HRTEM and SAED pattern(inset)images of CM3 with submicronsized particles.(f-h)Elemental mapping of Mn,Co and O for CM3(e).

    In this study,the spinel MnCo2O4(CM3)has been synthesized through a facile co-precipitation method.X-ray diffraction spectroscopy(XRD),scanning electron microscopy(SEM)and transmission electron microscopy(TEM)were carried out to verify its crystal structure and morphology.The performance test results show that the spinel CM3 possesses excellent performance in the decomposition of H2O2due to the synergistic effect of Co and Mn.The rate constant of H2O2degradation rate constant for CM3 was about 15.03 and 4.21 times higher than those of Co3O4and Mn2O3,respectively.Meanwhile,as the typical organic quinolones,CIP was selected for the target organic pollutant to evaluate the efficiency of AOPs among catalysts.Compared with single metal oxides,spinel CM3 can remarkably reduce the energy barrier of producing?OH.Therefore,CM3/H2O2system shows great degradation ratio of CIP(10 mg/L),which reach up to 81%in 100 min,and it is higher than that of Co3O4and Mn2O3.The experimental results and density functional theory(DFT)calculations reveal the synergistic effect of Co and Mn in CM3 for outstanding catalytic performance.Thus,the CM3 shows outstanding catalytic performance and provides feasible way for treating practical environmental problems.

    The crystal structure of the synthesized samples was analyzed by XRD(Fig.1a)[39–41].The crystal structure of control samples is consistent with the standard sample,which can be correspond to the cubic Mn2O3(PDF#41–1442)and cubic spinel Co3O4(PDF#74–1657),respectively.Among the binary transition metal oxide,the obtained CM3 agrees well with the standard spinel MnCo2O4(PDF#23–1237),indicating the successful synthesis of single-phase cubic spinel.

    Fig.2.XPS spectra of CM3,Co3O4 and Mn2 O3:(a)Co 2p,(b)Mn 2p.

    To characterize the morphology and structure of catalysts,SEM and TEM were carried out(Figs.1b-h).Clearly,the CM3 has a diameter of about 150 nm with well nanoflower-like structures and assembled by nanosheets(Fig.1b).The CM3 shows high specific surface area of 111.4 m2/g(Table S1 and Fig.S1 in Supporting information),favoring for the heterogeneous catalytic reaction.On the contrary,the prepared Mn2O3and Co3O4show a morphology of nanoparticle(Fig.S2 in Supporting information).

    TEM image confirms the nanoflower-like structure which is assembled by nanosheets(Fig.1c).The high-resolution transmission electron microscopy(HRTEM)image and the selected area electron diffraction(SAED)of CM3 are shown in Fig.1d.The inter-planar distance measured in HRTEM image was measured to be 2.9?A,which matches well to the(220)planes of the spinel MnCo2O4(Fig.1d).The SAED pattern exhibits concentric rings composed of bright discrete diffraction spots of CM3,indicating that the polycrystalline nature for CM3.The diffraction rings are indexed to(111),(220),(311),(400),(511),and(440)planes of XRD patterns in MnCo2O4structure[42].The investigation based on energy dispersive X-ray spectroscopy(Figs.1e-h)reveals a uniform distribution of Mn,Co and O in the CM3 nanoflower-like structure.

    In order to identify the oxidation state of Co and Mn in the CM3,Co3O4and Mn2O3,the X-ray photoelectron spectroscopy(XPS)of the Co and Mn 2p were recorded and fitted as Fig.2[43].For the Co3O4(Fig.2a),two main peaks of Co 2p3/2and Co 2p1/2are located at 781.05 and 796.40 eV,respectively[44].For the CM3(Fig.2a),these two main peaks are located at 781.12 and 796.26 eV,which indicates co-exist of Co2+and Co3+species in the Co3O4and CM3[45].For the Mn2O3(Fig.2b),two main peaks are located at 643.1 and 654.9 eV,respectively[46].For the CM3(Fig.2b),these two main peaks shift to 642.9 and 654.5 eV,demonstrating that introducing Co can well adjust the valence state of Mn[47].

    The catalytic degradation experiments were conducted to evaluate the catalytic performances of different catalysts.The concentration of H2O2was determined by titanium potassium oxalate method(Fig.S3 in Supporting information)[48,49].As shown in Fig.3a,within 15 min,the H2O2degradation efficiencies for Mn2O3and Co3O4are about 40%and 20%,respectively.Notably,the H2O2degradation efficiency for CM3 is up to 99%.The rate constant(k)was then evaluated based on linear fitting between?ln(C/C0)and timet[50,51].As shown in Fig.3b,the H2O2degradation rate constant in the CM3(0.284 min?1)was about 15.03 and 4.21 times higher than those of Co3O4(0.0189 min?1)and Mn2O3(0.0675 min?1),confirming the high performance of CM3.Furthermore,the catalytic activity did not decrease obviously,indicating its good stability and long lifetime(Fig.S4 in Supporting information).

