分子动力学模拟和实验研究铝屑脱油、水技术及机理

通过热重分析、扫描电子显微镜、响应曲面和分子动力学等方法,阐明铝屑脱油脱水的过程和机理。结果表明,铝屑表面切削液在200~300℃质量损失明显,超过400℃时被碳化。水、表面活性剂和油分子在室温下分层排列。表面活性剂中的O—H和水中的O原子之间分别在1.63、3.27和5.05A处存在强氢键、强范德华力和弱范德华力。随着温度的升高,弱范德华力相互作用消失,氢键减弱。超过277℃时强范德华力和氢键被破坏,导致水-表面活性剂-油分层界面的失稳及破坏。在370℃和3 cm装料厚度下加热70 min时,铝屑的油、水脱除率达99.7%。

Recovery of waste rare earth fluorescent powders by two steps acid leaching

The effects of the acid leaching and alkali fusion on the leaching efficiency of Y,Eu,Ce,and Tb from the waste rare earth fluorescent powders were investigated in this paper.The results show that hydrochloric acid is better than sulfuric acid in the first acid leaching,and NaOH is better than Na2CO3in the alkali fusion.In the first acid leaching,the Wloss is 20.94%when the waste rare earth fluorescent powders are acid leached in H?concentration 3 mol L-1and S/L ratio 1:3 for 4 h due to red powders dissolved.The better results of the alkali fusion can be got at 800℃ for 2 h when the NaOH is used.The blue powders and the green powders can be dissolved into NaAlO2and oxides such as rare earth oxide(REO).The REO can be dissolved in H?concentration 5 mol L-1,S/L1:10 for 3 h in the second acid leaching.The leaching rates of the Y,Eu,Ce,and Tb are 99.06%,97.38%,98.22%,and 98.15%,respectively.The leaching rate of the total rare earth is 98.60%.

Electromagnetic and microwave absorbing properties of FeCoB powder composites

The electromagnetic and microwave absorbing properties of FeCoB powder composites prepared by single-roller melt-spinning and mechanical milling processes were investigated in this paper.The result indicates that the flake-like powders are obtained.As milling time increases,the flake-like powder particles tend to agglomerate,causing the flake-like powders decrease gradually.The milling time plays an important role in the electromagnetic parameters which relates to the shape and size of the powder particles.The calculation shows that the sample milled for 6 h could achieve an optimal reflection loss of-11.5 dB at 5.8 GHz,with mass fraction of 83%and a matching thickness of1.8 mm.The result also indicates that the microwave absorbing properties of the FeCoB powder composites are adjustable by changing their thickness,and can be applied as a thinner microwave absorbing material in the range of2–8 GHz.

Recycle of valuable products from oily cold rolling mill sludge

Oily cold rolling mill(CRM)sludge contains lots of iron and alloying elements along with plenty of hazardous organic components,which makes it as an attractive secondary source and an environmental contaminant at the same time.The compound methods of"vacuum distillation+oxidizing roasting"and"vacuum distillation+hydrogen reduction"were employed for the recycle of oily cold rolling mill sludge.First,the sludge was dynamically vacuum distilled in a rotating furnace at 50 r/min and 600 C for 3 h,which removed almost hazardous organic components,obtaining 89.2wt%ferrous resultant.Then,high purity ferric oxide powders(99.2wt%)and reduced iron powders(98.9wt%)were obtained when the distillation residues were oxidized and reduced,respectively.The distillation oil can be used for fuel or chemical feedstock,and the distillation gases can be collected and reused as a fuel.

Effects of overaging temperature on the microstructure and properties of 600MPa cold-rolled dual-phase steel

C–Mn steels prepared by annealing at 800°C for 120 s and overaging at 250–400°C were subjected to pre-straining(2%) and baking treatments(170°C for 20 min) to measure their bake-hardening(BH_2) values. The effects of overaging temperature on the microstructure, mechanical properties, and BH_2 behavior of 600 MPa cold-rolled dual-phase(DP) steel were investigated by optical microscopy, scanning electron microscopy, and tensile tests. The results indicated that the martensite morphology exhibited less variation when the DP steel was overaged at 250–350°C. However, when the DP steel was overaged at 400°C, numerous non-martensite and carbide particles formed and yield-point elongation was observed in the tensile curve. When the overaging temperature was increased from 250 to 400°C, the yield strength increased from 272 to 317 MPa, the tensile strength decreased from 643 to 574 MPa, and the elongation increased from 27.8% to 30.6%. Furthermore, with an increase in overaging temperature from 250 to 400°C, the BH_2 value initially increases and then decreases. The maximum BH_2 value of 83 MPa was observed for the specimen overaged at 350°C.

