氧化石墨烯的制备及其对罗丹明B的吸附性能

采用改进Hummers法以石墨粉为原料制备氧化石墨烯(GO),利用红外光谱仪、X射线衍射仪和扫描电镜对其官能团、物相结构和表面形貌进行表征分析。研究所制备的GO对阳离子染料罗丹明B(RB)的吸附性能,考察了吸附时间、GO用量、吸附温度和溶液初始pH对吸附性能的影响。结果表明:GO吸附RB的适宜条件为:吸附时间70min、GO用量0.01g、温度30℃、pH=3,GO对RB的最大吸附量为2002.71mg/g。由吸附动力学及等温吸附模型分析可知,GO对RB的吸附符合准二级动力学模型及Langmuir等温吸附模型。     

氧化石墨烯辐射接枝4-乙烯基吡啶及其对Cr(Ⅵ)吸附性能研究

通过辐照接枝法在氧化石墨烯(GO)的表面接枝4-乙烯基吡啶(4-VP)制备了一种新型Cr(Ⅵ)吸附剂,并研究了单体浓度和吸收剂量对4-VP接枝率的影响。结果表明:聚4-乙烯基吡啶成功接枝到GO表面。接枝产物对Cr(Ⅵ)具有较好的吸附性能,在40min即可达到吸附平衡,吸附机理为离子交换机理,吸附过程符合朗格缪尔吸附等温模型,理论最大吸附量为114.9mg/g。在pH=3.12时,吸附剂对Cr(Ⅵ)吸附量可以达到最大值99.8mg/g。     

氧化石墨烯/改性磁性壳聚糖复合材料对Cu2+的吸附研究

以石墨粉和壳聚糖为原料,采用Hummers法制备氧化石墨烯,再用四氧化三铁、二乙烯三胺和柠檬酸改性壳聚糖,合成了羧甲基氨基化改性磁性壳聚糖;通过超声分散制备氧化石墨烯水溶胶,再与改性磁性壳聚糖进行复合,成功制得氧化石墨烯/改性磁性壳聚糖复合吸附材料。研究结果表明,在pH=6,吸附剂用量为50mg,吸附时间为90min条件下,氧化石墨烯/改性磁性壳聚糖复合吸附材料对100mL、50mg/L铜离子(Cu~(2+))的吸附容量达到70.3mg/g,且吸附行为符合Freundlich等温吸附模型。     

中空磁性氧化石墨烯的制备及其对亚甲基蓝吸附性能

用共沉淀法将Fe₃O₄沉淀在PS微球上并用甲苯去除PS制备出Fe₃O₄@PS,再用超声将用Hummers法制备的氧化石墨烯包裹在Fe₃O₄@PS表面制备出中空磁性氧化石墨烯,研究了这种复合材料对模拟亚甲基蓝废水的吸附。结果表明：在55℃,用中空磁性氧化石墨烯对亚甲基蓝染料吸附60 min达到平衡,最大吸附量为349.85 mg·g^-1。吸附剂循环8次,吸附效率仍高于80%。用准二级动力学模型可很好地拟合中空磁性氧化石墨烯对亚甲基蓝的吸附。结果表明,吸附速率对亚甲基蓝染料的初始浓度较为敏感,主要为化学吸附。吸附过程符合Langmuir等温吸附模型,说明这种吸附为单层表面吸附。     

离子印迹磁性壳聚糖微球对铀离子的吸附特性

以U(VI)为模板,利用印迹-交联技术制备具有良好吸附性能的离子印迹磁性壳聚糖微球(IMCR)。IMCR粒径为10μm~35μm,磁化强度为29.7 emu/g,对U(VI)吸附最佳pH为5.0,随温度升高,U(VI)吸附容量下降。吸附符合拟二级动力学,且为自发放热过程。吸附等温线符合Langmuir模型,为单分子层吸附。由Dubinin-Radushkevich模型计算的E>8 kJ/mol,表明为化学吸附。IMCR对U(VI)最大吸附容量为187.3 mg/g,高于非印迹树脂(NIMCR 160.8 mg/g),并且有更好的选择性。吸附后的IMCR可用0.5 mol/L EDTA溶液洗脱再生。     

