• <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 ?

    An insight into aggregation kinetics of polystyrene nanoplastics interaction with metal cations

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

    Yucheng Zhng ,Xiotong Su,Nor F.Y.Tm,Xioln Lo ,Meiling Zhong ,Qihng Wu,*,Huifng Lei ,Zihui Chen,Zhng Li ,Jie Fu,*

    a Key Laboratory for Water Quality and Conservation of the Pearl Stream Delta,Ministry of Education,School of Enviro nmental Science and Engineering,Guangzhou University,Guangzhou 510006,China

    b State Key Laboratory of Marine Pollution and Department of Chemistry,City University of Hong Kong,Hong Ko ng,China

    c School of Science and Technology,Open University of Hong Kong,Hong Kong,China

    d School of Environmental Science and Engineering,Huazhong University of Science and Technology,Wuhan 430074,China

    Keywords:Polystyrene nanoplastics Lead cation Aggregation kinetics Critical coagulation concentration Size effect

    ABSTRACT Once inevitably released into the aquatic environment,polystyrene nanoplastics(PS-NPs)will present complicated environmental behaviors,of which the aggregation is a key process determining their environmental fate and impact.In this study,the aggregation kinetics of different sizes(30 nm and 100 nm)of PS-NPs with metal cations(Na+,K+,Ca2+,Mg2+and Pb2+)at different solution pH(3,6 and 8)were investigated.The results showed that the aggregation of PS-NPs increased with cation concentration.Taking Pb2+as an example,the adsorption behavior of cations onto PS-NPs was determined by transmission electron microscopy(TEM)and energy dispersive X-ray(EDX)spectroscopy,which demonstrated Pb2+could be adhered onto the surface of PS-NPs with the effect of charge neutralization.The critical coagulation concentrations(CCC)of smaller PS-NPs were higher than that of larger PS-NPs for monovalent cations,whereas a different pattern is observed for divalent cations.It was suggested that there were other factors that DLVO theory does not consider affect the stability of NPs with different particle sizes.In addition,it should be noted that PS-NPs had the capacity of adsorbing large amounts of heavy metal cations and carried them transport to a long distance,and the corresponding ecological risks need to further elucidate.

    Plastics,known as revolutionary materials,have been widely used in various fields since their birth in 1905[1].The global consumption of plastics is growing at an annual rate of 4%,increasing from 1.3 million tons in 1950 to 322 million tons in 2015,and then reaching 369 million tons in 2018[2].Due to the failure of effective collection,disposal and control of plastic wastes,some plastic fragments or particles are discharged into the natural environment,affecting the normal operation of the ecosystem.Plastic particles with a size less than 100 nm,called nanoplastics,are supposed to be a new type of contaminant,which have ignited the research passion of scholars around the world over the last decade[3].On one hand,nanoplastics from cosmetics,personal hygiene products,and industrial products such as 3D printing and nanocapsules are constantly released into the environment during their use and production[4].On the other hand,polymer-based materials are easy to degrade into plastic fragments under the action of high salinity,light,heat and microorganisms[5].

    The biological effects of nanoparticles are closely related to particle size.Moore[6]found that the bioavailability of microplastics was largely affected by their particle size.There is a growing body of literature that recognizes the toxic effects of nanoplastics on hydrobiont,which were mainly evaluated through energy consumption,oxidative damage,enzyme activity,reproduction and growth rate[7–9].Some researchers believe that the aggregation behavior of nanoplastics in water environment is one of the main factors affecting their environmental migration and biological toxicity,and thus focus on the colloidal stability and aggregation dynamics of nanoplastics[10,11].Surface chemical properties of nanoplastics play an important role in colloid aggregation,and ultimately affect their behavior and fate in water environment[12].Yuet al.[13]have investigated the aggregation of a series of surfacemodified polystyrene nanoplastics,and found that the negatively charged and positively charged nanoplastics exhibited different aggregation behaviors.In addition,it has previously been observed that solution properties such as pH,ionic strength,and valence of ions influence the colloidal stability and aggregation behavior of nanoparticles[14].Metal cations have been demonstrated to significantly affect the stability of nanoplastics when they are adhered on nanoplatics[15–17].Conversely,nanoplastics can adsorb large amounts of metal cations in heavy metals polluted water,and carry them to migrate,posing a greater potential risk[17].

    In this study,two commercial polystyrene nanoplastics(PSNPs)with different sizes,30 nm representing small size(PS-S)and 100 nm representing large size(PS-L),were used as model nanoplastics to systematically explore their aggregation kinetics in water with monovalent(Na+and K+)and divalent(Ca2+,Mg2+and Pb2+)metal cations.Polystyrene is one of the most widely used plastic materials[18],and Pb2+is also a common ion in heavy metal polluted water[19].The attachment efficiencies and critical coagulation concentrations of PS-NPs under different conditions were calculated.The research purpose is to reveal the important roles of particle size and metal cations in the aggregation process of nanoplastics.The provided information could improve the understanding of the environmental behavior and ecological risks of nanoplastics.

