Use of lignocellulose materials as sorption media for phosphorus removal

Abstract

The suitability of modified bark or wood fiber derived from southern yellow pine to function as P sorbents was investigated. Sorbent preparation process included grinding, size fractionation] extraction for surface activation] and treatment with polyallylamine hydrochloride (PAA HCI) or 3-chloro-2-hydroxypropyltrimethlyammonium chloride. SEM images revealed surface morphology changes of these fibers due to extraction and chemical treatment. A greater than 200% increase in N content of PAA-bark compared to control (extracted bark) together with the appearance of a strong CI peak in the EDXA spectra of the treated bark or wood provided evidence of attachment PAA HCI to these fibers. Surface charge of PAA-treated bark was positive in the pH range 2.5 - 8, and turned negative at pH greater than 8. In contrast, the surface charge of untreated bark remained negative throughout the pH range, 2.5 - 9. Percent P removal decreased with increasing P concentration, with PAA-bark having a higher sorption capacity (11.96 mg P/g fiber) than PAA-wood (7.45 mg P/g fiber). Two distinct sorption regions, corresponding to high and low affinity sites, could be identified and the batch data were described using a multi-site Langmuir model. Both the sorption capacity and binding energy decreased with increasing ionic strength, due to competition for the available anion exchange sites. We propose that the mechanism for P sorption involves electrostatic attraction and/or specific interactions (between the surface functional groups containing -NH2 +- and H2PO4–/HPO42–) and ion-exchange (between Ct and H2PO4–/HPO42–).

Citation

Karthikeyan, K.G.; Tshabalala, Mandla A.; Wang, Dongmei. 2002. Use of lignocellulose materials as sorption media for phosphorus removal. [2002 ASAE annual international meeting : CIGR XVth World Congress : Chicago, Illinois, USA, July 28-July 31, 2002. St. Joseph, MI : ASAE, 2002]: 15 pages.