Chenglun Liu

Preparation and characterization of composite magnetic photocatalyst MnxZn1−xFe2O4/β-Bi2O3

Composite magnetic photocatalyst MnxZn1−xFe2O4/β-Bi2O3 was synthesized by a dip-calcination method using manganese zinc ferrite as a magnetic substrate. The effects of composite mass ratio, reaction time and calcination temperature on the degradation of Rhodamine B (RhB) under the simulated sunlight were observed with various investigations. The as-prepared MnxZn1−xFe2O4/β-Bi2O3 was characterized by XRD, FTIR, VSM, UV-vis DRS and SEM. The photodegradation rate of RhB in MnxZn1−xFe2O4/β-Bi2O3 was higher (99.1%) than that (83.6%) in pure β-Bi2O3 within 2.5 h. XRD spectra revealed that the composites presented a tetragonal type, which was similar to that of β-Bi2O3. FTIR spectra exhibit peaks for the absorption of both Bi–O bonds and MnxZn1−xFe2O4. The saturation magnetization (Ms) and coercivity (Hc) of the composite photocatalyst were 7.01 A m2 kg−1 and 25.38 A m−1, respectively. DRS analysis revealed that the optical band gap of this composite was 2.31 eV, which was lower than that of β-Bi2O3 (2.45 eV). Moreover, the photocatalytic activity was still maintained at 82.7% after five cycles. The magnetic property with an appropriate amount of manganese zinc ferrite inhibited the recombination of photo-produced electrons (e−) and holes (h+), and enhanced the photocatalytic property of β-Bi2O3.

Fractal-like kinetic characteristics of rock salt dissolution in water

Abstract Fractal-like kinetic characteristics of rock salt dissolution in water have been studied by using fractal geometry theory. The results show that the dissolution kinetics of rock salt in static and dynamic state is fractal-like. The kinetic parameters k o and h in static state increase while temperature is increased, and those in dynamic state decrease with the increase of flow.

Reduction of Graphite Oxide Using Ammonia Solution and Detection Cr(VI) with Graphene-Modified Electrode

Graphene (reduction of graphite oxide, rGO) was successfully prepared by using ammonia solution (NH3·H2O) as a reductive agent. The molecular structure and electrochemical properties of rGO were characterized by FTIR, XRD, Raman, SEM, EIS, and cyclic voltammetry (CV). The electrochemical sensing of chromium (Cr(VI)) at graphene-modified electrode (rGO/GCE) was investigated by differential pulse cathodic stripping voltammetry. The result showed that the charge transfer resistance of [Fe(CN)6]3−/4− at rGO/GCE was 75.02 Ω·cm2 decreased by about nine times comparing as that of GCE. The reduction peak potential of Cr(VI) at rGO/GCE was shifted positively by 116 mV and the peak current increased by about eight times. Meanwhile, the detection limit was 1.5 × 10−7 mol/L. It was worth noting that the synthesis of rGO by reducing GO with NH3·H2O was more friendly to environment and human health relative to hydrazine hydrate (NH2-NH2·H2O) or other poisonous reductants.

Dielectric and magnetic response of Sr–Zn ferrite composite

Sr–Zn ferrite composites were synthesized by chemical coprecipitation with different sintering process. The composites were characterized by XRD, XPS, IR, VSM, and N2-adsorption. The results revealed that the composites were composed of S-type ZnFe2O4 and M-type SrFe12O19. Zn2+ ions inserted and occupied the 12k or 2a sites for Fe3+ ions in M-type SrFe12O19. The Zn2+ ions were therefore not on the external surface of the composites. The microwave absorption properties at a frequency range of 0–18 GHz were estimated using the electromagnetic parameters obtained through the agency of microwave vector network analyzer. The microwave absorbing properties of composites were excellently superior to that of the pure SrFe12O19 or ZnFe2O4 due mainly to the exchange coupling between the hard- and soft-magnetic phases. The synthesis process was found to facilitate mass production for various composite materials, especially the two phases or multiphase composite materials.

Compressibility of coal matter and coal pore

Abstract In the light of definition of compressibility of matter and fractal description of coal pore volume, a calculating formula on pore compressibility of coal (βP) has been obtained, and that βP and βS (compressibility of coal matter) decrease with the increase of experimental pressure, and they are relative to sampling sites of coals.

Preparation of strontium ferrite from strontium residue

Strontium ferrite was prepared from Strontium Waste Residue (SWR) as a material. Strontium chloride was obtained by leaching SWR with ammonia chloride, and then SrCl2 was converted to SrCO3. Strontium ferrite (SrFe12O19) was formed by roasting the mixture of SrCO3 and FeCl3 in a proper proportion. The structure and magnetic susceptibility of strontium ferrite were investigated. The results showed that strontium conversion ratio increased with decreasing SWR grain diameter. The largest ratio was presented when n(NH4Cl/Sr) was 3.6. What is more, the conversion process coincided with the kinetic characteristics of fractal reaction. The magnetic susceptibility of strontium ferrite decreased with increasing Fe3+/Sr2+ mole ratio and pH. SrFe12O19 exhibited face-centered and cubic closely-packed hexagonal structures. There were the strong diffraction peaks of Fe2O3 in the X-ray diffractogram of strontium ferrite. Strontium recovery ratio was 87.0%.