    The PS-S-NPs suspension(1.0%w/v,15 mL,30 nm)was obtained from Thermo Fisher Scientific(Shanghai,China),and PS-L-NPs suspension(2.5%w/v,10 mL,100 nm)was purchased from Tianjin BaseLine ChromTech Research Center(Tianjin,China).The NaCl,KCl,MgCl2,CaCl2and Pb(NO3)2of analytical grade were used as the experimental electrolytes.The solution pH was adjusted using 0.1 mol/L HCl and 0.1 mol/L NaOH(Titrisol,Merck,Austria).All the nanoplastics suspensions were diluted to about 10 mg/L with ultrapure water(18.2 MΩ,Milli-Q,Millipore).After adding different concentrations of electrolytes and adjusting to the desired pH,the experimental nanoplastics suspensions were prepared.The hydrodynamic diameter and zeta potential of each sample were measured by dynamic light scattering(DLS)with a 90°scattering angle(ZetaPALS/BI-90 Plus,Brookhaven Instruments Corp.,New York,USA).The suspension temperature was maintained at 25°C.The characteristic of PS-NPs before and after experiments were visualized using a TecnaiG2F20 S-Twin transmission electron microscope(TEM,FEI,USA).The distribution of elemental composition was analyzed by an energy-dispersive X-ray spectroscopy(EDX)system(X-MaxN 80T,Oxford Instruments NanoAnalysis,USA).Fourier transform-infrared(FT-IR)spectra were performed to identify the structural and functional groups of PS-NPs.

    The initial aggregation rate constant of PS-NPs(k)is proportional to the change of hydrodynamic diameter(Dh)from the timeresolved DLS measurements with respect to time(t),but inversely proportional to the primary particle concentration of PS-NPs(C)(Eq.1)[20]:

    In aggregation experiments,theCwas maintained at 10 mg/L.can be acquired by performing the linear least-squares regression for the initial increase inDh(t)witht.For most experiments,the regression analysis was performed over a time fromDh(0)to 1.3Dh(0),whereDh(0)represented the initialDh.Under some unfavorable conditions thatDh(t)fail to reach 1.3Dh(0),the aggregation of PS-NPs was negligible andwas determined with the achieved maximumDh(t).For some extremely fast aggregation thatDh(t)may go beyond 1.3Dh(0)when experiment has just begun,only the points that showed a linear relationship were chosen to calculate the aggregation rate.

    The attachment efficiency(α)was employed to calculate critical coagulation concentrations(CCC)to make a quantitative description of aggregation kinetics of PS-NPs.αwas calculated by normalizing the aggregation rate constantk(acquired in a certain suspension)to the rate constant at the fast aggregation conditionskfast(obtained in the diffusion limited aggregation regime,where the aggregation rate was independent on electrolyte concentrations)(Eq.2):

    Eventually,the experimental CCC values were determined from the intersect of extrapolated lines through the diffusion and reaction limited regimes.

    The Derjaguin-Landau-Verwey-Overbeek(DLVO)theory with particle-particle model was used to give further elucidation of the observed results.Under various chemical conditions,the interaction energy,including van der Waals attractionVA(h),and electrostatic double-layer(EDL)repulsionVR(h),were calculated[21–23].The total interaction energyVT(h)was calculated using the following equations(Eqs.3–8):

    where APWPwas the combined Hamaker constant for PS-NPs interacting through water for a PS-water-PS system,and the Hamaker constants of PS-L-NPs and PS-S-NPs were 3.5×10?21J and 2.3×10?21J respectively[23].b=5.32λwas the characteristic wavelength of the interaction with an often assumed value of 100 nm.Rwas the radius of PS-NPs.hwas separation distance between particles,which was much smaller than their radius(h<

    Fig.S1(Supporting information)presents the FT-IR spectra of PS-L-NPs and PS-S-NPs.Peaks at 700,750,and 3020 cm?1were designated to the benzene ring structure,and those peaks at 1490 and 1450 cm?1were ascribed to the aromatic C–H deformation[24,25].The broad and sharp bands at 1600 and 2920 cm?1were attributed to the stretching vibration of aromatic C=C group and deformation of aliphatic C–H group,respectively[26].Peak at 3450 cm?1was ascribed to hydroxyl stretching,originated from water adsorption[27].The peak at 1700 cm?1for PS-S-NPs probably contributed to C=O group related to the presence of carboxyl groups[28].

    Fig.1.TEM images and hydrodynamic size distributions of PS-L-NPs(a,b),and PSS-NPs(c,d).

    The size and shape of PS-L-NPs were detected by TEM,and it showed that PS-L-NPs had a spherical shape with an average diameter of 100 nm(Fig.1a).The hydrodynamic size distribution of PS-L-NPs measured by DLS was ranged from 80 nm to 150 nm with an average diameter of 110 nm(Fig.1b).The morphology of PS-SNPs was also confirmed by TEM(Fig.1c).The hydrodynamic size distribution of PS-S-NPs was ranged from 20 nm to 70 nm with an average diameter of 33 nm(Fig.1d).