    Fig.3.(a)H2O2 degradation in the different catalyst systems.Conditions:[H2O2]ini=30 mmol/L,catalyst=0.05 g/L in 100 mL reaction solution.(b)The fitted plots of?ln(C/C0)with the reaction time in H2O2 degradation.(c)Effects of H2O2 dosage on CIP degradation in CM3 catalyst system.Conditions:catalyst=0.2 g/L,[CIP]ini=10 mg/L in 100 mL reaction solution.(d)CIP degradation in the different catalyst systems.Conditions:[CIP]ini=10 mg/L,[H2O2]ini=68 mg/L and catalyst=0.2 g/L in 100 mL reaction solution.

    The catalytic performances of the as-prepared oxides for wastewater treatment were further compared.CIP,as a typical industrial pollutant,is chosen as a model to examine the degradation efficiency of organic pollutants by the as-prepared oxides.The effects of catalyst dosage and temperature on CIP degradation were studied(Figs.S5 and S6 in Supporting information).The influence of H2O2dosage on the performance of CM3 is shown in Fig.3c.The results showed that degradation efficiency of CIP increased to 81%with the dosage of H2O2increasing from 0 mg/L to 68 mg/L.While a further increase of H2O2dosage(from 68 mg/L to 136 mg/L)hindered the degradation of ciprofloxacin(decreased from 81%to 64%).The reason can be attributed to that the residual H2O2can act as a sacrificial agent for free radicals(?OH)[52].These results showed that the optimal H2O2concentration was 68 mg/L.Under the optimal H2O2dosage,the binary transition metal oxides CM3(81%)have excellent CIP degradation performance compared with single metal oxides Co3O4(22%)and Mn2O3(34%)in Fig.3d.The initial rate constants of CM3,Mn2O3and Co3O4catalyst systems are 0.11 min?1,0.023 min?1and 0.01 min?1,respectively(Fig.S7 and Table S2 in Supporting information)[53,54].And the CM3 Fenton-like system can improve the TOC removal rate of CIP from 10.23%and 22.6%to 50.33%comparing to the Co3O4and Mn2O3,respectively(Figs.S8 and S9 in Supporting information)[55].

    In order to explore which free radicals involved the CIP degradation,p-benzoquinone(BQ)andt-butanol(TBA)were added to the reaction solution to detect the reactive radicals[16,56].Fig.4a shows that the degradation of CIP was greatly inhibited by adding 50 mmol/L BQ or 50 mmol/L TBA,indicating that both O2??and?OH promoted the degradation of CIP.Apparently,significant inhibiting effect was observed in the presence of 50 mmol/L TBA,implying that?OH radicals play the most important role in CIP degradation.In order to reveal the reaction mechanism of the CIP degradation,we detect free radical species by oxidation current,free radical quenching,5,5-dimethylpyrroline-1-oxide(DMPO)trapped electron paramagnetic resonance(EPR)technique and photoluminescence spectra of benzoic acid mixed[57,58].In the chronoamperometry curves,it can be observed that the oxidation current in H2O2solution increases after adding CM3.While the change before and after adding CM3 in blank solution is negligible(Fig.4b).This indicates that some species are produced in the interaction between CM3 and H2O2.Due to its high reducibility,the most likely increase in oxidation current is?OOH,which is more reducible than H2O2.In addition,we detected the?OH in different catalyst systems with DMPO trapped EPR technique[59].As shown in Fig.4c,there are more?OH in CM3-H2O2system.We detected?OH in different systems by photoluminescence[16].The CM3 has a high fluorescence intensity from the photoluminescence spectra(Fig.4d).The H2O2decomposition efficiency can be obviously increased in the CM3 Fenton-like reaction.Usually,benzoic acid(BA)was used as a probe molecule to detect concentration of?OH[60].In subsequent experiments,2 mmol/L BA was selected as the initial probe concentration.The generation of radicals in the different systems is shown in Fig.4e.Compared with single metal oxides Co3O4and Mn2O3,the addition of the CM3 greatly increased?OH generation.These results demonstrated that CM3 could facilitate the production of more?OH due to the improved decomposition efficiency of H2O2,which leads to the efficient degradation of CIP in CM3-H2O2system.

