Sulfidization regulation of cuprite by pre-oxidation using sodium hypochlorite as an oxidant

The direct sulfidization of cuprite is inefficient because cuprite is a copper-oxide mineral with a strong surface hydrophilicity.In this study,oxidant was used to modify cuprite surfaces to regulate the sulfidization of cuprite.Microflotation tests showed that the flotation recovery of pre-oxidized cuprite was nearly25% higher than that of direct sulfidization flotation,which indicates that the cuprite surface activity was enhanced after pre-oxidation by Cu(Ⅰ) species(weak affinity with sulfur ions) transformation to Cu(Ⅱ)species(strong affinity with sulfur ions).Zeta potential,scanning electron microscopy-energy dispersive X-ray spectroscopy,X-ray photoelectron spectroscopy,and time-of-flight secondary ion mass spectrometry results showed that pre-oxidation improved cuprite sulfidization and promoted the formation of copper-sulfide species on the cuprite surfaces.The mineral surface stability and thus,xanthate species adsorption on the cuprite surfaces were improved.The surface-adsorption measurements and infrared spectroscopy showed that a large amount of xanthate species was adsorbed onto the sulfidized cuprite surfaces after pre-oxidation,which enhanced the cuprite hydrophobicity and improved the cuprite flotation.

Complete stabilization of severely As-contaminated soil by a simple H2O2 pre-oxidation method combined with non-toxic TMT-15 and FeCl3·6H2O

The stabilization of severely As-polluted soil has been a challenge, especially for the extremely toxic As(Ⅲ) contaminants. In this study, soil with a high As concentration(26084 mg/kg) was availably stabilized by a H2O2 pre-oxidation assisted TMT-15(Na3S3C3N3 solution with a mass fraction of 15%) and FeCl3·6 H2O stabilization method. The results showed that the combination of the two stabilizers(i.e., TMT-15 and FeCl3·6 H2O) presented a better stabilization behavior than either stabilizer used individually. The use of the H2O2 pre-oxidation assisted TMT-15 and FeCl3·6 H2O stabilization approach not only converted the As(Ⅲ) to As(Ⅴ) but also reduced the toxic leaching concentration of As to 1.61 mg/L, which is a safe level, when the additions of TMT-15 and FeCl3·6 H2O were 2 mL and 0.20 g, respectively. Thus, using only a simple H2O2 pre-oxidation to combine clean stabilization with non-toxic stabilizers TMT-15 and FeCl3·6 H2O could render the severely As-contaminated soil safe for disposal in a landfill.

Effects of Pre-oxidation Conditions on Adsorption Performance of Activated Carbon Fibers

In order to investigate the effects of pre-oxidation conditions on adsorption performance of activated carbon fibers ( ACFs) ,electrospun polyacrylonitrile ( PAN) fiber webs were adopted as precursors for preparing ACFs. Firstly,the webs were stabilized under different pre-oxidation conditions; secondly,the pre-oxidative fibers were chemically activated by high temperature treatment in nitrogen. Pre-oxidation temperature,heating rate,and treatment time are the main factors on affecting the adsorption performance of the ACFs. Scanning electron microscope ( SEM) , differential scanning calorimeter ( DSC ) ,and Fourier transform infrared spectroscopy ( FTIR ) were used to characterize the structure and property of the pre-oxidative fibers,and the dynamic benzene adsorption capacity of benzene of ACFs was measured. The results indicate that the moderate pre-oxidation condition is necessary to prepare the ACFs with better adsorption capacity,and the optimal oxidation conditions are to increase from room temperature to 230 ℃ with a heating rate of 0. 75 ℃·min - 1 ,held at the peak temperature for 30 min.

Effect of pre-oxidation on strength and thermal shock behavior of ZrB_2-SiC-graphite ceramic composites

A novelty technique,namely,pre-oxidation,has been proposed to improve the strength and thermal shock behavior of ZrB2-SiC-graphite ceramic composites,which is a promising candidate for ultra-high temperature ceramics (UHTCs) in aerospace engineering. The composite is pre-oxidized at temperatures of 900 ℃ and 1100 ℃ for 1 h and 3 h in air. A theoretical model considering surface heat transfer has been given and analyzed. A water-quenching technique is adopted at different temperatures from 300 ℃ to 600 ℃ in order to investigate the thermal shock behavior of pre-oxidized composites. The critical thermal shock temperature improves more than 40% after pre-oxidizing at 1100 ℃ for 3 h. However,the composites strength is not improved as a result of the insensitivity to surface defects.

