In this study, the
highly crosslinked hyperbranched polyamide-amines
(H-PAMAMs) were first prepared via one-pot methods and then modified
with thiourea to synthesize a novel adsorbent containing sulfhydryl
groups (CHAP-SH), which was used to adsorb Hg(II) ions from aqueous
solutions. The adsorption characteristics and mechanism of CHAP-SH
for Hg(II) ions were systematically studied. As expected, CHAP-SH
exhibited a rapid removal performance toward Hg(II), and the maximum
adsorption capacity was 282.74 mg/g at 318 K and pH = 4.5. The whole
adsorption behavior could be well described by the pseudo-second-order
kinetic model and Langmuir and Redlich–Peterson adsorption
isotherm models, which reflected that the adsorption process was mainly
monolayer chemisorption. Meanwhile, CHAP-SH had strong selectivity
for Hg(II) in the presence of multimetal ions, and it had excellent
recoverability after five cycles. In order to further elucidate the
adsorption mechanism, the adsorbents before and after adsorption were
characterized by Fourier transform infrared spectroscopy, scanning
electron microscopy, X-ray photoelectron spectroscopy, thermogravimetric
analysis, and energy-dispersive X-ray spectroscopy, and the results
showed that the nitrogen-containing, oxygen-containing, and sulfur-containing
groups in the adsorbent molecule had synergistic complexation with
Hg(II). These results indicated that the adsorbents had great potential
in the future treatment of aqueous solutions containing Hg(II).