Ag–AgBr/TiO2/RGO nanocomposite: Synthesis, characterization, photocatalytic activity and aggregation evaluation

Ag–AgBr/TiO_2 supported on reduced graphene oxide(Ag–AgBr/TiO_2/RGO) with different mass ratios of grapheme oxide(GO) to TiO_2 were synthesized via a facile solvothermal-photo reduction method. Compared to the single-, two-and three-component nanocomposites,the four-component nanocomposite, Ag–AgBr/TiO_2/RGO-1 with mass ratio of GO to TiO_2at 1%, exhibited a much higher photocatalytic activity for the degradation of penicillin G(PG)under white light-emitting diode(LED-W) irradiation. The PG degradation efficiency increased with the increase of mass ratio of GO to TiO_2 from 0.2% to 1%, then it decreased with the increase of mass ratio of GO to TiO_2 from 1% to 5%. The zeta potentials of RGO-nanocomposites became more negative with the presence of humic acid(HA) due to the negatively charged HA adsorption, resulting in the shift of points of zero charge to lower values of pH. The aggregations of nanocomposites were more significant due to the bridging effect of HA. Furthermore, the aggregated particle sizes were larger for RGO-nanocomposites compared to other nanoparticles, due to the bindings of the carboxylic and phenolic functional groups in HA with the oxygen-containing functional groups in the RGO-nanocomposites.The microfiltration(MF) membrane was effective for the nanocomposites separation. In the continuous flow through submerged membrane photoreactor(sMPR) system, backwashing operation could efficiently reduce membrane fouling and recover TiO_2, and thus indirectly facilitate the PG removal.     

氧化石墨烯电催化高效降解有机染料RBk5

电化学高级氧化技术是处理有机染料废水的有效技术方法之一，但其应用受传统贵金属电极成本高、易毒化失活等缺陷的限制.本研究采用廉价易得的石墨粉材料，制备氧化石墨烯（GO）催化剂，用于活性黑5（RBk5）染料废水的电催化氧化降解研究.利用透射电子显微镜、X射线光电子能谱、红外光谱、拉曼光谱、循环伏安法和电化学阻抗谱分析材料的结构特性及电化学性能.结果显示，氧化石墨烯具有较高的电子迁移速率，良好的亲水性和电催化活性.不同的RBk5浓度、外加电流、电解质、初始pH值等条件对RBk5的降解效率也有一定程度的影响.其中，电解质因素对材料性能影响最为显著.在RBk5浓度为10mg/L、外加电流为20mA、反应时间为35min、电解质为NaCl的条件下，电催化降解效率可以达到100%.     

Transesterification of Pistacia chinensis seed oil using a porous cellulose-based magnetic heterogeneous catalyst

In the present work, a novel cellulose-based porous heterogeneous solid acid catalyst encapsulation of ferriferous oxide (Fe₃O₄) and sulfonated graphene (GO-SO₃H) into cellulose to form composite porous microspheres catalyst (GO-SO₃H/CM@Fe₃O₄)was synthesized and evaluated for biodiesel production from Pistacia chinensis seed oil. The SEM, EDS and FTIR analysis revealed that the catalyst GO-SO₃H/CM@Fe₃O₄ owned stronger active sites and GO-SO₃H dispersed well in porous surface and inside of cellulose support. Under the optimum conditions, microwave-assisted transesterification process was carried out with the best catalyst amount, i.e. 5 wt% GO-SO₃H/CM@Fe₃O₄ (weight ratio of GO-SO₃H/cellulose), and conversion yield reached 94%. The prepared catalyst could be easily separated from reaction solution by extra magnetic field and reclaimed at least five runs.     

石墨烯电极电活化过硫酸盐降解含酚废水研究

以苯酚为目标污染物,利用石墨烯电极自身性质及电活化共同作用下活化过硫酸盐(PDS)产生氧化性自由基降解苯酚,对影响苯酚降解的因素(包括电流密度、初始pH值、PDS浓度及影响反应的主导自由基)进行探讨。通过系统中加入一定量的甲醇和叔丁醇作为自由基猝灭剂的猝灭试验确定降解过程中的主导自由基。结果表明,在未通电情况下石墨烯电极对苯酚也具有去除作用,可以吸附苯酚。在通电情况下,由于电活化和石墨烯活化的双重作用,相比于单一石墨烯体系和单一PDS体系,石墨烯/PDS体系对苯酚的降解率显著提高,在n(PDS)∶n (phenol)为50∶1、苯酚初始质量浓度为25mg/L、pH值为11、电流密度为30 mA/cm²的条件下,在90 min内苯酚的降解率可达98.91%。通过淬灭试验确定在石墨烯/PDS降解苯酚体系中以硫酸根自由基为主(SO₄^-·)、羟基自由基(·OH)为辅。综上所述,在未通电情况下,石墨烯可以利用自身吸附作用去除苯酚,在通电情况下,石墨烯电极利用自身性质以及电活化活化过硫酸盐,与单一PDS体系和单一石墨烯体系相比,有效提高了过硫酸盐的活化程度,提高了苯酚的降解率。     