    To assess the effect of pH on PS-NPs aggregation,the attachment efficiencies(α)of PS-L-NPs and PS-S-NPs with different concentrations of NaCl were calculated and displayed in Fig.2.Whenαapproaches to 1,the aggregation process is regarded as diffusionlimited[29].Different solution pH(3,6 and 8)led to differences in the aggregation profiles,and a higher pH value hindered the approaching ofαto 1.Correspondingly,the experimental CCC of NaCl for PS-L-NPs at pH of 3,6 and 8 were 193.86 mmol/L,349.06 mmol/L and 470.41 mmol/L,respectively,and for PS-S-NPs were 380.13 mmol/L,540.44 mmol/L and 755.26 mmol/L,respectively.There was a strong linear correlation between CCC and pH value(Fig.S2 in Supporting information).From this data,the aggregation of PS-NPs was suppressed with decreasing the solution pH,which is consistent with the phenomenon reported in previous study[30].The DLVO theoretical calculations were accorded with the experimental CCC values under different pH conditions.As shown in Fig.S3(Supporting information),the energy barrier decreased with increasing the concentration of NaCl,which is also reported by other studies[31].

    Previous studies have indicated the protonation and deprotonation on the surface of PS-NPs play an important role in the aggregation behavior[32].Therefore,the zeta potential of PS-NPs was measured and it was found that the zeta potential became more negative with increasing the pH values(Fig.S4 in Supporting information).For example,the zeta potential of PS-L-NPs in NaCl solution of 400 mmol/L decreased from?6.69 mV to?14.97 mV with increasing the pH from 6 to 8(Fig.S4a),indicating that electrostatic repulsion between PS-NPs could be increased under alkaline conditions,which may reduce the aggregation between nanoplastics particles.It is suggested that the surface of PS-NPs could be easily deprotonated with increasing the pH,leading to improved stability of PS-NPs[33].

    For convenience,the subsequent aggregation experiments were carried out at pH 6.Fig.3 presents the increases of hydrodynamic diameter of PS-NPs along time with different types and concentrations of cations.In the presence of low concentration of cations,like 100 mmol/L NaCl,PS-NPs kept a relative stability due to the dominance of electrostatic repulsive forces[14].With the increase of cation concentration,hydrodynamic diameter of PS-NPs increased quickly.According to the DLVO theory,the addition of cations led to characteristic adsorption and charge neutralization,where van der Waals forces dominated and the repulsion barrier was compressed.Thus,it was shown in Fig.S3 that the energy barriers of PS-NPs had been weakened as the cation concentration increased.When the cation concentration reached the CCC value,the PS-NPs were extremely unstable due to diffusion limitation,which eventually led to agglomeration between particles(Fig.S5 in Supporting information).

    Compared the effects of mono-and divalent cations on PS-NPs aggregation,it is found that divalent cations were easier to induce the aggregation of PS-NPs relative to monovalent cations.For instance,the CCC values of NaCl and KCl for PS-L-NPs were ranged from 232.60 mmol/L to 349.06 mmol/L,while those of MgCl2,CaCl2and Pb(NO3)2were reduced to 16.25–40.31 mmol/L(Fig.S5).The ratio between the CCC values of Ca2+and Na+was proportional toz?3.37(wherez=2 was the counterion valence for calcium)(Table S1 in Supporting information),consisting with the Schulze-Hardy Rule[34].For the differences in CCC values of cations with the same valence state,a possible explanation was ascribed to the hydration layer forming between metal cations and water molecules.In other words,cations with larger radii tend to interact with more water molecules[30,35],thus producing a higher promotion effect on the aggregation of PS-NPs.Correspondingly,the promotion effects of divalent cations were in the same order with their radii:Pb2+>Ca2+>Mg2+(Table S1).

    At present,a large number of studies have reported the size effect on the agglomeration and stability of nanoparticles,however,the size effect on the aggregation of PS-NPs has not been investigated explicitly in the existing literature[36–40].The DLVO theory predicts a marked decrease in rates of coagulation of colloidal particles with an increase in particle size[41].In this study,the CCC values of divalent ions(Ca2+,Mg2+and Pb2+)for PS-S-NPs were lower than for PS-L-NPs(Fig.S5),which agreed with DLVO prediction.This revealed that the PS-L-NPs needed a higher concentration of divalent cations to break the stable state.The more negative zeta potential of PS-L-NPs relative to PS-S-NPs also confirmed the recalcitrance of PS-L-NPs to aggregation(Fig.S4).Besides,a common view was that higher adsorption rate of divalent cations occurred on the smaller particle,owing to the higher Gibbs free energy associated with the smaller particles.Figs.4 and 5 present the TEM and EDX spectra of PS-NPs after the aggregation experiments with Pb2+.From Fig.4a,we can see that PS-L-NPs strikingly aggregated each other.At the same time,the EDX spectra showed the enrichment of Pb on the surface of PS-L-NPs,indicating that Pb2+cations were adsorbed on PS-L-NPs(Figs.4b-d).This characterization demonstrated the important role of Pb2+in the induction of PS-NPs aggregation by the charge neutralization.Relatively,after the aggregation experiment with Pb2+,the PS-S-NPs agglomerated closely into larger particles(>1μm)and the surfaces were studded with Pb(Fig.5).This result demonstrated a stronger adsorption capacity of PS-S-NPs for Pb2+,which might be the key reason to explain the higher aggregation potential of smaller PS-NPs relative to larger PS-NPs with divalent cations.

