Yufeng Guo,Chao Wang,Shuai Wang,Feng Chen,Xueyuan Wang,Zhiwei An,Lingzhi Yang
Vanadium tailings are a common solid waste in the vanadium industry. As they are rich in Fe, vanadium tailings could be a potential raw material for the blast furnace. However, the presence of approximately 4% Na2O in vanadium tailings is a major impediment to its return to the blast furnace. A novel method for removing sodium from vanadium tailings by calcification roasting and subsequent NaOH leaching was proposed in this work. The method demonstrated that calcification roasting of vanadium tailings can not only volatilize a part of sodium but also facilitate the dissolution of sodium during the subsequent NaOH leaching process. The thermodynamic analysis and behaviors of vanadium tailings during calcification roasting were systematically investigated. The transformation of sodium-containing phases in vanadium tailings during calcification roasting was studied. Further, the promoting effect of calcification roasting on sodium leaching by NaOH was clarified. The total removal efficiency of sodium was 80.37% under optimal conditions, and the residue obtained after sodium removal can be used as a raw material in the blast furnace process for in-plant recycling.Keywords:vanadium tailings;sodium removal;calcification roasting;volatilization;leaching
Spent anodes (butts) are the remaining portion of prebaked anodes after consumption, which are reintroduced into the production of prebaked anodes after treatment. Among these residues, the main harmful element, sodium, tends to accumulate with the repeated recycling of the butts. This accumulation increases the air reactivity of prebaked anodes and consequently reduces their quality. In this study, aluminum sulfate hydrothermal acid leaching was used to remove sodium from the butts. The effects of leaching temperature, Al 3+ concentration, leaching time, and liquid-to-solid ratio on the removal of sodium from the butts were investigated. The sodium removal rate reached 99.42% at a leaching temperature of 90°C, an Al 3+ concentration of 1.5 mol/L, a leaching time of 2.5 h, and a liquid-to-solid ratio of 25 mL/g. This method significantly reduced the sodium content in the butts, offering a new approach for the high-quality recovery of the butts.
Xin Mi,Shuangxi Zhou,Ziming Zhou,Mohammadtaghi Vakili,Yue Qi,Ye Jia,Donghai Zhu,Wei Wang
Covalent organic frameworks (COFs) with great application potential in environmental remediation exist as the form of powder, which are difficult to separate and recycle. Two magnetic COFs with good recyclability were prepared through simple impregnation-precipitation method in this study. The prepared magnetic COFs were used for the adsorptive removal of diclofenac sodium (DCF). The introduction of hydroxyl group on magnetic COF (OH-MCOF) could greatly enhance its adsorption amount for DCF, and OH-MCOF was selected to study the effect of adsorption time, initial concentrations, solution pH and ionic strength on its adsorption for DCF, as well as its regeneration and reuse performance were investigated. In this study, the OH-MCOF had a high adsorption capacity for DCF of 203.4 mg/g based on the Langmuir model fitting, and exhibited quickly adsorption for DCF within 30 min. The adsorption efficiency was better than that of most reported adsorbents. Furthermore, the role of hydroxyl group on magnetic COF was highlighted through density functional theory (DFT) and electrostatic potential (ESP) calculation. After 5 cycles of regeneration, the OH-MCOF still maintained the same adsorption amount for DCF, showing good reusability and stability. This study reveals OH-MCOF with high removal and reusability in the further application of environmental remediation.
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