Study on water-dispersible colloids in saline-alkali soils by atomic force microscopy and spectrometric methods

Abstract

Recent studies have revealed that water-dispersible colloids play an important role in the transport of nutrients and contaminants in soils. In this study, water-dispersible colloids extracted from saline-alkali soils have been characterized by atomic force microscopy (AFM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and UV absorption spectra. AFM observation indicated that the water-dispersible colloids contain some large plates and many small spherical particles. XRD, XPS, and UV absorption measurement revealed that the water-dispersible colloids are composed of kaolinite, illite, calcite, quartz and humic acid. In addition, UV absorption measurement demonstrated that the humic acids are associated with clay minerals. Water-dispersible colloids in the saline-alkali soils after hydrolyzed polymaleic anhydride treatment and an agricultural soil (nonsaline-alkali soil) were also investigated for comparison. The obtained results implied that the saline-alkali condition facilitates the formation of a large quantity of colloids. The use of AFM combined with spectrometric methods in the present study provides new knowledge on the colloid characteristics of saline-alkali soils. Microsc. Res. Tech. 79:525-531, 2016. © 2016 Wiley Periodicals, Inc.

Co-transport of Pb (II) and Cd (II) in saturated porous media: effects of colloids, flow rate and grain size

“…The HA content of the stock solution was measured to be 30 mg L −1 by UVvisible spectrophotometry (UV-2800, UNICO Instrument Co., Ltd., USA) based on a known dissolved mass concentration [23]. The zeta (ζ) potential of the colloids was determined by measuring the electrophoretic mobility with a Zeta-Plus (Zetasizer nano ZS90, Malvern Instruments, UK) [24]. Quart sand (Shaanxi Zhouzhi Counry Quartz Sand Company, China) with a size ranges of 0.4-0.8 mm and 0.8-2.0 mm was used in this study as the porous media.…”