Hongjuan Ma

Ultra-light, compressible and fire-resistant graphene aerogel as a highly efficient and recyclable absorbent for organic liquids

Compressive graphene aerogels were obtained by the one-step reduction and self-assembly of graphene oxide with ethylenediamine and then freeze-drying. The aerogels hold good compressibility, variable electrical resistance and fire-resistance. The high porosity with a hydrophobic nature, allows the aerogels to absorb different organic liquids, and the absorption–squeezing process has been demonstrated for oil collection.

Electrospun nanofibrous adsorbents for uranium extraction from seawater

Here we report a nanoadsorbent design, which integrates the high affinity of amidoxime (AO) groups and size effect of nanomaterials in nanofibrous composite mats prepared by a two-nozzle electrospinning process, for the adsorption of uraniumin simulated seawater with an uptake capacity of 1.6 mg U g(-1) adsorbent in the presence of massive amounts of interference ions.

Flexible graphene fibers prepared by chemical reduction-induced self-assembly

Flexible graphene fibers (GFs) with an ultimate elongation of 20% and a tensile strength up to 150 MPa were prepared by a facile low temperature chemical reduction-induced self-assembly method using graphene oxide (GO) suspensions reacted with vitamin C and then dried at room temperature.

Study on the mechanism of photo-degradation of p-nitrophenol exposed to 254 nm UV light

The degradation mechanism of p-nitrophenol (p-NP) exposed to 254 nm UV light was studied in the presence and the absence of oxygen respectively via both steady-state photolysis and time-resolved laser flash photolysis (LFP) experiments. It has been confirmed that p-NP can be photo-ionized to produce its radical cation (p-NP(+)) and hydrated electron (e(aq)(-)) with a quantum yield of 0.52. In neutral solution p-NP(+) will be quickly deprotonated to form its phenoxyl radical (p-NP) which will react with oxygen to promote the breakage of benzene ring of p-NP. The degradation efficiency of p-NP exposed to 254 nm UV is as low as commonly reported. However, oxygen could improve the photo-degradation efficiency, which is due to the reaction of oxygen with p-NP. The reaction between oxygen and p-NP has been experimentally confirmed both in LFP and in pulse radiolysis.

Graphene Oxide Transparent Hybrid Film and Its Ultraviolet Shielding Property

Herein, we first reported a facile strategy to prepare functional Poly(vinyl alcohol) (PVA) hybrid film with well ultraviolet (UV) shielding property and visible light transmittance using graphene oxide nanosheets as UV-absorber. The absorbance of ultraviolet light at 300 nm can be up to 97.5%, while the transmittance of visible light at 500 nm keeps 40% plus. This hybrid film can protect protein from UVA light induced photosensitive damage, remarkably.

Transient and steady-state photolysis of p-nitroaniline in aqueous solution

Both transient photolysis and steady-state photo-degradation experiments were performed to gain insight into the kinetics and mechanisms of degradation of p-nitroaniline (p-NA) in aqueous solutions. Monophotonic photo-ionization of p-NA was characterized by 266 nm Laser Flash Photolysis (LFP). The quantum yield of e(aq)(-) was calculated. Radical cations and neutral radicals of p-NA were identified, respectively. The LFP of p-NA with H(2)O(2) in aqueous solutions was investigated for the first time. For steady-state photo-degradation, degradation of p-NA was observed at diverse irradiation conditions under 254 nm UV light. Direct photo-degradation of p-NA by 254 nm UV light in aqueous solution was very difficult. Once H(2)O(2) was added into the experimental system, degradation of p-NA was enhanced remarkably. In the absence of O(2), degradation rate increased rapidly along with the irradiation time and reached 80% at 10 min. p-NA could be totally removed after 15 min in UV/H(2)O(2) process. In the presence of O(2) and H(2)O(2), degradation rate increased linearly along with the irradiation time and reached 80% at 7.5 min. p-NA could be totally removed after 10 min. The mechanisms behind the photo-degradation of p-NA were discussed.

Built-up superhydrophobic composite membrane with carbon nanotubes for water desalination

Superhydrophobic porous composite membranes are successfully prepared by using poly(vinyl acetate) functionalized multi-walled carbon nanotubes and tested for water desalination under a direct contact membrane distillation (DCMD) method. The permeate flux of the composite membranes remains greater than 20 kg m−2 h−1 and the salt rejection greater than 99.5% when tested with 3.5% NaCl solution at 70 °C. The water contact angle of the composite membranes remains greater than 150° after DCMD testing for 2 hours.

Solar-thermochromism of a hybrid film of VO2 nanoparticles and CoII–Br–TMP complexes

A hybrid film consisting of VO2 nanoparticles and CoII–Br–TMP complexes was prepared. The CoII–Br–TMP complexes containing cobalt(II), trimethylolpropane (CH3CH2C(CH2OH)3, TMP) and bromine were selected to be combined with VO2 nanoparticles for the first time. Evident colour-change behaviour in response to temperature change and enhanced optical performance of this composite were reported.

Electrospun nanofibrous polyethylenimine mat: a potential adsorbent for the removal of chromate and arsenate from drinking water

Herein, water-soluble polyethylenimine (PEI) was turned into a water-resistant composite nanofibrous adsorbent via methacrylation and electrospinning. The PEI-based nanofibrous adsorbent possesses an excellent adsorption capacity of chromate and arsenate in aqueous solution and it also can remove them at a sub-ppm level effectively, which would be promising for drinking water purification.

Synergistic nanofibrous adsorbent for uranium extraction from seawater

Huge reserves of uranium (U) in seawater have been of interest to scientists and energy companies since the 1950s. However, extracting trace concentrations (3.3 ppb) of U from seawater is economically unfeasible without new, high-performance adsorbents. Here, a mat-like nanofibrous composite adsorbent containing binary coordination groups (amidoxime (AO) and carboxyl (AC−)) in a highly porous network of nanofibers is constructed via a parallel-blend electrospinning method. Its U uptake in artificial seawater is more than double those of adsorbents containing AO or AC− groups alone. Density functional theory (DFT) calculations reveal that this synergistic effect is because the AC− group promotes both the U 5f/6d orbital contribution to U–AO bonding and the dissociation of uranyl tricarbonate ions in seawater. In a continuous flow-through experiment with simulated seawater, the nanofibrous adsorbent achieves an adsorption capacity up to 2.86 mg U gads−1 in 30 d but without saturation, indicating a high efficiency for U extraction.