Abstract
The poly(acrylic acid-acrylamide/starch) composite was synthesized by solution polymerization, aiming to adsorb mercury (II) in water. The resulted copolymer was characterized by particle size exclusion chromatography (SEC), Fourier transform infrared spectroscopy (FTIR), thermogravimetry (TG), scanning electron microscopy (SEM) and dynamic light scattering particle size analyzer (DLS). It turned out that starch was successfully incorporated with the macromolecular polymer matrix and played a key role for improving the performance of the composites. These characterization results showed that the graft copolymer exhibited narrow molecular weight distribution, rough but uniform morphology, good thermal stability and narrow particle size distribution. The graft copolymer was used to remove Hg(II) ions from aqueous solution. The effects of contact time, pH value, initial mercury (II) concentration and temperature on the adsorption capacity of Hg(II) ions were researched. It was found that after 120 min of interaction, poly(acrylic acid-acrylamide/starch) composite achieved the maximum adsorption capacity of 19.23 mg·g−1 to Hg(II) ions with initial concentration of 15 mg·L−1, pH of 5.5 at 45 °C. Compared with other studies with the same purpose, the composites synthesized in this study present high adsorption properties for Hg(II) ion in dilute solution. The adsorption kinetics of Hg(II) on the poly(acrylic acid-acrylamide/starch) composite fits well with the pseudo second order model.
Highlights
The starch-g-poly graft copolymer was prepared by solution polymerization through free radical mechanism [24,25]
The molecular weight of the PAA-AM/St composite was determined by size exclusion chromatography (SEC)
The composite was run in the chromatographic column and the molecular weight distribution curve was constructed by fraction elution and calibration plot
Summary
Starch is a kind of natural and renewable macromolecule carbohydrate, which has the characteristics of broad obtaining source, low cost, good biodegradability and no secondary pollution [1,2]. Modified starch adsorbent has become a research hotspot in removing pollutants from water [3,4,5]. Starch does not have good water resistance and processability. It can be graft-copolymerized with vinyl carboxylic acid monomer to make composite materials to enhance its swelling, water resistance and adsorption properties, expanding the application of starch in the functional material field. Starch based copolymer adsorbents have been studied for many years, but most of the composite materials with high adsorption performance are aiming at high concentration of metal ion solution [6,7]
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