New technology for recycling materials from oily cold rolling mill sludge

Oily cold rolling mill(CRM)sludge is one of metallurgical industry solid wastes.The recycle of these wastes can not only protect the environment but also permit their reutilization.In this research,a new process of "hydrometallurgical treatment + hydrothermal synthesis" was investigated for the combined recovery of iron and organic materials from oily CRM sludge.Hydrometallurgical treatment,mainly including acid leaching,centrifugal separation,neutralization reaction,oxidizing,and preparation of hydrothermal reaction precursor,was first utilized for processing the sludge.Then,micaceous iron oxide(MIO)pigment powders were prepared through hydrothermal reaction of the obtained precursor in alkaline media.The separated organic materials can be used for fuel or chemical feedstock.The quality of the prepared MIO pigments is in accordance with the standards of MIO pigments for paints(ISO 10601-2007).This clean,effective,and economical technology o?ers a new way to recycle oily CRM sludge.

Effect of hot-dip galvanizing processes on the microstructure and mechanical properties of 600-MPa hot-dip galvanized dual-phase steel

A C–Mn dual-phase steel was soaked at 800°C for 90 s and then either rapidly cooled to 450°C and held for 30 s(process A) or rapidly cooled to 350°C and then reheated to 450°C(process B) to simulate the hot-dip galvanizing process. The influence of the hot-dip galvanizing process on the microstructure and mechanical properties of 600-MPa hot-dip galvanized dual-phase steel(DP600) was investigated using optical microscopy, scanning electron microscopy(SEM), transmission electron microscopy(TEM), and tensile tests. The results showed that, in the case of process A, the microstructure of DP600 was composed of ferrite, martensite, and a small amount of bainite. The granular bainite was formed in the hot-dip galvanizing stage, and martensite islands were formed in the final cooling stage after hot-dip galvanizing. By contrast, in the case of process B, the microstructure of the DP600 was composed of ferrite, martensite, bainite, and cementite. In addition, compared with the yield strength(YS) of the DP600 annealed by process A, that for the DP600 annealed by process B increased by approximately 50 MPa because of the tempering of the martensite formed during rapid cooling. The work-hardening coefficient(n value) of the DP600 steel annealed by process B clearly decreased because the increase of the YS affected the computation result for the n value. However, the ultimate tensile strength(UTS) and elongation(A80) of the DP600 annealed by process B exhibited less variation compared with those of the DP600 annealed by process A. Therefore, DP600 with excellent comprehensive mechanical properties(YS = 362 MPa, UTS = 638 MPa, A_(80) = 24.3%, n = 0.17) was obtained via process A.

Synthesis and properties of SrFe_(12)O_(19) obtained by solid waste recycling of oily cold rolling mill sludge

The aim of this study was to develop a new approach for the preparation of environmentally friendly, high-value products from oily cold rolling mill(CRM) sludge. Utilizing oily CRM sludge as a source of iron, strontium hexaferrite(SrFe_(12)O_(19)) powders were prepared by multi-step processes involving acid leaching, chemical conversion treatment, and synthesis by a citrate precursor. The influences of citric acid dosage and the pH of the sol system on the formation, crystallite size, and magnetic properties of the obtained SrFe_(12)O_(19) powders were investigated. High saturation magnetization(74.8 mA·m^2·g^(–1)) and intrinsic coercivities(614.46 mT) were achieved for pH 7.0 of the sol system, for which the molar ratio of citric acid dosage to the total dosage of Fe^(3+) and Sr^(2+) was 1.5. This study presents a new approach to utilizing oily CRM sludge, and even refractory iron-containing solid waste.

