A Novel Fabrication of Hematite Nanoparticles via Recycling of Titanium Slag by Pyrite Reduction Technology.

An enormous quantity of titanium slag has caused not merely serious environment pollution, but also a huge waste of iron and sulfur resources. Hence, recycling iron and sulfur resources from titanium slag has recently been an urgent problem. Herein, hematite nanoparticles were fabricated through a pyrite reduction approach using as-received titanium slag as the iron source and pyrite as the reducing agent in an nitrogen atmosphere. The physicochemical properties of the hematite nanoparticles were analyzed using multiple techniques such as X-ray diffraction pattern, ultraviolet-visible spectrophotometry, and scanning electron microscopy. The best synthesis conditions for hematite nanoparticles were found at 550 °C for 30 min with the mass ratio of 14:1 for titanium slag and pyrite. The results demonstrated that hematite nanoparticles with an average particle diameter of 45 nm were nearly spherical in shape. The specific surface area, pore volume, and pore size estimated according to the BET method were 19.6 m2/g, 0.117 cm3/g, and 0.89 nm, respectively. Meanwhile, the fabricated hematite nanoparticles possessed weak ferromagnetic behavior and good absorbance in the wavelength range of 200 nm-600 nm, applied as a visible light responsive catalyst. Consequently, these results show that hematite nanoparticles formed by the pyrite reduction technique have a promising application prospect for magnetic material and photocatalysis.

Environmental-friendly and effectively regenerate anode material of spent lithium-ion batteries into high-performance P-doped graphite.

Recycling graphitefrom spentlithium-ionbatteries has been largely ignored.In the present work, we propose a novel purification process, which modifies the structure of graphite through phosphoric acid leaching-calcination to obtain high-performance phosphorus (P)-doped graphite (LG-temperature) and lithium phosphate products. The content analysis of X-ray photoelectron spectroscopy (XPS), X-ray fluorescence (XRF) and scanning electron microscope focused ion beam (SEM-FIB) indicates that the LG structure is deformed by the doped P atom. The results of In-situ fourier transform infrared spectroscopy (In-situ-FTIR), density functional theory (DFT) calculation and XPS analysis show that the surface of the leached spent graphite contains rich oxygen groups, which react with phosphoric acid at high temperatures and form stable C-O-P and C-P bonds, making it easier to form stable solid electrolyte interface (SEI) layer. The increase of layer spacing is confirmed by X-ray diffraction (XRD), Raman and transmission electron microscope (TEM), which is conducive to the formation of efficient Li+ transport channels. What is more, Li/LG-800 cells possess high reversible specific capacities of 359, 345, 330 and 289 mA h g-1 at 0.2C, 0.5C, 1C and 2C, respectively. After100cyclesat0.5C, the specific capacityis as high as 366 mAh g-1, demonstrating the outstanding reversibility and cycle performance. This study proves and highlights a promising recovery route for exhausted lithium-ion batteries anodes, making complete recycling possible.

Fe3O4@C Nanoparticles Synthesized by In Situ Solid-Phase Method for Removal of Methylene Blue.

Fe3O4@C nanoparticles were prepared by an in situ, solid-phase reaction, without any precursor, using FeSO4, FeS2, and PVP K30 as raw materials. The nanoparticles were utilized to decolorize high concentrations methylene blue (MB). The results indicated that the maximum adsorption capacity of the Fe3O4@C nanoparticles was 18.52 mg/g, and that the adsorption process was exothermic. Additionally, by employing H2O2 as the initiator of a Fenton-like reaction, the removal efficiency of 100 mg/L MB reached ~99% with Fe3O4@C nanoparticles, while that of MB was only ~34% using pure Fe3O4 nanoparticles. The mechanism of H2O2 activated on the Fe3O4@C nanoparticles and the possible degradation pathways of MB are discussed. The Fe3O4@C nanoparticles retained high catalytic activity after five usage cycles. This work describes a facile method for producing Fe3O4@C nanoparticles with excellent catalytic reactivity, and therefore, represents a promising approach for the industrial production of Fe3O4@C nanoparticles for the treatment of high concentrations of dyes in wastewater.

