In recent years, the problem of heavy metal pollution has become increasingly prominent, so it is urgent to develop new heavy metal adsorption materials. Compared with many adsorbents, the polyamide-amine dendrimers (PAMAMs) have attracted extensive attention of researchers due to its advantages of macro-molecular cavity, abundant surface functional groups, non-toxicity, high efficiency and easy modification. But in fact, it is not very suitable as an adsorbent because of its solubility and difficulty in separation, which also limits its application in environmental remediation. Therefore, in order to make up for the shortcomings of this material to a certain extent, the synthesis and development of polymer composite materials based on PAMAMs are increasingly prominent in the direction of solving heavy metal pollution. In this paper, the application of composites based on PAMAMs and inorganic or organic components in the adsorption of heavy metal ions is reviewed. Finally, the prospects and challenges of PAMAMs composites for removal of heavy metal ions in water environment are discussed.
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).
In order to prepare a new adsorbent material for the treatment of waste water containing Pb(II), hyperbranched polyamide-amines (H-PAMAMs) were prepared via one-pot method, then the H-PAMAMs were crosslinked by epichlorohydrin. The crosslinked hyperbranched polyamide-amines (C-H-PAMAMs)were prepared and characterized. The selective adsorption of coexisting ions shows that the C-H-PAMAMs have high adsorption capacity and selectivity for Pb(II). The adsorption characteristics and mechanism of the C-H-PAMAMs for Pb(II) were systematically investigated. The results of batch adsorption experiments showed that the maximum Pb(II) adsorption capacity was 180.83 mg/g at pH 4.0 and 318 K. The adsorption process on the C-H-PAMAMs was well described by the Langmuir model, which indicated the adsorption process was spontaneous and endothermic. The X-ray photoelectron spectroscopy analysis showed that the adsorption mechanism of the C-H-PAMAMs for Pb(II) was the synergistic chelation of COO and CO NH . Four adsorption/ desorption recycling tests showed that the the C-H-PAMAMs still had a high adsorption capacity for Pb(II).
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