丙烯酸接枝改性氧化石墨烯及其对Ce(Ⅲ)的吸附性能研究

以氧化石墨烯为基材，通过接枝丙烯酸单体，对其进行功能化改性，制备出对Ce(Ⅲ)具有良好吸附性能的吸附材料(GO-g-PAA)。系统研究了吸附时间、溶液pH值等不同实验条件对Ce(Ⅲ)吸附行为的影响。结果表明，GO-g-PAA用于吸附Ce(Ⅲ)时可在100 min达到吸附平衡，吸附过程符合准二级吸附动力学方程和Langmuir等温吸附模型，属于化学吸附和单分子层吸附，其理论最大吸附量为251.9 mg/g。XPS谱图证实GO-g-PAA吸附Ce(Ⅲ)时属于阳离子交换机理。此外，GO-g-PAA在pH=1时对Ce(Ⅲ)的吸附量仍可达到101.9 mg/g,说明该吸附剂可在强酸性条件下使用，因此GO-g-PAA在去除废水中的稀土离子污染物方面具有良好的应用前景。     

聚乙烯醇/壳聚糖/氧化石墨烯复合水凝胶的制备及对Pb(Ⅱ)吸附性能研究

制备聚乙烯醇(PVA)/壳聚糖(CTS)/氧化石墨烯(GO)复合水凝胶球,通过红外光谱(IR)、扫描电子显微镜(SEM)对复合水凝胶进行了表征。研究了pH值、吸附时间及重金属离子初始浓度对吸附Pb(Ⅱ)(二价铅离子)容量的影响,结果表明在pH=5.5、30℃时,复合水凝胶对Pb(Ⅱ)的饱和吸附量达到198.00mg/g,吸附符合二级动力学模型,吸附过程符合Langmuir等温吸附模型,吸附为熵推动的自发吸热过程。与未加氧化石墨烯相比,复合水凝胶的最大吸附容量明显提高。对Pb(Ⅱ)吸附,可再生重复使用6次而吸附量基本保持不变。     

吸附温度对MgAl金属氧化物微观结构和吸附Cr(VI)性能的影响

研究了MgAl水滑石(LDH)焙烧产物(LDO)对Cr(VI)的吸附性能。考察了吸附温度对LDO吸附性能的影响, 研究了吸附过程的热力学和动力学行为。结合XRD和FT-IR表征, 阐明其吸附机理。结果表明, CrO₄^2–已成功插入水滑石层间, 适当提高吸附温度有利于LDO恢复LDH晶相。在20~60℃范围内, 随吸附温度升高, LDO对Cr(VI)吸附量增大, 50~60℃时, Cr(VI)吸附量为91 mg/g。Cr(VI)的吸附平衡数据符合Langmuir模型方程, ΔG_o为负值说明吸附过程为自发过程, ΔS_o和ΔH_o为正值表明吸附为熵增的吸热过程。吸附动力学符合伪二级动力学模型, LDO 的吸附活化能为20.04 kJ/mol, 表现为扩散控制的活性化学吸附过程。     

三元水滑石负载的硫化纳米零价铁对铀的高效去除与机理研究

纳米零价铁材料(NZVI)被广泛用于环境中放射性核素U(VI)的去除, 但是单纯的NZVI存在稳定性差、去除效果差等不足。本研究结合表面钝化技术与负载技术制备得到Ca-Mg-Al水滑石负载的硫化纳米零价铁材料(CMAL-SNZVI), 并将其用于U(VI)的高效去除。结合宏观试验与光谱分析表征得到的结果表明, CMAL-SNZVI材料具有出色的理化性质与较高的活性, 对水溶液中U(VI)的去除具有优良的效果, 在2 h内可以达到反应平衡, 且最大吸附量可达175.7 mg·g ^-1。CMAL-SNZVI对U(VI)的去除主要是由吸附过程与氧化还原反应相结合的方式: 吸附过程中U(VI)与材料中的CMAL基底、SNZVI的表层通过内层表面络合作用结合; 还原过程中材料的NZVI内核将U(VI)还原成低毒难溶的U(IV)后去除。CMAL-SNZVI可为NZVI材料的改性方法提供新的研究方向, 同时, CMAL-SNZVI在污染物去除方面表现优异, 可以作为出色的环境修复材料。     

