Department of Civil & Environmental Engineering, University of Alaska Fairbanks, PO Box 755900, Fairbanks, AK 99775, USA.
J Hazard Mater. 2010 May 15;177(1-3):899-907. doi: 10.1016/j.jhazmat.2010.01.001. Epub 2010 Jan 11.
Biosorption by cheaply and abundantly available materials such as citrus peels can be a cost efficient method for removing heavy metals from wastewater. To investigate the role pectin plays in metal binding by citrus peels, native orange peels, protonated peels, depectinated peels, and extracted pectic acid were compared. Kinetic experiments showed that equilibrium was achieved in 1h. The 1st-order model was more effective in describing the kinetics than the 2nd-order model. Titrations showed two acidic sites with pK(a) values around 4 (carboxyl) and 10.5 (hydroxyl), respectively. The pH dependent surface charge was described well by a two-site model. Sorption isotherms were best modeled assuming a 1:2 binding stoichiometry, followed by the Langmuir and the Freundlich model. The binding capacity was highest for pectic acid (2.9 mequiv./g) followed by protonated peels and native peels, being lowest for depectinated peels (1.7 mequiv./g). This showed the importance of pectin in metal binding by citrus peels. However, even depectinated peels were still good sorbents which still provided carboxyl groups that were involved in metal binding. FTIR spectra confirmed the presence of carboxyl and hydroxyl groups in all materials and their involvement in metal binding.
采用价格低廉、来源丰富的材料（如柑橘皮）进行生物吸附，可能是一种从废水中去除重金属的经济有效的方法。为了研究果胶在柑橘皮结合金属中的作用，比较了天然橙皮、质子化果皮、脱果胶果皮和提取的果胶酸。动力学实验表明，1 小时内达到平衡。与二级模型相比，一级模型更有效地描述了动力学。滴定表明，分别有两个酸性位点，pK(a)值约为 4（羧基）和 10.5（羟基）。用双位点模型很好地描述了 pH 依赖性表面电荷。吸附等温线最好假设 1:2 的结合化学计量比进行建模，其次是 Langmuir 和 Freundlich 模型。果胶酸的结合能力最高（2.9 mequiv./g），其次是质子化果皮和天然果皮，脱果胶果皮的结合能力最低（1.7 mequiv./g）。这表明果胶在柑橘皮结合金属中的重要性。然而，即使是脱果胶果皮仍然是良好的吸附剂，它们仍然提供参与金属结合的羧基。FTIR 光谱证实了所有材料中均存在羧基和羟基，并且它们参与了金属结合。
