Two-stage leaching of calcium and vanadium from high-calcium steelmaking slag.

Vanadium (V) is a critically important element in many industries. A widely used recovery process is a combination of roasting and leaching. However, roasting is an energy-intensive stage. Generally, basic oxygen furnace (BOF) slag is high in calcium (Ca) but low in V. Ca content and its chemical nature can prevent V leaching. This study presents a potential two-stage leaching process for Ca and V from BOF slag. The method is environmentally friendly using low temperatures and enabling leachate recycling. Furthermore, the utilisation rate of the slag can be higher due to Ca recovery. Ca is first leached using ammonium nitrate and nitric acid solution. The V-containing residue is directed to the second stage, where V is leached using ammonium carbonate ((NH4)2CO3). Ca leaching efficiency was 71% achieved with a low temperature (40°C) and in 20 min. > 99% of the dissolved element was Ca. Increasing the total nitrate concentration increased the leaching efficiency. Reducing the L/S ratio improved selectivity. The solid material was analysed after the leaching stages and a clear change was observed after the Ca-stage. The V leaching efficiency was 50%. > 88% of dissolved element was V (L/S 8, [(NH4)2CO3] 200 g/L, 60°C, and 60 min). Increasing [(NH4)2CO3] and L/S ratio slightly improved the leaching efficiency but decreased selectivity. The studied process implements circular economy principles and has been developed for side streams with low V concentrations. However, further optimisation and developments are required regarding the effectiveness of the process.

Production and properties of ferrite-rich CSAB cement from metallurgical industry residues.

Blast furnace slag from the steel industry is commercially utilized as a cement replacement material without major processing requirements; however, there are many unutilized steel production slags which differ considerably from the blast furnace slag in chemical and physical properties. In this study, calcium sulfoaluminate belite (CSAB) cement clinkers were produced using generally unutilized metallurgical industry residues: AOD (Argon Oxygen Decarburisation) slag from stainless steel production, Fe slag from zinc production, and fayalitic slag from nickel production. CSAB clinker with a target composition of ye'elimite-belite-ferrite was produced by firing raw materials at 1300 °C. The phase composition of the produced clinkers was identified using quantitative XRD analyses, and the chemical composition of the clinker phases produced was established using FESEM-EDS and mechanical properties were tested through compressive strength test. It is demonstrated that these metallurgical residues can be used successfully as alternative raw materials for the production of CSAB cement that can be used for special applications. In addition, it is shown that the available quantities of these side-streams are enough for significant replacement of virgin raw materials used in cement production.

Twenty-year results of the Evans operation for lateral instability of the ankle.

Twenty-four patients (25 ankles), operated on using the static modification of the Evans tenodesis for lateral instability, were evaluated 19 to 21 years after surgery. Twelve of the patients (12 ankles) had excellent results, seven patients (eight ankles) had good results, three patients (three ankles) had fair results, and two patients (two ankles) had poor results. The subjective results had no clear correlation to the stress radiographs, which showed minor or moderate anterior talar translation in 10 ankles. Moreover, the difference between the surgically treated and the contralateral ankle was not significant. Static modification of the Evans tenodesis is recommended if an anatomic reconstruction of the lateral ligaments is not feasible (general laxity of joints, reoperation).