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Heavy metal pollution is a worldwide and stringent concern following many decades of industrialization and intensive mining without (in some cases) consideration for environmental protection. This review aims to identify the existing and emerging techniques for heavy metals (HM) removal/recycling from water and wastewater, with an emphasis on cobalt. Unlike many other heavy metals, cobalt has not been considered a detrimental element for the environment and human beings until recently. Thus, several methods and applicable techniques were evaluated to identify the best treatment approaches applicable to cobalt-polluted water and wastewater. The most feasible depollution methods adapted to the source, environment, and economic conditions were investigated and concluded. The operations and processes presented in this paper are conventional and innovative as well, including precipitation, membrane separation, with emphasis on ultrafiltration (UF) and nanofiltration (NF), but also reverse osmosis/forward osmosis (RO/FO), sorption/chemisorption processes, flotation/mechanical separation operations combined with coagulation/flocculation, photocatalysis, and electrochemical processes. For each one, depending on the frequency of use, physicochemical mechanisms and optimal operational conditions were identified to carry out successful cobalt removal and recovery from aqueous environments. [ABSTRACT FROM AUTHOR]

The current work proposes the development of composite membranes based on bacterial cellulose (BC) loaded with silver (Ag) and zinc oxide (ZnO) nanostructures by in situ impregnation. The research involves the production and purification of BC, followed by its loading with different types of phases with the help of different precipitating solutions, turmeric extract (green synthesis) and ammonia (classic route). Additionally, the combination of both antibacterial agents into a single BC matrix to valorise the benefits of each, proposing a novel BC-Ag-ZnO composite with distinct characteristics, was explored. Overall, the synthesis was marked by colour changes from the light beige of the BC membrane to dark brown, dark orange and dark green for BC-Ag, BC-ZnO and BC-Ag-ZnO samples, which is proof of successful composites formation. The results proved that the antibacterial phases are attached as nanoparticles or nanosheets on BC fibres, with Ag being in a crystalline state, while ZnO showed a rather amorphous structure. Regarding the antibacterial efficiency, the BC-ZnO composite obtained by employing two precipitating solutions turned out to be the best material against both tested Gram-negative and Gram-positive bacterial strains. [ABSTRACT FROM AUTHOR]