Controlled Hydrothermal Precipitation of Alunite and Natroalunite in High-Aluminum Vanadium-Bearing Aqueous System

Abstract

During the acid leaching process of black shale, with the destruction of the aluminosilicate mineral structure, a large amount of aluminum (Al) is leached, accompanied by the release of vanadium (V). To separate aluminum from the vanadium-containing solution, the precipitation behavior of aluminum ions (Al3+) was investigated under hydrothermal conditions with the formation of alunite and natroalunite. In the solution environment, alunite and natroalunite are able to form stably by the Al3+ hydrolysis precipitation process at a temperature of 200 °C, a pH value of 0.4 and a reaction time of 5 h. When Al3+ was precipitated at a K/Al molar ratio of 1, the aluminum precipitation efficiency and the vanadium precipitation efficiency were 64.77% and 1.72%, respectively. However, when Al3+ was precipitated at a Na/Al molar ratio of 1, the precipitation efficiency of the aluminum decreased to 48.71% and the vanadium precipitation efficiency increased to 4.36%. The thermodynamics and kinetics results showed that alunite forms more easily than natroalunite, and the reaction rate increases with increasing temperature, and the precipitation is controlled by the chemical reaction. Vanadium loss increases as the pH value increases. It can be deduced that the ion state of tetravalent vanadium (VO2+) was transformed into the ion state of pentavalent vanadium (VO2+) in the hydrothermal environment. The VO2+ can be adsorbed on the alunite or natroalunite as a result of their negative surface charges, ultimately leading to vanadium loss.

The Effects of Chloride on the High Temperature Pressure Oxidation of Chalcopyrite: Some Insights from Batch Tests—Part 2: Leach Residue Mineralogy

“…There are two exceptions: the first is the formation of antlerite, equation (30), and this is consistent with the study of Yoder et al [113] who reported that this phase cannot be formed at room temperature from reactions between 0.05-1.2 M CuSO 4 and 0.05-1.0 M NaOH solutions. The second is the formation of natroalunite, Equation (28) which typically employs temperatures above 100 • C for synthesis (e.g., [152]).…”

Sorption in an ammonioalunite-ammoniojarosite solid solution: results for the 1, 2, 4, 7, 11, 12 and 13 group elements and LREEs

“…Ad sorp tion phe nom ena are also im por tant, e.g., for Al, Cd, Cu and Zn, as shown by the computer sim u la tions of Hud son-Ed wards and Wright (2011). The ad sorp tion is pos si ble due to the neg a tive charge of the ASM sur face (Wang et al, 2021).…”

Leaching Characteristics of Potentially Toxic Metals from Tailings at Lujiang Alum Mine, China

“…Alum mines are distinguished from metal and coal mines by the production of waste slag containing alunite (KAl(SO₄)₂·12H₂O) [ 32 ]. The ionization of alunite can further aggravate the degree of water acidification caused by pyrite [ 33 ]. In the past, alum mining activities produced large amounts of waste slag, some of which comprised low-grade ores discarded from open-pit mining, which accumulated on many parts of the surface without any anti-pollution measures.…”