A low-cost solvent-free method to synthesize α-Fe2O3 nanoparticles with applications to degrade methyl orange in photo-fenton system.

Hematite nanoparticles (α-Fe2O3 NPs) were successfully synthesized by a low-cost solvent-free reaction using Ferrous sulfate waste (FeSO4·7H2O) and pyrite (FeS2) as raw materials and employed for the decolorization of Methyl Orange by the photo-Fenton system. The properties of α-Fe2O3 NPs before and after photo-Fenton reaction were characterized by X-ray powder diffraction (XRD), Field emission scanning electron microscopy (FESEM), Fourier transform infrared (FT-IR) spectrum and X-ray photoelectron spectroscopy (XPS), and the optical properties of α-Fe2O3 NPs were analyzed by UV-vis diffuse reflectance spectra (UV-vis DRS) and Photoluminescence (PL) spectra. The analytic results showed that the as-formed samples having an average diameter of ~50 nm exhibit pure phase hematite with sphere structure. Besides, little differences were found by comparing the characterization data of the particles before and after the photo-Fenton reaction, indicating that the photo-Fenton reaction was carried out in solution rather than on the surface of α-Fe2O3 NPs. A 24 central composite design (CCD) coupled with response surface methodology (RSM) was applied to evaluate and optimize the important variables. A significant quadratic model (P-value<0.0001, R2 = 0.9664) was derived using an analysis of variance (ANOVA), which was adequate to perform the process variables optimization. The optimal process conditions were performed to be 395 nm of the light wavelength, pH 3.0, 5 mmol/L H2O2 and 1 g/L α-Fe2O3, and the decolorization efficiency of methyl orange was 99.55% at 4 min.

Heterogeneous activation of persulfate by ZnCo x Fe2-x O4 loaded on rice hull carbon for degrading bisphenol A.

A new low-cost composite of ZnCo x Fe2-x O4 loaded on rice hull carbon (ZnCo x Fe2-x O4-RHC) was synthesized via waste ferrous sulfate (the industrial waste produced in the process of producing titanium dioxide) and rice hull as raw materials, which was applied for the degradation of bisphenol A (BPA) by heterogeneous activated peroxodisulfate (PS). A series of characterizations including XRD, SEM, FTIR, and BET analysis were carried out to analyze the structure and morphology of the materials. It is confirmed that the ZnCo x Fe2-x O4-RHC composites show better catalytic activity and performance than other control samples, which can be attributed to the synergistic effect of Fe and Co, ZnCo x Fe2-x O4 and RHC based on these analyses. The degradation rate of BPA by ZnCo1.3Fe0.7O4-50%RHC reached 100% within 15 min, and it can still maintain good catalytic efficiency after 5 cycles. ESR test and XPS results showed that free radical and non-free radical processes were involved in BPA degradation. These findings offer a novel, low cost and simple strategy for rational design and modulation of catalysts for the industrial degradation of organic pollutants, and provide a new idea for the utilization of waste ferrous sulphate in titanium dioxide industry.

Chromium (VI) adsorption from wastewater using porous magnetite nanoparticles prepared from titanium residue by a novel solid-phase reduction method.

Porous magnetite nanoparticles were successfully synthesized by reduction of titanium residue with pyrite under nitrogen protection, and characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, vibrating sample magnetometer, X-ray photoelectron spectroscope, zeta potential and Brunauer-Emmett-Teller method. The XRD analysis confirmed the formation of porous magnetite nanoparticles with single spinel structure. The SEM image demonstrated that porous magnetite nanoparticles displayed spherical shape with the average diameter of ~51nm. The surface area of porous magnetite nanoparticles with high magnetic moment (78emu·g-1) was 11.1m2g-1. The experimental results revealed that equilibrium adsorption behavior of Cr(VI) was well described by Langmuir isotherm model with the maximum adsorption capacity of 14.49mgg-1 at 298.15K, and kinetic data was found to fit well with pseudo-second-order model. The adsorption rate for Cr(VI) was controlled by both boundary layer diffusion and intraparticle diffusion. Thermodynamics analysis showed that the adsorption processes of Cr(VI) were endothermic and spontaneous. In addition, the adsorption of Cr(VI) on porous magnetite nanoparticles was classified as chemisorption adsorption, which depended on electrostatic attraction accompanied with reduction of Cr(VI) to Cr(III). Porous magnetite nanoparticles were readily regenerated and used repeatedly for Cr(VI) adsorption at least five cycles. Furthermore, the experimental results indicate that porous magnetite nanoparticles have a promising application for Cr(VI) adsorption from wastewater.

