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For the whole world to deliver net zero by 2050, large-scale mining is more critical for metals such as lithium, cobalt, platinum, palladium, REE, gallium, tungsten, tellurium, and indium as these metals are essential for green technology applications such as making wind turbines, solar panels, fuel-cells, electric vehicles, and data storage systems required to transition to a low-carbon economy. Since land-based mineral deposits are depleting fast, seabed resources are seen as a new resource frontier for mineral exploration and extraction. They include mainly deep-ocean mineral deposits, such as massive sulfides, manganese nodules, ferromanganese crusts, phosphorites, and REE-rich marine muds. Manganese nodules contain mainly manganese and iron, but also valuable metals like nickel, cobalt, and copper, as well as REE and platinum, which are used in making several high-technology and green technology products. For example, deep-sea mud enriched in REE (> 2000 µg/g) was found in the western North Pacific Ocean. High concentrations of REE range from 1,727 to 2,511 μg/g in the crust samples collected from the Afanasy Nikitin Seamount (ANS) in the Indian Ocean. However, these deposits usually have lower REE grades than land-based REE deposits such as carbonatite-hosted deposits but form greater potential volumes. Though the mining companies and their sponsoring countries are in the process of developing the required technologies to mine the three deep-sea environments: abyssal plains, seamounts, and hydrothermal vents, due to severe concerns about the possible environmental damages, the International Seabed Authority (ISA) has not granted any mining permissions so far, although deep-sea mining becomes inevitable in the future green energy revolution. LESS      Full article

Due to its high efficiency, ease of operation, and superior selectivity, flotation separation has emerged as a promising technique for the extraction of ilmenite from natural resources. In light of the solution chemistry of ilmenite, it is widely accepted that ferrous ions and ferrous hydroxy compounds serve as the primary active sites for collector adsorption across a broad range of slurry pH values. The commonly used collectors like sodium oleate and hydroxamic acid are capable of chemical bonding with Fe²⁺ to form complexes and then enhance the floatability of ilmenite. However, Fe³⁺ ions perform a higher affinity to both collectors rather than Fe²⁺, the formed stronger complexes are advantageous for enhancing the hydrophobicity of ilmenite and increasing the probability for air bubble attachment, resulting in an improved ilmenite flotation recovery. Consequently, how to maximize the conversion efficiency of Fe²⁺ to Fe³⁺ and provide additional Fe³⁺ active sites on ilmenite surface for collector attachment have become the hot spot. Herein, this review aims to firstly analyze the crystal structure and solution chemistry of ilmenite and then provide a concise summary of recent advances in different oxidation technologies for promoting the conversion of Fe²⁺ to Fe³⁺, including hydroxyl radicals oxidation, direct chemical oxidation, and thermal oxidation, and the in-depth activation mechanisms are well illustrated. Also, current challenges and perspectives in this field are discussed. This review would benefit the development of next-generation flotation techniques for earth-abundant titanium resources. LESS      Full article

Antibiotics generally cause drug-resistant genes (ARGs) and drug-resistant bacteria (ARBs). With a complex class of antibiotics, it is very crucial to select specific adsorbents for different kinds of antibiotics. Zn-Al layered double hydroxide (LDH) and calcined layered double hydroxide (LDO) were prepared as absorbents for tetracycline hydrochloride (TCH) and ofloxacin (OFX), which were two antibiotics with different structures. According to the results of the adsorption experiments, LDO has the best adsorption capacity on TCH, reaching 322.58 mg/g. Acid-base titration, XRD, TEM, SEM, BET, and FI-TR analyses indicate that LDO has more active sites on the surface, the “memory effect”, and a larger specific surface area. In contrast, the removal rate of OFX by LDO is low because OFX has a more stable quinolone ring structure. Furthermore, after five adsorption-desorption cycles, the adsorption rate of TCH remains at 94.9%, demonstrating that LDO has good cyclic adsorption capacity for TCH. This study creatively combines acid-base buffering characteristics to study the mechanism of the adsorption of antibiotics by hydrotalcite, and proposes that LDO can be used as a special adsorbent for TCH. LESS      Full article

Improving the power generation performance and pollutant removal of photosynthetic microalgae microbial fuel cells (PMMFCs) is the key to their large-scale application. In this work, microalgae (Chlorella sp. QB-102) were used as a biocatalyst in the cathode, and foam nickel modified by graphene oxide with two degrees of oxidation was used as the electrode. The results showed that the maximum power density of PMMFCs with high oxidation degree graphene oxide modified electrode (NF-GO-H) reached 209.07 mW·m^-2, which was 6 times that of PMMFCs with low oxidation degree graphene oxide modified electrode (NF-GO-L), indicating that the use of the NF-GO-H electrode can effectively improve the electrical properties of PMMFCs. Simultaneously, the NF-GO-H electrode can effectively remove Cd(II), with a capacity of 6.039 g·m^-2, which is twice that of the NF-GO-L electrode. Moreover, through the synergistic electrochemical action of Chlorella sp. QB-102, a large number of hydroxyl groups can be generated to convert the adsorbed Cd(II) into a more stable Cd(OH)₂ precipitate. The results of this work will further expand the application of PMMFCs in power generation and heavy metal removal. LESS      Full article