    To explore the surface acid sites on CM3,the distribution of Br?nsted(B)and Lewis(L)acidity were measured byin-situdiffuse-reflectance infrared Fourier-transform(DRIFT)spectra with pyridine using pyridine as a probe(Fig.4f).Because H2O2is a Lewis base that is readily absorbed by the Lewis acid sites and produces a large number of?OH[28].The band at 1550–1640 cm?1and 1450 cm?1are assigned to found for pyridine absorbed at L acid sites while the 1540 cm?1band is absorption intensity at B acid sites[61].The experimental results show that CM3 exhibited much stronger signal intensity,which indicates that the L acid sites in CM3 are far more than other comparison samples.Note that H2O2was a L base,the enhanced adsorption of H2O2onto these CM3 should contribute to the activation of H2O2for CIP oxidation.Compared with Co3O4and Mn2O3,the formation of L acid sites indicating the presence of synergistic effect between the Co and Mn sites.In addition,the voltammetric integral area of the cyclic voltammetry(CV)was another parameter to reflect the redox-active sites of the catalysts(Fig.S10 in Supporting information)[45,62].CM3 has a large voltammetric integral areas.Indicating the bimetallic oxides has more redox-active sites,which is beneficial for catalytic reactions.This is consistent with the results ofin-situDRIFT spectra.

    From the above analyses,it can be concluded that the freely diffusible?OH formed by the catalyst is the main active substance in the oxidation reaction of the pollutant.In order to understand the synergy between Mn and Co,DFT calculations were performed to compare catalytic activity of Co3O4,Mn2O3and CM3 systems[63].Fig.5 illustrated the free energy change of H2O2decomposition into?OH by the cleavage of O–O bonds on CM3,Co3O4and Mn2O3surface,respectively.The free energy differences of?OH generation on Co3O4,Mn2O3and CM3 were 2.35,2.55 and 3.95 eV,respectively.Compared with Co3O4and Mn2O3,CM3 is more conducive to activation of H2O2to produce?OH.The adsorption of H2O2and the desorption of?OH were calculated(Fig.S11,Tables S3 and S4 in Supporting information).From the adsorption energy of H2O2,the adsorption energy of MnCo2O4(CM3)is more negative,and the O–O bond almost breaks during the adsorption.This indicates that MnCo2O4(CM3)has excellent ability to activate H2O2.From the perspective of?OH desorption energy,Mn2O3has a lower desorption energy,but a higher dissociation energy,which affects its catalytic performance.Moreover,the surface?OH of MnCo2O4(CM3)has moderate desorption energy.In general,MnCo2O4(CM3)is more capable of activating H2O2and generating?OH to degrade CIP.

    Fig.4.(a)Inhibiting effects of different radical scavengers on degradation of CIP by CM3.Conditions:[CIP]ini=10 mg/L,[BQ]=50 mmol/L,[TBA]=50 mmol/L,catalyst=0.2 g/L and[H2O2]ini=68 mg/L in 100 mL reaction solution.(b)Chronoamperometry curves in blank solution,blank solution with CM3,H2O2 solution,and H2 O2 solution with CM3.Tests were made in 50 mmol/L Na2SO4 electrolyte at a scanning rate of 20 mV/s.(c)DMPO spin trapping EPR spectra of?OH.(d)Photoluminescence spectra of benzoic acid mixed with different solutions for the Fenton-like reaction within 100 min.Conditions:[CIP]ini=10 mg/L,[BA]=2 mmol/L,catalyst=0.2 g/L and[H2O2]ini=68 mg/L in 100 mL reaction solution.(e)The generation of radicals in different systems.Conditions:[CIP]ini=10 mg/L,[BA]=2 mmol/L,catalyst=0.2 g/L and[H2 O2]ini=68 mg/L in 100 mL reaction solution.(f)In-situ DRIFTS spectra of catalysts with pyridine as probe at 25°C.

    Fig.5.Free energy diagrams for the H2 O2 decomposition into?OH on surface of CM3(a),Co3 O4(b)and Mn2O3(c),respectively.