Pyruvate decarboxylase and alcohol dehydrogenase overexpression in Escherichia coli resulted in high ethanol production and rewired metabolic enzyme networks.

Pyruvate decarboxylase and alcohol dehydrogenase are efficient enzymes for ethanol production in Zymomonas mobilis. These two enzymes were over-expressed in Escherichia coli, a promising candidate for industrial ethanol production, resulting in high ethanol production in the engineered E. coli. To investigate the intracellular changes to the enzyme overexpression for homoethanol production, 2-DE and LC-MS/MS were performed. More than 1,000 protein spots were reproducibly detected in the gel by image analysis. Compared to the wild-type, 99 protein spots showed significant changes in abundance in the recombinant E. coli, in which 46 were down-regulated and 53 were up-regulated. Most proteins related to tricarboxylic acid cycle, glycerol metabolism and other energy metabolism were up-regulated, whereas proteins involved in glycolysis and glyoxylate pathway were down-regulated, indicating the rewired metabolism in the engineered E. coli. As glycolysis is the main pathway for ethanol production, and it was inhibited significantly in engineered E. coli, further efforts should be directed at minimizing the repression of glycolysis to optimize metabolism network for higher yields of ethanol production.

Combined process for ethanol fermentation at high-solids loading and biogas digestion from unwashed steam-exploded corn stover.

A combined process was designed for the co-production of ethanol and methane from unwashed steam-exploded corn stover. A terminal ethanol titer of 69.8 g/kg mass weight (72.5%) was achieved when the fed-batch mode was performed at a final solids loading of 35.5% (w/w) dry matter (DM) content. The whole stillage from high-solids ethanol fermentation was directly transferred in a 3-L anaerobic digester. During 52-day single-stage digester operation, the methane productivity was 320 mL CH4/g volatile solids (VS) with a maximum VS reduction efficiency of 55.3%. The calculated overall product yield was 197 g ethanol + 96 g methane/kg corn stover. This indicated that the combined process was able to improve overall content utilization and extract a greater yield of lignocellulosic biomass compared to ethanol fermentation alone.

[Display cellulolytic enzymes on Saccharomyces cerevisiae cell surface by using Flo1p as an anchor protein for cellulosic ethanol production].

In this study, we constructed a yeast consortium surface-display expression system by using Flo1 as an anchor protein. Endoglucanase II (EGII) and cellobiohydrolase II (CBHII) from Trichoderma reesei, and ß3-glucosidase 1 (BGLI) from Aspergillus aculeatus were immobilized on Saccharomyces cerevisiae Y5. We constructed the cellulose-displaying expression yeast consortium (Y5/fEGII:Y5/fCBHII:Y5/fBGLI = 1:1:1) and investigated the enzymatic ability and ethanol fermentation. The displayed cellulolytic enzymes was stabile during the 96-h fermentation. The yeast consortium produced 0.77 g/L ethanol from 10 g/L phosphoric acid swollen cellulose (PASC) within 96 h. The yield (in grams of ethanol produced per gram of carbohydrate consumed) was 0.35 g/g, which correspond to 68.6% of the theoretical yield.

Comparative proteomic analysis of a new adaptive Pichia Stipitis strain to furfural, a lignocellulosic inhibitory compound.

