Mining wastewater can have adverse effects on the ecosystem; thus, treatment before discharging into the environment is of utmost importance. This manuscript reports on the effect of mining wastewater on the environment. Moreover, the currently used, effective and commercialised mine wastewater treatment technologies such as SAVMIN®, SPARRO®, Biogenic sulphide, and DESALX® are reported in this study. These technologies integrate two or more separation processes, which have been proven to be effective for the high recovery of salts and water for reuse. Some of the technologies reported can significantly recover salts and >95% of water. Modern pilot-stage and laboratory-scale treatment systems used for the recovery and removal of metals are also reported herein. Since some treatment technologies can generate highly toxic sludge and other waste products, the management of the generated waste was also considered. Some studies have focused on the treatment of wastewater at the laboratory level using the adsorption process. Most adsorbents exhibit promising results; however, there is insufficient research on reusability, toxic sludge management, and the economic analysis of the systems. Moreover, the implementation of adsorption systems in wastewater is necessary. Furthermore, the integration of treatment systems to recover precious metals at low concentrations is desirable in addition to water reclamation to achieve circular mine water.

The need to drive towards sustainable metal resource recovery from end-of-cycle products cannot be overstated. This review attempts to investigate progress in the development of recycling strategies for the recovery of strategic metals, such as precious metals and base metals, from catalytic converters, e-waste, and batteries. Several methods for the recovery of metal resources have been explored for these waste streams, such as pyrometallurgy, hydrometallurgy, and biohydrometallurgy. The results are discussed, and the efficiency of the processes and the chemistry involved are detailed. The conversion of metal waste to high-value nanomaterials is also presented. Process flow diagrams are also presented, where possible, to represent simplified process steps. Despite concerns about environmental effects from processing the metal waste streams, the gains for driving towards a circular economy of these waste streams are enormous. Therefore, the development of greener processes is recommended. In addition, countries need to manage their metal waste streams appropriately and ensure that this becomes part of the formal economic activity and, therefore, becomes regulated.

Reliance on crude oil remains high while the transition to green and renewable sources of fuel is still slow. Developing and strengthening strategies for reducing sulfur emissions from crude oil is therefore imperative and makes it possible to sustainably meet stringent regulatory sulfur level legislations in end-user liquid fuels (mostly less than 10 ppm). The burden of achieving these ultra-low sulfur levels has been passed to fuel refiners who are battling to achieve ultra-deep desulfurization through conventional hydroprocessing technologies. Removal of refractory sulfur-containing compounds has been cited as the main challenge due to several limitations with the current hydroprocessing catalysts. The inhibitory effects of nitrogen-containing compounds (especially the basic ones) is one of the major concerns. Several advances have been made to develop better strategies for achieving ultra-deep desulfurization and these include: improving hydroprocessing infrastructure, improving hydroprocessing catalysts, having additional steps for removing refractory sulfur-containing compounds and improving the quality of feedstocks. Herein, we provide perspectives that emphasize the importance of further developing hydroprocessing catalysts and pre-treating feedstocks to remove nitrogen-containing compounds prior to hydroprocessing as promising strategies for sustainably achieving ultra-deep hydroprocessing.

Platinum group metals (PGMs) play a key role in modern society as they find application in clean technologies and other high-tech equipment. Spent catalytic converters as a secondary resource contain higher PGM concentrations and the recovery of these metals via leaching is continuously being improved but efforts are also directed at the purification of individual metal ions. The study presents the recovery of PGMs, namely, rhodium (Rh), platinum (Pt) and palladium (Pd) as well as base metals, namely, zinc (Zn), nickel (Ni), iron (Fe), manganese (Mn) and chromium (Cr) using leachates from spent diesel and petrol catalytic converters. The largest amount of Pt was leached from the diesel catalytic converter while the petrol gave the highest amount of Pd when leached with aqua regia. Merrifield beads (M) were functionalized with triethylenetetramine (TETA), ethane-1,2-dithiol (SS) and bis((1H-benzimidazol-2-yl)methyl)sulfide (NSN) to form M-TETA, M-SS and M-NSN, respectively, for recovery of PGMs and base metals from the leach solutions. The adsorption and loading capacities of the PGMs and base metals were investigated using column studies at 1 M HCl concentration. The loading capacity was observed in the increasing order of Pd to be 64.93 mmol/g (M-SS), 177.07 mmol/g (M-NSN), and 192.0 mmol/g (M-TETA), respectively, from a petrol catalytic converter. The M-NSN beads also had a much higher loading capacity for Fe (489.55 mmol/g) compared to other base metals. The finding showed that functionalized Merrifield resins were effective for the simultaneous recovery of PGMs and base metals from spent catalytic converters.

Despite various methods currently used in cancer therapy, breast cancer remains the leading cause of morbidity and mortality worldwide. Current therapeutics face limitations such as multidrug resistance, drug toxicity and off-target effects, poor drug bioavailability and biocompatibility, and inefficient drug delivery. Nanotechnology has emerged as a promising approach to cancer diagnosis, imaging, and therapy. Several preclinical studies have demonstrated that compounds and nanoparticles formulated from platinum group metals (PGMs) effectively treat breast cancer. PGMs are chemically stable, easy to functionalise, versatile, and tunable. They can target hypoxic microenvironments, catalyse the production of reactive oxygen species, and offer the potential for combination therapy. PGM nanoparticles can be incorporated with anticancer drugs to improve efficacy and can be attached to targeting moieties to enhance tumour-targeting efficiency. This review focuses on the therapeutic outcomes of platinum group metal nanoparticles (PGMNs) against various breast cancer cells and briefly discusses clinical trials of these nanoparticles in breast cancer treatment. It further illustrates the potential applications of PGMNs in breast cancer and presents opportunities for future PGM-based nanomaterial applications in combatting breast cancer.

A series of oxidovanadium( iv ) complexes based on 2-(2′-hydroxyphenyl)imidazole (HPIMH), with substituent groups of different electronegativities on the phenolic para position (HPIMX; X = –H, –Br, –OMe and –NO ₂ ), were synthesized and characterized.