The Application of KMnO_4 Pre-oxidation in Emergency Treatment of High-algae Source Water

Mobile emergency pilot water plant was used to carry out pilot study of KMnO4 pre-oxidation enhanced coagulation treating high-algae source water. Research showed that the optimal dosages of coagulant and KMnO4 in the process were 6 and 0. 4- 0. 6 mg / L respectively. Under the dosage,removal rate of water turbidity after precipitation rose by 11% than simple coagulation,and removal rate of algae rose by 15%. Removal rates of total amount of odor and GSM by the process were respectively 73% and 59%. The removal rate of total amount of algae by KMnO4 preoxidation was 40%,and removal effect of THM precursors was obvious.

A solvothermal pre-oxidation strategy converting pitch from soft carbon to hard carbon for enhanced sodium storage

Due to its low cost and easy availability, the pitch is considered a promising precursor for soft carbon anodes. However, pitch-derived soft carbon shows a high graphitization degree and small interlayer spacing, resulting in its much lower sodium storage performance than hard carbon. We propose a novel preoxidation strategy to introduce additional oxygen atoms into the low-cost soft carbon precursor pitch to fabricate a defect-rich and large-interlayer spacing hard carbon anode(HPP-1100). Compared with the direct pyrolysis of pitch carbon, the sodium storage capacity of HPP-1100 is significantly improved from 120.3 m Ah/g to 306.7 m Ah/g, with an excellent rate and cycling capability(116.5 m Ah/g at 10 C). Moreover, when assorted with an O_(3)-Na(NiFeMn)1/3O_(2)cathode, the full cell delivers a high reversible capacity of 274.0 m Ah/g at 0.1 C with superb cycle life. This work provides a new solution for realizing the application of low-cost pitch anodes in Na-ion batteries.

Pre-oxidation enhanced cyanobacteria removal in drinking water treatment: A review

Cyanobacterial bloom has many adverse effects on source water quality and drinking water production. The traditional water treatment process can hardly achieve satisfactory removal of algae cells. This review examines the impact of pre-oxidation on the removal of cyanobacteria by solid-liquid separation processes. It was reported that the introduction of chemical oxidants such as chlorine, potassium permanganate, and ozone in algae-laden water pretreatment could improve algae removal by the subsequent solid-liquid separation processes. However, over dosed oxidants can result in more serious water quality risks due to significant algae cell lysis and undesirable intracellular organic matter release. It was suggested that moderate pre-oxidation may enhance the removal of cyanobacteria without damaging algae cells. In this article, effects of moderate pretreatment on the solid-liquid separation processes(sedimentation, dissolved air flotation, and membrane filtration) are reviewed.

Influence of Pre-oxidation on the Hot Corrosion of DZ68 Superalloy in the Mixture of Na_2SO_4-NaCl

DZ68 alloy is a new Ni-base directionally solidified superalloy for the blade of advanced turbine engine with high ratio of thrust-mass.In order to investigate the influence of pre-oxidation on the hot corrosion resistance of DZ68 alloy,pre-oxidation treatment was conducted at 950℃ in air for 20 h.A mixture of 75% Na2SO4 ＋25% NaCl （in mass fraction） was used for hot corrosion study at 900℃.The microstructure of specimens was investigated by using a scanning electron microscope （SEM） equipped with an energy dispersive spectroscopy （EDS）.The compositions of the corroded specimens were determined by X-ray diffraction （XRD）.After preoxidation at 950℃ in air for 20 h,a protective scale consisting of Cr2O3,Al2O3,NiO,NiCr2O4,and Ni2Ti4O formed on the DZ68 superalloy surface.The pre-oxidation treatment improved the initial incubation stage of the alloy in the mixture of 75% Na2SO4 ＋25% NaCl melts at 900℃.The oxide layer degraded gradually with increasing the time of hot corrosion.Once the oxide layer was damaged,the corrosion rate would increase rapidly,accompanied by obvious spallation of the corrosion products.At 900℃,the pre-oxidation treatment could not inhibit the accelerated hot corrosion of DZ68 in the mixture of 75% Na2SO4 ＋25% NaCl melts,with a high corrosion rate.