The development of inhibitor-tolerant ethanologenic yeast is one of the most significant challenges facing bio-ethanol production. Adaptation of Pichia stipitis to inhibitors is one of the most efficient ways for dealing with inhibitor problems. The molecular mechanisms involved in the tolerance and adaptation of P. stipitis are, however, still unclear. In the present study, we developed a yeast strain from P. stipitis Y7 that has improved tolerance against inhibitors. We performed comparative proteomic investigations with sodium dodecyl sulfate polyacrylamide gel electrophoresis and quadrupole time-of-flight mass spectrometry. These investigations gave insights into the tolerance of yeast strains to biomass conversion inhibitors at the protein level. Many proteins involved in glycolysis, the pentose phosphate pathway, and the tricarboxylic acid (TCA) cycle were found to be differentially expressed due to the presence of furfural. Quantitative real-time reverse transcription-PCR (RT-PCR) and metabolite analysis were utilized to provide orthogonal evidence for the results obtained. Our results provide a deeper understanding of the molecular mechanisms involved in the response of P. stipitis to furfural. These findings will benefit the design and development of inhibitor-tolerant yeast.

[Development and application of Saccharomyces cerevisiae cell-surface display for bioethanol production].

Saccharomyces cerevisiae is useful as a host for genetic engineering, since it allows the folding and glycosylation of expressed heterologous eukaryotic proteins and can be subjected to many genetic manipulations. Recent advancements in the yeast cell surface engineering developed strategies to genetically immobilize amylolytic, cellulolytic and xylanolytic enzymes on yeast cell surface for the production of fuel ethanol from biomass. We reviewed the basic principle and progress of S. cerevisiae cell-surface engineering and gave an insight into the recent technological developments in the production of bioethanol using surface engineered yeast.

Ethanol Production from Nondetoxified Dilute-Acid Lignocellulosic Hydrolysate by Cocultures of Saccharomyces cerevisiae Y5 and Pichia stipitis CBS6054.

Saccharomyces cerevisiae Y5 (CGMCC no. 2660) and Issatchenkia orientalis Y4 (CGMCC no. 2159) were combined individually with Pichia stipitis CBS6054 to establish the cocultures of Y5 + CBS6054 and Y4 + CBS6054. The coculture Y5 + CBS6054 effectively metabolized furfural and HMF and converted xylose and glucose mixture to ethanol with ethanol concentration of 16.6 g/L and ethanol yield of 0.46 g ethanol/g sugar, corresponding to 91.2% of the maximal theoretical value in synthetic medium. Accordingly, the nondetoxified dilute-acid hydrolysate was used to produce ethanol by co-culture Y5 + CBS6054. The co-culture consumed glucose along with furfural and HMF completely in 12 h, and all xylose within 96 h, resulting in a final ethanol concentration of 27.4 g/L and ethanol yield of 0.43 g ethanol/g sugar, corresponding to 85.1% of the maximal theoretical value. The results indicated that the co-culture of Y5 + CBS6054 was a satisfying combination for ethanol production from non-detoxified dilute-acid lignocellulosic hydrolysates. This co-culture showed a promising prospect for industrial application.

Screening and characteristics of a butanol-tolerant strain and butanol production from enzymatic hydrolysate of NaOH-pretreated corn stover.

As a gasoline substitute, butanol has advantages over traditional fuel ethanol in terms of energy density and hydroscopicity. However, solvent production appeared limited by butanol toxicity. The strain of Clostridium acetobutylicum was subjected to mutation by mutagen of N-methyl-N'-nitro-N-nitrosoguanidine for 0.5 h. Screening of mutants was done according to the individual resistance to butanol. A selected butanol-resistant mutant, strain 206, produced 50 % higher solvent concentrations than the wild-type strain when 60 g glucose/l was employed as substrate. The strain was also able to produce solvents of 23.47 g/l in 80 g/l glucose P2 medium after 70 h fermentation, including 5.41 g acetone/l, 15.05 g butanol/l and 3.02 g ethanol/l, resulting in an ABE yield and productivity of 0.32 g/g and 0.34 g/(l h). Subsequently, Acetone-butanol-ethanol (ABE) production from enzymatic hydrolysate of NaOH-pretreated corn stover was investigated in this study. An ABE yield of 0.41 and a productivity of 0.21 g/(l h) was obtained, compared to the yield of 0.33 and the productivity of 0.20 g/(l h) in the control medium containing 52.47 mixed sugars. However, it is important to note that although strain 206 was able to utilize all the glucose rapidly in the hydrolysate, only 32.9 % xylose in the hydrolysate was used after fermentation stopped compared to 91.4 % xylose in the control medium. Strain 206 was shown to be a robust strain for ABE production from lignocellulosic materials and has a great potential for industrial application.

