Guar Gum-Grafted Terpolymer Hydrogels for Ligand-Selective Individual and Synergistic Adsorption: Effect of Comonomer Composition

Abstract

Grafting of guar gum (GG) and in situ strategic attachment of acrylamidosodiumpropanoate (ASP) via solution polymerization of acrylamide (AM) and sodium acrylate (SA) resulted in the synthesis of a sustainable GG- g -(AM- co -SA- co -ASP)/GGAMSAASP interpenetrating polymer network (IPN)-based smart superadsorbent with excellent physicochemical properties and reusability, through systematic optimization by response surface methodology (RSM) for removal of methyl violet (MV) and/or Hg(II). The relative effects of SA/AM ratios, in situ allocation of ASP, grafting of GG into the AMSAASP terpolymer, ligand-selective superadsorption mechanism, and relative microstructural changes in individually/synergistically-adsorbed MV–/Hg(II)–/Hg(II)–MV–GGAMSAASPs were determined by extensive analyses using Fourier transform infrared (FTIR), proton nuclear magnetic resonance, ultraviolet–visible (UV–vis), and O 1s-/N 1s-/C 1s-/Hg 4f 7/2,5/2 -X-ray photoelectron spectroscopies, thermogravimetric analysis, differential scanning calorimetry, X-ray diffraction, field emission scanning electron microscopy, and energy-dispersive spectroscopy and were supported by % gel content, pH PZC , and % graft ratio. The ionic/covalent-bonding, monodentate, bidentate bridging, and bidentate chelating coordination between GGAMSAASPs and Hg(II), and MV + –Hg(II) bonding were rationalized by FTIR, UV–vis, fitment of kinetics data to the pseudo-second-order model, and thermodynamic parameters. The maximum adsorption capacities of 49.12 and 53.28 mg g –1 were determined for Hg(II) and MV, respectively, under optimized conditions.

Tetrapolymer Network Hydrogels via Gum Ghatti-Grafted and N–H/C–H-Activated Allocation of Monomers for Composition-Dependent Superadsorption of Metal Ions

“…The −COO – specific O 1s peak of GGTI- g -TetraP1 at 532.35 eV was shifted to 533.81 eV (Figure 3k) in Cu(II)-GGTI- g -TetraP1, indicating the prevalence of BB and BC interactions. 1 Additionally, participation of −COOH/–COO – in strong bonding was also ascertained from the shifting of peaks from 530.32 (>C= O ) and 534.10 eV (−CO O H) to 529.79/531.97 and 536.11 eV, respectively, during Cu(II) adsorption (Figure 3k). 2 In fact, Cu–O bond formation could also be rationalized from the significant lowering of the characteristic Cu 2p 3/2 /Cu 2p 1/2 peaks from 935.50/953.70 eV of pure Cu(NO 3 ) 2 to 933.07/953.02 eV in Cu(II)-GGTI- g -TetraP1 (Figure 3l).…”

“…Introduction of GGTI enhanced the population of −COO – in GGTI- g -TetraPs, which made these more suitable for M(II) adsorption. In this regard, several works were devoted to produce natural polymer-based hydrogels containing pectin, 2 guar gum, 1,3 chitosan, 11 xanthan gum, 12 agarose, 13 wheat bran, 14 and GGTI. 15 Similarly, several homo-, co-, ter-, and tetrapolymeric hydrogels were already reported for drug delivery and water treatment.…”

In Situ Allocation of a Monomer in Pectin-g-Terpolymer Hydrogels and Effect of Comonomer Compositions on Superadsorption of Metal Ions/Dyes

“…The activation energies ( E a ) of chemisorption were 21.78/20.16, 20.44/25.65, and 23.97/22.13 kJ mol –1 for Cd(II)-, Hg(II)-, and Cr(III)-PANIPN41/21, respectively (Figure S10). 2…”

“…Although the use of different hydrogels, such as homo-/co-/terpolymers 16,17 and IPN 1,2 -based polymers is available in the literature for the adsorptive removal of dyes and M(II/III), unorthodox synthesis of natural polymer-grafted-terpolymer IPN hydrogels through in situ strategic attachment of a third monomer using optimized compositions of SA/NIPAm, temperature, and other ingredients, appearance of several physicochemical effects during synergistic removals of structurally distinct dyes and extensive characterization of loaded and/or unloaded hydrogel(s) to understand the changes in physicochemical properties of PANIPNs of varying copolymer compositions is comprehensively reported. In addition, the relative effects of varied copolymer compositions of PANIPNs on diversified interactions between M(II/III) and N- or O-donor ligands, such as −COO – , −COOH, and −CONH–, resulting in the formation of different coordinate and/or ionic bond(s) and, hence, varied ACs have thoroughly been investigated.…”

Structures, Properties, and Performances—Relationships of Polymeric Membranes for Pervaporative Desalination

“…Similarly, crosslinking of O–H of PVA with MA in composite PVA membranes supported on PVS-based hollow fibers was realized from the loss of PVA-specific free O–H and –COOH of MA [114]. Condensation of –COOH of PMDA crosslinker and O–H of PVA in preparing the PVA-PAN composite membrane was detected from the continuous loss of intensity for O–H specific broad peak centered at 3320 cm −1 [178,179,180,181,182,183], along with the consequent gain in C=O and –C–O–C– peaks of aromatic ester at 1750 and 1275 cm −1 , respectively [127].…”