Abstract:

Amphoteric cellulose copolymers(CO-AC) adsorbents were prepared though free radical polymerization in one-pot process using cellulose as raw material and methacryloxyethyl trimethyl ammonium chloride(METAC), acrylamide(AM), 2-acryloamino-2-methyl-1-propane sulfonic acid(AMPS) as monomers and potassium persulfate as initiator. The structure and properties of CO-AC were characterized by elemental analyzer and fourier infrared spectrometer(FT-IR). It was found that active groups, e.g., quaternary amine, amide and sulfonic acid group were successfully introduced into the molecular chains of cellulose. Taking the removal rate and equilibrium adsorption capacity of CO-AC to NH₄⁺ and H₂PO₄^- as the evaluation indexes, the adsorption conditions were optimized and the influence of various factors on the adsorption capacity of CO-AC were also evaluated. The results showed that the adsorption capacity of the adsorbent, derived under the conditions of 1:2:3:3 molar ratio of cellulose glucose unit to AMPS, AM and METAC, was the best. In 50 mL of NH₄⁺ and H₂PO₄^- solution with a mass concentration of 150 mg/L, the maximum adsorption capacity of NH₄⁺ was 77.4 mg/g when the addition amount of CO-AC was 100 mg and pH value was 7.0. The maximum adsorption capacity of H₂PO₄^- was 61.2 mg/g, while the addition amount was 100 mg and the pH value was 5.0. The adsorption process of NH₄⁺ and H₂PO₄^- on CO-AC was well characterized by the quasi-second-order kinetic, internal diffusion of particle and Langmuir models, indicating that chemisorption and internal particle diffusion processes were the main rate-limiting steps, and the adsorption process was homogeneous monolayer adsorption.

Key words: cellulose, modification, amphoteric adsorbent, ammonium and phosphorus adsorption