Simultaneous leaching of seafloor massive sulfides (SMS) from Loki’s Castle on the Arctic Mid-Ocean Ridge (AMOR) and polymetallic nodules (PN) from Clarion Clipperton Zone (CCZ) of the Central Pacific Ocean was studied. Leaching tests were conducted using sulfuric acid and sodium chloride, at a temperature of 80 °C for 48 h under reflux. The effect of PN-to-SMS ratio was examined. It was shown that simultaneous leaching of two different types of marine resources was possible resulting in high dissolution rates of metals. The proposed process has many advantages as it does not require pyrometallurgical pretreatment, and yields solid products (i.e., silica, barite, elemental sulfur, albite, microcline, muscovite), which might be utilized for various industrial applications.

This paper reports the leaching of seafloor massive sulphides (SMS) from the Loki’s Castle area at the Arctic Mid-Ocean Ridge in sulphuric acid with manganese dioxide and sodium chloride. The results presented are of various leaching experiments conducted under different conditions in order to optimise the dissolution of copper and silver. It was shown that the main copper bearing minerals in the SMS were chalcopyrite and isocubanite, while silver could occur as an admixture in the crystallographic lattice of sulphides or as disseminated micro inclusions. Based on the results, the leaching mechanism was discussed and elucidated. It was shown that the dissolution of the SMS was mainly due to galvanic interactions between the primary marine minerals of SMS and manganese dioxide. Addition of sodium chloride promoted the extraction mechanism.

Deep-sea mining is a multidimensional concept that requires interdisciplinary research and development to close the current knowledge gaps. This study conducts a bibliometric analysis of the research focus, publishing structures and international and inter-institutional cooperation as evident in academic publishing. This could aid in the identification of knowledge gaps, research opportunities, potential inter-institutional cooperation and the need for strategic investment and policy development. The analysis is based on a sample of 1935 journal papers (from 1968 to 2021) obtained by searching Elsevier’s Scopus database for publications containing an explicit reference to deep-sea mining (or equivalent terms) in their title, abstract or keywords. Publication numbers are broken down by publication year, subject area, author affiliations and source. The scientific output mirrors the commercial interest and the growing environmental concern. A detailed analysis of content is performed on the 2017–2021 subset, containing one third of the total publications. Here, China (152 publ.), the United Kingdom (133), the United States (115) and Germany (107) are the top contributors. China has had a comparatively stronger focus on engineering aspects and produces very few publications with international co-authorship. Almost half of the 2017–2021 publications focus on environmental aspects, whereas engineering aspects (especially vertical transport) are addressed by close to one third. Little is published on site remediation and ore processing, or specifically on ferromanganese crusts.

The growing demand for mineral resources followed by the steady increase in mining activity result in the need for the disposal of large amount of tailings. Submarine tailings placements (STPs) is a viable option to land-based waste disposal. However, disposal of tailings with accumulated chemicals continues to contribute to the degradation of the marine environment. Replacement of chemicals towards more environmentally friendly alternatives is a good initiative aimed at preservation and protection of the marine ecosystem. Among the cationic surfactants esterquats-containing reagents have attracted particular attention due to their specific ability to degrade rapidly into non-surface-active and environmentally friendly fragments followed by inorganic end products. The important decomposition reaction is the hydrolysis in the presence of water. In this study the rate of esterquats-containing reagent FLOT 2015 desorption by seawater and the probable mechanism of its chemical degradation in aqueous mediums were investigated with the aid of a simple and adequate UV-spectrophotometric technique. By investigating the desorption characteristics of the adsorbed collector FLOT 2015 on mineral samples, important information regarding its mobility and stability was obtained that would be valuable for environmental impact assessment.