MgO−V_(2)O_(5)二元系固相反应相变及产物溶解行为

研究不同摩尔比MgO−V_(2)O_(5)混合物的固相反应行为。采用等温溶解平衡法测定25~55℃下反应产物(钒酸镁)在水中的溶解度,并研究其在稀硫酸中的溶解行为和动力学。结果表明,MgO与V_(2)O_(5)的摩尔比和焙烧温度对固相反应产物的相变有较大影响;MgV_(2)O_(6)在水中溶解度最大,其次是Mg_(2)V_(2)O_(7)和Mg_(3)V_(2)O_(8);随着pH值从4.0降低到2.5,温度从30℃增加到70℃,钒酸镁在稀硫酸中的溶解率显著增加,其在稀硫酸中的溶解符合二级伪均相反应模型。

Recovery of vanadium from vanadium slag by composite roasting with CaO/MgO and leaching

A novel process of composite roasting with CaO/MgO and subsequent acid leaching was proposed to improve the recovery rate of vanadium from Linz–Donawiz(LD)converter vanadium slag.The effects of the MgO/(CaO+MgO)molar ratio and the roasting and leaching parameters on the recovery of vanadium were studied.The results showed that the leaching efficiency of vanadium decreased from 88%to 81%when CaO was replaced completely by MgO;however,it could be improved by roasting with the composite of CaO/MgO.The maximum vanadium leaching efficiency of 94%was achieved under the optimum MgO/(CaO+MgO)mole ratio of 0.5:1.The results from X-ray diffractometry(XRD)and scanning electron microscopy with energy-dispersive X-ray spectroscopy(SEM−EDS)confirm that the formation rate of acid-soluble vanadates can be enhanced during roasting with the composite of CaO/MgO and that the leaching kinetics can be accelerated owing to the suppression of calcium sulfate precipitation.

Cervical spondylotic myelopathy with syringomyelia presenting as hip Charcot neuroarthropathy:A case report and review of literature

BACKGROUND Charcot neuroarthropathy(CN)is a systemic disease characterized by progressive bone loss and destruction,which is usually closely related to diabetes,HIV,etc.However,CN caused by syringomyelia accounts for only 5%of CN cases;the shoulder and elbow are most often involved,and the hip joint is rarely affected.As a rare factor,cervical spondylotic myelopathy(CSM)can be associated with syringomyelia,which is scarcely reported in the literature.Here,we present the first case report to date of CN of the hip caused by syringomyelia secondary to CSM.CASE SUMMARY We describe a 76-year-old male patient who was diagnosed with CSM due to neck pain and weakness of limbs 16 years ago.Four years ago,he noticed recurrent swelling of the right hip with pain and was diagnosed with degenerative arthritis.Recently,however,his symptoms gradually worsened,and because of progressive pain,destabilization and weakness of the right hip,he was admitted to our hospital.Through systematic physical,radiographic and laboratory examinations,we finally reached a diagnosis:CN of the right hip associated with syringomyelia secondary to CSM.After comprehensive evaluation of the patient's condition,we performed right total hip arthroplasty.During the follow-up,the patient felt well clinically and could walk independently with a knee brace.CONCLUSION We suggest a possible etiological association between CSM and syringomyelia,which may reflect a potential pathogenesis of CN.We encourage clinicians to actively carry out a detailed medical history and comprehensive physical and imaging examinations in patients with joint lesions,especially chronic shoulder neck pain,to rule out the possibility of this association,which plays a crucial role in the early diagnosis of CN.Arthroplasty may no longer be an absolute contraindication to surgical treatment of CN.Reasonable selection of the surgical strategy can markedly improve the clinical symptoms and quality of life of patients.

Solid-state reaction of a CaO−V_(2)O_(5)mixture:A fundamental study for the vanadium extraction process

The aim of this study was to investigate the phase transformation and kinetics of the solid-state reaction of CaO−V_(2)O_(5),which is the predominant binary mixture involved in the vanadium recovery process.Thermal analysis,X-ray diffraction spectroscopy,scanning electron microscopy,and energy dispersive spectrometry were used to characterize the solid-state reaction of the samples.The extent of the solid reac-tion was derived using the preliminary quantitative phase analysis of the X-ray patterns.The results indicate that the solid reaction of the CaO−V_(2)O_(5)mixture is strongly influenced by the reaction temperature and CaO/V_(2)O_(5)mole ratio.The transformation of calcium vanadate in-volves a step-by-step reaction of CaO−V_(2)O_(5),CaO−CaV_(2)O_(6),and CaO−Ca_(2)V_(2)O7 depending on the CaO/V_(2)O_(5)mole ratio.The kinetic data of the solid reaction of the CaO−V_(2)O_(5)(1:1)mixture followed a second-order reaction model.The activation energy(Ea)and preexponential factor(A)were determined to be 145.38 kJ/mol,and 3.67×10^(8)min^(−1),respectively.