Effect of temper rolling on the bake-hardening behavior of low carbon steel

In a typical process,low carbon steel was annealed at two different temperatures(660℃ and 750℃),and then was temper rolled to improve the mechanical properties.Pre-straining and baking treatments were subsequently carried out to measure the bake-hardening(BH)values.The influences of annealing temperature and temper rolling on the BH behavior of the steel were investigated.The results indicated that the microstructure evolution during temper rolling was related to carbon atoms and dislocations.After an apparent increase,the BH value of the steel significantly decreased when the temper rolling reduction was increased from 0%to 5%.This was attributed to the increase in solute carbon concentration and dislocation density.The maximum BH values of the steel annealed at 660℃ and 750℃ were 80 MPa and89 MPa at the reductions of 3%and 4%,respectively.Moreover,increasing the annealing temperature from 660 to 750℃ resulted in an obvious increase in the BH value due to carbide dissolution.

Effects of pre-strain and baking parameters on the microstructure and bake-hardening behavior of dual-phase steel

In a typical process, C-Mn steel was annealed at 800°C for 180 s, and then cooled rapidly to obtain the ferrite-martensite microstructure. After pre-straining, the specimens were baked and the corresponding bake-hardening(BH) values were determined as a function of pre-strain, baking temperature, and baking time. The influences of pre-strain, baking temperature and baking time on the microstructure evolution and bake-hardening behavior of the dual-phase steel were investigated systematically. It was found that the BH value apparently increased with an increase in pre-strain in the range from 0 to 1%; however, increasing pre-strain from 1% to 8% led to a decrease in the BH value. Furthermore, an increase in baking temperature favored a gradual improvement in the BH value because of the formation of Cottrell atmosphere and the precipitation of carbides in both the ferrite and martensite phases. The BH value reached a maximum of 110 MPa at a baking temperature of 300°C. Moreover, the BH value enhanced significantly with increasing baking time from 10 to 100 min.

Enrichment of Ni-Mo-V via pyrometallurgical reduction from spent hydrogenation catalysts and the multi-reaction mechanism

Spent hydrogenation catalysts are important secondary resources due to richness in the valuable metals of Ni,Mo and V.Recovery of valuable metals from spent catalysts has high economic value and environmental benefits since they are hazardous wastes as well.Traditional recycling processes including hydrometallurgical leaching and soda roasting-leaching have disadvantages such as generating large amounts of wastewater,long process,and low recovery efficiency of valuable metals.Thus,this paper proposed synergistic enrichment of Ni,Mo and V via pyrometallurgical reduction at 1400-1500℃.The melting temperature and viscosity of slag were reduced through slag designing by software FactSage 7.1.The phase diagram of Al_(2)O_(3)-Cap-SiO_(2)-Na_(2)O-B_(2)O_(3)was drawn,and low-temperature region(≤1300℃)was selected as target slag composition.Ni,Mo,and V can be collaborative captured and recovered through the mutual solubility at molten state.Increasing the melting temperature and the amount of CaO,Na_(2)O and C were conducive to improving the metals recovery rates.The kilogram-scale experiments were carried out,and the recovery efficiencies of Ni,Mo and V were 98.3%,95.3%and 97.9%under optimized conditions:at 1500℃,with the basicity of 1.0,13.1 wt%SiO_(2),7.0 wt%B_(2)O_(3),7.7 wt%Na_(2)O and 20.0wt%C.The distribution behavior of valuable metals was clarified by investigating the melting process of slag and the reduction in valuable metals.Ni was preferentially reduced and acted as a capturing agent,which captured other metals to form NiMoV alloys.

Slag design and optimization for iron capturing platinum group metals from alumina-based spent catalysts

