Sorption and degradation of α-terpineol in soils with distinct physicochemical properties

Mining operations release substantial quantities of organic flotation reagents into aquatic environments. These compounds could subsequently enter soil systems through irrigation, runoff, or overflow, posing significant pollution and potential ecological risks. Nevertheless, the environmental fates of these reagents, particularly foaming agent, in soils remains poorly understood. This study investigated the sorption and degradation of α-terpineol (a typical foaming agent) in six soils with distinct physicochemical properties, using batch experiments coupled with solid-phase extraction and gas chromatography-mass spectrometry. The sorption kinetics followed a pseudo-first-order model, involving intra-particle and liquid film diffusion, while the sorption isotherms were best described by the Langmuir model, indicating monolayer sorption. The sorption process was governed mainly by hydrophobic interactions associated with soil organic matter (OM) and bridging effects facilitated by clay components. Higher OM content, higher clay content, neutral pH, greater abundance of dissolved OM, and higher cation concentrations promoted α-terpineol sorption. The logarithmic organic carbon partition coefficient of α-terpineol mainly ranged from 1.7 to 3.0, suggesting its weak sorption capacity in soils. The degradation kinetics conformed to a first-order model, with the degradation half-lives varying between 9.4 and 69.1 h cross different soils. This degradation was promoted by lower initial compound concentration, reduced moisture, moderate temperature, and enhanced microbial activity. A distinct lag phase in α-terpineol degradation highlighted its potential environmental persistence. These findings provide critical insights into the environmental fate and potential ecological risks of foaming agents in soil.