Abstract
Poly(methacrylic acid) (P(MAA)), poly(acrylamide) (P(AAm)) and poly(3-acrylamidopropyltrimethyl ammonium chloride) (P(APTMACl)) were synthesized as anionic, neutral and cationic hydrogels, respectively. The synthesized hydrogels have the ability to be used as absorbents for the removal of selected heavy metal ions such as Cu2+, Co2+, Ni2+ and Zn2+ from aqueous media. Absorption studies revealed that the absorption of metal ions by the hydrogels followed the order Cu2+ > Ni2+ > Co2+ > Zn2+. For the mechanism of absorption, both Freundlich and Langmuir absorption isotherms were applied. Metal ion entrapped hydrogels were treated using an in situ chemical reduction method in order to convert the metal ions into metal nanoparticles for the synthesis of hybrid hydrogels. The synthesis and morphology were confirmed using FT-IR and SEM, while the absorbed metal amounts were measured using TGA and AAS. The hybrid hydrogels were further used as catalysts for the reduction of macro (methylene blue, methyl orange and congo red) and micro (4-nitrophenol and nitrobenzene) pollutants from the aqueous environment. The catalytic performance and re-usability of the hybrid hydrogels were successfully investigated.
Highlights
Addressing water pollution is an immense task for researchers, as over the past few years, it has become more and more of an issue due to manufacturing effluents, which are directly added to seas, rivers, lakes, oceans, etc. without initial treatment
The process of polymerization was initiated and accelerated by APS and TEMED, respectively, and a three dimensional network of the hydrogel was achieved due to the presence of the cross linker BIS in the reaction mixture. Both P(MAA) and P(APTMACl) are ionic in nature and they change their behavior with the pH of the surrounding medium, while P(AAm) is neutral with homogeneous properties at any environmental pH value
The prepared P(MAA)–M, P(AAm)–M and P(APTMACl)–M hybrid hydrogels were used as catalysts for the reduction of dyes (MB, MO and CR) and nitroarenes (4-NP and NB)
Summary
Addressing water pollution is an immense task for researchers, as over the past few years, it has become more and more of an issue due to manufacturing effluents, which are directly added to seas, rivers, lakes, oceans, etc. without initial treatment. The amounts of the metal ions calculated for different concentrations are illustrated, which shows that the order of metal ions uptaken by hydrogels was Cu > Ni > Co > Zn, while the uptake capacity of the hydrogels follows the order P(MAA) > P(AAm) > P(APTMACl).
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