Springer Science and Business Media LLC

The global transition to a circular economy calls for research and development on technologies facilitating sustainable resource recovery from wastes and by-products. Metal-bearing materials, including electronic wastes, tailings, and metallurgical by-products, are increasingly viewed as valuable resources, with some possessing comparable or superior quality to natural ores. Bioleaching, an eco-friendly and cost-effective alternative to conventional hydrometallurgical and pyrometallurgical methods, uses microorganisms and their metabolites to extract metals from unwanted metal-bearing materials. The performance of bioleaching is influenced by pH, solid concentration, energy source, agitation rate, irrigation rate, aeration rate, and inoculum concentration. Optimizing these parameters improves yields and encourages the wider application of bioleaching. Here, we review the microbial diversity and specific mechanisms of bioleaching for metal recovery. We describe the current operations and approaches of bioleaching at various scales and summarise the influence of a broad range of operational parameters. Finally, we address the primary challenges in scaling up bioleaching applications and propose an optimisation strategy for future bioleaching research.

Belgrade, capital city of Serbia, has over 1,600,000 inhabitants and over 400,000 vehicles trafficking every day on its streets. The investigation of soil pollution was performed by sequential extraction analysis to investigate the availability of potentially toxic metals (Zn, Cd, Pb, Co, Ni, Cu, Cr and Mn) under different oxidation and pH conditions. All investigated metals were mainly extracted from soils with neutral or acidic extractants. Serious pollution was observed along roads and streets with high traffic frequency, but Pb and Ni pollution was the highest since their concentrations exceed both soil Serbian standard and Canadian guidance values and is characteristic for all investigated sites. Cd, Cu, Cr and Zn concentrations are moderately high since they are between Canadian guideline and Serbian standard.

Bioaccumulative metals such as mercury are found in increasing amounts in fish and their consumers. In the region of the Madeira River, in the Brazilian Amazon, mercury (Hg) is a predominant contaminant in the aquatic ecosystem. There is therefore a need to find specific biomarkers of mercury toxicity in fish to monitor contaminations. Here, mercury-bound proteins were identified in the liver tissues of fishes Mylossoma duriventre and Brachyplatystoma rousseauxii. Mercury was quantified in liver tissue, pellets and protein spots by graphite furnace atomic absorption. Proteins were fractionated by two-dimensional polyacrylamide gel electrophoresis and identified by mass spectrometry with electrospray ionization. We identified nine proteins linked to mercury and that presented biomarker characteristics of mercury. Among the proteins identified, isoforms of parvalbumin, ubiquitin-40S ribosomal protein S27a, brain-specific angiogenesis inhibitor 1-associated protein 2-like protein 2 and betaine–homocysteine S-methyltransferase 1 are notable for having the molecular function of binding to metallic ions.

Cell biosensors are currently emerging as novel, sensitive techniques to monitor the toxicity of environmental pollutants. Here, we have developed electric cell-substrate impedance sensing (ECIS) for on-line monitoring of the behavior of insect cells. Cells were cultured on a microarray of eight small gold electrodes, deposited on the bottom of tissue culture wells. Upon inoculation, cells showed a tendency to drift downward and attached to the gold surface precoated with the protein Concanavalin A to accelerate the cell attachment. The impedance increased because the cells acted as insulating particles to restrict the current flow. The resulting impedance, a coordination of many biological reactions within the cell, was continuously monitored in real-time to reveal information about cell spreading and micromotion. As the cell behavior was sensitive to external chemicals, the applicability of ECIS for inhibition assays was demonstrated with HgCl2, 2,4,6-trinitrotoluene (TNT), 2-amino 4,6-dinitrotoluene (2-ADNT) and 1,3,5-trinitrobenzene (TNB).

Cyclodextrins are valuable natural or synthetically modified cyclic oligosaccharides that are widely used for ameliorating properties of biologically active compounds such as food additives and ingredients or medicinal compounds. They protect these compounds against light and oxidative degradation and provide host–guest supramolecular complexes having controlled release properties by molecular encapsulation, enhancing the water solubility and bioavailability. Among many characterization methods that are applicable in both solution and solid state, thermal techniques were widely used for analysis and stability evaluation of cyclodextrins and cyclodextrin complexes. This updated review deals with the use of thermal methods for analysis of cyclodextrins and cyclodextrin complexes. Classical and modern thermal techniques used for evaluation of inclusion compound formation were reviewed. Special attention was gave for thermogravimetry–differential thermogravimetry, differential thermal analysis, differential scanning calorimetry, hot stage microscopy, as well as for the more recent techniques thermogravimetry–mass spectrometry, gas chromatography-time-of-flight-mass spectrometry and isothermal titration calorimetry. In order to evaluate the cyclodextrin complexation capability by thermal methods, we grouped for the first time the guest compound as drugs by anatomical therapeutic chemical classification (ATC), as well as odorants, essential oils and vegetable extracts, antioxidants, fatty acids, oils, fatty acid-based derivatives, other organic, organometallic and inorganic compounds. The formation of cyclodextrin inclusion complexes was emphasized by disappearance of the signal corresponding to the melting or boiling points of the guest compound and the behavior of the hydration water molecules in the complex in comparison with the raw host and guest compounds. The thermal stability of the guest compound after cyclodextrin complexation was also discussed. It was emphasized that thermal methods are some of the most valuable techniques for analyzing cyclodextrin complexes and together with other methods can complete the information related to the host–guest molecular inclusion process and the specific properties of these cyclodextrin complexes.

The overuse of antibiotics has led to an increase in bacterial resistance and, in turn, to a decreasing efficiency of the rare available antibiotics. Alternatively, gold nanoparticles are promising antibacterials due to their high specific surface area, easy modification by functional groups and broad-spectrum antibacterial activity. Their antibacterial properties are closely related to particle size, dispersibility and surface modification, which can be tuned by adjusting reaction conditions. Here, we review the synthesis and antibacterial performance of gold nanoparticles in the raw form or modified with metal, organic compounds and carbon. We present the effect of reaction conditions on particle dispersibility and size. We compare the various synthesis methods. Antibacterial activities and their mechanisms are discussed.

Highly active TiO2 photocatalysts prepared at a low temperature are promising reagents to degrade organic pollutants.  Moreover, the addition of macroporous resins should overcome the poor adsorption properties of TiO2. Here we prepared N-doped TiO2/macroporous resin composites at low temperatures using a hydrothermal-assisted sol–gel method. The results show that the composites have a spherical appearance, which is controlled by the macroporous resin. The composites exhibit high specific surface areas, and the microstructure can be tuned by the temperature. N can be doped into the TiO2 crystal by substitution of oxygen at a lower temperature. N-doped TiO2 particles are distributed on the surface with a dominant crystal form of anatase. The composite prepared at 200 °C gave the best performance for the photocatalytic degradation of rhodamine B, with removal efficiency of 74.8% following 240-min irradiation.