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Organo‐Modification Effects on Soil Particles—Inorganic Cations Interactions as Revealed by Wien Effect Measurements
Author(s) -
Wang Yujun,
Li Chengbao,
Wang Lingxiang,
Zhou Dongmei,
Si Youbin,
Friedman Shmulik P.
Publication year - 2013
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj2012.0301
Subject(s) - chemistry , adsorption , latosol , inorganic chemistry , context (archaeology) , environmental chemistry , soil water , soil science , organic chemistry , geology , paleontology
The behavior of soil and clay particles modified with organic cations and anions (surfactants) is of interest mostly in the context of the enhanced retentive properties of the modified particles to organic pollutants. However, the adsorption of organic ions on the surfaces of the soil particles has other consequences, and the present article addresses one of them, that is, the effects of preadsorbed organic ions on the interactions between soil particles and inorganic cations. To characterize this effect we applied the previously established method of measuring the Wien effect, that is, the increase in electrical conductivity of dilute suspensions with increasing applied electrical field. A paddy soil and a latosol were modified with two surfactants—cationic cetyl‐trimethylammonium bromide (CTAB) and anionic sodium dodecyl‐sulfonate (SDS)—and were used to study the effects of organo‐modifiers on the interactions between counter ions and soil particles by means of Wien effect measurements. The variations with field strength ( E ) of the electrical conductivities (EC) of the suspensions of the paddy soil were strongly related to the concentration of preadsorbed cetyl‐trimethylammonium (CTA), whereas the EC vs. E curves of the organo‐modified and natural latosol suspensions were almost flat. The mean free binding energies, Δ G bi , of K + and Cd 2+ to the paddy soil decreased with increasing concentration of CTA and the Δ G bi of Cd 2+ to the natural paddy soil was larger than that of K + , but the Δ G bi of Cd 2+ to organo‐modified paddy soils were lower than those of K + . The stripping intensities (Is) of K + and Cd 2+ adsorbed on surfaces of natural paddy soil were 0.155 and 0.165 μS kV −1 , respectively; they rapidly decreased with increasing CTA concentration, and then decreased slowly toward zero. In the organo‐modified paddy soil Is values of K + were always larger than those of Cd 2+ . The Is values of inorganic cations adsorbed on surfaces of latosols were close to zero for both the natural and the SDS‐modified soil particles.