Asynchronous extraction of vanadium and chromium from vanadium slag by stepwise sodium roasting–water leaching

Calcification roasting–acid leaching of high-chromium vanadium slag (HCVS) was conducted to elucidate the roasting and leaching behaviors of vanadium and chromium. The effects of the purity of CaO, molar ratio between CaO and V2O5 (n(CaO)/n(V2O5)), roasting temperature, holding time, and the heating rate used in the oxidation–calcification processes were investigated. The roasting process and mechanism were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetry–differential scanning calorimetry (TG–DSC). The results show that most of vanadium reacted with CaO to generate calcium vanadates and transferred into the leaching liquid, whereas almost all of the chromium remained in the leaching residue in the form of (Fe0.6Cr0.4)2O3. Variation trends of the vanadium and chromium leaching ratios were always opposite because of the competitive reactions of oxidation and calcification between vanadium and chromium with CaO. Moreover, CaO was more likely to combine with vanadium, as further confirmed by thermodynamic analysis. When the HCVS with CaO added in an n(CaO)/n(V2O5) ratio of 0.5 was roasted in an air atmosphere at a heating rate of 10°C/min from room temperature to 950°C and maintained at this temperature for 60 min, the leaching ratios of vanadium and chromium reached 91.14% and 0.49%, respectively; thus, efficient extraction of vanadium from HCVS was achieved and the leaching residue could be used as a new raw material for the extraction of chromium. Furthermore, the oxidation and calcification reactions of the spinel phases occurred at 592 and 630°C for n(CaO)/n(V2O5) ratios of 0.5 and 5, respectively.

Roasting and leaching behaviors of vanadium and chromium in calcification roasting–acid leaching of high-chromium vanadium slag

Green one-step roasting method for efficient extraction of vanadium and chromium from vanadium-chromium slag

Petroleum coke (petcoke) has been burned at kraft pulp mills to partially substitute for natural gas and fuel oil used in lime kilns Due to the high vanadium and sulfur contents in petcoke, there had been concerns over the impact of burning petcoke on kiln and chemical recovery operations Laboratory studies were performed to examine the fate of vanadium and sulfur in lime kilns and chemical recovery cycle The results suggest that most of the vanadium in petcoke quickly forms calcium vanadates with lime in the kiln, mostly 3CaO•V2O5 In the causticizers, calcium vanadates react with Na2CO3 in green liquor to form sodium vanadate (NaVO3) Due to its high solubility, NaVO3 dissolves in the liquor circulating around the chemical recovery system V becomes enriched in the liquor, leading to vanadium build-up in the system The S in petcoke would stay in the reburned lime, lower the lime availability, increase SO2 emissions from the kiln stack, alter the S balance, increase the liquor sulphidity, and potentially contribute to ring formation in the kiln

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The Fates of Vanadium and Sulfur Introduced with Petcoke to Lime Kilns

Increase of acid-surface reactivity through water molecules adsorption process: V2O5-CaCO3 behaviour

The interaction of V2O5 with calcium oxide and calcium carbonate was studied by thermal analysis. The results indicated that the macrosuccession of the phase transformations in the systems CaO-V2O5 and CaCO3-V2O5 corresponds to an increasing calcium content in each successively formed calcium vanadate. Thermodynamical calculations carried out by methods available in the literature for determining the primary products and the succession of the subsequently formed products demonstrate that chemical reactions proceeding in the above systems are controlled by kinetic and not by thermodynamic factors.

A thermoanalytical study of the interaction of vanadiumoxide(v) with calcium oxide and calcium carbonate

BACKGROUND: The techniques for the surgical correction of a hindfoot valgus deformity usually include both bony and soft-tissue techniques, depending on the deformity severity. Medializing calcaneal osteotomy (MCO) is one of the main surgical techniques used to correct such deformities. However, the degree of deformity in different patients can vary significantly; thus, using the above principle, the degree of calcaneal postoperative correction can vary considerably. Based on data from various authors, patients with an insufficient correction of the heel bone axis have a residual valgus in the hindfoot. However, the lack of complete correction may result in the persistence of complaints and corrected limb recurrence. 
OBJECTIVE: To improve the surgical treatment of hindfoot malalignment. 
MATERIAL AND METHODS: The study analyzed treatment results of patients with ankle sprain in the Center Traumatology and Orthopedics (Moscow) between 2012 and 2020. All implantations were performed by two surgeons. The total number of patients is 60. Fifty-five patients with follow-up periods of over 12 months after the procedure were available for a retrospective analysis and assessment of results. The study enrolled 20 men and 35 women, with a mean age of 61.6 (18,540,7) years years. The mean follow-up period is 62 (1880) months. 
RESULT: The mean change in the Foot and Ankle Outcome Score (FAOS) pain subscale was 27.9 (range, 8.3 to 63.9) for the moderate varus group (n = 16), 41.2 (range, 5.666.7) for the mild varus group (n = 17), and 22.3 (range, 58.3 to 63.9) for the valgus group (n = 18). In addition, patients with mild varus demonstrated better clinical outcomes than those with valgus; however, this difference was not statistically significant (p=0.11). No differences were found between groups in the change in scores for daily activities (p=0.26), sports activities (p=0.06), or quality of life (p=0.17) subscales of the FAOS. 
CONCLUSION: Patients with mild varus hindfoot alignment showed significantly greater improvement than those with valgus with respect to the FAOS pain subscale and significantly greater improvement than those with moderate varus in the FAOS symptoms subscale.

https://journals.eco-vector.com/0869-8678/article/download/321523/pdf_2

Anatomical and functional guidelines for the correction hindfoot malalignment

Category: Hindfoot; Ankle Introduction/Purpose: Number of fractures of the calcaneus amounts to 1-5.7% of all fractures of skeleton bones according to various authors. Moreover, these figures correspond to 50% of all fractures of feet bones. Consequences of calcaneus malunion leads to early disability, arthrosis, pain syndrome, disorder of the entire low extremity axis of motion alongside cosmetic defects and shoe wearing discomfort. Purpose of the study: classification of calcaneal malunions based on a geometrically normal position and dimensions of hindfoot in order to develop optimal type of treatment for multicomponent calcaneal deformity. Methods: Twelve patients with post traumatic deformed hindfoot after malunited calcaneal fractures and as a result varus and valgus deformity, subtalar arthritis, pain syndrome, shoe wear discomfort at different stages after trauma (from 1 to 10 years) were examined, underwent surgical alignment of calcaneus and were followed up for 24 months. All cases were assessed clinically using the American Orthopaedic Foot & Ankle Society (AOFAS) and visual analog scale (VAS); radiologically by measuring hindfoot varus/valgus, talus tilt, Meary's angle, and hight of calcaneal. Results: It was found a significant improvement in AOFAS (55.2 preoperatively to 78.8 after 24 months) and VAS (65 preoperatively to 30.1). Moreover, our study revealed a significant improvement in the radiographic measurements including hindfoot varus/valgus, the talar inclination, Meary's angle, and hight of calcaneus. Conclusion: The elimination of angular hindfoot varus or valgus deformation, exostectomy of the lateral wall and subtalar fusion, as well as the use of a tricortical autograft for distarction arthrodesis at III-V type Zwipp and Rammelt classification, resulted in reduced pain, improved function, cosmetic results and shoe wearing.

I. A. Arapova

Papers

A thermoanalytical study of the interaction of vanadiumoxide(v) with calcium oxide and calcium carbonate

Anatomical and functional guidelines for the correction hindfoot malalignment

Calcaneal Malunions Management and Types of Surgical Correction