Effects of pellet surface roughness and pre-oxidation temperature on CMAS corrosion behavior of Ti_(2)AlC

Calcium–magnesium–alumina–silicate(CMAS)corrosion is a serious threat to thermal barrier coatings(TBCs).Ti_(2)AlC has been proven to be a potential protection layer material for TBCs to resist CMAS corrosion.In this study,the effects of the pellet surface roughness and temperature on the microstructure of the pre-oxidation layer and CMAS corrosion behavior of Ti_(2)AlC were investigated.The results revealed that pre-oxidation produced inner Al_(2)O_(3)layer and outer TiO_(2)clusters on the pellet surfaces.The content of TiO_(2)decreased with decreasing pellet surface roughness and increased along with the pre-oxidation temperature.The thickness of Al_(2)O_(3)layer is also positively related to the pre-oxidation temperature.The Ti_(2)AlC pellets pre-oxidized at 1050℃could effectively resist CMAS corrosion by promoting the crystallization of anorthite(CaAl_(2)Si_(2)O_(8))from the CMAS melt rapidly,and the resistance effectiveness increased with the pellet surface roughness.Additionally,the CMAS layer mainly spalled off at the interface of CaAl_(2)Si_(2)O_(8)/Al_(2)O_(3)layer after thermal cycling tests coupled with CMAS corrosion.The Al_(2)O_(3)layer grown on the rough interface could combine with the pellets tightly during thermal cycling tests,which was attributed to obstruction of the rough interface to crack propagation.

Impact of pre-oxidation on the formation of byproducts in algae-laden water disinfection:Insights from fluorescent and molecular weight

Pre-oxidation has been reported to be an effective way to remove algal cells in water, but the released algal organic matter (AOM) could be oxidized and lead to the increment in disinfection by-product (DBP) formation. The relationship between pre-oxidation and AOM-derived DBP formation needs to be approached more precisely. This study compared the impact of four pre-oxidants, ozone (O), chlorine dioxide (ClO), potassium permanganate(KMnO) and sodium hypochlorite (NaClO), on the formation of nitrogenous (N-) and carbonaceous (C-) DBPs in AOM chlorination. The characterization (fluorescent properties,molecular weight distribution and amino acids concentration) on AOM samples showed that the characterization properties variations after pre-oxidation were highly dependent on the oxidizing ability of oxidants. The disinfection experiments showed that Oincreased DBP formation most significantly, which was consistent with the result of characterization properties variations. Then canonical correspondent analysis (CCA) and Pearson’s correlation analysis were conducted based on the characterization data and DBP formation. CCA indicated that C-DBPs formation was highly dependent on fluorescent data. The formation of haloacetic acids (HAAs) had a positive correlation with aromatic protein-like component while trichloromethane (TCM) had a positive correlation with fulvic acid-like component.Pearson’s correlation analysis showed that low molecular weight fractions were favorable to form N-DBPs. Therefore, characterization data could provide the advantages in the control of DBP formation, which further revealed that KMnOand ClOwere better options for removing algal cells as well as limiting DBP formation.

Effect of pre-oxidation degree on gaseous reduction of pre-oxidized ilmenite concentrate by CO

The effect of pre-oxidation degree of Panzhihua ilmenite concentrate on the gaseous reduction by carbon monoxide was investigated.The raw ilmenite concentrates were pre-oxidized at 600,700,800,900,and 1000°C for 2 h,respectively.The phase change,FeO content,and morphology after the oxidation at various temperatures were characterized.The oxidation degree was calculated according to the change of FeO content.Thermogravimetry was performed on the oxidized ilmenite concentrate samples(oxidized at 600,800,and 1000°C)at 850,900,and 950°C,respectively.The results show that the pre-oxidation of ilmenite concentrate can accelerate the reduction process:the higher pre-oxidation degree,the faster reduction rate.The high pre-oxidation degree of ilmenite concentrate is beneficial to accelerate the subsequent reduction process in two ways.Three stages of the reduction process were divided via the first derivatives of reduction degree,and the reduction mechanism and apparent activation energy were discussed subsequently.

