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Title: N-Isopropylacrylamide Based Hybrid Microgels for Catalytic Degradation of Toxic Chemicals in Aqueous Medium
Authors: Shahid, Muhammad
Keywords: Physical Sciences
Issue Date: 2021
Publisher: University of the Punjab , Lahore
Abstract: Polymer microgels loaded with inorganic nanoparticles have gained much attention as catalytic systems for reduction of toxic chemicals. Enhanced catalytic properties of hybrid microgels are related to the stimuli responsive nature of microgels and extraordinary stability of nanoparticles within network of polymer microgels. Catalytic properties of hybrid microgels can be tuned very easily by slight variation in environmental conditions. Herein, we have summarized catalytic reduction of toxic chemicals such as nitroarenes and organic dyes in the presence of appropriate hybrid microgel catalytic systems under different operating conditions of reaction. Recent advancements in catalytic behaviour of hybrid microgels with special emphasis on their ability to catalytically degrade various toxic chemicals has been presented here. Poly(N-isopropylacrylamide-acrylamide-methacrylic acid) polymer microgels were prepared by free radical precipitation polymerization method. Silver nanoparticles were fabricated in the sieves of polymer network by chemical reduction using AgNO3 salt as a precursor of silver ions. Various techniques like dynamic light scattering (DLS), transmission electron microscopy (TEM), Fourier transform infrared microscopy (FTIR), and UV-Visible spectroscopy were used for characterization of pure and composite microgels. The diameter of AgNPs fabricated in polymeric network was found to be in the range of 10-15 nm. Stimuli responsive behavior of hybrid microgels was found to be same as that of pure microgels. Catalytic efficiency of the hybrid microgels was investigated by reducing 4-Nitroaniline into 4-Aminoaniline using NaBH4 as reducing agent under different conditions of temperature of the medium, concentration of reducing agent, 4-Nitroaniline and hybrid microgels to explore the catalysis process. Kinetic and thermodynamic aspects of reduction of 4-Nitroaniline in the presence of catalyst were also discussed on the basis of values of Arrhenius and Eyring iv parameters like pre-exponential factor, activation energy, enthalpy of activation and entropy of activation. Catalytic activity of the hybrid microgels was found to be thermally tunable in the temperature range of 25-70°C. The value of rate constant (kapp) for reduction of 4-NA was found to be minimum at 55°C which can be attributed to volume phase transition of the hybrid microgels. Stimuli responsive Ag-poly(N-isopropylacrylamide-acrylamide-methacrylic acid) Ag-p(NAM) system was used as catalyst for reductive removal of toxic dyes including Methyl Orange (MO) and Congo Red (CR) from aqueous medium. Hybrid polymer microgels catalyzed reduction of dyes was carried out under different reaction conditions to explore the catalytic process of degradation. The hybrid polymer microgel catalytic system is recyclable and reusable with almost same catalytic activity up to four cycles. Microgels obtained by method of free radical precipitation polymerization were used as adsorbent for removal of toxic metal ions from aqueous medium. Adsorption of Co2+ ions was studied under various conditions of pH, concentration of metal ions and that of microgels. Different adsorption isotherms were applied to study mechanism of adsorption process. Kinetics and mechanism of the adsorption process was investigated by pseudo 1st order, pseudo 2nd order and intra-particle diffusion modeling. In situ reduction of Co2+ ions loaded into the polymer microgel was carried out to get hybrid system for catalytic degradation of 4-nitrophenol, Eosin and Methylene blue.
Gov't Doc #: 22299
Appears in Collections:PhD Thesis of All Public / Private Sector Universities / DAIs.

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