Synthetic control of three-dimensional porous cellulose-based bioadsorbents: correlation between structural feature and metal ion removal capability

Abstract

To understand the correlation between structural feature and removal capability, a series of cellulose-based bioadsorbents with controlled pore size and functional group contents were designed and synthesized by grafting acrylic acid and acrylamide onto cellulose backbone chains. The adsorption behavior of these bioadsorbents to three metal ions [Cr(III), Cu(II) and Co(II)] in aqueous solution was investigated. The correlation between structural feature of cellulose-based bioadsorbents and their removal capability was studied in detail. The obtained cellulose-based bioadsorbents interacted with different metal ions, exhibiting highly effective ion removal from aqueous solution at a wide pH range of 3.0–5.0. The maximum adsorption of Cr(III), Cu(II) and Co(II) was determined as 220.64, 213.49 and 137.55 mg/g, respectively, when the cellulose-based bioadsorbents were treated by 2000 mg/L metal solution at pH 3.0 for 14 h. Moreover, the competitive adsorption showed that cellulose-based bioadsorbents had higher adsorption selectivity for Cr(III) (54.72 mg/g) with the coexistence of Cu(II) and Co(II). The adsorption mechanisms were interpreted considering the functional groups of bioadsorbent, ion characteristics, and varitation of solution acidity. The higher adsorption of Cr(III) could be ascribed to the stronger attraction to the lone pair of electrons both in oxygen and nitrogen atom to form more stable complexes, while only carboxyl/carbonyl groups participated in the adsorption of Cu(II) and Co(II). These results are important because they provide not only a approach to structure-controlled adsorbent for pollutant removal, but also interesting information concerning the adsorption capability of these structures based on pore size and surface functional groups.