Removal of methylene blue from aqueous solution by adsorption onto zeolite synthesized from coal fly ash and its thermal regeneration

BACKGROUND: The removal of cationic dyes from wastewater is of great importance. Three zeolites synthesized from coal fly ashes (ZFAs) were investigated as adsorbents to remove methylene blue (MB), a cationic dye, from aqueous solutions. Experiments were conducted using the batch adsorption technique under different conditions of initial dye concentration, adsorbent dose, solution pH, and salt concentration. RESULTS: The adsorption isotherm data of MB on ZFAs were fitted well to the Langmuir model. The maximum adsorption capacities of MB by the three ZFAs, calculated using the Langmuir equation, ranged from 23.70 to 50.51 mg g^?1. The adsorption of MB by ZFA was essentially due to electrostatic forces. The measurement of zeta potential indicated that ZFA had a lower surface charge at alkaline pH, resulting in enhanced removal of MB with increasing pH. MB was highly competitive compared with Na⁺, leading to only a < 6% reduction in adsorption in the presence of NaCl up to 1.0 mol L^?1. Regeneration of used ZFA was achieved by thermal treatment. In this study, 90–105% adsorption capacity of fresh ZFA was recovered by heating at 450 °C for 2 h. CONCLUSION: The experimental results suggest that ZFA could be employed as an adsorbent in the removal of cationic dyes from wastewater, and the adsorptive ability of used ZFA can be recovered by thermal treatment. Copyright © 2010 Society of Chemical Industry     

蒙脱石/TiO2复合材料制备及其光催化性能研究

以蒙脱土和钛酸丁酯为原料,采用溶胶凝胶法制备出蒙脱石/TiO2复合材料,利用XRD、SEM、光催化亚甲基蓝溶液对其物相组成、晶体结构、微观结构和光催化性能进行了研究.结果表明:TiO2以锐钛矿相分布于蒙脱石的层间域和表面,并使蒙脱石d001有不同程度的增大.蒙脱石/TiO2复合材料的加入量和Ti/蒙脱石比值、亚甲基蓝溶液的初始质量浓度对蒙脱石/TiO2复合材料的吸附和光催化效率均有影响.     

凝胶-溶胶法制备纳米二氧化钛的pH控制

利用凝胶-溶胶法制备纳米二氧化钛，采用透射电镜（TEM）和X射线衍射（XRD）对产物进行了表征，考察了体系pH变化和电解质（高氯酸钠）对它的影响，以及初始pH（pH0）对二氧化钛形貌及体系组成的影响。结果表明，产物为锐钛矿型二氧化钛，平均粒径5～15nm；体系pH变化是由于OH^-（或H^＋）在氢氧化钛或二氧化钛表面的吸附和脱附，添加0．1mol／L高氯酸钠能促进OH^-（或H^＋）的吸附和脱附过程。pH0显著影响二氧化钛形貌和体系组成，pH0=1．0时为球状晶体，pH0=9．4时为较规则的立方晶体，至pH0=11．5变为椭球形。pH0〉9．4时，二氧化钛物质的量分数显著下降，至pH0=12．0时无二氧化钛生成，因此应控制pH0〈9．4。     

负载型光催化剂Al/TiO_2的制备及性能研究

以钛酸正丁酯为前驱物,盐酸为水解抑制剂、无水乙醇为溶剂,采用溶胶-凝胶法进行了铝粉表面包覆二氧化钛薄膜的研究,制备了Al/TiO2光催化剂。以亚甲基蓝为有机污染模拟物,其降解率作为评价手段,考察了不同条件下制备样品的光催化性能。研究表明,当水钛比n[H2O]∶n[Ti(OC4H9)4]为40∶1,水解温度为35℃,pH值为4.5,反应时间为5 h,煅烧温度为500℃时,制备的样品经紫外灯光照3 h,降解率能达到85%。采用粒度分析、XRD等方法对包覆后的样品进行了表征,证明了片状铝粉表面包覆了锐钛矿型二氧化钛。并对样品的光催化性能进行了研究,结果表明,紫外灯光照6 h,样品对亚甲基蓝溶液的降解率能达到97%,优于商用光催化剂P25。     

