Polymetallic manganese nodules (PMN), cobalt-rich manganese crusts (CRC) and seafloor massive sulfides (SMS) have been identified as important resources of economically valuable metals and critical raw materials. The currently proposed mineral processing operations are based on metallurgical approaches applied for land resources. Thus far, significant endeavors have been carried out to describe the extraction of metals from PMN; however, to the best of the authors’ knowledge, it lacks a thorough review on recent developments in processing of CRC and SMS. This paper begins with an overview of each marine mineral. It is followed by a systematic review of common methods used for extraction of metals from marine mineral deposits. In this review, we update the information published so far in peer-reviewed and technical literature, and briefly provide the future perspectives for processing of marine mineral deposits.

A novel atmospheric pressure glow microdischarge system coupled with chemical vapor generation was applied to the optical emission spectrometry determination of Hg in samples of mosses (Pleurozium schreberi) from parks and surrounding forests of Wroclaw (Poland). The design of experiment (DOE) was used to optimize the operating parameters of the microdischarge system combined with a reaction/separation unit used for chemical vapor generation. Seven experimental factors were examined, i.e., concentrations of NaBH₄ and HCl, the discharge current and flow rates of reagents, the jet-supporting gas, the shielding gas and the liquid cathode solution on the intensity of the Hg I 253.7 nm emission line and the standard deviation of the background in its vicinity. The optimized operating conditions allowed us to obtain a detection limit of 0.066 μg L⁻¹ for Hg, which was close to the predicted value with a fitted model. To separate Hg species from moss samples, a 2-step extraction procedure with a 5.0 mol L⁻¹ HCl solution was carried out instead of complete wet digestion with concentrated HNO₃. To validate the reliability of results, the spike-and-recovery experiment was performed. The obtained results were close to 100% proving the good accuracy of the methodology proposed. The average concentration of Hg in mosses in the urban area of Wroclaw was high (0.37 μg g⁻¹) but no specific source of contamination was found.

In recent years, the demand for lithium, essential to the high-tech and battery sectors, has increased rapidly. The majority of lithium carbonate is now sourced from continental brines in Latin America, owing to the lower production costs and reduced environmental impact. In Europe, often overlooked but promising lithium resources could include highly mineralized underground waters. Therefore, this study investigates the enrichment of these low-grade solutions (<100 mg/L Li) through evaporation followed by solvent extraction (SX) processes under specific conditions. The effectiveness and the technical feasibility of lithium extraction were evaluated using binary synthetic, multicomponent semi-synthetic, and real brine samples. The popular tributyl phosphate/methyl isobutyl ketone (TBP/MIBK) system, supplemented with FeCl₃ and AlCl₃ as co-extractants, was employed as the organic phase. Evaporation resulted in significant lithium losses (up to 80%), reduced to ~10% by washing the crystallisate obtained during evaporation with ethanol. The results from SX tests revealed differences between the synthetic and real brines. While the synthetic brines exhibited satisfactory lithium extraction yields (91%), the real brines showed a significantly lower extraction efficiency (~32%), rendering the tested system ineffective. Solid phase precipitation during the SX trials was observed for both the synthetic and real brines, which were concentrated before the SX stage, highlighting the challenges in lithium-recovery processes. However, semi-synthetic brine trials yielded promising results, with a satisfactory extraction efficiency (76%), and the absence of physical problems (emulsion, long disengagement, etc.). This reveals the importance of the chemical composition of brines and emphasizes the need for varied procedural approaches in lithium-recovery processes.