Hot Corrosion Behavior of Ti45Al8.5Nb Alloy: Effect of Anodization and Pre-oxidation

The hot corrosion behavior of Ti45 A18.5 Nb alloy was studied in the salt of Na_(2)SO_(4)and/or NaCl at 700℃.To improve the hot corrosion resistance,Ti45 A18.5 Nb alloy was anodized in fluorine-containing solution and pre-oxidized in air.Results showed that the combination of anodization and pre-oxidation can efficiently enhance the hot corrosion resistance of Ti45 A18.5 Nb alloy contaminated with Na_(2)SO_(4)or Na_(2)SO_(4)+NaCl deposits.This is because anodization and pre-oxidation result in the formation of compact AlOlayer which can act as a diffusion barrier to prevent sulfur,chlorine,and oxygen from attacking the alloy,therefore providing good resistance against hot corrosion.When exposed to NaCl deposit,however,no obvious improvement was achieved on the hot corrosion behavior no matter the alloy was anodized or further pre-oxidized in air.

Analysis and Characterization of Orientation Structure of Pre-oxidized PAN Fibers in High Magnetic Fields

PAN fibers pre-oxidized at 240℃, 260℃, 280℃, 300℃ were treated in 8 T, 12 T, 16 T high magnetic fields, respectively. The experimental result implied that there were two kinds of magnetic units cyan and carbon-nitrogen heterocycle in pre-oxidized PAN fibers, and the movement of magnetic units resulted in changes of orientation structure of pre-oxidized PAN fibers in high magnetic fields. Overall orientation increased with increase of magnetic field intensity and extension of processing time, whereas change of crystalline orientation depended on magnetic field intensity and content of carbon-nitrogen heterocycle due to the competition of two magnetic units. Furthermore, magnetic fields induced the conversion from amorphous region to crystal region and improved crystalline orooerties of ore-oxidized PAN fibers.

Improvement in electrical properties of high-κ film on Ge substrate by an improved stress relieved pre-oxide method

High-κ /Ge gate stack has recently attracted a great deal of attention as a potential candidate to replace planar silicon transistors for sub-22 generation. However, the desorption and volatilization of GeO hamper the development of Ge-based devices. To cope with this challenge, various techniques have been proposed to improve the high-κ /Ge interface. However,these techniques have not been developed perfectly yet to control the interface. Therefore, in this paper, we propose an improved stress relieved pre-oxide（SRPO） method to improve the thermodynamic stability of the high-κ /Ge interface. The x-ray photoelectron spectroscopy（XPS） and atomic force microscopy（AFM） results indicate that the GeO volatilization of the high-κ /Ge gate stack is efficiently suppressed after 500℃ annealing, and the electrical characteristics are greatly improved.

Quantitative Analysis of FeMo Alloys by X-Ray Fluorescence Spectrometry

A quantitative analysis method of molybdenum in FeMo alloys by X-ray spectrometry using borate fusion technique was compared with that with pressed pellet. The complete pre-oxidation of FeMo alloys for the preparation of homogeneous fused discs was achieved by employing an automated fusion machine equipped with specially designed O2-blowing nozzles, which used lithium tetra-borate as flux with the addition of lithium nitrate (LiNO3) as oxidizer. The calibration curves of Mo and Fe were used in the quantitative analysis of standard materials and unknown plant samples with satisfactory accuracy and precision, utilizing the corrections of the matrix effects and line overlap. It was confirmed that the newly proposed method of preparing fused glass discs of FeMo alloys can replace the conventional wet chemical analyses requiring the labor intensive and time consuming procedure.

Catalytic effect of alkali chlorides on carbothermic reduction of pre oxidized ilmenite

A computer monitoring thermogravimetric system was used to study the effect of alkali chlorides(MCl, M=Li, Na, K and Cs) on the carbothermic reduction of pre oxidized ilmenite in the course of a linear rise in temperature from 600 ℃ to 1 000 ℃. The experimental results indicate that all the alkali chlorides can speed up the reduction process of pre oxidized ilmenite, moreover, KCl is the most effective catalyst of the chlorides, while the catalytic effects of LiCl and CsCl are relatively weaker. It seems that the catalytic mechanism of LiCl is different from those of the other alkali chlorides. The cross sectional morphology of the partially reduced pre oxidized ilmenite particles and the distribution of potassium ions within them were examined by means of scanning electronic microscopy and electronic probe microanalysis, respectively, which shows that the reduction proceeds topochemically and the alkali ion enriches at the periphery of the particles.[

An Improvement on Adhesion of Sputtered TiC Coating to Steel Substrate

Introducing N_2 during sputtering and pre-oxidation of substrate were investigated to improve the adhesion of sputtered TiC coating to steel substrate. The results show that yeactive gas N_2 increases the adhesion of TiC coating to steel because of a graded interface existing between coating and substrate. The interaction of discharge plasma with the surface of substrate was discussed. Pre-oxidation of substrate is effective for improving the adhesion due to the fomation of FeTi0_3 which appeared as an inteylayer between coating and pre-oxidized substrate.

