Enhanced adsorption of arsenate onto a natural polymer-based sorbent by surface atom transfer radical polymerization

Arsenic contamination in water, especially in groundwater, has been recognized as an important issue of concern because of its high mobility and toxicity. In this study, N-methylglucamine was immobilized onto crosslinked chitosan beads via atom transfer radical polymerization for an efficient adsorption of arsenic. It was demonstrated that the immobilization significantly enhanced the adsorption capacity. The uptake onto the adsorbent was highly pH dependent, and a maximum adsorption capacity as high as 69.28 mg/g was obtained at the optimum pH of 5. Most of arsenate was rapidly adsorbed in the first 5 h, and the adsorption equilibrium was established in 16 h, which was well described by an intraparticle diffusion model. The adsorbent exhibited a great uptake of the humic acid, which led to a decrease in the adsorption of arsenate. The effects of competitive anions on the adsorption exhibited the following descending sequence: sulfate ≫ phosphate > fluoride (negligible effect). Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy indicated that the arsenic adsorption resulted from the presence of tertiary amine and hydroxyl functional groups grafted on the crosslinked chitosan.

The adsorption of arsenate onto the N-methylglucamine-modified chitosan adsorbent was highly pH dependent, and the optimum pH for adsorption of arsenate onto the adsorbent was around 5.Figure optionsDownload high-quality image (96 K)Download as PowerPoint slideResearch highlights
► A N-methylglucamine-modified chitosan adsorbent was successfully developed for arsenate removal.
► The adsorption of arsenate onto the adsorbent was highly pH dependent, and the optimum pH was 5. The maximum adsorption capacity was 69.28 mg/g.
► The Freundlich isotherm well described the adsorption behaviour.
► The adsorption equilibrium was obtained in 16 h, which was controlled by surface diffusion.
► Spectroscopic analysis showed that tertiary amine and hydroxyl groups played important roles in the adsorption.