Solution Chemistry Effects on Orthophosphate Adsorption by Cationized Solid Wood Residues
详细信息 查看全文
- 作者：K. G. Karthikeyan ; Mandla A. Tshabalala ; D. Wang ; and M. Kalbasi
- 刊名：Environmental Science & Technology
- 出版年：2004
- 出版时间：February 1, 2004
- 年：2004
- 卷：38
- 期：3
- 页码：904 - 911
- 全文大小：144K
- 年卷期：v.38,no.3(February 1, 2004)
- ISSN：1520-5851
文摘
Adsorption of orthophosphate anions in aqueous solutionby cationized milled solid wood residues was characterizedas a function of sorbate-to-sorbent ratio (
0.001-2.58mmol of P/g substrate), pH (3-9), ionic strength, I (no Icontrol; 0.001 and 0.01 M NaCl), reaction time (4 min to 24h), and in the presence of other competing anions (0.08-50 mM SO42-; 0.08-250 mM NO3-). Sorption isothermsrevealed the presence of two kinds of adsorption sitescorresponding to high and low binding affinities fororthophosphate anions. Consequently, a two-site Langmuirequation was needed to adequately describe the dataover a range of solution conditions. In addition to highersorption capacity, cationized bark possessed a higher bindingenergy for orthophosphate anions compared to cationizedwood. The sorption capacity and binding energy forbark were 0.47 mmol of P g-1 and 295.7 L mmol-1, respectively,and for wood, the corresponding values were 0.27 mmolg-1 and 61.4 L mmol-1. Both the sorption capacity and bindingenergy decreased with increasing I, due to competitionfrom Cl- ions for the available anion-exchange sites. Thesurface charge characteristics of cationized bark (pHzpc= 7.9) acted in concert with orthophosphate speciation tocreate a pH-dependent sorption behavior. Orthophosphateuptake was quite rapid and attained equilibrium levels after3 h. Both SO42- and NO3- influenced percent removalbut required high relative competing anion to H2PO4- molarratios, i.e., 2.5-3 for SO42- and 25 for NO3-, to causeappreciable reduction. These results support our hypothesisthat adsorption of orthophosphate anions on cationizedbark involves ion exchange and other specific Lewis acid-base interactions.
0.001-2.58mmol of P/g substrate), pH (3-9), ionic strength, I (no Icontrol; 0.001 and 0.01 M NaCl), reaction time (4 min to 24h), and in the presence of other competing anions (0.08-50 mM SO42-; 0.08-250 mM NO3-). Sorption isothermsrevealed the presence of two kinds of adsorption sitescorresponding to high and low binding affinities fororthophosphate anions. Consequently, a two-site Langmuirequation was needed to adequately describe the dataover a range of solution conditions. In addition to highersorption capacity, cationized bark possessed a higher bindingenergy for orthophosphate anions compared to cationizedwood. The sorption capacity and binding energy forbark were 0.47 mmol of P g-1 and 295.7 L mmol-1, respectively,and for wood, the corresponding values were 0.27 mmolg-1 and 61.4 L mmol-1. Both the sorption capacity and bindingenergy decreased with increasing I, due to competitionfrom Cl- ions for the available anion-exchange sites. Thesurface charge characteristics of cationized bark (pHzpc= 7.9) acted in concert with orthophosphate speciation tocreate a pH-dependent sorption behavior. Orthophosphateuptake was quite rapid and attained equilibrium levels after3 h. Both SO42- and NO3- influenced percent removalbut required high relative competing anion to H2PO4- molarratios, i.e., 2.5-3 for SO42- and 25 for NO3-, to causeappreciable reduction. These results support our hypothesisthat adsorption of orthophosphate anions on cationizedbark involves ion exchange and other specific Lewis acid-base interactions.