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.

The use of recycled polypropylene (RPP) as raw material for various industries has been known. However, the mechanical and thermal properties of recycled products are lower than those of raw material. The objective of this study was to obtain and investigate the modified recycled polypropylene (RPP) with commercial elastomers for possible applications. The compounded RPP-based thermoplastic elastomers were investigated in order to determine their thermal properties (melt flow index (MFI), differential scanning calorimetry (DSC), VICAT softening temperature (VST), and heat deflection temperature (HDT)), structural characteristics (optical microscopy, atomic force microscopy (AFM), and X-ray diffraction (XRD)), and mechanical properties (tensile properties, density, and IZOD impact). The RPP compounded with 10% elastomer recorded higher tensile properties than the unmodified RPP. Also, IZOD impact strength increased from4.3±0.2 kJ/m²(registered for RPP) to21.7±2.5 kJ/m²for the PPR/SIS30 compound, while the degree of crystallinity decreased for all compounds. The obtained results recommend the RPP/elastomers compounds both for environmental remediation from postconsumer PP wastes and to realize new goods with high performance for various applications.

The goal of the present paper is to explore the properties of medium molecular-weight chitosan/polyvinyl alcohol blends mixed in volume ratios of 75:25, 50:50, and 25:75 obtained by solution casting. Cross-linked chitosan/poly(vinyl alcohol) nanostructures were obtained by treating these blends with 5% (v/v) glutaraldehyde. The prepared chitosan/polyvinyl alcohol films were characterized by attenuated total reflectance – Fourier transform infrared spectroscopy (FT-IR), dynamic light scattering, and cytotoxicity, while the nanostructured materials were examined by scanning electron microscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and X-ray diffraction. Also, the removal of lead(II) ions from aqueous solution by adsorbents nanostructures was studied in the batch adsorption mode. The effects of adsorbent dosages, initial metal concentration, and contact time on the adsorption capacity were investigated. The FT-IR spectra indicated the interactions of polyvinyl alcohol with chitosan. DSC and TGA analyses revealed the loss of water up to 100 °C. The zeta potential and mobility of the prepared nanostructures were enhanced with the increasing ratio of the cationic polymer. The results showed that the 100% chitosan adsorbent provided the highest removal of Pb(II) during the first 15 min (̴94%). The chitosan100/polyvinyl alcohol0 and chitosan75/polyvinyl alcohol25 nanostructures fitted well with the Langmuir isotherm model. The maximum adsorption capacities for Pb(II) ions reached maxima of 7.36 and 7.67 mg/g, respectively. The Freundlich isotherm model best described the Pb(II) adsorption on the 50% chitosan/50% polyvinyl alcohol and 25% chitosan/75% polyvinyl alcohol adsorbents. Furthermore, (3-(4,5-dimethylthiazol-2-yl)-2,5- diphenyltetrazolium bromide (MTT) assay results demonstrated that chitosan/polyvinyl alcohol films are biocompatible with more than 90% cell viability.

A nanocomposite (ION-CS) consisting of magnetite nanoparticles (ION) physically mixed with chitosan (CS) was synthesized by a green protocol in order to investigate the adsorption of hexavalent chromium Cr(VI) from synthetic aqueous solutions. X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM) were used to characterize the ION-CS nanomaterial in comparison with magnetite. Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy, absorption spectroscopy, and equilibrium sorption of Cr(VI) on ION-CS and CS described by the Langmuir and Freundlich isotherm models were investigated. Finally, the reusability of the ION-CS nanomaterial was investigated by successive three sorption/desorption cycles. The results revealed that the magnetite nanoparticles were entrapped into the chitosan matrix, having an average particle size in the range from 10 to 15 nm. The removal of Cr(VI) by ION-CS and CS was explored; a significant enhancement in the percentage of Cr(VI) removed was obtained using the ION-CS nanomaterial. The remarkable sorption capacities and high reusability and stability of the ION-CS nanomaterial suggest the promising potential of this novel sorbent for the removal of Cr(VI).

In this study, sodium alginate film (Alg) was coated with electrospun collagen glue (Col) extracted from rabbit skin waste, loaded with different commercial antimicrobial agents (chitosan, AG425K and ZnONPs) and investigated in terms of morphological, structural and biological properties. The coated nanostructures were characterized using scanning electron microscopy coupled with the energy-dispersive X-ray (SEM/EDS), Attenuated Total Reflectance Fourier-Transform Infrared spectroscopy (ATR FT-IR), and Atomic Force Microscopy (AFM) tests. The cytotoxicity was investigated on murine L929 fibroblasts using 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide salt (MTT) and lactate dehydrogenase (LDH) assays. Microbiological tests were performed against Staphylococcus aureus ATCC 25923, Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853 and Candida albicans ATCC 27853 standard strains. In vitro cell culture tests showed a good cytocompatibility of the coated nanostructured systems, except the sample loaded with ZnONPs, which exhibited a highly cytotoxic effect. Alg-Col-ZnONPs nanostructure inhibited the growth and multiplication of the Staphylococcus aureus ATCC 25923 and Escherichia coli ATCC 25922 bacterial strains. The results of new coated nanostructures may be useful for the development of sustainable biomaterials in a circular economy, with bioactive properties for medical wound dressings.

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.