Poly (N-Isopropylacrylamide) Microgel-Based Assemblies for Organic Dye Removal from Water

Abstract

Poly(N-isopropylacrylamide)-co-acrylic acid (pNIPAm-co-AAc) microgel assemblies (aggregates) were synthesized via polymerization of the cross-linker N,N'-methylenebisacrylamide (BIS) in the presence of microgels in solution. In this case, the microgels were entrapped in the polymerized cross-linker network. The aggregates were investigated for their ability to remove the organic, azo dye molecule 4-(2-hydroxy-1-napthylazo) benzenesulfonic acid sodium salt (Orange II) from water at both room and elevated temperatures. These results were compared with unaggregated microgels that were previously reported (Parasuraman, D.; Serpe, M. J. ACS. Appl. Mater. Interfaces 2011, 3, 2732.). It was found that the removal efficiency increased at elevated temperature, most likely due to the thermoresponsive nature of the pNIPAm-based aggregates, which expel water of solvation and deswell at higher temperature and reswell when they are cooled back to room temperature. Furthermore, increasing the number of cycles the aggregates are heated and cooled enhanced the percent removal of the dye from water. We also evaluated the effect of increasing cross-linker concentration on the removal efficiency, where we found the removal efficiency to increase with increasing cross-linker concentration in the aggregates. The maximum removal efficiency reached by the microgel aggregates at elevated temperatures was calculated to be 73.1%. This enhanced uptake is due to the presence of larger internal volume between the microgels in the aggregates, which the individual microgels lack. Control studies reveal that the structure and hydrophobicity of the aggregates lead to the enhanced uptake efficiencies and is not due to the presence of BIS alone. We determined that aggregates leak 75.6% of the dye that was originally removed from solution. The removal of Orange II by the aggregates at room temperature was fit by a Langmuir sorption isotherm.

Functional Elastic Hydrogel as Recyclable Membrane for the Adsorption and Degradation of Methylene Blue

“…This is due to the competitive adsorption among MB molecules, which is confirmed by the values of rate constants from different MB concentrations (Table 1). The MB adsorption onto the hydrogel membrane could be a rate controlling process, which may involve valence forces through the associated electrons between dye and adsorbent [19]–[21].…”

Thermoresponsive Magnetic Hydrogels as Theranostic Nanoconstructs

“…12−15 It has thus been used in a wide range of biomedical applications such as drug delivery carriers, 16,17 tissue engineering scaffolds, 18 cell growth/separation supports, 19 fluorescence thermo-sensing, 20 DNA sensing 21 and water remediation through organic dyes removal 22 among others. 23 Here we demonstrate tailoring of the MNS surface via different ligands conjugation; poly-ethylene glycol (PEG) and polyhedral oligomeric silsesquioxane (POSS) using reported methods, 24,25 to enable uniform encapsulation throughout the NIPAAm ( N -isopropylacrylamide) cross-linking process.…”

Enhanced sorption of methylene blue from aqueous solutions by semi-IPN composite cryogels with anionically modified potato starch entrapped in PAAm matrix

“…Among these methods, adsorption is considered an effective and economical method to remove dyes having some advantages such as flexibility in the selection of the adequate sorbent and operation, and the production of effluents suitable to be reused [1,[6][7][8][9][10][11]. Activated carbon is perhaps the most widely used sorbent for the removal of dyes from the wastewaters, but it is an expensive material.…”