Preparation of TiO2 Nanoparticles Coated Cotton Fibers at Low Temperature and Their Photocatalytic Activity

TiO_2 nanoparticles coated cotton fiber composite was successfully prepared by using a sol-gel method at low temperature(about 100℃) using tetrabutyl-titanate [Ti(OBu)_4] as raw material.The preparation of the TiO_2 colloid and the composite were described.The properties of resulting materials were characterized by SEM and XRD,the photocatalytic degradation performance was tested using methylene blue(MB) as the target pollutant in aqueous solution.The results showed that the amorphous TiO_2 nanoparticles were distributed evenly on the outer surfaces of cotton fibers,which shows efficient photocatalytic properties when exposed to UV light,the degradation rate of MB reached 95.35% under the conditions of catalyst dosage 2.5 g/L,MB concentration 50 mg/L,irradiation time 120 min,and pH 10,and the photocatalytic activity of TiO_2/cotton fibers remained above 90% of its activity as-prepared after being used four times,the degradation rate of MB could reach 88.78% when irradiation time was 120 min.The photocatalytic degradation of MB could be properly described by the first-order kinetic law.By comparison of the removal rates of MB with and without UV light,it could be affirmed that the disappearance of MB was due to photodegradation rather than adsorption on cotton fibers.     

Synthesis,Characterization, and Applications of a New Chelating Resin Containing 4-2-(Thiazolylazo) Resorcinol (TAR)

A new phenol–formaldehyde based chelating resin containing 4-(2-thiazolylazo) resorcinol (TAR) functional groups has been synthesized and characterized by Fourier transform infrared spectroscopy and elemental analysis. Its adsorption behavior for Cu(II), Pb(II), Ni(II), Co(II), Cd(II), and Mn(II) has been investigated by batch and column experiments. The chelating resin is highly selective for Cu(II) in the pH range 2 ～ 3, whereas alkali metal and alkaline earth metal ions such as Na(I), Mg(II), and Ca(II) are not adsorbed even at pH 6. Quantitative recovery of most metal ions studied in this work except Co(II) is achieved by elution with 2M HNO₃ at a flow rate of 0.2 mL min^?1. A similar trend is observed for distribution coefficient values. The quantitative separations achieved on a mini-column of chelating resin include Cd(II) – Cu(II), Mn(II) – Pb(II), Co(II) – Cu(II), Mn(II) – Ni(II), and Mn(II) – Co(II) – Cu(II). The recovery of copper(II) is quantitative (98.0–99.0%) from test solutions (10–50 mg/L) by 1 mol/L HNO₃-0.01 mol/L EDTA. The chelating resin is stable in acidic solutions below 2.5 M HNO₃ or HCl as well as in alkaline solution below pH 11. The adsorption behavior of the resin towards Cu(II) was found to follow Langmuir isotherm and second order rate.     

星形聚丙烯酸钠的合成及动力学研究

以二羟基二过碘酸合铜(Ⅲ)钾(简称DPC)为氧化剂与季戊四醇二聚体(简称DPE)组成氧化还原体系,在碱性介质中引发丙烯酸钠(简称AA-Na)通过自由基聚合得到了星形聚丙烯酸钠(简称SSPAA-Na)。合成工艺条件为:反应温度35℃,反应时间1 h,单体浓度c(AA-Na)=1.0 mol/L,氧化剂浓度c(DPC)=1.4×10-3mol/L,还原剂浓度c(DPE)=1.0×10-4mol/L,反应体系pH=13.0。测定不同反应条件对聚合反应速率和动力学的影响,得到聚合反应的动力学方程为:Rp=kc(AA-Na)2.0c(DPC)1.97c(DPE)0.31,反应活化能为38.6 kJ/mol。通过红外光谱、核磁共振氢谱等对聚合物结构进行了表征。     

