Hai-Tao Ren

Response surface optimization of enzyme-assisted extraction polysaccharides from Dictyophora indusiata.

An enzyme-assisted procedure for the extraction of the water-soluble polysaccharides from the stipe of Dictyophora indusiata was investigated using response surface methodology. The orthogonal array design was employed to optimize the concentration of three kinds of enzyme (cellulase, papain and pectolyase) and the optimal cellulose, papain and pectolyase concentration were 2.0% (wt.% of D. indusiata powder), 2.0% and 1.5%, respectively. And then the effect such as temperature, time and pH was studied based on a three-level three-factor Box-Behnken design. The optimized conditions were as follows: extraction temperature 52.5 °C, extraction time 105 min and pH 5.25. Under these conditions, the experimental yield of polysaccharides was 9.77±0.18%, which was well matched with the predictive yield of 9.87%. As it turned out, enzyme-assisted procedure was an effective method.

Adsorptive removal of dibenzothiophene from model fuels over one-pot synthesized PTA@MIL-101(Cr) hybrid material.

Hybrid nanomaterials comprising phosphotungstic acid (PTA) and MIL-101(Cr) were prepared through one-pot synthesis and post-modification methods and then were used as adsorbents of dibenzothiophene (DBT) from simulated diesel fuels. Samples obtained by different ways (encapsulation and impregnation) were characterized by nitrogen adsorption, transmission electron microscope (TEM), X-ray diffraction (XRD), Fourier transform infrared spectrum (FT-IR) and series of adsorption experiments. The equilibrium adsorption capacities of PTA@MIL-101(Cr) illustrated that the direct introduction of PTA into MIL-101(Cr) during synthesis resulted in a 10.7% increase compared with MIL-101(Cr). However, porous hybrid adsorbent PTA/MIL-101(Cr) prepared via post-modification method exhibited lower adsorption capacity than virgin MIL-101(Cr). The theoretical maximum adsorption capacity (Q0) of PTA@MIL-101(Cr) is 136.5mg S/g adsorbent, 4.2 times of MIL-101(Cr). Even in competitive adsorption between aromatic compounds, which possess strong affinity with MOFs, and DBT, PTA@MIL-101(Cr) and MIL-101(Cr) remained their effectiveness in removal of DBT in the system. Based on these results, it can be presumed that MIL-101(Cr), modified properly, can be used as a promising adsorbent for eliminating aromatics and S-compounds in commercial fuels simultaneously.

Drying effects on the antioxidant properties of polysaccharides obtained from Agaricus blazei Murrill.

Three polysaccharides (ABMP-F, ABMP-V, ABMP-A) were obtained from Agaricus blazei Murrill via methods such as freeze drying, vacuum drying and air drying, respectively. Their chemical compositions were examined, and antioxidant activities were investigated on the basis of assay for hydroxyl radical, DPPH radical, ABTS free radical scavenging ability and assay for Fe(2+)-chelating ability. Results showed that the three ABMPs have different physicochemical and antioxidant properties. Compared with air drying and vacuum drying methods, freeze drying method resulted to ABMP with higher neutral sugar, polysaccharide yield, uronic acid content, and stronger antioxidant abilities of hydroxyl radical, DPPH radical, ABTS radical scavenging and Fe(2+)-chelating. As a result, Agaricus blazei Murrill polysaccharides are natural antioxidant and freeze drying method serves as a good choice for the preparation of such polysaccharides and should be used to produce antioxidants for food industry.

Effects of extraction methods on the antioxidant activities of polysaccharides from Agaricus blazei Murrill.

Five polysaccharides were obtained from Agaricus blazei Murrill (ABM) through different extraction methods including hot water extraction, single enzyme extraction (pectinase, cellulase or papain) and compound enzymes extraction (cellulase:pectinase:papain). Their characteristics such as the polysaccharide yield, polysaccharide content, protein content, infrared spectra were determined, and antioxidant activities were investigated on the basis of hydroxyl radical, DPPH free radical, ABTS free radical and reducing power. The results showed that five extracts exhibited antioxidant activities in a concentration-dependent manner. Compared with other methods, the compound enzymes extraction method was found to present the highest polysaccharides yield (17.44%). Moreover, compound enzymes extracts exhibited the strongest reducing power and highest scavenging rates on hydroxyl radicals, DPPH radicals and ABTS radicals. On the contrary, hot water extraction method had the lowest polysaccharides yield of 11.95%, whose extracts also exhibited the lowest antioxidant activities. Overall, the available data obtained in vitro models suggested that ABM extracts were natural antioxidants and compound enzymes extraction was an appropriate, mild and effective extracting method for obtaining the polysaccharide extracts from Agaricus blazei Murrill (ABM).

Effects of Mn(II) on the sorption and mobilization of As(V) in the presence of hematite.

