The significant release of arsenic observed from ferric arsenate minerals in the presence of elevated phosphate levels underscores the complexity of their stability in natural environments. Our findings highlight the need to reconsider phosphate treatments in extraction procedures involving ferric arsenates, emphasizing the importance of cautious application in managing polymetallic mine wastes. For sustainable land management, minimizing long-term phosphate additions to arsenic-contaminated soils and mine tailings containing ferric arsenates is crucial to mitigate As(V) export into surface waters and groundwater.

Petra Stubbe (Venhauerova), Irena Matulková, Christian Mikutta, Petr Drahota (2024): Dissolved phosphate decreases the stability of amorphous ferric arsenate and nano-crystalline yukonite. Journal of Hazardous Materials 471, 134374. (DOI)

Wastewater treatment plants are an important source of phosphorus to the environment. They are estimated to bring between 25 and 45 % of total phosphorus in freshwaters. This study describes how discharged phosphate releases arsenic from streambed sediments into freshwaters. After seven years, the concentration of total As in the streambed sediment below the wastewater treatment plant decreased by 25 % due competitive desorption of arsenate by phosphate.

Petra Venhauerova, Petr Drahota, Ladislav Strnad, Šárka Matoušková (2022): Effects of a point source of phosphorus on the arsenic mobility and transport in a small fluvial system. Environmental Pollution 315, 120477. (DOI)

This study explores the oxidation of arsenopyrite (FeAsS) and löllingite (FeAs₂) at high relative humidity (RH: 75%-100%). Long-term oxidation (40 months) experiments show that oxidation of arsenopyrite and löllingite led to formation of different assemblages of secondary phases. Arsenopyrite oxidized to poorly-crystalline ferric arsenate, while löllingite oxidized to scorodite (FeAsO₄·2H₂O) and arsenolite (As₂O₃). Our results showed that the exposure of arsenopyrite and löllingite to different RH levels significantly influenced the amounts of newly formed phases. The major environmental impact of sulfide weathering occurs in well aerated environments characterized by high humidity – such as underground workings and some unsaturated mine wastes and tailings deposits.

Drahota, P., Ettler, V., Culka, A., Rohovec, J., Jedlička, R. (2022): Effect of relative humidity on oxidation products of arsenopyrite and löllingite. Chemical Geology 605, 120945. (DOI)

Cobalt is one of the most important critical metals which could be potentially extracted from the old metallurgical slags in the Zambian Copperbelt. The slags from Luanshya, the oldest mining and smelting site in the Copperbelt, contain up to 5990 ppm Co (median: 2370 ppm). The detailed mineralogical investigation combined with the sulfuric acid leaching simulating hydrometallurgical recovery indicated that up to 67% of Co can be extracted from slag in a short period of time (24 h). However, despite the dramatic increase of Co prices on the global market, its recovery from the Luanshya slags appears to be non-economical due to the high costs of the mechanical and chemical processing of the slag materials. The paper is freely available via open access:

Ettler V., Mihaljevič M., Drahota P., Kříbek B., Nyambe I., Vaněk A., Penížek V., Sracek O., Natherová V. (2022): Cobalt-bearing copper slags from Luanshya (Zambian Copperbelt): Mineralogy, geochemistry, and potential recovery of critical metals. Journal of Geochemical Exploration 237, 106987. (DOI)