Removing heavy metals from wastewaters is a challenging process that requires constant attention and monitoring, as heavy metals are major wastewater pollutants that are not biodegradable and thus accumulate in the ecosystem. In addition, the persistent nature, toxicity and accumulation of heavy metal ions in the human body have become the driving force for searching new and more efficient water treatment technologies to reduce the concentration of heavy metal in waters. Because the conventional techniques will not be able to keep up with the growing demand for lower heavy metals levels in drinking water and wastewaters, it is becoming increasingly challenging to implement technologically advanced alternative water treatments. Nanotechnology offers a number of advantages compared to other methods. Nanomaterials are more efficient in terms of cost and volume, and many process mechanisms are better and faster at nanoscale. Although nanomaterials have already proved themselves in water technology, there are specific challenges related to their stability, toxicity and recovery, which led to innovations to counteract them. Taking into account the multidisciplinary research of water treatment for the removal of heavy metals, the present review provides an updated report on the main technologies and materials used for the removal of heavy metals with an emphasis on nanoscale materials and processes involved in the heavy metals removal and detection.

Bionanocomposites including poly(lactic acid) (PLA), collagen, and silver nanoparticles (AgNPs) were prepared as biocompatible and stable films. Thermal properties of the PLA-based bionanocomposites indicated an increase in the crystallinity of PLA plasticized due to a small quantity of AgNPs. The results on the stability study indicate the promising contribution of the AgNPs on the durability of PLA-based bionanocomposites. In vitro biocompatibility conducted on the mouse fibroblast cell line NCTC, clone 929, using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay showed high values of cell viability (>80%) after cell cultivation in the presence of bionanocomposite formulations for 48 h, while the percentages of lactate dehydrogenase (LDH) released in the culture medium were reduced (<15%), indicating no damages of the cell membranes. In addition, cell cycle analysis assessed by flow cytometry indicated that all tested bionanocomposites did not affect cell proliferation and maintained the normal growth rate of cells. The obtained results recommend the potential use of PLA-based bionanocomposites for biomedical coatings.

Copper matrix nanocomposites reinforced with magnetite nanoparticles were developed using powder metallurgy. Various processing parameters were taken into consideration, such as magnetite content, compaction pressure, sintering time and temperature. The nanopowder blends were compacted using various uniaxial pressures and sintered at 650 and 800 °C in order to study the influence of processing parameters on morphology, structure, thermal, magnetic and mechanical properties. The structure and morphology of the nanocomposites analyzed by X-ray diffraction (XRD), bright field transmission electron microscopy (TEMBF) and scanning electron microscopy (SEM) showed that sintered composites retained the nanoscale characteristics of the initial Fe₃O₄ and Cu nanopowders. These nanocomposites have good cold-rolling deformability and Vickers micro-hardness. The Cu-xFe₃O₄ nanocomposites have thermal and magnetic properties that make them suitable for electronical applications.

Innovative composites based on polypropylene waste impurified cu HDPE (PPW) combined with two thermoplastic block-copolymers, namely styrene-butadiene-styrene (SBSBC) and styrene-isoprene-styrene (SISBC) block-copolymers, and up to 10 wt% nano-clay, were obtained by melt blending. SBSBC and SISBC with almost the same content of polystyrene (30 wt%) were synthesized by anionic sequential polymerization and used as compatibilizers for PPW. Optical microscopy evaluation of the PPW composites showed that the n-clay was encapsulated into the elastomer. Addition of n-clay, together with SBSBC or SISBC, increased the interphase surface of the components in the PPW composites and enhanced the superficial area/volume ratio, which led to a recycled material with improved performance. The data resulting from differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), mechanical evaluation, and dynamic mechanical analysis (DMA) revealed that PPW reinforcement with n-clay and styrene-diene block-copolymers allows the obtaining of composites with favorable mechanical and thermal properties, and excellent impact strength for potential engineering applications.

A comparison was performed between Co-Ni thin films and template-assisted nanowires arrays obtained by electrochemical co-deposition. To reduce the effects of anomalous deposition and increase the Ni content in the deposit, an electrolyte with three times more Ni than Co in atomic ratio was chosen. Electrochemical deposition was performed at constant potentials chosen in the range from E = −0.8 to −1.2 V vs. Ag/AgCl. Cyclic voltammetry, chronoamperometry, and charge stripping techniques were used to characterize and compare the electrochemical behavior of Co-Ni films and nanowires. Morphological and compositional characterization was performed by scanning electron microscopy (SEM/EDAX) to assess the influence of the deposition potential on the growth of film and nanowires. A comprehensive analysis of the deposit growth rates for thin films and nanowires is presented taking into consideration the hydrogen evolution and anomalous deposition. The comparative study of the composition of film and nanowires obtained at different deposition potentials has shown that deposition of nanowires with a film-like composition takes place at more positive potential than thin film.