In this study, the effects of Mn(II) on the sorption and mobilization of As(V) by synthetic hematite were investigated. Our results showed that As(V) removal by hematite was evidently dependent on pH, and simultaneous addition of Mn(II) and As(V) into hematite suspension resulted in more removal of As(V) via electrostatic attraction at pH 4.0, 7.0 and 8.3. However, in Mn(II) pre-loaded system, the removal percentages of As(V) at pH 8.3 decreased by 17.0%, 20.7% and 26.7% after 24h at the aging time of 2, 12 and 36 h, respectively. The concentrations of the released As(V) after the addition of 1mM Mn(II) were 23.6, 12.9 and 7.0 μM at pH 8.5 in 2, 3 and 4 g L(-1) hematite suspension, respectively. But Ca(2+) did not show such an effect under similar experimental conditions. Abiotic oxidation of Mn(II) on hematite played an important role in As(V) mobilization. The growing thin layer of Mn(III, IV) (hydr)oxides (MnO(x)) formed on hematite would take up the sorption sites pre-occupied by As(V) and resulted in the release of the adsorbed As(V) back into solution. This study enriched our understanding on As(V) fate in the coexistence of iron oxides and Mn(II).

Abiotic oxidation of Mn(II) induced oxidation and mobilization of As(III) in the presence of magnetite and hematite

Manganese (hydr)oxides are powerful oxidants mediating the transformation of As(III) to As(V) under natural conditions, however, the presence of Mn(II) on the oxidation of As(III) in the pH range of 7.0-9.0 has not been reported so far. In this study, abiotic oxidation of Mn(II) to amorphous Mn(III, IV) (hydr)oxides (MnOx) on magnetite and hematite was confirmed, and the impact of newly formed MnOx on the fate of As(III) was investigated. With the addition of Mn(II) into As(III)-preloaded systems, the dissolved and the adsorbed As(III) was oxidized to As(V) at high pH, and Mn(II) mobilized the adsorbed As(III) and As(V) in hematite system. High production of dissolved As(V) and significant mobilization of As(III) were even more significant in hematite suspension (total As was 18.96 mgL(-1) after 60 h at pH 8.62) with simultaneous addition of Mn(II) and As(III), while magnetite showed a higher capacity for the retention of As(III) and As(V). It could therefore be deduced that the newly formed MnOx on iron oxides could oxidize the dissolved and the adsorbed As(III) to As(V). In addition, the MnOx formed at high pH would take up the sorption sites previously occupied by the adsorbed As(III), and then mobilized a fraction of the adsorbed As(III) into solution. The present study reveals that MnOx formed via abiotic oxidation on iron oxides plays an important role in the oxidation and mobilization of both dissolved and adsorbed As(III) in aquatic environment.

Effects of PH and Metal Cations on the Oxidation of as(III) by Pyrolusite

In this study, the effects of pH and metal cations such as Mn(II) and Ca(II) on the oxidation of As(III) by pyrolusite were investigated. Our results showed that the oxidation of As(III) was significantly dependent on pH values. The oxidation rate increased with a decrease of pH from 4.0 to 6.0 or an increase of pH from 8.0 to 9.0, while be the lowest at pH 7.0. The removal of aqueous As(III) and the release of produced As(V) were inhibited when Mn(II) was simultaneously added into the system, which could be explained that added Mn(II) bounded to pyrolusite and consequently blocked the adsorption and oxidation of As(III). Higher concentration of Mn(II) lowered the oxidation of As(III) at both pH 5.83 and 7.82. The addition of Mn(II) caused a greater decrease in the oxidation rate of As(III) than did the addition of Ca(II). The lower oxidation rate of As(III) was observed with the higher concentration of Ca(II) at pH 5.83, while the trend was opposite at pH 8.72.

Effects of pH and Anion Species on Cr(VI) Removal by Magnetite

Magnetite was prepared to remove poisonous hexavalent chromium [Cr(VI)] from aqueous solution. Batch experiments were conducted to measure the effects on removal of Cr(VI) of different parameters such as ionic strength, pH, and initial concentration. Results demonstrated that the removal of Cr(VI) on magnetite was decreased with the increase of pH in the range of 3.4-5.0, but independent of ionic strength. The removal percentage of Cr(VI) also decreased with the increase of Cr(VI) concentration in the range of 50-200 mg/L. At pH 3.5 and 5.0, the presence of SO42−retarded the removal of Cr(VI) via electrostatic interactions and/or competition for surfaces sites on magnetite. The pH of the medium and presence of anion species were critical factors in the removal of Cr(VI) from aqueous solution.

Emulsion Synthesis and Properties of Polyaniline Spherical Nanoparticles

In this article, the polyaniline(PANI) spherical nanoparticles were synthesized by the way of emulsion polymerization. The effects of emulsifier concentration on the morphology and electrical properties were systematic studied. The structure of PANI prepared by this method was characterized by Fourier transform infrared spectroscopy (FT-IR), transmission electron microscope (TEM). The electrochemical and capacitive behavior of PANI prepared by this way was systematically studied by cyclic voltammetry(CV) and electrochemical impedance spectroscopy (EIS) tests. The results showed that we obtained PANI spherical nanoparticles with diameter about 100nm and it had good electrochemical performance.