Structure and catalytic activity of magnetic composite photocatalyst SrFe12O19/SrTiO3

Abstract SrFe12O19/SrTiO3 photocatalyst was synthesized with solgel method. The as-prepared composite catalyst was characterized by XRD, IR, SEM, BET, UV–vis and VSM. It was revealed that the specific surface area of SrFe12O19/SrTiO3 was larger than that of pure SrTiO3. The maximum absorption wavelength (λmax) of the composite was 550 nm, which located in visible light region. The saturation magnetizations (Ms), remanent magnetization (Mr) and coercivity (Hc) of the magnetic composite were 19.8emu/g, 10.5emu/g and 2500G, respectively. The activity of the catalysts was evaluated by photodegradation of methylene blue (MB), and the degradation ratio with 25% SrFe12O19/SrTiO3 was 98.6% at 2 h under the visible light illumination, while the degradation ratio with pure SrTiO3 was 30% at the same condition. The results indicated that 25% SrFe12O19/SrTiO3 held excellent photocatalytic activity as well as strong magnetization, which was beneficial to separate and recover completely. The recycling test confirmed that the magnetic composite catalyst was capable of using repeatedly, and the photocatalytic activity was above 80% after 5 cycles.

Preparation and magnetic properties of Sm–Co doped strontium ferrite

Abstract: In this work, Sm–Co doped strontium ferrite, SrFe12-xSmxCoxO19 (x = 0·1–0·5) composites were prepared by adding Sm3+ and Co2+ cations into M-type strontium ferrite using one-step chemical coprecipitation method. The composites were characterized by FTIR and XRD. The magnetic properties of the samples were measured and analyzed by VSM. The results indicated that the average crystallite sizes located in a range of 29·7–32·9 nm. Lattice constants, a and c were close to 5·88 and 23·05 Å for the M-type strontium ferrite phase. The analyses of magnetic properties demonstrated that when x = 0·2 and 0·4, Sm3+ and Co2+ ions substituted Fe3+ ions at 12 k (↑) or 2a (↑) site. While, as x = 0·1, 0·3, and 0·5, Fe3+ ions at 12 k (↑) or 2a (↑) site were replaced by Sm3+ ions and Fe3+ ions at 4f2 (↓) site were substituted by Co2+ ions. Meanwhile, the proposed substitute mechanism in this work was expected to provide a good concept to modify directionally M-type strontium ferrite in order to extend its application field.

A novel magnetic heterojunction photocatalyst TiO2/SrFe12O19: synthesis strategy, photocatalytic activity, and unprecedented migration mechanism of photoexcited charge carrier

ABSTRACT A novel magnetic heterojunction photocatalyst TiO2/SrFe12O19 was synthesized from self-made strontium carbonate and Tetra-n-butyl Titanate by ultrasound technique. Acting as magnetic substrate, multifunctional strontium ferrite (SrFe12O19) played an important role in the magnetic heterojunction photocatalyst system. On the one hand, as n-type semiconductors, SrFe12O19 was in contact with TiO2, and a heterojunction was generated. On the other hand, as a hard-magnetic material SrFe12O19 can produce a stable magnetic field. This facilitates the recovery of photocatalyst from reaction solution with an extra magnet. More important, the stable magnetic field stemming from SrFe12O19 can promote separation between photo-induced electrons and holes and enhance the quantum efficiency for TiO2. In this work, we proposed an unprecedented migration mechanism of photoexcited charge carriers. It is hope to provide new insight into photocatalytic mechanism for extending our understanding.

An effective approach to improve ethanol productivity by simultaneous saccharification and fermentation of rice straw

ABSTRACT Fuel ethanol was produced using rice straw with the simultaneous saccharification and fermentation (SSF) method. The influence of cellulose liquefaction pretreatment and Fe2+ quantity on ethanol productivity was investigated in detail. At the same time, the optimized conditions including fermentation temperature, Fe2+ amount, yeast inoculation quantity, and the inoculated cellulose enzyme dosage in the SSF process were systematically investigated by analyzing fuel ethanol yield. The result indicated that fuel ethanol yield was 0.319 g per gram rice straw by SSF approach when appropriate amount of Fe2+ was added into the reaction system. The optimal technology parameters were: fermenting temperature of 36°C, Fe2+ amount of 4 mg · g−1, inoculating proportion of 20%, cellulose enzyme of 20 IU · g−1, and Pachysolen tannophilu/saecharomyces cerevisiae of 1:2 ratio. The ethanol yield under the best conditions was larger than that of the control group. We hope that this research can facilitate to achieve large-scale comprehensive utilization for rice straw.