Solvent extraction offers a better option for gallium recovery among many techniques. The liquid–liquid extraction of gallium(III)–copper(II) solution from hydrochloric acid medium using di-2-ethyl-hexylphosphoric acid (D₂EHPA) in kerosene was studied. The effect of the reagent concentration and other parameters on the extraction of gallium(III)–copper(II) was also studied. The stoichiometry of the extracted species of gallium(III) was determined based on the slope analysis method. The maximum extraction efficiency of gallium was 99.9%. The gallium that contained organic phase could be stripped completely by 1 M HCl.

The purpose of this study was to investigate the reuse of desulfurization slag in cement clinker production and its influence on the formation of clinker phases. The desulfurization slag that mainly contained Ca and Si was identified as non-toxic, and thus it should be suitable to be reused in clinker production. The addition of desulfurization slag increased the melt phase during clinkerization, but the excess melt phase inhibited the formation of clinker phases. This could be attributed to the sulfur and fluoride derived from the De-S slag. At low desulfurization slag addition (5.4 wt %), the resulting clinker had a mineralogical composition similar to that of the reference clinker. The desulfurization slag added can lower the clinkerization temperature and increase the amount of Ca₃SiO₅ at 1300 °C, which may be beneficial to energy conservation in clinker burning. Moreover, reusing desulfurization slag additionally has the potential to reduce the energy needed for clinker grinding.

In this study, the engineering properties of Ordinary Portland Cement (OPC) and alkali-activated slag (AAS) mortar with electric arc furnace ladle slag (EAFLS) were investigated to reveal the effects of EAFLS on the expansion of cementitious mortars. Additionally, the effects of these two types of mortar were explored based on their compressive strength, especially at high temperatures. EAFLS in OPC mortars significantly reduced the compressive strength and caused serious soundness problems in the mortars after autoclaving due to the presence of free-CaO and free-MgO in the EAFLS slag. On the other hand, the AAS mortars produced with EAFLS had compressive strength comparable to ordinary OPC mortars and maintained soundness after autoclaving. During a 550 °C heat treatment, the OPC mortar cracked and lost residual strength, but the AAS mortar retained more than 90% of its residual strength. Even after an 800 °C heat treatment, the AAS mortar maintained 14% of its residual strength (about 4 MPa), sufficient to prevent the collapse of the specimen structure. The main reason is that alkali-activated technology can accelerate the hydration process and solve the delayed hydration problem. The results of this study indicated that EAFLS is suitable to partially replace the binder used in the production of AAS mortars, and the resulting AAS mortars have high volume stability, high compression strength, and good high temperature resistance.

The purpose of this study was to investigate the mechanism causing the unsoundness of ladle slag. Calcination temperature may have an impact on the level of reactivity of f-CaO. When CaO was produced at a higher temperature, the reactivity of CaO was lower. For example, dead burnt CaO (DCaO) was produced at higher temperatures than light burnt CaO (LCaO); therefore, DCaO had less reactivity than LCaO. In a hydration test, DCaO (1500 °C) showed 62 times lower reactivity than LCaO (900 °C), which meant that DCaO would result in the delay of hydration of CaO easily. Additionally, DCaO would cause unsoundness more easily than LCaO when adding the same number of cementitious materials. For this reason, using ASTM C114-18 (Standard Test Methods for Chemical Analysis of Hydraulic Cement) to quantify DCaO content may underestimate DCaO content by up to 20%. Conversely, this method was more suitable for f-CaO since it had high reactivity. Moreover, this study demonstrated that ladle slag would cause unsoundness when added into the cementitious material because it was produced from a higher temperature process (over 1500 °C), which generates the DCaO. Therefore, when reusing ladle slag, the problem of low reactivity of DCaO should be considered.