Recovery of vanadium from vanadium slag by composite additive roasting-acid leaching process

To minimize the vanadium content in the vanadium extraction tailings, composite additive roasting with (CaO + MgO) and subsequent acid leaching process was carried out dealing with vanadium-bearing converter slag. The effect of additive with different MgO/(CaO + MgO) molar ratios on the roasting and leaching behaviours of vanadium slag was investigated, and the optimum process conditions were obtained. The results show that in the roasting experiment, under the conditions of roasting temperature of 850 ℃ and roasting time of 2 h, the main kinds of vanadate transformed from Ca_(2)V_(2)O_(7) to Ca_(5)Mg_(4)V_(6)O_(2)4 and then to Mg_(2)V_(2)O_(7) with the increase in the MgO/(CaO + MgO) molar ratio. In the leaching experiment, under the conditions of particle size less than 75 μm, leaching temperature of 50 ℃, pH of 2.5, liquid–solid ratio of 20:1, and MgO/(CaO + MgO) molar ratio of 1:3, the leaching efficiency of vanadium is increased by about 5%, but the substitution of MgO for most or all of CaO will significantly reduce the leaching efficiency of vanadium. Furthermore, the leaching efficiency of impurities (P and Cr) can also be decreased by a composite addictive (CaO + MgO) roasting process. The X-ray diffraction, scanning electron microscopy, energy dispersive spectrometry, and X-ray photoelectron spectroscopy of the original vanadium slag and solid products of both roasting and leaching processes were also evaluated.

Synthesis of vanadium powder by magnesiothermic reduction of V_(2)O_(3)in a reactive molten salt

As an important strategic metal,vanadium is generally used to prepare special steels,titanium alloys,and hydrogen storage materials.A new method of producing vanadium(metal)powder from V_(2)O_(3)using block Mg is presented herein.Using an auxiliary molten salt,V_(2)O_(3)was successfully transformed into V by Mg reduction.The by-product,MgO,was transformed into MgCl_(2)by adding ZrCl_(4),which prevented the generation of MgV_(2)O_(4)and allowed the reaction to proceed smoothly.The rod-like alloy phases,Zr_(0.03)V_(1.97),which formed in the presence of excess Mg,may hinder the diffusion of oxygen from the product.The recovery rate of vanadium after separation and purification was approximately 45%–50%,where the main loss occurred during ball milling.Under the optimal conditions(Mg content of 48.3%,reduction time of 1.5 h,and temperature of 850℃),the purity of vanadium exceeded 99 wt.%,and the O content decreased to 0.34 wt.%.

Effect of TiO2 on reduction behavior of Cr2O3 in CaO-SiO2-Al2O3-MgO-TiO2-Cr2O3 by carbon from Fe-C melt

The chromium-bearing titanomagnetite ore will turn to be the important raw material for blast furnace process in Panxi area,China.The reduction behavior of Cr2O3 between CaO-SiO2-Al2O3-TiO2-Cr2O3 and Fe-C systems was investigated.The effect of TiO2 content in the slag system on the reduction of Cr2O3,TiO2,and SiO2 and the con sumption of C in hot metal was investigated by both theoretical calculation and physical experiment.The theoretical calculation results reveal that higher reduction temperature promotes the reduction of Cr and Ti,while high basicity and TiO2 content have little influence on the reduction of chromium but significantly influence the reduction of Ti.The smelting reduction experiment results show that the content of Cr in hot metal significantly in creases with extendi ng the reduction time and decreases with the increase in TiO2 content.However,the content of Ti in hot metal significantly increases as the TiO2 increases,reaching 0.073,0.085,0.107,and 0.121 wt.%for 5,10,15,and 20 wt.%of TiO2 input,respectively.Kinetic studies proved that the reduction of Cr2O3 was a first-order reaction.The addition of TiO2 inhibited the reduction of Cr2O3 and resulted in the decrease in reaction rate constant.