Abstract
A novel polyamine-type starch/glycidyl methacrylate (GMA) copolymer with a high capacity for the adsorption of heavy metal ions was prepared via graft copolymerization of GMA and corn starch and a subsequent amination reaction between amino group of diethylenetriamine and epoxy group in GMA. The copolymers were characterized by Fourier transform infrared spectrometry, X-ray diffraction and scanning electron microscopy, and adsorption properties on modified starch of Cu(II), Pb(II), Cd(II) and Cr(III) were studied. By analysing the relationship between adsorption capacity and pH, adsorption isotherms and adsorption kinetics, it is proved that the adsorption of the four metal ions is mainly based on the chemical adsorption of coordination. The maximum adsorption capacities of the copolymer were up to 2.33, 1.25, 0.83 and 0.56 mmol g−1 for Cu(II), Pb(II), Cd(II) and Cr(III), respectively. The adsorption of the four concerned metal ions was hardly affected by common coexisting ions such as Na(I), K(I), Ca(II) and Mg(II), whereas it was slightly decreased when Fe(II) and Zn(II) coexisted in the solution, which illustrates the selective adsorption of Cu(II), Pb(II), Cd(II) and Cr(III) from wastewater. After 10 cycles of adsorption–desorption experiments, there was no significant change in the adsorption capacity, indicating that the polyamine-type starch/GMA copolymer has high adsorption capacity and good reusability.
Highlights
With the rapid development of modern industrial technology, the problem of heavy metal pollution in water is worsening day by day [1,2]
After the adsorption was completed, the copolymer was separated by membrane filtration of 0.2 μm, the concentration of metal ions in the filtrate was measured by atomic absorption spectroscopy (AAS), and the adsorption amount of the copolymer was calculated by the following equation: Qe
The adsorption selectivity of the copolymer was studied under the condition of competition; a binary system consisting of 0.1 g polyamine-type starch/GMA copolymer (PAMS) and 100 ml solution containing Cu(II), Pb(II), Cd(II) and Cr(III) and coexisting ions (Na(I), K(I), Ca(II), Mg(II), Fe(III) and Zn(II), 10.0 mmol l−1) were added into a series of 250 ml conical flasks, the mixtures were shaken on a shaker at 25°C
Summary
With the rapid development of modern industrial technology, the problem of heavy metal pollution in water is worsening day by day [1,2]. The traditional methods of heavy metal wastewater treatment include chemical precipitation, ion exchange, reverse osmosis, membrane technology, distillation, electrochemical treatment and electrodialysis [3–6]. These methods have good results to a certain extent; the problems of high cost, low removal rate and easy secondary pollution are common. Graft copolymerization of vinyl monomer is the main method of starch modification Grafted starch copolymers, such as acrylamide, acrylonitrile, acrylic ester and acrylic acid, have been reported as adsorbents for heavy metal wastewater [14–17]. There are fewer reports on further functional modification of starch graft copolymers to obtain adsorbents with high nitrogen content and their applications for heavy metal wastewater treatment. It provides some theoretical basis for the application of PAMS in the treatment of heavy metal wastewater
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