Production of petrochemical catalysts accounts for one of the largest shares of platinum group metals(PGMs) consumption;thus,recycling of spent petrochemical catalysts holds great economic value.Conventionally,PGMs are recovered through hydrometallurgical processes which have a low recovery efficiency and produce a large amount of waste.In this regard,this paper proposed a method to use iron-capturing PGMs based on CaO-Al_(2)O_(3)-Na_(2)O slag.This method avoided the formation of Fe-Si alloy and achieved efficient enrichment of PGMs.The droplet force model showed that the recovery efficiency of PGMs could be improved if the slag had low density and low viscosity.Based on this result,FactSage software optimized the composition of slag.Furthermore,the effect of B_(2)O_(3) on the 1400 ℃ liquidus of CaO-Al_(2)O_(3)-Na_(2)O_(3)-B_(2)O_(3) phase diagram was revealed.Moreover,it was found that the recovery efficiency of PGMs exceeded 99% under the following optimized conditions:basicity of 1.0,20 wt%Na_(2)O,15 wt% B_(2)O_(3),15 wt% Fe,3 wt% C and a temperature range of 1400-1500℃.The thermodynamic model revealed the mechanism of iron capture.Different chemical bonds prevented the formation of bonds between the alloy and slag,resulting in the separation of the slag from the alloy.PGMs particles and iron microspheres had significant surface Gibbs free energy.Only when iron microspheres and PGMs particles collided and fused with each other to reduce their surface area could the Gibbs free energy of the system be reduced.

Using coal fly ash-based geopolymer to immobilize Cd from lead fuming furnace slag

Lead fuming furnace slag(LFFS)is a by-product of lead metal production,which is a toxic solid waste according to toxicity characteristic leaching procedure(TCLP)test.It was investigated the feasibility of preparation of geopolymer using coal fly ash(CFA)and LFFS and the immobilization efficiency of Cd in geopolymer.The synthesized geopolymer samples were examined by compressive strength,Fourier transform transmission infrared spectroscopy(FTIR)spectra,X-ray diffraction(XRD)and backscattered electron(BSE)microscope.There is a certain mass ratio(2:3)of the LFFS to the CFA at which the compressive strength of the geopolymeric matrix is the highest.Leaching test shows that Cd in LFFS can be effectively immobilized in the geopolymer structure.Geopolymerization is not only a potential technological solution for reusing LFFS but also an effective immobilization method for LFFS treatment and disposal.

Integrated utilization of municipal solid waste incineration fly ash and bottom ash for preparation of foam glass-ceramics

For the purpose of solid waste co-disposal and heavy metal stabilization,foam glass-ceramics were produced by using municipal solid waste incineration(MWSI)bottom ash and fly ash as main raw materials,calcium carbonate(CaCO3) as foamer and sodium phosphate(Na3PO4) as foam stabilizer.The influences of the raw material composition,foaming temperature and foaming time on the properties were investigated.Porosity,bulk density,mechanical property and leaching of heavy metals were analyzed accordingly.The product,foamed at 1150℃ for 30 min with 14% fly ash and 74% bottom ash,exhibits excellent comprehensive properties,such as high porosity(76.03%),low bulk density(0.67 g·cm-3) and high compressive strength(10.56 MPa).Moreover,the amount of leaching heavy metals,including Cr,Pb,Cu,Cd and Ni,in foam glass-ceramics is significantly lower than that of the US EPA hazardous waste thresholds.This study not only realizes the integrated utilization of bottom ash and fly ash,but also addresses a new strategy for obtaining foam glass-ceramics.

Production of glass-ceramics using Municipal solid waste incineration fly ash

Municipal solid waste incineration(MSWI) fly ash is a by-product from municipal waste incineration.According to incomplete statistics, each year more than one million tons MSWI fly ash was produced in China. Owing to high heavy elements content, widely used disposal methods of landfill are not suitable for MSWI fly ash treatment. In this study, by using MSWI fly ash as raw materials, glassceramics was synthesized for the solidification of heavy metals and waste recycle. Process parameters, including composition, heat treatment temperature and time, were studied and optimized. Under optimizing conditions, the product has good properties of density of 3.42 g·cm^(-3) and Vickers hardness of 6.91 GPa. Moreover, the leaching concentration of heavy metal elements meets allowable values of toxicity characteristic leaching procedure(TCLP).This study offers an alternative for MSWI fly ash recycle.