    Fig.2.Attachment efficiencies(α)of PS-L-NPs(a)and PS-S-NPs(b)with different concentrations of NaCl at different solution pH.

    Fig.3.Aggregation kinetics of PS-L-NPs(left)and PS-S-NPs(right)with different concentrations of NaCl(a,b),KCl(c,d),CaCl2(e,f),MgCl2(g,h)and Pb(NO3)2(i,j)at pH 6.

    Fig.4.The characterization of PS-L-NPs aggregates with Pb(NO3)2:(a)TEM image,(b)EDX spectrum,and mapping for element of carbon(c)and lead(d).

    Fig.5.The characterization of PS-S-NPs aggregates with Pb(NO3)2:(a)TEM image,(b)EDX spectrum,and mapping for element of carbon(c)and lead(d).

    However,for the monovalent cation system,the larger PS-NPs showed a higher tendency to aggregate,which is different with the situation in divalent cation system.The CCC values of Na+and K+for PS-L-NPs were 349.06 mmol/L and 232.60 mmol/L,which were smaller than that for PS-S-NPs(540.44 mmol/L and 412.66 mmol/L)(Fig.S5).By comparison on the zeta potential of PS-NPs(Fig.S4),PS-S-NPs had more negative charges in the same concentration of NaCl solution,indicating the smaller size of PS-NPs were indeed more stable.In fact,there are differences between studies exploring size effect on the stability of nanoparticles,even finding that the stability of colloid is insensitive to particle size[40].For instance,Afshinnia,Sikder,Cai and Baalousha[39]observed a negatively strong association between the CCC and particle size of nano-silver for monovalent cations,but no clear trend was observed for divalent cations.Deposition in secondary minimum and the narrow range of surface potential were used to explain the observed anomalous particle size effect.In DLVO theory,the surface charge of particles is assumed to be distribution uniformly,that all particles have a constant surface potential[41].In other words,it is most likely that the discrepancies with respect to particle size effects are related to the failure of the DLVO theory to consider hydrodynamic interaction and dynamics of interaction.

    In conclusion,this study set out to systematically explore the aggregation kinetics of different sizes of PS-NPs with monovalent(Na+,K+)and divalent(Ca2+,Mg2+and Pb2+)cations at different solution pH.The primary results of this investigation are summarized as follows:(1)Due to deprotonation,PS-NPs were more stable in alkaline conditions.(2)Compared with monovalent cations,divalent cations have a greater effect on the stability of PS-NPs;the hydration ability of cations with the same valence state led to the difference in the stability of PS-NPs.(3)The smaller size of PSNPs in monovalent cation system was more stable but easier to agglomerate in divalent cation system,and there were other unknown factors that DLVO theory does not consider affect the stability of NPs with different particle sizes.

    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

    The project is supported by Scientific Research Project of Guangzhou University(No.YK2020017),the Program Foundation of Institute for Scientific Research of Karst Area of NSFC-GZGOV(No.U1612442),Research Grants Council of the Hong Kong Special Administrative Region,China(No.UGC/IDS(R)16/19),Industry-University Cooperation and Collaborative Education Project of the Ministry of Education of the People’s Republic of China(No.202101134012)and Innovative training program for College Students of Guangzhou University(No.S202111078039).

    Supplementary materials

    Supplementary material associated with this article can be found,in the online version,at doi:10.1016/j.cclet.2022.01.056.