    In this study,the spinel type CM3 with significant H2O2decomposition efficiency was fabricated through a co-precipitation method.CM3 has more L acid sites due to the synergistic effect of Co and Mn.Compared with Co3O4and Mn2O3,CM3 plays a significant role on the decomposition of H2O2in a Fenton-like system.The rate constant of H2O2degradation rate constant by CM3 was about 15.03 and 4.21 times higher than that by pure Co3O4and Mn2O3,respectively.Accordingly,the CM3/H2O2system shows great degradation ratio of CIP(10 mg/L),and reaches up to 81%in 100 min,which is higher than that of Co3O4and Mn2O3.Meanwhile,the CM3 shows favorable stability for several cycles.DFT calculations further elucidate the dissociation of H2O2.This work provides a new way to design efficient,stable and harmless Fentonlike catalysts and achieve excellent environmental remediation effect.

    Declaration of competing interest

    The authors declare no conflict of interest.

    Acknowledgments

    The authors gratefully thank the International Science and Technology Cooperation Program (Nos.2017YFE0127800 and 2018YFE0203400),National Natural Science Foundation of China(Nos.21872174,22002189 and U1932148),Hunan Provincial Science and Technology Program(Nos.2017XK2026 and 2017TP1001),Hunan Provincial Natural Science Foundation(Nos.2020JJ2041,2020JJ5691 and 2021JJ30864),Key R&D Program of Hunan Province(No.2020WK2002),Shenzhen Science and Technology Innovation Project(No.JCYJ20180307151313532).

    Supplementary materials

    Supplementary material associated with this article can be found,in the online version,at doi:10.1016/j.cclet.2022.01.055.