Soaking pretreatment of corn stover for bioethanol production followed by anaerobic digestion process.

The production of ethanol and methane from corn stover (CS) was investigated in a biorefinery process. Initially, a novel soaking pretreatment (NaOH and aqueous-ammonia) for CS was developed to remove lignin, swell the biomass, and improve enzymatic digestibility. Based on the sugar yield during enzymatic hydrolysis, the optimal pretreatment conditions were 1 % NaOH+8 % NH(4)OH, 50°C, 48 h, with a solid-to-liquid ratio 1:10. The results demonstrated that soaking pretreatment removed 63.6 % lignin while reserving most of the carbohydrates. After enzymatic hydrolysis, the yields of glucose and xylose were 78.5 % and 69.3 %, respectively. The simultaneous saccharification and fermentation of pretreated CS using Pichia stipitis resulted in an ethanol concentration of 36.1 g/L, corresponding only to 63.3 % of the theoretical maximum. In order to simplify the process and reduce the capital cost, the liquid fraction of the pretreatment was used to re-soak new CS. For methane production, the re-soaked CS and the residues of SSF were anaerobically digested for 120 days. Fifteen grams CS were converted to 1.9 g of ethanol and 1337.3 mL of methane in the entire process.

Evaluation of Saccharomyces cerevisiae Y5 for ethanol production from enzymatic hydrolysate of non-detoxified steam-exploded corn stover.

Saccharomyces cerevisiae Y5 was used to produce ethanol from enzymatic hydrolysate of non-detoxified steam-exploded corn stover, with and without a nitrogen source, and decreasing inoculum size. The results indicated that the ethanol concentration of 44.55 g/L, corresponding to 94.5% of the theoretical yield was obtained after 24 h, with an inoculum size of 10% (v/v) and nitrogen source (corn steep liquor, CSL) of 40 mL/L. With the same inoculum size, and without CSL, the ethanol concentration was 43.21 g/L, corresponding to 91.7% of the theoretical value after 60 h. With a decreased inoculum size of 5% (v/v), and without CSL, the ethanol concentration was 40.00 g/L, corresponding to 85.8% of the theoretical value after 72 h. The strain offers the potential to improve the economy of cellulosic ethanol production by simplifying the production process and reducing the costs associated with the process such as water, capital equipment and nutrient supplementation.

Ethanol production from the enzymatic hydrolysis of non-detoxified steam-exploded corn stalk.

To reduce water consumption and equipment investment, and simplify the technological process, a Pichia stipitis-adapted strain with improved tolerance against inhibitors and ethanol was used in ethanol production. The steam-exploded corn stalk was directly enzymatically hydrolyzed without detoxification, and then the enzymatic hydrolysate was used as the fermentation substrate. Results from laboratory experiments in shake flasks and fermentation tanks indicated that, after fermentation for 48 h, ethanol concentration reached to 43.42 g/L; the ethanol yield was 0.47 g(p)/g(s), which was 92.16% of the theoretical ethanol yield. The results of the present research demonstrated that the application of this strain avoided detoxification of the steam-pretreated material through washing, thus simplifying the technological process. In addition, the application of the adapted strain reduced water consumption and lowered the equipment investment of ethanol production from corn stalk, which are important factors in further promotion of the development of ethanol production from straw.

Yeast strains for ethanol production from lignocellulosic hydrolysates during in situ detoxification.