Competitive role of nitrogen functionalities of N doped GO and sensitizing effect of Bi2O3 QDs on TiO2 for water remediation

The promising solar irradiated photocatalyst by pairing of bismuth oxide quantum dots (BQDs) doped TiO₂ with nitrogen doped graphene oxide (NGO) nanocomposite (NGO/BQDs-TiO₂) was fabricated. It was used for degradation of organic pollutants like 2,4-dichlorophenol (2,4-DCP) and stable dyes, i.e. Rhodamine B and Congo Red. X-ray diffraction (XRD) profile of NGO showed reduction in oxygenic functional groups and restoring of graphitic crystal structure. The characteristic diffraction peaks of TiO₂ and its composites showed crystalline anatase TiO₂. Morphological images represent spherical shaped TiO₂ evenly covered with BQDs spread on NGO sheet. The surface linkages of $\text{NO}?\mathrm{O}?\text{Ti}$, $\mathrm{C}?\mathrm{O}?\text{Ti}$, $\mathrm{B}\mathrm{i}?\mathrm{O}?\text{Ti}$ and vibrational modes are observed by Fourier transform infrared spectroscopy (FTIR) and Raman studies. BQDs and NGO modified TiO₂ results into red shifting in visible region as studied in diffused reflectance spectroscopy (DRS). NGO and BQDs in TiO₂ are linked with defect centers which reduced the recombination of free charge carriers by quenching of photoluminescence (PL) intensities. X-ray photoelectron spectroscopy (XPS) shows that no peak related to $\mathrm{C}?\mathrm{O}$ in NGO/BQDs-TiO₂ is observed. This indicated that doping of nitrogen into GO has reduced some oxygen functional groups. Nitrogen functionalities in NGO and photosensitizing effect of BQDs in ternary composite have improved photocatalytic activity against organic pollutants. Intermediate byproducts during photo degradation process of 2,4-DCP were studied through high performance liquid chromatography (HPLC). Study of radical scavengers indicated that ${\mathrm{O}}_2^{·?}$ has significant role for degradation of 2,4-DCP. Our investigations propose that fabricated nanohybrid architecture has potential for degradation of environmental pollutions.     

GO/(CeO2-TiO2)改性复合膜紫外光催化去除氨氮、DOC

以二氧化铈-二氧化钛（CeO₂-TiO₂）、氧化石墨烯-二氧化铈（GO-CeO₂）、氧化石墨烯-二氧化钛（GO-TiO₂）和氧化石墨烯/二氧化钛-二氧化铈[GO/（CeO₂-TiO₂）]为改性物质,借助真空过滤法对聚偏氟乙烯（PVDF）微滤膜进行改性制备复合膜,利用X射线粉末衍射仪、紫外可见漫反射、扫描电子显微镜、傅里叶红外变换光谱等手段探究了复合膜的结构和光吸收能力.选择常州太湖支浜水样作为原水,研究了复合膜在黑暗及紫外光条件下对氨氮及DOC的去除效果.结果表明,黑暗条件下,（GO-CeO₂）复合膜氨氮去除率最高可达到28.21%,GO/（CeO₂-TiO₂）复合膜DOC去除率最高达29.58%;紫外光条件下,GO、CeO₂、TiO₂间的协同作用使得GO/（CeO₂-TiO₂）复合膜氨氮（65.4%）及DOC （54.7%）去除效果最佳.     