制备液pH值对TiO2光催化性能的影响

以钛酸四丁酯为前驱体,通过添加表面活性剂CTAB和调节制备母液的pH值,制得纳米尺度的二氧化钛催化剂。利用XRD、N2物理吸附-脱附、紫外-可见光漫反射以及CO2-TPD等技术对催化剂进行了表征。研究结果发现,随着制备母液pH值提高,催化剂的比表面积逐渐增大、表面碱性中心位也逐步增多,有利于光催化降解亚甲基蓝(MB)效率的提高。     

N/F/TiO2的制备及光催化氧化性能

以钛酸四丁酯为钛源,以尿素和氟化铵为N、F源,制备N/F/TiO2光催化材料,用于亚甲基蓝降解效率研究.结果表明,摩尔比为N∶F∶Ti=1∶4∶5的光催化剂在锻烧温度为600℃、pH =7的条件下,100 mg N/F/TiO2光催化剂对100 mL浓度为20 mg/L的亚甲基蓝溶液光催化降解4h时效率最高.     

二氧化钛纳米管对亚甲基蓝的吸附

采用水热法制备了TiO2纳米管,借助X射线衍射(XRD)、透射电镜(TEM)对产物进行了表征。以亚甲基蓝溶液为体系,考察了TiO2纳米管的吸附性能。结果表明:TiO2纳米管为锐钛矿相,管径小、管形均匀。黑暗条件下TiO2纳米管对亚甲基蓝具有优异的吸附活性,30 min可达到吸附平衡,吸附量达38.3mg/g,最佳吸附质量比为w(MB):w(TiO2)≈0.075。     

二氧化钛水热合成单分散立方形貌PZT粉体

本文以TiO2、ZrOCl2·8H2O和Pb（NO3）2为反应物、KOH为矿化剂水热合成得到组成均一且外观具有规则立方形貌的单分散PZT粉体．研究了矿化剂浓度、水热反应温度和反应时间对产物相组成和外观形貌的影响。结果表明：在KOH浓度为2．0mol／L、水热合成温度为160℃、反应时间为18h时可得到最佳形貌和颗粒尺寸（1．5～2μm）的PZT。进一步的研究表明,水热温度的增加有利于得到大尺寸立方形貌的PZT粉体,这一现象与以钛的醇盐为原料时所得的结果正好相反。反应机制的分析表明：在本合成体系中,PZT的形成过程主要是TiO2的溶解、Pb^2＋和ZrOCl2的水解以及PZT晶核的形成和生长过程。其中矿化剂对TiO2的溶解是整个水热过程的控制步骤。     

钛柱撑蒙脱石光催化降解甲基橙的性能研究

以钛酸丁酯为前驱体、钠基蒙脱石为载体,采用溶胶-凝胶法制备了二氧化钛柱撑蒙脱石（TiO2—MMT）纳米复合材料。采用X-射线衍射仪、透射电子显微镜、全自动比表面积及中孔、微孔分析仪（BET）等分析手段对TiO2—MMT进行了表征,并研究了其对甲基橙的光催化降解活性。结果表明：TiO2—MMT主要由锐钛矿型TiO2和蒙脱石组成,呈层片状结构,TiO2柱撑到蒙脱石层间,并使其（001）晶面间距明显增大。在中性和碱性奈件下,TiO2-MMT对甲基橙的光催化降解能力较弱;在酸性条件下,TiO2-MMT对甲基橙的降解率远远高于中性和碱性条件下的降解率。TiO2—MMT光催化降解甲基橙的优化条件为：pH值4、甲基橙初始浓度30mg·L-1、TiO2-MMT投加量10g·L-1,在优化条件下光照2h,TiO2-MMT对甲基橙的催化降解率为99．4％。     