    国产高清国产精品国产三级 | 国产免费视频播放在线视频| 精品国产三级普通话版| 一区二区三区精品91| 网址你懂的国产日韩在线| 内地一区二区视频在线| 丝袜美腿在线中文| 一个人观看的视频www高清免费观看| 搡老乐熟女国产| 狂野欧美激情性xxxx在线观看| 国产黄片视频在线免费观看| 精品少妇久久久久久888优播| 国产伦精品一区二区三区视频9| 一区二区av电影网| 欧美性猛交╳xxx乱大交人| 听说在线观看完整版免费高清| 18禁在线播放成人免费| 亚洲av男天堂| 亚洲真实伦在线观看| 久久久久久久久久人人人人人人| 在线天堂最新版资源| 男女那种视频在线观看| 欧美一级a爱片免费观看看| 人人妻人人看人人澡| 亚洲国产日韩一区二区| 欧美最新免费一区二区三区| 两个人的视频大全免费| 男女边摸边吃奶| 亚洲一区二区三区欧美精品 | 又大又黄又爽视频免费| 国产乱人视频| 欧美97在线视频| 亚洲av在线观看美女高潮| 亚洲精品乱码久久久v下载方式| 免费看日本二区| 免费看日本二区| 干丝袜人妻中文字幕| 好男人在线观看高清免费视频| 亚洲自偷自拍三级| 久久久久久久久久成人| 中文在线观看免费www的网站| 国产伦精品一区二区三区四那| 日本熟妇午夜| 日韩,欧美,国产一区二区三区| 亚洲在久久综合| 十八禁网站网址无遮挡 | 又粗又硬又长又爽又黄的视频| 精品人妻偷拍中文字幕| 亚洲第一区二区三区不卡| 亚洲精品久久久久久婷婷小说| 国产一区二区三区av在线| 精品一区二区免费观看| 成人国产av品久久久| 国产亚洲av片在线观看秒播厂| 人妻一区二区av| 日韩欧美 国产精品| 精品国产乱码久久久久久小说| 亚洲国产欧美在线一区| 欧美国产精品一级二级三级 | 免费看光身美女| 国产一区二区三区综合在线观看 | 亚洲最大成人av| 青青草视频在线视频观看| 丝袜美腿在线中文| 在线 av 中文字幕| 亚洲精品日本国产第一区| 在线免费观看不下载黄p国产| 干丝袜人妻中文字幕| 亚洲久久久久久中文字幕| 亚洲在线观看片| 热re99久久精品国产66热6| 婷婷色av中文字幕| 免费黄频网站在线观看国产| 日韩电影二区| a级一级毛片免费在线观看| 一个人看视频在线观看www免费| 免费看光身美女| 色综合色国产| 你懂的网址亚洲精品在线观看| 欧美日韩一区二区视频在线观看视频在线 | 91精品一卡2卡3卡4卡| 久久精品国产鲁丝片午夜精品| 国产日韩欧美在线精品| 亚洲精品一二三| 亚洲最大成人中文| 黄色一级大片看看| 赤兔流量卡办理| 高清视频免费观看一区二区| 中国美白少妇内射xxxbb| 色综合色国产| 大话2 男鬼变身卡| 自拍偷自拍亚洲精品老妇| 最新中文字幕久久久久| 国产一区亚洲一区在线观看| 久久久久久久午夜电影| 久久综合国产亚洲精品| 狂野欧美激情性xxxx在线观看| 丰满乱子伦码专区| 亚洲欧美日韩卡通动漫| 2021少妇久久久久久久久久久| 三级国产精品片| 特大巨黑吊av在线直播| 日日啪夜夜爽| 一级毛片aaaaaa免费看小| 免费av观看视频| 免费看光身美女| 在线a可以看的网站| 日本黄大片高清| 男女边摸边吃奶| 少妇丰满av| 七月丁香在线播放| 深爱激情五月婷婷| 美女xxoo啪啪120秒动态图| 王馨瑶露胸无遮挡在线观看| 免费在线观看成人毛片| 国产久久久一区二区三区| 亚洲天堂国产精品一区在线| 青春草视频在线免费观看| 亚洲无线观看免费| 大香蕉久久网| 日本免费在线观看一区| 2022亚洲国产成人精品| 亚洲美女视频黄频| 久久久国产一区二区| 日日摸夜夜添夜夜爱| 狂野欧美激情性bbbbbb| 亚洲精品国产av蜜桃| 一级爰片在线观看| 久久精品熟女亚洲av麻豆精品| videos熟女内射| 成人一区二区视频在线观看| 小蜜桃在线观看免费完整版高清| 特级一级黄色大片| 大陆偷拍与自拍| 国产精品一区二区性色av| 日韩一本色道免费dvd| 欧美亚洲 丝袜 人妻 在线| 日日啪夜夜撸| 日韩av在线免费看完整版不卡| 26uuu在线亚洲综合色| 高清av免费在线| 18禁在线播放成人免费| 亚洲国产最新在线播放| 精品人妻熟女av久视频| 男女那种视频在线观看| 欧美+日韩+精品| 99视频精品全部免费 在线| 国产一区二区三区av在线| 一边亲一边摸免费视频| 国精品久久久久久国模美| 最近的中文字幕免费完整| 中文字幕亚洲精品专区| 一级爰片在线观看| 女人久久www免费人成看片| 