Sorption behavior of dodecylbenzene sulfonic acid on humic acids from Mollisol and Alluvial soils

Abstract

Dodecylbenzene sulfonic acid (DBSA), the acid form of sodium dodecylbenzenesulfonate (SDBS), is often identified and detected in soils. However, it still has less awareness of the sorption behavior of DBSA with soil organic matter. In this paper, the sorption behaviors of DBSA on two different types of soils (Mollisol and Alluvial soils) and soil humic acids (HAs) were studied and compared, and the mechanisms of HAs and DBSA interactions were discussed. Sorption dynamics and isotherms were studied using the batch equilibrium method. The sorption kinetics was relatively slow, and the sorption equilibrium can be reached within 10 h. In the designed concentration range of DBSA in this work, the maximum DBSA sorption capacities on the Alluvial soil HA (AHA) and the Mollisol soil HA (MHA) were 115.0 and 112.2 mg/g, respectively, which were higher than those of the Alluvial soil (AS) and Mollisol soil (MS). The sorption isotherms were well fitted by the Freundlich equation. The sorption capacity of the AHA was greater than that of the MHA, AS and MS. Furthermore, the sorption complexes of HAs and DBSA were characterized using elemental analysis, micro-Fourier transform infrared spectroscopy (FTIR), solid-state 13C nuclear magnetic resonance (NMR) spectroscopy and electron spin resonance spectroscopy (ESR), it reveals that the sorption of DBSA on HAs mainly occurred on the C=O, C–O and aromatic functional groups. Moreover, the sorption data indicated that the sorption behavior was complicated, probably due to the formation of H bonds, hydrophobic interactions and electron donor–acceptor mechanisms.