结构调节剂辅助水热法制备分等级Mg-Al水滑石焙烧产物及其Cr(VI)吸附性能

以廉价的硝酸镁为镁源、硝酸铝为铝源、尿素为沉淀剂,分子量或化学结构不同的P123、F127和聚丙烯酸钠为结构调节剂,采用水热均相沉淀—焙烧法成功地制备出系列分等级多孔Mg-Al水滑石焙烧产物(LDOs)。采用X射线衍射(XRD)、扫描电镜(SEM)、氮气吸附-脱附和UV紫外分光光度计等手段,对产物的物相、形貌和织构性质及其对重金属Cr(VI)的吸附性能进行了比较表征和测试。研究发现,以P123为结构调节剂时制备的微米级椭球体和棒状结构共存的LDO的比表面积为131.8m2/g、孔容为0.31cm3/g、平均孔径为9.6nm,一定条件下其对Cr(VI)的平衡吸附量达46.5mg/g,该吸附过程符合拟二级动力学模型。     

Use of o-phenylene dioxydiacetic acid impregnated in Amberlite XAD resin for separation and preconcentration of uranium(VI) and thorium(IV)

The impregnation of o-phenylene dioxydiacetic acid (OPDA) into a polymeric matrix, Amberlite XAD-2000, is reported and was characterized by infrared spectroscopy. The amount of attached OPDA to the polymer resin was found to be 1.77mmolg(-1) resin. The resin was used for the sorption of U(VI) and Th(IV) from aqueous solution. This sorbent was capable of preconcentrating U(VI) and Th(IV) from weakly acidic or neutral solution. The retained metals were eluted sequentially using 0.25molL(-1) HCl for U(VI) and 1molL(-1) HCl for Th(IV) and determined spectrophotometrically using arsenazo-(III). The capacity of the resin for U(VI) and Th(IV) was found to be 0.121 and 0.113mmolg(-1), respectively. The impregnated resin exhibits a high chemical stability, reusability and fast equilibration. The method was used for the determination of U(VI) and Th(IV) in synthetic samples and rock samples.     

羟基铁插层膨润土的制备及其对铀(VI)的吸附特性与机制

通过羟基铁对钠基膨润土插层改性制备了羟基铁插层膨润土（OH-Fe-Bent）,用于去除废水中的U（VI）。实验考察了pH值、U（VI）初始浓度、温度和吸附时间对OH-Fe-Bent吸附U（VI）效果的影响,并进行吸附动力学和热力学分析。采用FTIR、SEM、XRD等手段分析相关吸附机制。实验结果表明:OH-Fe-Bent吸附U（VI）的最佳pH为4,在温度为15℃,投加量为0.8 g/L,U（VI）初始浓度为10 mg/L时,OH-Fe-Bent对U（VI）的去除率达到99.55%,吸附平衡时间为90 min。Langmuir等温吸附模型和准二级动力学模型（相关系数的平方约为1）均可较好地拟合其吸附过程,理论饱和吸附量可达97.09 mg/g,OH-Fe-Bent对U（VI）是单分子层吸附。FTIR、SEM分析表明OH-Fe-Bent吸附U（VI）后自身结构没有改变,XRD分析表明羟基铁已经成功插入膨润土层间。      

磁性介孔TiO2/氧化石墨烯复合材料的制备及其对U(Ⅵ)的吸附

以氧化石墨烯（GO）、纳米Fe₃O₄、钛酸四丁酯（TBOT）为原料,合成了磁性介孔TiO₂/GO（Fe₃O₄@TiO₂/GO）复合材料,用其处理浓度为10 mg·L-1的含U（Ⅵ）废水。研究了Fe₃O₄@TiO₂/GO复合材料中GO含量、溶液初始pH值、Fe₃O₄@TiO₂/GO复合材料投加量、反应时间、U（Ⅵ）初始浓度及共存离子对U（Ⅵ）吸附的影响。结果表明:在pH值为6、GO质量分数为60wt%、Fe₃O₄@TiO₂/GO复合材料投加量为10 mg的条件下,Fe₃O₄@TiO₂/GO复合材料对U（Ⅵ）的吸附效果最佳,较同等条件下磁性介孔Fe₃O₄@TiO₂复合材料和GO的吸附量分别高了10.99 mg·g-1和1.91 mg·g-1。Fe₃O₄@TiO₂/GO复合材料对U（Ⅵ）的吸附180 min即达到平衡,准二级动力学模型和Freundlich吸附等温模型能很好地描述其吸附过程。解吸实验表明,经5次吸附-解吸后,U（Ⅵ）的吸附率仍高达90.86%,说明Fe₃O₄@TiO₂/GO复合材料具有较高的循环利用性能。      

