The critical applications of vanadium in metallurgical field and the growth in commercialization of vanadium redox flow batteries (VRFB) have led to the increased demand of vanadium. It is thus important to ensure the sustainability of vanadium production. Vanadium bearing slags, the solid byproducts in iron- and steel-making plants, are the principal source of vanadium production, accounting for more than 69% of total vanadium in terms ofthe raw material types. Academic researches and engineering investigations have been addressed to develop such metallurgical processes for treating the vanadium bearing slags. This article presents a comprehensive review on the metallurgical treatments of vanadium bearing slags. The composition and phase/mineralogical characterization of vanadium bearing slags from various sources are given. Literature review shows that the vanadium bearing slags have been traditionally treated through the roasting-assisted leaching with the recent efforts of integrating the state-of-the arts technologies in extractive metallurgy and developing direct leaching methodologies. Some promising methods are worth discussing and quite encouraging, and expected to be the future focuses of this area. Discussion also highlights the separation of vanadium from silica, phosphorus and chromium as the major interfering elements/metal in the leach solutions of vanadium slags. Recommendation is made for taking up future works in order to develop a sustainable metallurgical process for vanadium bearing slag.

A review on the metallurgical recycling of vanadium from slags: towards a sustainable vanadium production

Efficient extraction and separation of vanadium and chromium in high chromium vanadium slag by sodium salt roasting-(NH4)2SO4 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

A cleaner and efficient process for extraction of vanadium from high chromium vanadium slag: Leaching in (NH4)2SO4-H2SO4 synergistic system and NH4+ recycle

Efficient separation of chromium and vanadium by calcification roasting–sodium carbonate leaching from high chromium vanadium slag and V2O5 preparation

The extraction of vanadium and chromium from high chromium content vanadium slag by salt roasting and water leaching process has been investigated, which uses mixed sodium salts (Na2CO3 and NaOH) as additive agent in roasting process. The mineralogical morphology was prospected by TG-DSC, XRD, SEM and EDS. The oxidation of slag and transversion of V/Cr-containing phase and sodium salts have been discussed. It has been demonstrated that the presence of NaOH contributes to decompose spinel and olivine phases, which is beneficial to reduce the roasting temperature and elevate V, Cr leaching ratio. The roasting parameters have been studied as a function of roasting temperature, roasting time and ratio of alkali, in which the roasting temperature is the most effective factor on the leaching rate of vanadium and chromium. Under the optimum condition, the leaching rates of V and Cr reached 95.8% and 97.6%, respectively.

Effective Extraction of Vanadium and Chromium from High Chromium Content Vanadium Slag by Sodium Roasting and Water Leaching

Pressure injury often seriously affects the life quality of aged patients, especially the long‐term bedridden casualties. Widely adopted by different disciplines, negative pressure suction has its role in pressure injury. Microskin implantation has been demonstrated powerful in increasing the expansion ratio of donor area‐derived skin and accelerating wound healing by forming “skin islands”. The study was designed to evaluate the efficacy and safety of additional use of bedside microskin implantation in the palliative care of pressure injury of aged patients who cannot tolerate surgical treatment as a supplement for standard negative pressure suction. An open‐label within‐patient RCT was conducted in aged patients with pressure injury. Sixteen patients were enrolled. After granulation tissues formed, half of a pressure injury was randomised to receive the negative pressure suction as the control group, and the other half exposed to additional bedside microskin implantation as the experimental group. Efficacy was evaluated within 1 month after treatment, and the primary endpoints included the wound healing rate and pressure ulcer scale for healing (PUSH) scores. The secondary outcomes included survival rate of implanted microskin, pain intensity assessment, satisfaction surveys from patients or their family, and pressure ulcer healing complications. Sixteen patients completed the study. After 14 days of operation, 5.63 ± 1.78 out of 10 pieces of implanted microskin survived and formed neonatal epithelium. The wound healing rates of the control group and the experimental group at 1 month were (26.17 ± 9.03%) and (35.95 ± 16.02%), respectively (P < .01). The mean PUSH score before the surgery was 12.38 ± 2.23. At 1 month after surgery, the mean difference of PUSH score from baseline was 2.13 ± 0.96 in the control group and 2.81 ± 0.83 in the experimental group (P < .01). The treatment of microskin implantation did not cause additional pain or complications to the patients. Accompanied by a better ulcer status, the majority of patients or their guardians have a high degree of acceptance towards the microskin implantation. Bedside microskin implantation could accelerate wound healing with lower PUSH scores. As a complementary palliative treatment, supplementary microskin implantation is effective and well tolerated.

Within‐patient randomised clinical trial exploring the development of microskin implantation in the treatment of pressure ulcers

INTRODUCTION
New techniques are needed to manage chronic wounds in patients with contraindications to standard of care treatment.


OBJECTIVE
This case series investigated the viability and proliferative activity of split skin cells harvested from the discarded rolled edge of PIs for use in promoting reepithelialization in chronic wounds.


MATERIALS AND METHODS
The harvested skin was minced into particles with a scalpel. The structure of the skin particle was shown with hematoxylin-eosin staining. The viability of cells, isolated from skin particles, was identified with MTT. Skin particles were transferred to PIs. The size of PI was recorded before grafting and 1 month after grafting.


RESULTS
From January 2018 to January 2019, 5 patients (1 female, 4 males; mean age, 72.6 years ± 6.1) were enrolled in this study. The mean ulcer size was 27.8 cm2 ± 17.7. The cells from particles could survive and be amplified in vitro. One month after grafting, the average ulcer size was 16.2 cm2 ± 7.3.


CONCLUSION
The split skin particles harvested from the rolled edge of the wound consisted of keratinocytes and keratinized tissues and were found to be viable and proliferative. These particles had the capacity to survive and expand on the granulation tissue surface of PIs, which indicates this procedure could accelerate reepithelization in chronic wounds.

Zhi Xin Shi

Papers

Effective Extraction of Vanadium and Chromium from High Chromium Content Vanadium Slag by Sodium Roasting and Water Leaching

Within‐patient randomised clinical trial exploring the development of microskin implantation in the treatment of pressure ulcers

Wound repair using discarded skin tissue from the rolled edge of pressure injury: a feasibility study of five cases.