الفهرس 
Characterization of metal nanoparticlesOnly 14 pages are availabe for public view
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Abstract
The extensive use of nanomaterials presents a risk of environmental pollution due to the residues of these nanomaterials, particularly metallic ones. Hence, it’s crucial to explore environmentally friendly methods for treating and eliminating diverse nanoscale metal pollutants. The present study focused on the bio-removal of Copper (Cu), Zinc (Zn), Iron (Fe), Selenium (Se), and Silver (Ag) nanoparticles as potential nanoscale metal pollutants using multi-metal tolerant fungi. Aspergillus sp. has been isolated as multi-metal tolerant fungus, purified, and identified as Aspergillus niger isolate MR3 by ITS gene regions analysis and registered in NCBI under accession number OP861660.1. The chemical reduction method was used to synthesize the five mentioned metal nanostructures. A UV–Vis DRS Spectrophotometer analysis revealed that the metal nanostructures synthesized chemically were in the nanometer size range, and TEM analysis confirmed their nano-sized dimensions and spherical morphology. The impact of biomass age, pH, and contact time was investigated to establish the ideal biosorption conditions. The results showed a high removal percentage of metal nanoparticles (MNPs) via two-days-old A. niger biomass, where it reached 66.8, 39.3, 52.2, 91.7 and 76.8% for Cu-, Zn-, Fe-, Se-, and Ag-NPs, respectively and the biosorption at neutral pH was noted as the best one of all tested MNPs. The contact time required between living A. niger biomass and MNPs to obtain the best biosorption was only 10 min in the case of Cu-, Zn-, and Ag-NPs, while it was 40 min for both Fe- and Se-NPs. The study investigated the immobilization of fungal pellets to assess their efficiency in removing MNPs. Due to the possible importance in industrial applications, the study aimed to substitution of the utilized batch system with a simple fixed bed column and utilize dead A. niger biomass instead of living A. niger biomass.
The FTIR analysis of dead A. niger biomass after MNPs adsorption indicated the binding of A. niger with MNPs, forming polydentate complexes involving carboxylate and amide groups. Additionally, X-ray photoelectron spectroscopy (XPS) analysis of the same biomass after Cu-NPs adsorption supported the FTIR findings. The dead biomass, saturated with MNPs, was treated with three desorbing agents individually for 30 min. The findings demonstrated that HCl is highly effective in desorbing A. niger biomass, recovering 48.2, 50.9, 68.4, 48.9 and 68.0% of Cu-, Zn-, Fe-, Se-, and Ag-NPs, respectively. Six sequential adsorption cycles were performed using dead A. niger biomass for removal of MNPs mixture within real wastewater followed by desorbing the dead biomass using a 1% HCl solution. Subsequently, the dead biomass was utilized in two scenarios: directly after desorption (wet case) and after drying (dry case). Both cases involved reloading the biomass with MNPs and undergoing three sequential removal cycles using new MNPs suspension in each cycle. The results indicated that wet A. niger biomass was more efficient than dry A. niger biomass in removing MNPs. Specifically, wet biomass achieved removal percentages of 46.6, 77.5, 75.0, 42.8 and 89.0% for Cu-, Zn-, Fe-, Se-, and Ag-NPs, respectively at the third cycle. The obtained results support the possibility of using A. niger biomass in fixed bed column biofilter for MNPs removal from their aqueous solution.