Polymer hydrogel cross‐linked by inorganic nanoparticles for removing trace metal ions

Abstract

Hydrogels for absorbing metal ions in wastewater have attracted more attentions in the environmental field especially for recent years. The removal efficiency of hydrogel adsorbents for eliminating metal ions is highly related with the effective contact between adsorbents and adsorbates. However, poor water absorption capacity of the hydrogel adsorbents would restrict on the expose of adsorption sites to the targeted subjects, causing undesirable removal ratio (RR) especially for metal ions at trace level. Thereby, the reported hydrogel adsorbents mainly focus on the removal of high content but not the trace level of metal ions so far. In this work, poly(acrylamide) (PAM)/poly(acrylic acid) (PAA)/Ca(OH)2 composite hydrogel is applied to adsorb trace metal ions. Swelling ratio of such PAM/PAA/Ca(OH)2 gel reaches 2,530 g/g, resulting in effective exposure of active sites and further expected RR for trace metal ions. The RRs of such adsorbent for Cu2+ (initial concentration C0 = 0.064 mg/L), Al3+ (C0 = 0.27 mg/L), Co2+ (C0 = 0.59 mg/L), Cr6+ (C0 = 0.52 mg/L), Mn2+ (C0 = 0.55 mg/L), Ni2+ (C0 = 0.59 mg/L), Zn2+ (C0 = 0.65 mg/L), Ag+ (C0 = 1.08 mg/L), and La3+ (C0 = 1.39 mg/L) are 56.6, 80.8, 41.3, 29.3, 34.6, 44.6, 55.9, 45.8, and 35.5%, respectively. This work broadens the application of hydrogel adsorbent for eliminating trace metal ions from polluted water.

Inorganic Hydrogel Based on Low-Dimensional Nanomaterials

“…Metal ions (e.g., Fe 2+ , Mn 2+ , and Ce 3+ ) are the most commonly used inorganic additive agents. After mixing the GO suspension and metal ions together, those reductive metal ions tend to diffuse toward the GO sheets via electrostatic interactions, and the hydrogel is generated from the interconnection of the metal ions, water molecules, and GO sheets. ,− In addition, inorganic acids (e.g., hydrochloric acid (HCl) and sulfuric acid (H 2 SO 4 )) can also cross-link GO sheets together to generate a gel. With the decrease in the pH value, the ionization degree of carboxyl groups and the electrostatic repulsion between GO sheets decrease.…”

Application of Ionic Liquid Crosslinked Hydrogel for Removing Heavy Metal Ions from Water: Different Concentration Ranges with Different Adsorption Mechanisms

“…Hydrogels possess an extremely hydrophilic three-dimensional network structure, which can rapidly swell in water and retain a large volume of water without dissolving [15][16][17][18]. Due to their structural design, low cost, good water permeability, and biodegradability, hydrogels find wide applications in adsorbing heavy metal ions from wastewater [19][20][21][22][23]. Zahra [24] synthesized magnetic hydrogel beads based on poly(vinyl alcohol)/carboxymethyl starch-g-poly(vinylimidazole) for the removal of CuII and CdII, achieving removal rates (RR%) of 93.2% and 62.5%, respectively.…”

Improving the mechanical performance of P(N‐hydroxymethyl acrylamide/acrylic acid/2‐acrylamido‐2‐methylpropanesulfonic acid) hydrogel via hydrophobic modified nanosilica

“…In order to further increase the mechanical performance of the hydrophobic association hydrogel, another crosslinking method may be introduced into hydrogel 28–30 . Inorganic nanoparticles are effective hydrogel additives based on nano‐enhancement effect.…”