الفهرس 
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Abstract
Heavy metals (HM) are from the most toxic materials to the environment and water resources. The usage of natural materials for HM adsorption has numerous advantages. Biopolymers, algae derivatives and nanomaterials are ideal candidates for environmental remediation and heavy metal removal. Firstly, chitosan extracted from shrimp wastes and algal extracts from Ulva lactuca and Spirulina platensis were assessed as adsorbents to remove nickel, cadmium, copper and zinc from wastewater. Chitosan biopolymer exhibited prominent efficiency for removing the HM ions from wastewater. The effects of adsorption parameters (pH, adsorbent dose, temperature and initial HM ion concentration) were also determined. The optimum conditions obtained were the adsorbent dose of 10.0, 5.0, 4.0 and 2.50 g/L; pH of 7, 8, 6 and 7; temperature of 50, 25, 25 and 25 °C; initial ion concentration of 100, 100, 80 and 40 mg/l for the adsorption of nickel, cadmium, copper and zinc, respectively. The incorporation of algae extracts to chitosan could beneficially increase the HM adsorption capacity, especially with the usage of U. lactuca.
Secondly, as hexavalent chromium (Cr6+) is a hazardous toxic pollutant of water, this research innovatively aimed to synthesize nanopolymer composites and load them with phycosynthesized Fe nanoparticles for the full Cr6+ removal from aqueous solutions. The extraction of chitosan (Cht) from prawn shells and alginate (Alg) from brown seaweed (Sargassum linifolium) was achieved with standard characteristics. The tow biopolymers were combined and cross-linked to generate their composites nanoparticles (Cht/Alg NPs), which had a mean diameter of 311.2 nm and were negatively charged (-23.2 mV). The phycosynthesis of iron nanoparticles (Fe-NPs) was additionally attained using S. linifolium extract (SE), and the Fe-NPs had semispherical shapes with a 21.4 nm mean diameter. The conjugation of Cht/Alg NPs with SE-phycosynthesized Fe-NPs resulted in homogenous distribution and stabilization of metal NPs within the polymer nanocomposites. Both nanocomposites exhibited high efficiency as adsorbents for Cr6+ at diverse conditions (e.g., pH, adsorbent dose, contact time and initial ion concentration) using batch adsorption evaluation; the most effectual conditions for adsorption were a pH value of 5.0, adsorbent dose of 4 g/L, contact time of 210 min and initial Cr6+ concentration of 75 ppm.
These factors could result in full removal of Cr6+ from batch experiments. The bioremediation of water from HM (nickel, cadmium, copper and zinc), using natural products (e.g. chitosan and algae extracts), and the application of composited nanopolymers (Cht/AlgNPs) incorporated with SE-phycosynthesized Fe-NPs for complete removal of Cr6+, are strongly recommended for efficient removal of such toxic elements from aqueous environments.