S，N耦合掺杂TiO2柱撑蒙脱石催化剂制备

以Na基蒙脱石为吸附剂,二氧化钛（TiO2）水解溶胶、L-半胱氨酸为双组分吸附质,采用双组分竞争吸附的方法,制备了S,N耦合掺杂TiO2柱撑蒙脱石光催化剂。探讨了蒙脱石的吸附特点,修正了Langmuir双组分竞争吸附公式,利用二元回归方法,求出了修正因子Y1=1．00011,Y2=0．99938。吸附实验表明,双组分吸附体系中,吸附质之间的相互作用不容忽视;XRD分析：表明,催化剂中TiO2全部为锐钛矿相晶体;XPS光电子能谱分析表明,S^4＋替换Ti^4＋进入TiO2晶格,S^2-、N^2-替换晶格氧而进入TiO2晶格;光催化降解实验表明,可见光照射下,催化剂有较高的光催化活性,3h内亚甲基蓝脱色率达65％左右。     

GO物理形态对复合光催化剂性能的影响

以钛酸四丁酯以及固态和液态的氧化石墨烯(GO)为前驱物,分别制备了标记为TiO_2-RGO(s)和TiO_2-RGO(l)的复合光催化剂。对制备的2种复合光催化剂进行了表征,并以亚甲基蓝(MB)为目标物,对比研究了2种催化剂的光催化效能。结果表明,TiO_2-RGO(l)和TiO_2-RGO(s)的能级带宽分别降低至2.8、2.9 e V;二者光降解MB的效能均优于TiO_2自身,且降解效率随着GO含量的增加而增加;当TiO_2与GO的质量比为1∶0.06时,TiO_2-RGO(l)和TiO_2-RGO(s)对MB的降解率分别为96%和84%。动力学研究表明:TiO_2-RGO(l)和TiO_2-RGO(s)的准一级反应速率常数分别是TiO_2的3.2倍和2.2倍。     

碱性钙基膨润土对亚甲基蓝和刚果红的吸附去除

该文研究了碱性钙基膨润土(ACB)对水体中的亚甲基蓝(MB)和刚果红(CR)染料的吸附性能,考察了吸附剂用量、吸附时间及温度、pH及盐等因素对吸附效果的影响,同时进行了两种染料在碱性钙基膨润土上的吸附等温模型、吸附动力学模型研究。结果表明,ACB对MB、CR的脱色率随着吸附剂用量的增加而增加,在实验条件下,50 mg/L MB和100 mg/L CR的最佳吸附剂质量浓度分别为1.0 g/L和2.0 g/L;升高温度可以加快吸附速率,但对最终的脱色率影响很小;50 mg/L MB的吸附平衡时间在60 min左右,100 mg/L CR的吸附平衡时间在120 min左右;在pH=3～12时,ACB对MB的脱色率都稳定在99%左右,而适宜ACB吸附CR的pH=3～7,对CR的脱色率保持在90%左右;NaCl的加入对MB的吸附效果影响很小,对CR的吸附则有很强的抑制作用;ACB对MB的吸附同时符合Langmuir和Freundlich模型,而ACB对CR的吸附则更符合Langmuir模型;ACB对两种染料的吸附过程均符合准二级动力学模型,颗粒内扩散模型的拟合结果说明吸附过程存在颗粒内扩散作用。     

空心钛酸钡的制备及其形成机理

以二氧化钛（TiO₂）和八水合氢氧化钡[Ba（OH）₂·8H₂O]为原料,采用水热合成法,成功制备出具有四方相晶型和空心形貌结构的钛酸钡粉体。利用透射式电子显微镜（TEM）和X射线衍射（XRD）对样品的形貌结构和晶型做了表征,通过研究反应过程中钛酸钡粉体的结构和晶型随时间的变化过程,对空心钛酸钡的形成机理做了详细的探讨,并考察了不同反应温度和钡浓度对钛酸钡粉体结晶和生长的影响。研究结果表明：反应温度和钡浓度会影响钛酸钡粉体的晶型和形貌,并以此提出了一种空心钛酸钡的形成机理;当反应温度为180 ℃、钡浓度为3.0 mmol/L时,能获得粒径分布均匀的四方相晶型的空心钛酸钡粉体。     

