Insight into the dynamic adsorption behavior of graphene oxide multichannel architecture toward contaminants

Graphene oxide(GO) channels exhibit unique mass transport behaviors due to their flexibility, controllable thinness and extraordinary physicochemical properties, enabling them to be widely used for adsorption and membrane separation. Nevertheless, the adsorption behavior of nanosized contaminants within the channels of GO membrane has not been fully discussed. In this study, we fabricated a GO membrane(PGn, where n represents the deposition cycles of GO) with multi channels via the crosslinking of GO and multibranched poly(ethyleneimine)(PEI). Phenol was used as molecular probe to determine the correlations between dynamic adsorption behavior and structural parameters of the multilevel GO/PEI membrane. PG8 shows higher adsorption capacities and affinity, which is predominantly attributed to the multichannel structure providing a large specific surface for phenol adsorption, enhancing the accessibility of active sites for phenol molecules and the transport of phenol. Density functional theory calculations demonstrate that the adsorption mechanism of phenol within GO channel is energetically oriented by hydrogen bonds, which is dominated by oxygen-containing groups compared to amino groups. Particularly, the interfaces which facilitate strong π-π interaction and hydrogen bonds maybe the most active regions. Moreover, the as-prepared PG8 membrane showed outstanding performance for other contaminants such as methyl orange and Cr(VI). It is anticipated that this study will have implications for design of GO-related environmental materials with enhanced efficiency.

抗污染羧化二氧化钛/海藻酸钙水凝胶过滤膜的制备及染料截留性能

以纳米羧化二氧化钛为增强剂,海藻酸钠为成膜基材,通过Ca^(2+)离子交联制备抗污染羧化二氧化钛/海藻酸钙(TiO_(2)-COOH/CaAlg)水凝胶过滤膜。通过红外光谱和扫描电镜对复合膜的化学结构与形貌进行表征,并研究复合膜的力学性能、染料截留性能及抗污染性能。结果表明,相比于二氧化钛,羧化二氧化钛在复合膜中分散更均匀,利用Ca^(2+)离子对羧化二氧化钛中-COOH与海藻酸钠中-COOH的协同交联作用,提高了水凝胶膜的力学性能。羧化二氧化钛含量为20%时,复合膜的断裂强度、断裂伸长率、拉伸模量和断裂能均最大,对染料直接黑38的截留率可达到96%,且受原料液pH值、无机盐NaCl和Na2SO4的影响较小,在0.1 MPa操作压力下过滤直接黑38/Na_(2)SO_(4)混合溶液12 h,复合膜对直接黑38的截留率保持在93%以上,渗透通量在15 L/(m^(2)·h)左右。

Microencapsulated ammonium polyphosphate by polyurethane with segment of dipentaerythritol and its application in flame retardant polypropylene

Dipentaerythritol(DPER),4,40-diphenylmethanediisocyanate(MDI)and melamine(MEL)are used as raw materials to microencapsulate ammonium polyphosphate(MAPP)in situ polymerization.The MAPP is characterized by Fourier transform infrared(FT-IR),scanning electron microscopy(SEM),transmission electron microscopy(TEM)and thermal gravimetric analysis(TGA).The results show that the coating operation can effectively improve water resistance of ammonium polyphosphate(APP),and MAPP has higher residual rate than that of APP after combustion.The flame retardant action of MAPP and APP in polypropylene(PP)is investigated by the limited oxygen index(LOI),vertical burning test(UL-94),TGA,SEM,and cone calorimeter test(CCT).The LOI value of the PP/MAPP composite at the same loading is higher than that of PP/APP composite.UL 94 ratings of PP/MAPP composites are raised to V-0 at 20 wt%loading.The results of CCT also show that MAPP is more efficient than APP.The morphological structures observed by digital photos and SEM demonstrated that MAPP could be promoted to form the continuous and compact intumescent char layer.The flame retardant mechanism of PP/MAPP is also discussed.

Multicolor carbon dots with concentration-tunable fluorescence and solvent-affected aggregation states for white light-emitting diodes

Multicolor emissive carbon dots(M-CDs)have tremendous potential applications in manifold fields of bioimaging,biomedicine and light-emitting devices.Until now,it is still difficult to produce fluorescence tunable CDs with high quantum yield across the entire visible spectra.In this work,a type of M-CDs with concentration-tunable fluorescence and solvent-affected aggregation states was synthesized by solvothermal treatment of citric acid(CA)and 1-(2-pyridylazo)-2-naphthol(PAN)and the formation mechanism was monitored by different reaction time and raw material ratio.The fluorescence spectra of M-CDs in organic solvents can range from 350 to 750 nm by adjusting the concentration.M-CDs possess different aggregation states in water and organic solvents,accompanied by different fluorescence emission,which is attributed to the different surface states of various component CDs in M-CDs.Moreover,the obtained products can be uniformly dispersed into polymethylmethacrylate(PMMA)solutions as well as epoxy resins to fabricate transparent CDs/PMMA films and CDs/epoxy composites,which can effectively prevent the aggregation and produce multicolor and white light-emitting diodes(WLED).In addition,the prepared WLED with Commission Internationale de L’Eclairage(CIE)of(0.29,0.31)by using M-CDs/epoxy resin as packages,demonstrating the M-CDs exhibit potential applications for light-emitting devices.

Biologically inspired silk fibroin grafted polyacrylonitrile filtration membrane prepared in ZnCl_2 aqueous solution

In this study, biologically inspired silk fibroin grafted polyacrylonitrile(SF-g-PAN) filtration membrane was prepared using ZnCl_2 aqueous solution as solvent, avoiding the use of organic solvents. Phase inversion occurred when Zn^(2+)and Cl-ions gradually diffused into water, creating a well-connected ion channel network and the SF-g-PAN filtration membrane was obtained. The membranes were observed by SEM and 3D ultra-depth microscope. The hydrophilic property, pore size distribution and dye rejection of the membrane were investigated. Results showed that the membrane has no finger hole formation because ZnCl_2 aqueous solution has a lower curing rate parameter compared with organic solvents. SF-gPAN membrane possessed good anti-fouling properties and pH sensitivity. The pore size distribution of the SF-g-PAN membrane was 0.25–1.04 nm. The rejection of direct yellow 27(Mw = 662.6) and amaranth(Mw = 604.5) was 96.51% and 30.63%, with the flux of 72.32 L m^(-2) h^(-1) and 73.83 L m^(-2) h^(-1) respectively at0.1 MPa. The SF-g-PAN membrane has a wide range of applications prospect in fine separation, dye desalination, waste water treatment and biomedical fields.