功能化石墨烯对苯并[a]芘高效降解菌Paracoccus aminovorans HPD-2生长的促进作用

研究石墨烯对微生物生长的影响,深入探讨石墨烯和微生物之间的相互作用,对科学评估石墨烯的生态安全性具有重要的现实意义.本文研究了两种功能化石墨烯(氧化石墨烯和磺化石墨烯)对苯并[a]芘高效降解菌Paracoccus aminovorans HPD-2生长的影响,并采用扫描电子显微镜(SEM)、拉曼光谱及红外光谱技术深入探讨了石墨烯与菌HPD-2之间的作用机制.结果表明,两种石墨烯对菌HPD-2生长的影响与培养体系中营养水平有关,石墨烯的种类和浓度也是重要影响因素.低浓度石墨烯(0～10 mg·L~(-1))对菌HPD-2生长无影响,较高浓度石墨烯(100 mg·L~(-1))能够显著促进菌HPD-2的生长(p0.05).两种石墨烯均能促进菌HPD-2胞外聚合物的分泌.与菌HPD-2发生相互作用后,低浓度氧化石墨烯的D峰和G峰的相对强度比值(I_D/I_G)显著提高,结构无序性增加,较高浓度石墨烯与菌HPD-2发生了明显的相互作用,并在菌体表面存在一定程度的堆叠,细胞表面蛋白质、氨基酸和胞外多糖均参与了两者之间的相互作用;相比于氧化石墨烯,磺化石墨烯与菌HPD-2表面的作用较弱.研究结果有助于深入理解和科学评价石墨烯的微生物效应.     

Adsorption of VOCs on reduced graphene oxide

A modified Hummer's method was adopted for the synthesis of graphene oxide(GO) and reduced graphene oxide(rGO). It was revealed that the modified method is effective for the production of GO and rGO from graphite. Transmission electron microscopy(TEM) images of GO and rGO showed a sheet-like morphology. Because of the presence of oxygenated functional groups on the carbon surface, the interlayer spacing of the prepared GO was higher than that of rGO. The presence of \OH and C_O groups in the Fourier transform infrared spectra(FTIR) spectrum and G-mode and 2D-mode in Raman spectra confirmed the synthesis of GO and rGO. rGO(292.6 m~2/g) showed higher surface area than that of GO(236.4 m~2/g). The prepared rGO was used as an adsorbent for benzene and toluene(model pollutants of volatile organic compounds(VOCs)) under dynamic adsorption/desorption conditions. rGO showed higher adsorption capacity and breakthrough times than GO. The adsorption capacity of rGO for benzene and toluene was 276.4 and 304.4 mg/g, respectively.Desorption experiments showed that the spent rGO can be successfully regenerated by heating at 150.0°C. Its excellent adsorption/desorption performance for benzene and toluene makes rGO a potential adsorbent for VOC adsorption.     

Reduced graphene oxide-nano zero value iron (rGO-nZVI) micro-electrolysis accelerating Cr(VI) removal in aquifer

Nanoscale zero-valent iron (nZVI) assembled on graphene oxide (GO) (rGO-nZVI) composites were synthesized by reduction of GO and ferrous ions with potassium borohydride, for use in Cr(VI) removal from aqueous solution. The results showed that the two-dimensional structure of GO could provide a skeleton support for Fe⁰, thus overcoming the bottleneck of aggregation for nZVI. Also, rGO-nZVI would form a ferric-carbon micro-electrolysis system in Cr(VI)-contaminated aquifers, enhancing and accelerating electron transfer, exhibiting high rate and capacity for Cr(VI) removal. The optimum dosage of the applied rGO-nZVI was linearly correlated with the initial Cr(VI) concentration. Characterization of rGO-nZVI before and after reaction with Cr(VI) revealed the process of Cr(VI) removal: rGO-nZVI firstly transferred electrons from Fe⁰ cores via their Fe(II)/Fe(III) shells to the GO sheet; there, negatively charged Cr(VI) received electrons and changed into positively charged Cr(III), which was adsorbed by the negatively charged GO sheet, avoiding the capping and passivating of nZVI. rGO-nZVI formed a good electrically conductive network, and thus had long-term electron releasing properties, which was important for groundwater remediation.     

氧化石墨烯吸附Te (IV)性能与机理的模拟实验研究

²¹⁰Po是加速器驱动次临界系统（ADS）次临界堆铅铋冷却剂和散裂靶产生的重要放射性核素.本文以同主族元素Te（IV）代替Po（IV）,首先对氧化石墨烯（GO）吸附Po（IV）的性能进行了模拟实验研究.结果显示：GO对Te（IV）的吸附率随时间增加可分为快速增加阶段、缓慢上升阶段和吸附2.5 h后的饱和阶段;GO对Te（IV）的吸附率随溶液pH值增加呈先上升后下降的趋势,当pH值为4.7时,吸附率最大;随着吸附体系GO量逐渐增加,GO对Te（IV）的吸附率先线性上升后恒定,吸附量则呈现先不变后下降的趋势.进一步的吸附机理分析结果表明：GO对Te（IV）的吸附以弱化学作用为主,且随吸附过程进行,吸附限速步骤由内扩散转变为膜扩散,吸附表面由非均质转变为均质;羧基、环氧基和CC键是GO吸附Te（IV）的主要结合位点,且结合中Te（IV）化合价不变.