    成人无遮挡网站| 欧美bdsm另类| 亚洲人成网站在线观看播放| 午夜福利影视在线免费观看| 日本午夜av视频| 久久精品国产亚洲av涩爱| 99久久综合免费| 国产精品一国产av| 99国产综合亚洲精品| 99热全是精品| 国产男人的电影天堂91| 色网站视频免费| 在线观看一区二区三区激情| 日日爽夜夜爽网站| 国产av精品麻豆| 亚洲高清免费不卡视频| 最新的欧美精品一区二区| 精品亚洲成a人片在线观看| 成人影院久久| 久久久久国产网址| 亚洲五月色婷婷综合| 亚洲欧美精品自产自拍| 亚洲av综合色区一区| 欧美激情极品国产一区二区三区 | 成人影院久久| 老司机影院毛片| 天堂俺去俺来也www色官网| 精品少妇久久久久久888优播| 少妇被粗大猛烈的视频| 狠狠婷婷综合久久久久久88av| 精品视频人人做人人爽| 在线免费观看不下载黄p国产| 18禁在线播放成人免费| 一区二区av电影网| 亚洲成人av在线免费| 久久精品熟女亚洲av麻豆精品| 九色亚洲精品在线播放| 观看美女的网站| 日韩大片免费观看网站| 人成视频在线观看免费观看| 免费看光身美女| 乱人伦中国视频| 午夜91福利影院| 狂野欧美激情性xxxx在线观看| 亚洲熟女精品中文字幕| 欧美最新免费一区二区三区| 免费看光身美女| 国产精品麻豆人妻色哟哟久久| 下体分泌物呈黄色| 亚洲国产精品一区三区| 欧美人与性动交α欧美精品济南到 | 久久久久久久久大av| 精品酒店卫生间| 国产av一区二区精品久久| 乱码一卡2卡4卡精品| 香蕉精品网在线| a 毛片基地| 成人毛片a级毛片在线播放| 日韩电影二区| 特大巨黑吊av在线直播| 精品人妻熟女av久视频| 国模一区二区三区四区视频| 丰满迷人的少妇在线观看| 国产精品国产三级国产av玫瑰| 亚洲精品久久久久久婷婷小说| 欧美xxⅹ黑人| 成人免费观看视频高清| 一本一本久久a久久精品综合妖精 国产伦在线观看视频一区 | 亚洲色图综合在线观看| 亚州av有码| 国产一区二区在线观看日韩| 久久热精品热| 欧美激情极品国产一区二区三区 | 日本欧美国产在线视频| 啦啦啦中文免费视频观看日本| 国产成人精品婷婷| 亚洲一级一片aⅴ在线观看| 亚洲精品日韩在线中文字幕| av有码第一页| 欧美激情国产日韩精品一区| 另类亚洲欧美激情| 九九爱精品视频在线观看| 熟女人妻精品中文字幕| 99九九在线精品视频| 久久综合国产亚洲精品| √禁漫天堂资源中文www| 亚州av有码| 亚洲av.av天堂| 哪个播放器可以免费观看大片| 大香蕉久久成人网| 久久热精品热| 天天躁夜夜躁狠狠久久av| 狠狠婷婷综合久久久久久88av| 国产精品一区二区在线观看99| 在线精品无人区一区二区三| 国产欧美亚洲国产| 国产精品不卡视频一区二区| 一级毛片aaaaaa免费看小| 丝袜喷水一区| 涩涩av久久男人的天堂| 在线亚洲精品国产二区图片欧美 | a级毛片在线看网站| 亚洲av日韩在线播放| 美女脱内裤让男人舔精品视频| 欧美激情极品国产一区二区三区 | 久久久精品免费免费高清| 久久国产精品男人的天堂亚洲 | a 毛片基地| 夜夜骑夜夜射夜夜干| 丝袜美足系列| 男男h啪啪无遮挡| 校园人妻丝袜中文字幕| 黑人欧美特级aaaaaa片| 久久午夜综合久久蜜桃| 中文精品一卡2卡3卡4更新| 成人国产av品久久久| 久久97久久精品| 成人18禁高潮啪啪吃奶动态图 | 午夜91福利影院| 午夜老司机福利剧场| 插阴视频在线观看视频| 午夜福利视频精品| 国产av国产精品国产| 黑人欧美特级aaaaaa片| 男女国产视频网站| 91久久精品国产一区二区三区| 国产国拍精品亚洲av在线观看| 午夜激情久久久久久久| 2018国产大陆天天弄谢| 草草在线视频免费看| 欧美人与性动交α欧美精品济南到 | 91精品三级在线观看| 久久精品国产亚洲av天美| 日韩 亚洲 欧美在线| 性色avwww在线观看| 最近中文字幕高清免费大全6| 99九九线精品视频在线观看视频| 亚洲精品久久午夜乱码| 欧美少妇被猛烈插入视频| 久久热精品热| 男女边摸边吃奶| 久久久午夜欧美精品| 国产女主播在线喷水免费视频网站| 亚洲国产精品一区二区三区在线| 免费高清在线观看日韩| 欧美日本中文国产一区发布| kizo精华| 日韩在线高清观看一区二区三区| 亚洲丝袜综合中文字幕| 日韩精品免费视频一区二区三区 | 亚洲内射少妇av| 啦啦啦在线观看免费高清www| 亚洲国产av影院在线观看| 极品人妻少妇av视频| 99热网站在线观看| 十分钟在线观看高清视频www| 一级毛片 在线播放| 97超视频在线观看视频| 久久人人爽人人爽人人片va| 免费久久久久久久精品成人欧美视频 | 综合色丁香网| 在线观看国产h片| 99九九线精品视频在线观看视频| 黄色毛片三级朝国网站| 18禁在线播放成人免费| 在线观看美女被高潮喷水网站| 国产综合精华液| 男女国产视频网站| 亚洲精品国产色婷婷电影| xxx大片免费视频| 色吧在线观看| 国产精品国产三级国产av玫瑰| www.