الفهرس 
AbstractOnly 14 pages are availabe for public view
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Abstract
Environmental degradation is one of the most global concerns facing humanity today. Hence many researchers are striving to find environmentally sustainable, easy-to-use, and cost-effective solutions to this great challenge. Heavy metals are the most dangerous pollutants for human health and the ecosystem. As a result of that research, various technologies have emerged that can be used to treat these types of pollution. However, they are expensive, energy-consuming, and often produce a toxic waste that must be disposed of properly. As a result, we still need to identify more efficient, cost-effective, and environmentally friendly technologies for water purification.
Accordingly, in this study, three different types of nanocomposites were successfully prepared by different techniques from primary elements such as multiwalled carbon nanotubes (MWCNTs), dialdehyde cellulose (DAC), chitosan (Cs), alginate (ALG), Magnetic ferrite particles. The prepared nanocomposites are hydrogel-containing polyvinyl alcohol/chitosan/carbon nanotubes (Cs/MWCNTs/PVA), alginates/multiwalled carbon nanotubes/Dialdehyde cellulose (ALg/MWCNTs/DAC) and magnetic multiwalled carbon nanotubes/chitosan. (MWCNTs/Cs) beads. The prepared nanocomposites were confirmed using different techniques such as (FTIR), (XRD), (SEM), (FESEM), (HRTEM), (TGA), and (VSM). The results of the study showed the success of preparing these nanocomposites. These new nanocomposites were used to remove some heavy metals such as Cu+2 and Cr+6 ions from polluted artificial water with high efficiency. In addition to the simplicity of separating the adsorbents from the adsorption medium. Several adsorption coefficients have been effectively studied to reveal the adsorption efficiency. The effect of pH, contact time, adsorbent dose, and heavy metal ion concentration on removal efficiency was studied as follows.
Regarding the first nanocomposite, a new hydrogel sorbent material was prepared by coating multiwalled carbon nanotubes with polyvinyl alcohol/chitosan (Cs/MWCNTs/PVA) bound by glutaraldehyde. This nanocomposite has excellent efficiency in removing Cr+6 chromium ions. Since the experiments revealed that the optimal conditions are at pH 1.5. The maximum absorption capacity was 217.4 mg g-1 as estimated by the Langmuir isotherm model. Other models, such as Freundlich and Tempkin, were used to analyze the experimental data, and the model parameters were evaluated. Kinetic models of the first and second order, Elovich, intraparticle diffusion, and film diffusion were also examined. The results showed the possibility of using Cs/MWCNTs/PVA hydrogel to remove Cr+6 chromium ions from polluted water by adsorption.
For the second nanocomposite, multiwalled carbon nanotubes/alginate/ dialdehyde cellulose (ALg/MWCNTs/DAC) was studied to remove Cu+2 ions from contaminated synthetic water using the adsorption method under different control factors. The maximum absorption capacity (qm) value was 26.6 mg g-1. It was found that the time required to reach the adsorption equilibrium state is
2.5 hours. The best-fit kinetic model is the pseudo-second-order, while the Langmuir isotherm is the best suited for the Cu+2 ion adsorption process from its aqueous solution.
Finally, a new magnetic nano-adsorbent was prepared from carbon nanotubes with chitosan and crosslinked with citric acid using a facile sonochemical technique. The formation of this nanocomposite was confirmed using VSM, FTIR, FESEM, HRTEM and, XRD analyses and then screened for the removal of Cu+2 ions from the aqueous solution. The results showed an excellent adsorption efficiency of Cu+2 ions with a contact time of about 20 minutes. Batch equilibrium experiments showed that the most suitable pH for
copper adsorption ranged between 5.8 and 6.0. The experimental results were subjected to kinetic and isothermal analyses. The Langmuir isotherm model matched well with the experimental data with a maximum theoretical absorption capacity (12.12 mg g-1), close to the experimental value (11.77 mg g-1). Second order kinetic model is well compared to the experimental data with R2 approaching unity. Based on these results, the rapid removal of Cu+2 ions and the easy separation of the absorbent material from the water make the proposed compound more applicable for removing Cu+2 ions from aqueous solutions.
The combined equilibrium data of adsorbed metal ions at different concentration ranges suggested a physical (multilayer adsorption) and chemical (monolayer formation) reaction between the developed adsorbent and the investigated metal ions.
The current study showed that the prepared nanocomposites could be designed and used as effective adsorbents with high removal efficiency and easy adsorbent removal from the adsorption medium.