Organic waste processing ye? Graphene oxide tell you the answer!

1. Background and design ideas

green handle organic waste is one of the major challenges to the pharmaceutical industry much-needed face. According to statistics, the pharmaceutical process solution comprises an organic waste of about 80%, and 56% of drug intermediates. Require large amounts of organic waste separation and recovery, the pharmaceutical industry consumes 40-80% of human and financial resources. Nanofiltration membrane technology for treating organic waste compared with several other traditional approach has several significant advantages, including high energy efficiency, low cost, and small size. However, the graphene oxide-based nano-solvent separation membrane having a slower rate of penetration, poor stability disadvantages. To address these shortcomings, recently, Professor Tae-Hyun Bae Singapore\’s Nanyang Technological University laboratory with Tianjin University, Michael D. Guiver laboratory together in the \” Science Advance \”, delivered a speech entitled \”Realizing small-flake graphene oxide membranes for ultrafast size-dependent organic solvent nanofiltration\” of research papers reported using the trivalent lanthanide ions (La3 +) cross-linked pieces of graphene oxide (SFGO) film, to achieve the advantage of having a high filtration rate, high selectivity, high stability in organic solvent nanofiltration SFGO-La3 + membrane . The main author uses two strategies to achieve their goals. The first dimension is the horizontal plane of the graphene oxide nano control layer; second cation is embedded in the graphene oxide, the use of the cationic crosslinked graphene oxide. Nano-film material, the length, width and separation channel tortuous affect the separation efficiency of the nano-film. To shorten the distance of the channel through the lateral face of the graphene oxide dimension control, reduced tortuous channel to achieve high performance ultra-fast organic solvent nanofilter (FIG. 1). Selection of trivalent lanthanum ions into the graphene, as La3 + has strong coordination ability to provide good crosslinking effect.Large radius of trivalent lanthanum ions makes it suitable liner (spacer), the interlayer spacing can be adjusted graphene oxide film.

FIG. 1, as compared to film LFGO-La3 +, SFGO-La3 + membrane channel path is shorter, less tortuous, help to improve the transmission rate of the solvent.

2, thin SFGO-La3 + and LFGO-La3 Synthesis + membrane

On the graphene oxide prepared by Hummer method to obtain a single die graphene oxide (SFGO) and a large single graphene oxide (LFGO). SFGO and LFGO in the cross-plane dimensions show the gap several times. SFGO 0.03 square microns in area, has a smaller dimension distribution. 0.43-0.51 LFGO area in square micrometers, the larger dimension of the distribution (FIG. 2). Field emission scanning electron microscope (FESEM) LFGO displayed on a nylon base capable of forming a homogeneous layered structure. However, since the cross-plane aperture dimension is smaller than SFGO nylon substrate, a uniform continuous film is difficult to form on the substrate. In order to be prepared SFGO tough film of La3 + as a crosslinking agent using the network SFGO-La3 + is sufficiently large, thereby successfully prepared in a continuous uniform film SFGO-La3 +. Observed under FESEM, found SFGO-La3 + and LFGO film having a film surface topography similar. Ray energy dispersive X-ray (EDX) analysis confirmed the La3 + uniformly dispersed in the film inside SFGO-La3 +.

FIG. 2, the morphology SFGO, LFGO SFGO-La3 +, and three kinds of films, FIG EDX confirmed SFGO-La3 + La3 + membrane in a uniform distribution.

3, SFGO-La3 + membrane filtration performance and stability

On the test SFGO-La3 separation performance + membrane at a pressure 1bar of. First, the rate of penetration of water and evaluation of other organic solvents. The results showed that the solvent SFGO-La3 + penetration rate of the film primarily depend on the size and the viscosity of the solvent molecules of the solvent, the lower the viscosity of the solvent, the smaller the molecular size, The solvent, the higher the penetration rate of the film, herein, as a model of the methanol solvent is selected, because methanol is widely used in the pharmaceutical industry, and the organic dye to dissolve many small molecules, convenient selective membrane was evaluated. The results showed SFGO-La3 + membrane permeation rate for pure methanol is 2.7 times higher than the film LFGO-La3 +, LFGO than an order of magnitude (FIG. 3). In addition, the authors dissolved in methanol five different molecular weights, small organic dye molecules with different charge amounts are methyl orange (the MO), crystal violet (the CV), acid fuchsin (the AF), Acid Red 94 (AR) , and alcian blue (AB) selected membrane permeability experiments. When water is used as solvent, rate of five filter dye than 95%. When selecting methanol as the solvent, LFGO-La3 + membrane for a relatively large molecular weight dye molecules showing a high filtration rate for Acid Red 94 and Acid Magenta filter is higher than 95%, the filtration efficiency for alcian blue it is close to 100%. The authors also demonstrated SFGO-La3 + film exhibited good filtration rates and the ability to selectively filter the organic dye molecules in a dead-end filtration and crossflow filtration two modes.

FIG. 3, left, SFGO-La3 + for a number of different solvents film had good rate of penetration. Right, SFGO-La3 + membrane for AF, AR, AB three kinds of organic dye having good filtering capacity selection.

On the further explore the mechanism of film SFGO-La3 +. X-ray diffraction (XRD) results show SFGO-La3 + layer spacing film when water and methanol as compared to the absence of a solvent, respectively, an increase of 0.92 nm and 0.9 nm (FIG. 4A). Nanochannel expansion layer spacing can help reduce the resistance of the film to the solvent, the solvent for improving the transmission rate help. On the next X-ray photoelectron spectroscopy (XPS) analyzes of the chemical environment of La3 +, as shown in FIG. 4b and 4c, SFGO-La3 + XPS film exhibits a clear La-3d and La-4d peak confirmed La3 + graphene oxide carboxyl ligand. FTIR Fourier transform infrared spectroscopy in the 668 and 818 cm-1 ligand corroborated two peaks La3 + with a carboxyl group. In addition, the authors also make use of the density functionalLetter (DFT) and molecular dynamics (PFMD) calculations were corroborated La3 + coordination with the graphene oxide occurs. To confirm the stability of the film SFGO-La3 +, author 3bar pressure filtration test, test after 72 consecutive young, still has a very good rate of methanol permeation, acid fuchsin filtration rate remained greater than 95%. The authors also confirmed that the film not only has good stability in steady-state fluid, unsteady fluid, still has good stability.

FIG 4, A, XRD data SFGO-La3 + membrane in different solvents. B and C, SFGO-La3 + film XPS spectra

Total junction

in general, the successful implementation of the filter utilizing organic nano-scale effects based on the graphene oxide. La3 + and SFGO crosslinking provides thin, tough and continuous film SFGO-La3 +. Since SFGO-La3 + membrane having a smaller transverse dimension, but also shorten the path of passage of the solvent, reduces the solvent tortuous path, so SFGO-La3 + organic solvent having a high throughput rate, and organic dye molecules having strong selectivity. The film during a long unsteady fluid shear effects, still maintained a good stability, meaning SFGO-La3 + film having good usability.