Design and fabrication of an innovative and environmental friendly adsorbent for boron removal

Boron can pose adverse effects on human beings and plants species. It exists in various water environments and is difficult to be removed by conventional technologies. In this study, an efficient and environmental friendly sorbent was fabricated by the functionalization of a natural biopolymer, chitosan, with N-methylglucamine through atom transfer radical polymerization. The SEM and BET studies revealed that the sorbent had a rougher surface and a more porous structure than the chitosan. At the optimum neutral pH, the maximum sorption capacity was as high as 3.25 mmol/g, much higher than the commercial boron selective resins (e.g., Amberlite IRA-743) and many other synthesized sorbents. Almost 90% of boron sorption occurred within 8 h and the equilibrium was established in 12 h, which was well described by an intraparticle surface diffusion model. The presence of sodium chloride and sodium nitrate had no effect on the boron removal. The boron concentration in seawater could be reduced to less than 0.5 mg/L from 4.8 mg/L when a sorbent dosage of 1.2 g/L was used. It was therefore concluded that the sorption technology from this study could be promising for boron removal from aqueous solutions.

Research highlights
► An efficient and environmental friendly sorbent is designed and fabricated by the functionalization of a chitosan with N-methylglucamine through atom transfer radical polymerization.
► At pH 7, the maximum sorption capacity is as high as 3.25 mmol/g, much higher than the commercial boron selective resins (e.g., Amberlite IRA-743) and many other reported synthesized sorbents.
► The adsorption equilibrium can be established in 12 h; an intraparticle surface diffusion model well describes the adsorption history.
► The presence of sodium chloride and sodium nitrate have no effect on the boron removal.
► With a small dosage of adsorbent, the boron concentration in seawater can be reduced to less than 0.5 mg/L.