Degradation of iopamidol in the permanganate/sulfite process:Evolution of iodine species and effect on the subsequent formation of disinfection by-products

Permanganate/sulfite(Mn(VII)/S(IV))process is a promising pre-oxidation technology for sequestering the emerging organic contaminants in drinking water treatment plant.Iopamidol(IPM),a representative of iodinated X-ray contrast media,has been widely detected in water sources and has the risk of forming iodinated disinfection byproducts(I-DBPs)in water treatment system.In this study,we investigated the evolution of iodine species during the IPM degradation by the Mn(VII)/S(IV)process and its effect on the subsequent formation of I-DBPs during chlorination at pH 7.0 and 8.0.IPM could be effectively degraded in the Mn(VII)/S(IV)process at environmentally relevant pH(pH 7.0 and 8.0).The results of quenching and competitive oxidation kinetic experiments revealed that SO^(·-)_(4)was the major reactive oxidizing species contributing to the degradation of IPM whereas the contributions of HO·and reactive manganese species were negligible in the Mn(VII)/S(IV)process.I–and IO–3were generated while no HOI was detected during the degradation of IPM in the Mn(VII)/S(IV)process.The effects of IPM oxidation by Mn(VII)/S(IV)on the subsequent formation of chlorinated disinfection by-products(Cl-DBPs)during chlorination were related to the category of Cl-DBPs.The pre-oxidation of IPM by Mn(VII)/S(IV)resulted in the generation of I-DBPs during the disinfection process although no I-DBPs were detected if no pre-oxidation was applied.The finding of this study suggested that attention should be paid to the toxicity of DBPs when water containing iodinated organic contaminants is treated by Mn(VII)/S(IV)process or other pre-oxidation technologies.

High strength mullite-bond SiC porous ceramics fabricated by digital light processing

Fabricating SiC ceramics via the digital light processing(DLP)technology is of great challenge due to strong light absorption and high refractive index of deep-colored SiC powders,which highly differ from those of resin,and thus significantly affect the curing performance of the photosensitive SiC slurry.In this paper,a thin silicon oxide(SiO_(2))layer was in-situ formed on the surface of SiC powders by pre-oxidation treatment.This method was proven to effectively improve the curing ability of SiC slurry.The SiC photosensitive slurry was fabricated with solid content of 55 vol%and viscosity of 7.77 Pa·s(shear rate of 30 s^(−1)).The curing thickness was 50μm with exposure time of only 5 s.Then,a well-designed sintering additive was added to completely convert low-strength SiO_(2) into mullite reinforcement during sintering.Complexshaped mullite-bond SiC ceramics were successfully fabricated.The flexural strength of SiC ceramics sintered at 1550℃in air reached 97.6 MPa with porosity of 39.2 vol%,as high as those prepared by spark plasma sintering(SPS)techniques.

Effects of operating conditions on iron(hydr)oxides evolution and ciprofloxacin degradation in potassium ferrate-ozone stepwise oxidation system

In this study,a stepwise oxidation system of potassium ferrate(K_(2)FeO_(4))combined with ozone(O+3)was used to degrade ciprofloxacin(CIP).The effects of pH and pre-oxidation time of K_(2)FeO_(4) on the evolution of K_(2)FeO_(4) reduction products(iron(hydr)oxides)and CIP degradation were investigated.It was found that in addition to its own oxidation capacity,K_(2)FeO_(4) can also influence the treatment effect of CIP by changing the catalyst content.The presence of iron(hydr)oxides effectively enhanced the mineralization rate of CIP by catalyzing ozonation.The pH value can influence the content and types of the components with catalytic ozonation effect in iron(hydr)oxides.The K_(2)FeO_(4) pre-oxidation stage can produce more iron(hydr)oxides with catalytic components for subsequent ozonation,but the evolution of iron(hydr)oxides components was influenced by O_(3) treatment.It can also avoid the waste of oxidation capacity owing to the oxidation of iron(hydr)oxides by O_(3) and free radicals.The intermediate degradation products were identified by Fourier transform ion cyclotron resonance mass spectrometry(FT-ICR-MS).Besides,the degradation pathways were proposed.Among the degradation products of CIP,the product with broken quinolone ring structure only appeared in the stepwise oxidation system.