Adsorption of humic acid from aqueous solution by hematite: effects of pH and ionic strength

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• 作者：Xiaopeng Qin ; Fei Liu ; Guangcai Wang ; Guoxin Huang
• 关键词：Humic substances ; Salt concentration ; E 2/E 3 ; Adsorption ; Mineral ; Molecular weight
• 刊名：Environmental Earth Sciences
• 出版年：2015
• 出版时间：April 2015
• 年：2015
• 卷：73
• 期：8
• 页码：4011-4017
• 全文大小：274 KB
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• 刊物类别：Earth and Environmental Science
• 刊物主题：None Assigned
• 出版者：Springer Berlin Heidelberg
• ISSN：1866-6299

文摘

Batch experiments were conducted to investigate adsorption of humic acid (HA) on a commercial hematite. The point of zero charge (PZC) and specific surface area of hematite were 9.17?±?0.25 and 5.22?±?0.04?m2?g?, respectively. The concentrations of HA in solutions were quantified by the ultraviolet–visible spectrophotometer, and molecular weight (MW) was determined by E 2/E 3 (the ratio of absorbance at 250?nm (E 2) and 365?nm (E 3)) measurements of HA in solutions. The adsorption of HA on hematite was strongly dependent on solution pH. More HA was adsorbed at acidic conditions, which was also confirmed by Fourier transform infrared spectroscopy (FTIR) measurements. At pH E 2/E 3 of the HA remaining in solution after adsorption was higher than its initial value indicating that higher MW fractions of HA were preferentially adsorbed on hematite. At pH >9, no significant change in the E 2/E 3 of the residual HA was observed, so other interactions were involved besides electrostatic interactions. The presence of salt promoted HA adsorption on hematite due to electrostatic interactions. The fractionation of HA during adsorption by hematite would affect the fate of other organic contaminants and heavy metals in natural systems.