Elaboration of metal (M: Co, Cu, Ni, Fe) embedded poly(acrylic acid-co-acrylamide) hydrogel nanocomposites: An attempt to synthesize uncommon architectured “Auto-active” nanocatalysts for treatment of dyeing wastewater

• Poly(acrylic acid-co-acrylamide) templates for encompassing nano-metals.
• Amide-feed ratio in P(AA-co-AM) hydrogel controlled metallic structure/shape/size.
• Dye degradation operates in hydrogel embedding “surface-sited” metal nanocomposites.
• Dye mineralization operates in amide-enriched hydrogel embedding Fe3O4 and Ni.
• Nickel embedded amide-enriched hydrogel is a brilliant “Auto-active” nanocatalyst.

Herein, physicochemical features of poly(acrylic acid-co-acrylamide) hydrogels were studied via swelling, SEM, TGA, DTA and thermoporometric measurements as well Monte-Carlo simulations. Physicochemical characteristics of metal–embedded hydrogel nanocomposites were investigated by ICP-OES, XRD, SEM/EDX and HRTEM analysis. Catalytic behaviour of nanocomposites was examined through multi-repetitive oxidative degradation of methylene blue (MB) from wastewater. Decay of MB concentrations was followed up kinetically by UV–vis spectrophotometer and TOC analyzer. Poly(acrylic acid-co-acrylamide) hydrogels are promising candidates for embedding diverse-shaped nano-sized metallic species (Co, Cu, Ni and Fe) with advanced protectiveness behaviour against deactivation during degradation processes. Surface-sited nanometals developed pseudo-first ordered degradation profiles with inferior reusability trends. Bulk-sited nanometals exhibited strong tendency towards MB mineralization, obeying pseudo-second ordered progression. Hydrogel embedding nickel nanocomposite served as typical “Auto-active” catalyst regarding to its ability to gather reactants and radicals beneath nanometallic particles deep inside monolithics, thereby preserving the reduced metallic form throughout the degradation processes.

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