水热法合成二氧化锰及其对染料的脱色性能研究

采用水热法以十二烷基苯磺酸钠为模板合成二氧化锰,并研究水热温度对二氧化锰的结构和染料脱色性能的影响,以及样品投加量和染料溶液的pH对二氧化锰染料脱色性能的影响。结果表明:当水热温度为110 ℃时,得到2~8 μm球状γ-二氧化锰,对亚甲基蓝（MB）和罗丹明B（RhB）的脱色效果最好。当其投加量为6 g/L时,分别对50 mg/L的MB和RhB脱色率达到86.95%和76.07%。强酸和强碱条件下其对MB的脱色率有明显的提升,二氧化锰对MB的吸附过程符合Langmuir和Freundlich等温模型;强酸条件下其对RhB的脱色率有明显的提升,对RhB的吸附过程符合Freundlich等温模型。二氧化锰样品可循环使用,循环吸附3次后对MB和RhB的吸附量分别减少1.08 mg/g和2.66 mg/g。     

Photodegradation of Methylene Blue in a Batch Fixed Bed Photoreactor Using Activated Carbon Fibers Supported TiO2 Photocatalyst

A batch fixed bed photoreactor, using felt-form activated carbon fibers (ACF) supported TiO2 photocatalyst (TiO2/ACF), was developed to carry out photocatalytic degradation of methylene blue (MB) solution. The effects of TiO2 particle size, loaded TiO2 amount, initial MB concentration, airflow rate and successive run on the decomposition rate were investigated. The results showed that photodegradation process followed a pseudo-first-order reaction kinetic law. The apparent first-order reaction constant kapp was larger than 0.047 min-1 with half reaction time t1/2 shorter than 15 min, which was comparable to reported data using suspended Degussa P-25 TiO2 particles. The high degradation rate was mainly attributed to adsorption of MB molecules onto the surface of TiO2/ACF. The photocatalytic efficiency still remained nearly 90% after 12 successive runs, showing that successive usage of the designed photoreactor was possible. The synergic enhancement effect in combination of adsorption with ACF and photodegradation with TiO2 was proved by comparing MB removal rates in the successive degradation and adsorption runs, respectively.     

低温法制备二氧化钛薄膜及其光催化氧化处理电镀含铬废水

以钛酸四丁酯为原料,采用微波辅助低温法在玻璃表面制备锐钛矿结构的二氧化钛薄膜。分别用X射线衍射法(XRD)和扫描电子显微镜(SEM)表征其相结构和表面形貌;通过光催化降解实际电镀含铬废水实验,探讨了光源、废水pH、废水初始浓度、光照时间及涂膜层数对总铬去除率的影响。光催化氧化的最优条件为:废水初始浓度3 000~9 000 mg/L,pH=8.3,负载4层薄膜,254 nm紫外光照射3 h。在最优条件下,废水的总铬去除率高达99.8%。     

Preparation of Sodium carboxymethylcellulose/poly(methyl acrylate) IPN hydrogels and their application for adsorption

Sodium carboxymethylcellulose/poly(methyl acrylate) (NaCMC/PMA) interpenetrating polymer networks (IPNs) were prepared by fractional step in 40 wt % ethanol solution with N,N′‐methylenebisacrylamide as a crosslinker. Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and differential scanning calorimeter were used to characterize the NaCMC/PMA IPN hydrogels and confirm the IPN structure as well. Simultaneously, adsorption of the obtained IPN hydrogels to methylene blue (MB) was also investigated. It was observed that the adsorption of MB onto the hydrogels was mainly dependent on the initial concentration of MB and the pH of the solution. Adsorption rate of MB was much higher in the first 9 h than that in the following period and saturated adsorption amount of MB was 2370 mg/g at the initial MB concentration of 100 mg/L. Moreover, the adsorption capacity of the IPN hydrogels at the neutral pH condition is much higher than those at acid or alkaline pH conditions. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41101.