色视频.com| 国产成人免费观看mmmm| av又黄又爽大尺度在线免费看| 亚洲一级一片aⅴ在线观看| 国产精品免费大片| 国产亚洲最大av| 久久久久人妻精品一区果冻| 国产日韩一区二区三区精品不卡 | 亚洲婷婷狠狠爱综合网| 国语对白做爰xxxⅹ性视频网站| 夜夜骑夜夜射夜夜干| 高清欧美精品videossex| 亚洲四区av| 日韩亚洲欧美综合| 99九九在线精品视频| 欧美日韩国产mv在线观看视频| 国产免费视频播放在线视频| 婷婷色综合www| 一级黄片播放器| 少妇 在线观看| 日本欧美国产在线视频| 久久国内精品自在自线图片| 99九九在线精品视频| av卡一久久| 黄色毛片三级朝国网站| 青青草视频在线视频观看| 亚洲av电影在线观看一区二区三区| 各种免费的搞黄视频| 日本vs欧美在线观看视频| av福利片在线| 久久精品久久久久久噜噜老黄| 最新的欧美精品一区二区| av有码第一页| 人体艺术视频欧美日本| 成人亚洲欧美一区二区av| 少妇高潮的动态图| 日韩熟女老妇一区二区性免费视频| 亚洲国产日韩一区二区| 性高湖久久久久久久久免费观看| 欧美日本中文国产一区发布| 国产精品.久久久| 你懂的网址亚洲精品在线观看| 三级国产精品欧美在线观看| 22中文网久久字幕| 一级,二级,三级黄色视频| 18禁观看日本| 人妻少妇偷人精品九色| 午夜久久久在线观看| 内地一区二区视频在线| 亚洲人与动物交配视频| 亚洲精品一区蜜桃| 夜夜爽夜夜爽视频| 午夜免费男女啪啪视频观看| 久久久久久久久久成人| 99视频精品全部免费 在线| 日韩人妻高清精品专区| av免费观看日本| 爱豆传媒免费全集在线观看| 丰满迷人的少妇在线观看| 日本欧美视频一区| 国产成人一区二区在线| 亚洲成人av在线免费| 国产黄色免费在线视频| 草草在线视频免费看| 免费av中文字幕在线| 久久国产亚洲av麻豆专区| 五月天丁香电影| 久久 成人 亚洲| 最近手机中文字幕大全| 简卡轻食公司| av不卡在线播放| 国内精品宾馆在线| 丝袜美足系列| 高清欧美精品videossex| 三级国产精品片| 精品人妻一区二区三区麻豆| 蜜桃在线观看..| 波野结衣二区三区在线| 亚洲av欧美aⅴ国产| 日韩中字成人| 激情五月婷婷亚洲| 精品少妇内射三级| 韩国高清视频一区二区三区| 91成人精品电影| 精品酒店卫生间| 亚洲精品久久久久久婷婷小说| 美女国产视频在线观看| 色视频在线一区二区三区| 亚洲国产精品成人久久小说| 黑人巨大精品欧美一区二区蜜桃 | 久久久久久久国产电影| 一级毛片aaaaaa免费看小| 亚洲人成77777在线视频| 国产精品成人在线| 国产国拍精品亚洲av在线观看| 大片免费播放器 马上看| 另类精品久久| 80岁老熟妇乱子伦牲交| 日本免费在线观看一区| av免费观看日本| av一本久久久久| 亚洲四区av| av线在线观看网站| 国产在线视频一区二区| 久久热精品热| 五月玫瑰六月丁香| 久久午夜福利片| 性色av一级| 久久毛片免费看一区二区三区| 亚洲成人av在线免费| av免费观看日本| 久久久久人妻精品一区果冻| 久久国内精品自在自线图片| 成年av动漫网址| 99re6热这里在线精品视频| 亚洲精品自拍成人| 精品久久蜜臀av无| 一本大道久久a久久精品| 特大巨黑吊av在线直播| 一个人免费看片子| 欧美人与善性xxx| 男女免费视频国产| 五月伊人婷婷丁香| 狂野欧美激情性xxxx在线观看| 18禁在线无遮挡免费观看视频| 午夜激情av网站| 久久久久久人妻| h视频一区二区三区| 精品少妇黑人巨大在线播放| 精品人妻偷拍中文字幕| 久久久久久久久大av| 天美传媒精品一区二区| 狂野欧美白嫩少妇大欣赏| 