Yeast strains Y1, Y4 and Y7 demonstrated high conversion efficiencies for sugars and high abilities to tolerate or metabolize inhibitors in dilute-acid lignocellulosic hydrolysates. Strains Y1 and Y4 completely consumed the glucose within 24 h in dilute-acid lignocellulosic hydrolysate during in situ detoxification, and the maximum ethanol yields reached 0.49 g and 0.45 g ethanol/g glucose, equivalent to maximum theoretical values of 96% and 88.2%, respectively. Strain Y1 could metabolize xylose to xylitol with a yield of 0.64 g/g xylose, whereas Y4 was unable to utilize xylose as a substrate. Strain Y7 was able to consume sugars (glucose and xylose) within 72 h during hydrolysate in situ detoxification, producing a high ethanol yield (equivalent to 93.6% of the maximum theoretical value). Y1 and Y7 are the most efficient yeast strains yet reported for producing ethanol from non-detoxified dilute-acid lignocellulosic hydrolysates. These findings offer huge potential for improving the economics of bio-ethanol production from lignocellulosic hydrolysates.

[Evaluation of the activities of two promoters in Streptomycetes by reporter gene method].

OBJECTIVE: The mutated promoter of the erythromycin resistance gene (PermE *) is a strong promoter generally used in streptomycetes, and we evaluated the expression activities of a new promoter (Psf) and PermE * in Streptomycetes. METHODS: We used kanamycin resistance gene(neo) and catechol 2,3-dioxygenase gene (xylE) as reporters. RESULTS: Both promoters exhibited high level of promoter activities in Streptomyces clavuligerus NRRL3585, Streptomyces coelicolor M145, Streptomyces venezuelae ISP5230 and Streptomyces lividans TK54. The activities of Psf were higher than those of PermE * in S. clavuligerus and S. coelicolor. CONCLUSION: Both Psf and PermE * are strong promoters suitable for gene over-expression in Streptomycetes and Psf will offer an alternative for high-level gene expression.

Strain construction for ethanol production from dilute-acid lignocellulosic hydrolysate.

In order to construct a strain that converts sugar mixture and resist/metabolize inhibitors in lignocellulosic dilute-acid hydrolysate, the biotechnology of inactive intergeneric fusion between Saccharomyces cerevisiae and Pachysolen tannophilis was performed. Fusant 1 was successfully obtained as a hybrid strain, which was screened out by xylose and mixed sugar (xylose and glucose) fermentation. This strain showed good abilities of ethanol production, ethanol tolerance, and resistance to the toxic inhibitors presenting in the hydrolysate. The maximum volumetric yield of ethanol and yield of xylitol in mixed sugar was 9.52 g/l and 0.44 g/g, respectively. The results indicated that the constructed strain Fusant 1 was a good producer for ethanol and xylitol from lignocellulosic dilute-acid hydrolysate.

Construction of a recombinant S. cerevisiae expressing a fusion protein and study on the effect of converting xylose and glucose to ethanol.

Gene XYL1 from Candida shehatae and gene XYL2 from Pichia stipitis were amplified by polymerase chain reaction (PCR), and the two genes were both placed under the strong promoter of alcohol dehydrogenase (ADH) of plasmid pAD2 to produce the recombinant expression vector pAD2-P12. Because the amplified XYL1 fragment lacks the stop codon UAA, the polypeptide expressed in yeast cells should be a fusion protein, which is a fusion of xylose reductase and xylitol dehydrogenase. Subsequently, the pAD2-P12 vector was transformed into Saccharomyces cerevisiae YS58 to produce a recombinant S. cerevisiae YS58-12. It was indicated that S. cerevisiae YS58-12 has the ability of metabolizing xylose to produce ethanol by fermentation experiment. The result of cofermentation of glucose and xylose by using this recombinant S. cerevisiae YS58-12 showed a relatively satisfactory result. The highest percentage of xylose consumption rate reached 81.3% and the ethanol yield was equal to 67.14% of the ideal value.