Preparation of novel anion exchangers from pine sawdust and bark, spruce bark, birch bark and peat for the removal of nitrate

摘要

Novel anion exchangers were prepared from pine (Pinus sylvestris) sawdust and bark, spruce (Picea abies) bark, birch (Betula pubescens/Betula verrucosa) bark and peat for the removal of nitrate (NO_3 ~-). Chemical modification was applied by means of epichlorohydrin, ethylenediamine and triethylamine in the presence of N,N-dimethylformamide (DMF). The materials were characterized in terms of elemental composition (C, H, N and O), chemical composition, BET surface area, FT-IR spectra and FESEM. Nitrogen (NO_3 ~--N) removal efficiency (%) was used as a performance indicator for the anion exchangers. Modified pine sawdust exhibited the best nitrate removal efficiency. Over 80% of NO_3 ~--N was removed at doses of >3g/l with a NO_3 ~--N concentration of 30mg/l. The removal efficiency of modified pine sawdust remained unchanged at pH 3-10. Maximum sorption capacities of 24.2-30.1mg/g were achieved for NO_3 ~--N, which were very good compared to the literature values and to a commercial anion exchange resin. The sorption was very rapid and the linearized pseudo-second order kinetic model fitted the data well. The sorption data were best fitted in the linearized Langmuir model. Modified pine sawdust was tested in column as well, where it maintained its ion exchange ability well for five ion exchange cycles including successful desorption cycles.