Comparison of sorption behavior of Th(IV) and U(VI) on modified impregnated resin containing quinizarin with that conventional prepared impregnated resin

This paper reports the results obtained by studying the ion-exchange properties of a new solvent impregnated resin (SIR), which was prepared by impregnation of quinizarin (1,4-dihydroxyanthraquinone, QNZ) on Amberlite XAD-16 after nitration of the benzene rings present in its structure. The sorption behavior of Th(IV) and U(VI) on/in the modified SIR was compared with that of the SIR prepared via the conventional method. It was observed that sorption capacity and sorption rate of the modified SIR are significantly greater than the conventional one. The modified SIR was then applied to the extraction of Th(IV) and U(VI) ions at the presence of many co-existence metal ions. The results obtained denote on successful application of this new SIR to analysis of natural water samples spiked to Th(IV) and U(VI) ions.     

Enhanced removal of trace Cr(VI) ions from aqueous solution by titanium oxide-Ag composite adsorbents

Titanium oxide-Ag composite (TOAC) adsorbents were prepared by a facile solution route with Ag nanoparticles being homogeneously dispersed on layered titanium oxide materials. The as-synthesized TOAC exhibited a remarkable capability for trace Cr(VI) removal from an aqueous solution, where the concentration of Cr(VI) could be decreased to a level below 0.05 mg/L within 1h. We have systematically investigated the factors that influenced the adsorption of Cr(VI), for example, the pH value of the solution, and the contact time of TOAC with Cr(VI). We found that the adsorption of Cr(VI) was strongly pH-dependent. The adsorption behavior of Cr(VI) onto TOAC fitted well the Langmuir isotherm and a maximum adsorption capacity of Cr(VI) as 25.7 mg/g was achieved. The adsorption process followed the pseudo-second-order kinetic model, which implied that the adsorption was composed of two steps: the adsorption of Cr(VI) ions onto TOAC followed by the reduction of Cr(VI) to Cr(III) by Ag nanoparticles. Our results revealed that TOAC with high capacity of Cr(VI) removal had promising potential for wastewater treatment.     

Adsorption characteristics and separation of Cr(III) and Cr(VI) on hydrous titanium(IV) oxide

A hydrous titanium(IV) oxide was prepared to study the adsorption characteristics and the separation of chromium species. Batch sorption studies have been carried out to determine the effect of pH on the sorption of Cr(III) and Cr(VI) on hydrous TiO2. An excellent separation efficiency of Cr(III) and Cr(VI) was obtained at pH 2. The adsorption percentage of Cr(VI) was above 99%, whereas that of the Cr(III) was less than 1% at this pH. The adsorption isotherm of Cr(VI) on hydrous TiO2 at pH 2 was in good agreement with the Langmuir isotherm. The maximum adsorption capacity of Cr(VI) on TiO2 was 5 mg g(-1). The rate of adsorption of Cr(VI) by hydrous TiO2 with average particle diameter 250 and 500 microm has been studied under particle diffusion controlled conditions. The diffusion coefficients of Cr(VI) for both hydrous TiO2 having average particle diameter of 250 and 500 microm was calculated at pH 2 as 3.84 x 10(-10) m2 s(-1) and 8.86 x 10(-10) m2 s(-1), respectively.     