亚洲精品久久久久久婷婷小说| 99热网站在线观看| 午夜免费鲁丝| 五月天丁香电影| 久久久久久久久久久丰满| 午夜视频国产福利| 波野结衣二区三区在线| 日韩一本色道免费dvd| 自拍欧美九色日韩亚洲蝌蚪91 | 黄色日韩在线| av网站免费在线观看视频| 亚洲真实伦在线观看| 啦啦啦在线观看免费高清www| 综合色av麻豆| 日韩欧美精品免费久久| 女人被狂操c到高潮| 亚洲图色成人| 免费人成在线观看视频色| 午夜免费男女啪啪视频观看| 欧美最新免费一区二区三区| 日韩av在线免费看完整版不卡| 精品一区二区免费观看| 综合色av麻豆| 美女cb高潮喷水在线观看| 好男人视频免费观看在线| 下体分泌物呈黄色| 国产91av在线免费观看| 精品人妻一区二区三区麻豆| 麻豆成人av视频| 亚洲色图av天堂| 国产午夜福利久久久久久| 免费看a级黄色片| 五月玫瑰六月丁香| 国产av国产精品国产| 中文精品一卡2卡3卡4更新| 国产亚洲午夜精品一区二区久久 | 观看免费一级毛片| 精品酒店卫生间| 国产免费一级a男人的天堂| 亚洲成人精品中文字幕电影| 国产成人免费观看mmmm| 色视频在线一区二区三区| 国产黄色视频一区二区在线观看| 老女人水多毛片| 免费av不卡在线播放| 亚洲av欧美aⅴ国产| 在线观看三级黄色| 一二三四中文在线观看免费高清| 亚洲欧美一区二区三区国产| 国产日韩欧美在线精品| 内射极品少妇av片p| 街头女战士在线观看网站| 少妇的逼好多水| 王馨瑶露胸无遮挡在线观看| 内地一区二区视频在线| 麻豆成人av视频| 欧美日韩在线观看h| av一本久久久久| 黄色视频在线播放观看不卡| 久久久a久久爽久久v久久| av在线亚洲专区| 三级国产精品欧美在线观看| 99久久精品热视频| 色视频在线一区二区三区| 少妇熟女欧美另类| 联通29元200g的流量卡| 国产精品久久久久久久电影| 久久久久精品久久久久真实原创| 美女xxoo啪啪120秒动态图| 亚洲国产精品成人久久小说| 一级爰片在线观看| 九九在线视频观看精品| 看非洲黑人一级黄片| 18禁在线播放成人免费| 久久99热6这里只有精品| 国产成人午夜福利电影在线观看| 久久精品人妻少妇| 一本—道久久a久久精品蜜桃钙片 精品乱码久久久久久99久播 | 亚洲精品456在线播放app| 免费看不卡的av| 国内少妇人妻偷人精品xxx网站| 国产成人精品婷婷| 亚洲精品影视一区二区三区av| 日本黄色片子视频| 日韩在线高清观看一区二区三区| 寂寞人妻少妇视频99o| 国产精品秋霞免费鲁丝片| 97热精品久久久久久| 日日啪夜夜爽| 在线天堂最新版资源| 亚州av有码| 国产精品嫩草影院av在线观看| 男女那种视频在线观看| 制服丝袜香蕉在线| 国产男女内射视频| 久久久久国产精品人妻一区二区| 国产又色又爽无遮挡免| 精品人妻视频免费看| 日韩强制内射视频| 欧美xxxx性猛交bbbb| 欧美变态另类bdsm刘玥| 午夜福利网站1000一区二区三区| 久久久国产一区二区| 男人爽女人下面视频在线观看| 午夜精品一区二区三区免费看| 我的老师免费观看完整版| 大片电影免费在线观看免费| 亚洲精品日本国产第一区| 国产一区有黄有色的免费视频| 老司机影院毛片| 各种免费的搞黄视频| 最后的刺客免费高清国语| 国产91av在线免费观看| 国产精品.久久久| 久久久久精品久久久久真实原创| 午夜福利视频精品| 别揉我奶头 嗯啊视频| 欧美日韩综合久久久久久| 精品一区二区免费观看| 97热精品久久久久久| 九九爱精品视频在线观看| 国产精品久久久久久久电影| 啦啦啦在线观看免费高清www| 亚洲国产色片| 免费av观看视频| 国产精品国产三级专区第一集| av在线播放精品| 直男gayav资源| 插逼视频在线观看| 国产亚洲91精品色在线| 99热全是精品| 人妻制服诱惑在线中文字幕| 最新中文字幕久久久久| 能在线免费看毛片的网站| 在线亚洲精品国产二区图片欧美 | 亚洲精品久久久久久婷婷小说| 中国国产av一级| 国产亚洲一区二区精品| 一个人看视频在线观看www免费| 日韩大片免费观看网站| 亚洲国产精品成人久久小说| 久久久久久久久久成人| 精品国产三级普通话版| 久久人人爽av亚洲精品天堂 | 婷婷色综合www| 成年女人在线观看亚洲视频 | 别揉我奶头 嗯啊视频| 国产老妇女一区| 亚洲国产精品专区欧美| 男人和女人高潮做爰伦理| 亚洲三级黄色毛片| 日韩欧美 国产精品| 