国产精品久久久久久久久免| 中文字幕久久专区| 国产欧美亚洲国产| 超色免费av| 黑人高潮一二区| 精品卡一卡二卡四卡免费| 久久久久国产精品人妻一区二区| 日本91视频免费播放| 女人久久www免费人成看片| 精品熟女少妇av免费看| 最黄视频免费看| 国产综合精华液| 最近的中文字幕免费完整| 免费黄频网站在线观看国产| 天天躁夜夜躁狠狠久久av| 搡女人真爽免费视频火全软件| 亚洲精品久久午夜乱码| 一级黄片播放器| 青春草视频在线免费观看| 久久人妻熟女aⅴ| 亚洲综合色惰| 一区二区三区四区激情视频| 欧美丝袜亚洲另类| 一区二区日韩欧美中文字幕 | 性色avwww在线观看| 女的被弄到高潮叫床怎么办| 国产免费又黄又爽又色| 全区人妻精品视频| 一本—道久久a久久精品蜜桃钙片| 一本一本综合久久| 又黄又爽又刺激的免费视频.| 精品酒店卫生间| 国产一区二区三区av在线| 日日撸夜夜添| 亚洲情色 制服丝袜| 黄色视频在线播放观看不卡| 少妇精品久久久久久久| 国产毛片在线视频| 高清视频免费观看一区二区| 如日韩欧美国产精品一区二区三区 | 成年美女黄网站色视频大全免费 | 午夜精品国产一区二区电影| 久久av网站| 亚洲精品日韩在线中文字幕| 有码 亚洲区| 老司机影院成人| 精品一区二区三卡| 日韩av在线免费看完整版不卡| 国产男女内射视频| 亚洲精品日本国产第一区| 少妇精品久久久久久久| 人成视频在线观看免费观看| 久久精品国产自在天天线| 一区二区三区四区激情视频| 久热久热在线精品观看| 少妇高潮的动态图| 少妇被粗大猛烈的视频| 中文字幕av电影在线播放| 精品人妻一区二区三区麻豆| 欧美三级亚洲精品| 少妇的逼好多水| 99热全是精品| 国产探花极品一区二区| 国产精品成人在线| 91在线精品国自产拍蜜月| 欧美丝袜亚洲另类| 伊人久久精品亚洲午夜| 亚洲国产av新网站| 国产亚洲精品久久久com| 国产亚洲av片在线观看秒播厂| 日本黄大片高清| 亚洲综合色网址| 欧美xxxx性猛交bbbb| 国产成人一区二区在线| 亚洲天堂av无毛| 啦啦啦中文免费视频观看日本| 久久久久久久久久久丰满| 大陆偷拍与自拍| 亚洲av.av天堂| a级毛片黄视频| 国产又色又爽无遮挡免| 日本午夜av视频| 日日爽夜夜爽网站| 精品亚洲成a人片在线观看| av.在线天堂| 国产精品欧美亚洲77777| 国产精品嫩草影院av在线观看| 成人综合一区亚洲| 日产精品乱码卡一卡2卡三| 青青草视频在线视频观看| 三上悠亚av全集在线观看| 夜夜看夜夜爽夜夜摸| 亚洲精品乱久久久久久| 在线 av 中文字幕| 久久婷婷青草| 男女边摸边吃奶| 中国国产av一级| 在线亚洲精品国产二区图片欧美 | 十分钟在线观看高清视频www| 99久国产av精品国产电影| 一级毛片aaaaaa免费看小| 2022亚洲国产成人精品| 黄色毛片三级朝国网站| videos熟女内射| 人妻夜夜爽99麻豆av| 国产精品一区二区在线不卡| 三上悠亚av全集在线观看| 国产高清不卡午夜福利| 女人精品久久久久毛片| a级毛片黄视频| 在线精品无人区一区二区三| 精品久久久久久久久亚洲| 久久 成人 亚洲| 午夜福利视频在线观看免费| 久久久亚洲精品成人影院| 观看美女的网站| 日日啪夜夜爽| 成年美女黄网站色视频大全免费 | 午夜影院在线不卡| 蜜臀久久99精品久久宅男| 高清不卡的av网站| 国产一区有黄有色的免费视频| 亚洲精品视频女| 美女福利国产在线| 亚洲第一av免费看| 国产一区二区三区av在线| 热re99久久国产66热| 国产色爽女视频免费观看| 男女免费视频国产| 日韩强制内射视频| 女的被弄到高潮叫床怎么办| 边亲边吃奶的免费视频| 久久综合国产亚洲精品| 精品人妻一区二区三区麻豆| av网站免费在线观看视频| 亚洲情色 制服丝袜| 中文字幕人妻熟人妻熟丝袜美| 亚洲一区二区三区欧美精品| 久久97久久精品| 黄色欧美视频在线观看| 久久99蜜桃精品久久| 丝袜美足系列| 久久久精品免费免费高清| 视频区图区小说| 老司机影院成人| 国产一区二区三区综合在线观看 | 五月伊人婷婷丁香| 大香蕉97超碰在线| 久久久久久久久久成人| 日韩三级伦理在线观看| 欧美丝袜亚洲另类| 久久国产精品大桥未久av| 夫妻午夜视频| 九九爱精品视频在线观看| 永久网站在线| 日韩成人av中文字幕在线观看| 