Carbonate effects and pH-dependence of uranium sorption onto bacteriogenic iron oxides: kinetic and equilibrium studies

The removal of U(VI) from groundwaters by adsorption onto bacteriogenic iron oxides (BIOS) has been investigated under batch mode. The adsorbent dosage, the uranium concentration, the concentration of carbonate and the use of a real groundwater spiked with uranium comprised the examined parameters. In addition, the effect of pH was examined in two different water matrixes, i.e., in distilled water and in real groundwater. Equilibrium studies were carried out to determine the maximum adsorption capacity of BIOS and the data correlated well with the Langmuir and Freundlich models. The presence of carbonate affected adversely the adsorption of U(VI) onto BIOS. The maximum adsorption capacity of BIOS was 9.25 mg g(-1) at 0.1mM carbonate concentration and decreased to 6.93 mg g(-1) at 0.5mM carbonate concentration, whereas at carbonate concentration of 2mM practically no adsorption occurred. The data were further analyzed using the pseudo-second order kinetic equation, which fitted best the experimental results. The initial adsorption rate (h) was found to increase with decreasing the concentration of carbonate in all cases. When experiments were accomplished in the absence of carbonate, the pH values did not have an effect on the adsorption of U(VI). However, the extent of U(VI) adsorption was strongly pH-dependent when the experiments were carried out in the real groundwater. The maximum adsorption capacity increased sharply as the pH decreased and optimum removal was obtained in the pH range 3.2-4.0, thus bacteriogenic iron oxides can found application in the removal of U(VI) by adsorption from low pH or low carbonate waters.     

1,3-Bis[(diphenylphosphorylacetamido)methyl]benzene as reagent for extraction and sorption preconcentration of REE(III), U(VI), and Th(IV) from nitric acid solutions

The extraction of microamounts of REE(III), U(VI), and Th(IV) from HNO₃ solutions in the form of complexes with a polyfunctional neutral organophosphorus compound, 1,3-bis[(diphenylphosphorylacetamido)-methyl]benzene, was studied. The influence exerted by the structure of the bridge binding two carbamoylmethyl-phosphine oxide fragments on the efficiency of the extraction of REE(III), U(VI), and Th(IV) and on the stoichiometry of the extractable complexes was analyzed. The possibility of recovering and concentrating REE(III), U(VI), and Th(IV) from nitric acid solutions with a complexing sorbent prepared by noncovalent immobilization of 1,3-bis[(diphenylphosphorylacetamido)methyl]benzene on the surface of carbon nanotubes was examined.     

Adsorption of platinum(IV) and palladium(II) from aqueous solution by thiourea-modified chitosan microspheres

The chitosan microparticles were prepared using the inverse phase emulsion dispersion method and modified with thiourea (TCS). TCS was characterized by scanning electron microscope (SEM), the Fourier transform infrared (FT-IR) spectra, sulfur elemental analysis, specific surface area and pore diameter. The effects of various parameters, such as pH, contact time, initial concentration and temperature, on the adsorption of Pt(IV) and Pd(II) by TCS were investigated. The results showed that the maximum adsorption capacity was found at pH 2.0 for both Pt(IV) and Pd(II). TCS can selectively adsorb Pt(IV) and Pd(II) from binary mixtures with Cu(II), Pb(II), Cd(II), Zn(II), Ca(II), and Mg(II). The adsorption reaction followed the pseudo-second-order kinetics, indicating the main adsorption mechanism of chemical adsorption. The isotherm adsorption equilibrium was well described by Langmuir isotherms with the maximum adsorption capacity of 129.9 mg/g for Pt(IV) and 112.4 mg/g for Pd(II). The adsorption capacity of both Pt(IV) and Pd(II) decreased with temperature increasing. The negative values of enthalpy (ΔH°) and Gibbs free energy (ΔG°) indicate that the adsorption process is exothermic and spontaneous in nature. The adsorbent was stable without loss of the adsorption capacity up to at least 5 cycles and the desorption efficiencies were above 95% when 0.5 M EDTA–0.5 M H₂SO₄ eluent was used. The results also showed that the preconcentration factor for Pt(IV) and Pd(II) was 196 and 172, respectively, and the recovery was found to be more than 97% for both precious metal ions.     

纳米氧化石墨烯/聚丁二酸丁二醇酯复合材料的制备与性能

以天然石墨为原料,利用改进的HUMMERS'法制备了氧化石墨烯(GO);采用原位复合方式制备了纳米氧化石墨烯/聚丁二酸丁二醇酯(GO/PBS)复合材料,并对其性能进行了研究。结果表明:适量GO的加入能更有效地加快GO/PBS复合材料的结晶速度;GO的加入,提高了GO/PBS复合材料的力学性能和酶降解速率;随着GO添加量的增加,复合材料晶体尺寸减小,GO起到了成核剂的作用。