Abstract
A novel polyethylene glycol diacrylate-allylthiourea (ATU-PEGDA) hydrogel was simply synthesized through photo-reaction. Modified thiourea simultaneously employed chelation and electrostatic force to selectively recycle Ag(I) and Pd(II) from electrolytic wastewater. Sorption efficiency was nearly 100% for Ag(I) and Pd(II), which occurred at initial pH of 1 within 300 min. The adsorption characteristics of ATU-PEGDA followed Langmuir isotherm model and the maximum adsorption capacity of Ag(I) and Pd(II) achieved 83.33 and 152.81 mg g−1 sorbent, respectively where Pseudo-first order model demonstrate the adsorption kinetics. In the presence of other heavy metals, ATU-PEGDA performed high selectivity, 0.89 and 1.31 towards Ag(I) and Pd(II). ATU-PEGDA can be completely regenerated within 120 min using 0.5 M thiourea—0.001 M HNO3 and 1 M thiourea—4 M HCl after the adsorption of Ag(I) and Pd(II), respectively. Thiourea-branched structure was created after regeneration, improving the adsorption capacity. Compared to initial hydrogel, the adsorption capacity of Ag(I) and Pd(II) increased 31.83 ± 3.08% and 75.12 ± 11.02%, respectively. Over 10 consecutive adsorption–desorption cycles, ATU-PEGDA performed 111.34 and 263.79 mg g−1 sorbent in adsorption capacity of Ag(I) and Pd(II). Chromism of ATU-PEGDA hydrogel was a benefit to determine adsorption saturation and completely desorption of Ag(I) and Pd(II). Potentially, ATU-PEGDA can be extended to industrial applications.
Highlights
A novel polyethylene glycol diacrylate-allylthiourea (ATU-Poly(ethylene glycol) Diacrylate (PEGDA)) hydrogel was synthesized through photo-reaction
Tensile vibration of ester O=CO and COC at 1731 and 1102 cm−1 respectively are the characteristic peaks of PEGDA, while the characteristic signal of ATU is occurred at 1559 cm−1 that is due to the HC–N stretching and bending deviation of 1540 cm−1
The optimized conditions for these precious metal ions were occurred at pH 1 and even lower acidity
Summary
A novel polyethylene glycol diacrylate-allylthiourea (ATU-PEGDA) hydrogel was synthesized through photo-reaction. Among them, chelating resins are intensively focused due to their efficient adsorption capacity and high selectivity towards metal ions. Poly(ethylene glycol) Diacrylate (PEGDA) is an extremely hydrophilic, having three-dimensional network structure and colorless hydrogel This is a polymer that is formed through certain chemical and physical cross-linking while density is less than that of traditional resins. ATU has functional groups with chelating properties for precious metal ions This was used as an adsorbent to remove and recover Ag(I) and Pd(II) from electrolytic wastewater. Effect of pH value, contact time, selectivity, desorption time and regeneration, competitive ions, and application for on-site waste electrolyte on Ag(I) and Pb(II) adsorption were discussed. The adsorption efficiency for Ag(I) and Pd(II) was improved while maintaining more than 10 times reuse proving high application value
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