Treatment method of hazardous pickling sludge by reusing as glass–ceramics nucleation agent

Heavy metal containing pickling sludge(PS) is one of the by-products of the stainless-steel-making industry,which has been considered hazardous due to contained chromium and nickel.Traditional methods of PS disposing are landfill and cement solidification.This research is aimed at disposing PS by solidification/stabilization and reusing it as a nucleation agent of glass–ceramics.The crystallization behavior and the properties of a glass in the CaO–MgO–SiO_2–Al_2O_3 system were studied by considering PS as the nucleation agent.Experimental results confirm that introducing 14 wt% PS as the nucleation agent of glass–ceramics can decrease crystallization temperature by 110.8 °C,refine the grain size by forming isometric crystals with size of 2 lm,enhance Vickers hardness by 2690 MPa and decrease water absorption from(1.21 ± 0.10) wt% to(0.04 ± 0.01) wt%.Therefore,it is reasonable to conclude that PS can be utilized as a nucleation agent to improve the crystallization and mechanical properties of the glass–ceramics.The testing results of US EPA toxicity characteristic leaching procedure(TCLP)confirm the safety of this reusing method.

Crystallization mechanism of glass-ceramics prepared from stainless steel slag

Glass-ceramics have been prepared by using stainless steel slag, fly ash and coal fly ash that were figobtained from industrial solid waste. The crystallization behavior and mechanical characterization of the glass-ceramics with different(CaO +MgO)/(SiO_2+Al_2 O_3)content ratios were studied. While the basicity decreases from 1.2 to 0.9 cm^(-3),the bridge oxygen content increases from 1.18 ×10^(21) to 1.34 × 10^(21) cm^(-3). According to the deconvolution of Raman spectra, the relative abundance of the stretching of Si-O_(nb) bond(Q^n units) can be obtained.The increase in the Q^3 units dominates the polymerization in the process of decreasing basicity. This change in bonding is demonstrated to lead to polymerization of the glass network and the increase in crystallization activation energy from 336.0 to 360.7 kJ·mol^(-1). The results demonstrate that the production of the glass-ceramics from industrial steel slag, fly ash and coal fly ash is cost-effective and offers advantages over other production methods.

One-step Crystallization Kinetic Parameters of the Glass-ceramics Prepared from Stainless Steel Slag and Pickling Sludge

One-step crystallization is one of the most energy conserving methods for glass-ceramics preparation.However,only a few kinetics studies focused on the glass-ceramics prepared by the one-step crystallization.The onestep crystallization kinetic parameters were studied using differential scanning calorimetry.The activation energy(Ea)and the Avrami parameter(n)were calculated as 152.79kJ·mol-1 and 4.39,respectively.These parameters indicate that continuous nucleation and three-dimensional crystal growth are the dominating mechanisms in the one-step crystallization process of the parent glass.The properties of the obtained glass-ceramics can be compared to the glass-ceramics prepared by the two-stage heat treatment and sintering method.This crystallization kinetics research can be used to evaluate the one-step crystallization potential of a parent glass.

Recovery of copper and tin from stripping tin solution by electrodeposition

In this paper, the method of recycling copper and tin by constant-current and constant-voltage electrolysis from the stripping tin solution of tinned copper wastes was studied. The experimental results show that the elements could be deposited on the cathode in turn by different deposition potentials, therefore, the copper and tin were separated by constant-voltage electrolysis but not constant-current electrolysis. In this study, the influence of anode materials was also investigated. Graphite anode is stable without impurities dissolved into the stripping tin solution, while 316 stainless steel anode is dissolved into Fe2?and Fe3?as anodic corrosion, which could decrease the deposition efficiency of tin. The copper and tin in the stripping tin solution are separated orderly by electrodeposition at different voltages using the graphite anode. The recovery rate of copper is up to 100 % at 2.00 V, while that of tin is 80 % at 3.00 V.

Preparation of pure SnO_2 powders from tin slag of printed circuit boards waste

The recycling method and principle of SnO2 from the tin slag of printed circuit boards(PCB) waste were investigated. In this study, pure SnO2 powders were obtained through a multi-step process including ball-milling, roasting, dissolving, precipitating, and pickling. The total recovery rate of tin can be up to 91 %. The SnO2 powders obtained is the single phase, and the content of SnO2 is up to 99.9 %. However, the SnO2 particles are easier to agglomerate during the precipitation process. The agglomerate SnO2 particles are about 7.778 lm in mean particle size(D50). This preparation method presents a viable alternative for the tin slag recycling. The tin is not only recycled, but also reused directly to prepare pure SnO2 powders.