Calcium carbonate synthesis from Kambara reactor desulphurization slag via indirect carbonation for CO2 capture and utilization.

In this work, industrial Kambara reactor desulphurization slag (KR slag) was indirectly carbonated. The effects of leaching time, leaching temperature, leaching agent types, and leaching agent concentration on the leaching ratio of calcium from KR slag were investigated. Subsequently, precipitated calcium carbonate (PCC) was synthesized by bubbling CO2 gas (flow rate of 15 mL/min) into 400 mL leaching solutions at 40 °C for 120 min with magnetic stirring at 300 rpm. It is found that calcium in KR slag can be selectively extracted using a diluted solution of ammonium acetate (CH3COONH4) or ammonium chloride (NH4Cl), while ammonium sulfate ((NH4)2SO4) solution is not suitable as leaching agent due to the formation of slightly soluble calcium sulfate (CaSO4). The leaching ratio of calcium is improved by extending the leaching time or increasing the leaching solvent concentration. However, leaching temperature has little effect on calcium extraction. After carbonating the NH4Cl- and CH3COONH4-leachate for 120 min, calcite and vaterite type PCC with a purity of 99% is synthesized. Each gram of KR slag can produce 0.794 g and 0.803 g PCC using NH4Cl and CH3COONH4 leaching agents respectively. Calculations show that 349.6 kg CO2 is captured by per ton of KR slag. The CO2 capture capacity of KR slag is significantly higher compared with previously studied materials.

Hydrothermal Separation of Titanium Vanadium and Chromium from a Pregnant Oxalic Acid Leachate.

The separation of titanium, vanadium and chromium in vanadium slag (VS) is a difficult problem restricting the comprehensive utilization of VS. This paper presents the first study on the separation of titanium, vanadium and chromium from oxalic acid leachate of VS. Firstly, the separation of titanium from the leachate by hydrothermal method was studied. The results show that more than 99% of titanium in the leachate was precipitated in the form of spherical anatase TiO2 with the purity of 95.7%. Then, the extraction separation of vanadium and chromium from the titanium-free filtrate by three-stage extraction of acidified N235 extractant and four-stage stripping of HCl solution was investigated. The extraction mechanism was identified as the anion exchange reaction between acidified N235 extractant and vanadium and chromium complex anions, which were further stripped by HCl solution in the stripping process. After obtaining the concentrated and purified stripping solution containing vanadium and chromium, the separation of vanadium and chromium from the stripping solution by hydrothermal method was studied, and the product was mainly composed of VO2 and Cr2O3. This process provides an idea for the comprehensive utilization of titanium, vanadium and chromium in oxalic acid system.

Synergetic valorization of basic oxygen furnace slag and stone coal: Metal recovery and preparation of glass-ceramics.

A synergetic valorization method was proposed to convert the basic oxygen furnace (BOF) slag and stone coal into ferroalloy and glass-ceramic in this work. Effects of reduction time, temperature, and the mass ratio of BOF slag to stone coal on the reduction were studied. The reduction mechanism was investigated by in-situ observation and dissolution experiments. The effect of sintering temperature on the properties of glass-ceramics prepared from the final slag was further studied. The in-situ observation results indicate that the reduction reactions occurred mainly in the temperature range of 1673-1793 K. The reduction ratio of oxides and size of metal droplets can be improved by increasing reduction time, temperature, and decreasing stone coal addition. The recovered ferroalloys consisted of Fe, Mn, P, and V, which has the potential of returning to the steelmaking process or extracting vanadium. The modified final slag was suitable material for preparing glass-ceramic. Wollastonite-based glass-ceramic with a maximum bending strength of 95.83 MPa was prepared, which could be applied as abrasion-resistant and building decoration materials. Therefore, the present technological route can convert two kinds of industrial solid waste into two kinds of cleaner products and achieve the target of "zero waste".

FeP/C Composites as an Anode Material for K-Ion Batteries.

Owing to their natural abundance, the low potential, and the low cost of potassium, potassium-ion batteries are regarded as one of the alternatives to lithium-ion batteries. In this work, we successfully fabricated a FeP/C composite, a novel electrode material for PIBs, through a simple and productive high-energy ball-milling method. The electrode delivers a reversible capacity of 288.9 mA·h·g-1 (2nd) at a discharge rate of 50 mA g-1, which can meet the future energy storage requirements. Density functional theory calculations suggest a lower diffusion barrier energy of K+ than Na+, which allows faster K+ diffusion in FeP.