色视频在线一区二区三区| 国产爽快片一区二区三区| 国产精品一区二区三区四区免费观看| 一级毛片 在线播放| 最近2019中文字幕mv第一页| 国产成人午夜福利电影在线观看| eeuss影院久久| 国产成人精品婷婷| 男人添女人高潮全过程视频| 交换朋友夫妻互换小说| 黄色怎么调成土黄色| 国产精品麻豆人妻色哟哟久久| 国产成人精品久久久久久| 日本猛色少妇xxxxx猛交久久| 超碰97精品在线观看| 亚洲精品视频女| 午夜爱爱视频在线播放| 天天躁夜夜躁狠狠久久av| 好男人在线观看高清免费视频| 在线天堂最新版资源| 18禁在线无遮挡免费观看视频| 天天一区二区日本电影三级| 黄色怎么调成土黄色| 色5月婷婷丁香| 久久久久久久午夜电影| 午夜免费男女啪啪视频观看| 久久久精品欧美日韩精品| a级一级毛片免费在线观看| 久久人人爽人人爽人人片va| 99热这里只有是精品50| 一本色道久久久久久精品综合| av黄色大香蕉| 国产精品国产三级国产av玫瑰| 丝瓜视频免费看黄片| 免费播放大片免费观看视频在线观看| 丝瓜视频免费看黄片| 免费播放大片免费观看视频在线观看| 高清毛片免费看| 又大又黄又爽视频免费| 国产在线一区二区三区精| 亚洲美女视频黄频| 国产日韩欧美亚洲二区| 亚洲精品色激情综合| 国产日韩欧美亚洲二区| 黑人高潮一二区| 国产精品麻豆人妻色哟哟久久| 我的女老师完整版在线观看| 国产成人精品一,二区| 国产精品国产三级国产av玫瑰| 国产日韩欧美亚洲二区| 亚洲自偷自拍三级| 777米奇影视久久| 亚洲不卡免费看| 少妇丰满av| 亚洲久久久久久中文字幕| 五月伊人婷婷丁香| 亚洲图色成人| 又大又黄又爽视频免费| 精品人妻一区二区三区麻豆| 国产一区亚洲一区在线观看| 精品视频人人做人人爽| 国产精品爽爽va在线观看网站| 国产精品国产av在线观看| 国产视频首页在线观看| 欧美日本视频| 少妇裸体淫交视频免费看高清| 在线精品无人区一区二区三 | 日本黄色片子视频| 婷婷色综合大香蕉| av线在线观看网站| 久久久久久久久大av| 久久精品国产a三级三级三级| 日韩制服骚丝袜av| 又爽又黄a免费视频| 我的女老师完整版在线观看| 欧美97在线视频| 少妇的逼好多水| av专区在线播放| 精品久久国产蜜桃| 尾随美女入室| 一二三四中文在线观看免费高清| 成人亚洲欧美一区二区av| 一区二区三区乱码不卡18| 一级毛片黄色毛片免费观看视频| 五月天丁香电影| 男的添女的下面高潮视频| 狂野欧美激情性bbbbbb| 国产一区二区三区av在线| 欧美3d第一页| 久久精品国产自在天天线| 18禁动态无遮挡网站| 国内揄拍国产精品人妻在线| 国产亚洲av片在线观看秒播厂| 日韩三级伦理在线观看| 80岁老熟妇乱子伦牲交| 欧美日韩视频高清一区二区三区二| 亚洲在久久综合| 精品少妇久久久久久888优播| 九草在线视频观看| 一区二区三区乱码不卡18| 国产午夜福利久久久久久| av女优亚洲男人天堂| 日韩av在线免费看完整版不卡| 国产乱来视频区| 国产 一区精品| 欧美成人精品欧美一级黄| 久久精品国产自在天天线| av线在线观看网站| 国产男人的电影天堂91| 亚洲av中文字字幕乱码综合| 观看美女的网站| 99久久九九国产精品国产免费| 午夜福利视频精品| 国产午夜福利久久久久久| 午夜爱爱视频在线播放| 91aial.com中文字幕在线观看| 嘟嘟电影网在线观看| 亚洲av成人精品一二三区| 国产大屁股一区二区在线视频| 亚洲一级一片aⅴ在线观看| 国产探花在线观看一区二区| 亚洲av电影在线观看一区二区三区 | 欧美日韩在线观看h| 久久久久久久国产电影| 国产精品秋霞免费鲁丝片| av在线老鸭窝| 国产视频首页在线观看| 黄色一级大片看看| 国产亚洲av嫩草精品影院| 国产爱豆传媒在线观看| 韩国高清视频一区二区三区| 少妇丰满av| 国产 一区 欧美 日韩| 国产国拍精品亚洲av在线观看| 国产成人午夜福利电影在线观看| 91在线精品国自产拍蜜月| 欧美成人精品欧美一级黄| 欧美xxxx黑人xx丫x性爽| 国产 一区 欧美 日韩| 久久99蜜桃精品久久| 狂野欧美激情性bbbbbb| 国产精品偷伦视频观看了| 欧美丝袜亚洲另类| 精品人妻视频免费看| 国产精品蜜桃在线观看| 七月丁香在线播放| 赤兔流量卡办理| 成人漫画全彩无遮挡| 内射极品少妇av片p| 一区二区三区免费毛片| 制服丝袜香蕉在线| 99热6这里只有精品| 