人人妻人人添人人爽欧美一区卜| 春色校园在线视频观看| 热99久久久久精品小说推荐| 最近最新中文字幕免费大全7| 亚洲四区av| 亚洲久久久国产精品| 亚洲伊人久久精品综合| 免费黄色在线免费观看| 日韩熟女老妇一区二区性免费视频| 久久人人爽人人爽人人片va| 午夜精品国产一区二区电影| av网站免费在线观看视频| 久久久久久久精品精品| 天天影视国产精品| 日本午夜av视频| 亚洲av免费高清在线观看| 在线精品无人区一区二区三| 精品午夜福利在线看| 国产精品久久久久久久久免| 插逼视频在线观看| 午夜免费鲁丝| 大又大粗又爽又黄少妇毛片口| 亚洲精品日韩av片在线观看| 男人爽女人下面视频在线观看| 人妻制服诱惑在线中文字幕| 亚洲国产av影院在线观看| a级毛色黄片| 99国产综合亚洲精品| 天堂8中文在线网| 亚洲av成人精品一区久久| 欧美日韩视频精品一区| 美女国产高潮福利片在线看| 欧美激情极品国产一区二区三区 | 国产精品人妻久久久影院| 婷婷成人精品国产| 伊人亚洲综合成人网| 啦啦啦视频在线资源免费观看| 考比视频在线观看| 亚洲综合色惰| 91精品国产九色| 日韩一本色道免费dvd| 国产亚洲精品久久久com| 国产毛片在线视频| 我的女老师完整版在线观看| 我要看黄色一级片免费的| 99久久精品一区二区三区| 中文天堂在线官网| 欧美少妇被猛烈插入视频| 热99国产精品久久久久久7| 老熟女久久久| 黑丝袜美女国产一区| 最黄视频免费看| 午夜激情av网站| 国产高清不卡午夜福利| 人人澡人人妻人| av专区在线播放| 精品久久久久久电影网| 欧美亚洲日本最大视频资源| 亚洲精品亚洲一区二区| 亚洲综合精品二区| 欧美激情极品国产一区二区三区 | 日韩制服骚丝袜av| 成人二区视频| 亚洲精品亚洲一区二区| 午夜老司机福利剧场| 少妇高潮的动态图| 在线观看美女被高潮喷水网站| 久久毛片免费看一区二区三区| 国产一区亚洲一区在线观看| 国产爽快片一区二区三区| 亚洲精品久久久久久婷婷小说| 亚洲精品日本国产第一区| 国产av精品麻豆| 丝袜美足系列| 欧美日本中文国产一区发布| 在线观看国产h片| 精品人妻在线不人妻| 在线观看三级黄色| av在线app专区| 少妇人妻 视频| 国产日韩一区二区三区精品不卡 | 国产成人午夜福利电影在线观看| 日韩精品有码人妻一区| 在线免费观看不下载黄p国产| 三级国产精品欧美在线观看| 国语对白做爰xxxⅹ性视频网站| 久久精品人人爽人人爽视色| 亚洲欧洲精品一区二区精品久久久 | 少妇丰满av| 欧美丝袜亚洲另类| 91国产中文字幕| 国产成人aa在线观看| 成人毛片60女人毛片免费| av不卡在线播放| 中文字幕人妻丝袜制服| 王馨瑶露胸无遮挡在线观看| 久久精品人人爽人人爽视色| 久久精品久久精品一区二区三区| 欧美人与善性xxx| 午夜免费鲁丝| 99re6热这里在线精品视频| 黑人欧美特级aaaaaa片| 熟女av电影| 青春草亚洲视频在线观看| 97超碰精品成人国产| 国产视频首页在线观看| 久久毛片免费看一区二区三区| 一级a做视频免费观看| 黄色欧美视频在线观看| 亚洲综合色网址| 青春草视频在线免费观看| 亚洲内射少妇av| 精品人妻在线不人妻| 日韩强制内射视频| 蜜桃在线观看..| 18禁在线播放成人免费| 国产成人午夜福利电影在线观看| 久久久精品94久久精品| kizo精华| 日韩成人av中文字幕在线观看| 国产伦理片在线播放av一区| 亚洲情色 制服丝袜| 欧美激情国产日韩精品一区| 久久人人爽av亚洲精品天堂| 91精品三级在线观看| 黄色怎么调成土黄色| 久久久久国产网址| 嫩草影院入口| 欧美日韩一区二区视频在线观看视频在线| 一本久久精品| 永久网站在线| 精品人妻熟女av久视频| 视频在线观看一区二区三区| 亚洲人与动物交配视频| 免费人妻精品一区二区三区视频| 久久久精品区二区三区| 日本与韩国留学比较| 中文字幕亚洲精品专区| 亚洲国产av新网站| 中文字幕人妻熟人妻熟丝袜美| 黑人高潮一二区| av专区在线播放| 欧美性感艳星| 国产成人精品福利久久| 精品久久久精品久久久| 天堂中文最新版在线下载| 久久久久精品性色| 男女边摸边吃奶| 亚洲成人一二三区av| 亚洲欧美成人综合另类久久久| 在线观看一区二区三区激情| 日本wwww免费看| 中文字幕人妻熟人妻熟丝袜美| 午夜激情久久久久久久|