欧美日韩精品成人综合77777| 中文字幕人妻熟人妻熟丝袜美| 亚洲国产欧美在线一区| 国产毛片在线视频| 成人无遮挡网站| 国产精品一区二区性色av| 国产乱来视频区| 国内揄拍国产精品人妻在线| 男人添女人高潮全过程视频| 色视频在线一区二区三区| 国产男女超爽视频在线观看| 亚洲欧美一区二区三区国产| eeuss影院久久| tube8黄色片| 国产精品爽爽va在线观看网站| 九草在线视频观看| 好男人在线观看高清免费视频| 在线看a的网站| 一区二区三区乱码不卡18| 国产高清三级在线| 久久鲁丝午夜福利片| 国产一区二区亚洲精品在线观看| 新久久久久国产一级毛片| 国产黄频视频在线观看| 大香蕉97超碰在线| 久久久久国产网址| 亚洲欧美清纯卡通| 特级一级黄色大片| 大片电影免费在线观看免费| 亚洲天堂国产精品一区在线| 久久久久精品久久久久真实原创| tube8黄色片| 国产一区二区亚洲精品在线观看| 伦精品一区二区三区| 能在线免费看毛片的网站| 久久精品人妻少妇| 高清毛片免费看| 九色成人免费人妻av| 搞女人的毛片| 亚洲四区av| 中文欧美无线码| 中文在线观看免费www的网站| 精品一区在线观看国产| .国产精品久久| 色网站视频免费| 亚洲av免费在线观看| 人人妻人人看人人澡| 国产成人a∨麻豆精品| 成人毛片a级毛片在线播放| 极品教师在线视频| 亚州av有码| 国产毛片在线视频| 午夜福利视频1000在线观看| 中文欧美无线码| 国产大屁股一区二区在线视频| 噜噜噜噜噜久久久久久91| 欧美最新免费一区二区三区| 国产中年淑女户外野战色| 一区二区av电影网| 日韩一区二区视频免费看| 亚洲精品久久午夜乱码| 亚洲第一区二区三区不卡| 免费在线观看成人毛片| 一级毛片 在线播放| 熟女av电影| 卡戴珊不雅视频在线播放| 欧美精品人与动牲交sv欧美| 内地一区二区视频在线| 久久久久久国产a免费观看| 国产精品.久久久| 国产人妻一区二区三区在| 免费观看a级毛片全部| 国产色婷婷99| 校园人妻丝袜中文字幕| av在线蜜桃| 久久久久久久大尺度免费视频| 又粗又硬又长又爽又黄的视频| 亚洲最大成人中文| 人妻少妇偷人精品九色| 亚洲av成人精品一二三区| 久久久精品免费免费高清| 丝袜美腿在线中文| 亚洲激情五月婷婷啪啪| 尤物成人国产欧美一区二区三区| 亚洲av电影在线观看一区二区三区 | 永久网站在线| 蜜桃亚洲精品一区二区三区| 大片电影免费在线观看免费| 欧美人与善性xxx| 嫩草影院新地址| 久久鲁丝午夜福利片| 日本爱情动作片www.在线观看| 中文资源天堂在线| 欧美日韩视频高清一区二区三区二| 久久久久久久久久成人| 久久午夜福利片| 插逼视频在线观看| av女优亚洲男人天堂| 男人舔奶头视频| av在线app专区| 18禁在线播放成人免费| 国产成人精品久久久久久| 国产精品蜜桃在线观看| 国产一区二区亚洲精品在线观看| 国产高清不卡午夜福利| 国产69精品久久久久777片| 丰满人妻一区二区三区视频av| 亚洲无线观看免费| 好男人在线观看高清免费视频| 少妇被粗大猛烈的视频| 赤兔流量卡办理| 18禁裸乳无遮挡免费网站照片| 国产午夜精品久久久久久一区二区三区| 丝袜喷水一区| 久久久久久久精品精品| av在线蜜桃| 九九爱精品视频在线观看| 久久久精品欧美日韩精品| 肉色欧美久久久久久久蜜桃 | 国产成人91sexporn| 高清视频免费观看一区二区| 国产淫片久久久久久久久| 少妇丰满av| 在线播放无遮挡| 热99国产精品久久久久久7| 婷婷色综合大香蕉| 另类亚洲欧美激情| 免费观看的影片在线观看| 看非洲黑人一级黄片| 国产又色又爽无遮挡免| 国产亚洲av嫩草精品影院| 久久精品国产自在天天线| 久久久欧美国产精品| 插阴视频在线观看视频| 午夜日本视频在线| 91精品国产九色| 久久久成人免费电影| 国产伦精品一区二区三区四那| 久久影院123| 欧美最新免费一区二区三区| 国内精品宾馆在线| 国产精品福利在线免费观看| 精品人妻一区二区三区麻豆| 夫妻午夜视频| 国产一区二区三区综合在线观看 | 亚洲欧美一区二区三区国产| av免费在线看不卡| 一个人看视频在线观看www免费| 人妻少妇偷人精品九色| 99久久中文字幕三级久久日本| 久久鲁丝午夜福利片| 韩国av在线不卡| 国产男人的电影天堂91| .国产精品久久| 久热久热在线精品观看| 爱豆传媒免费全集在线观看| 久久亚洲国产成人精品v|