Sorption specificity and desorption hysteresis of gibberellic acid on ferrihydrite compared to goethite, hematite, montmorillonite, and kaolinite

Abstract

The pesticide gibberellic acid (GA) is a potential endocrine disruptor and environmental toxin; therefore, research into its environmental fate is warranted. Batch studies were conducted to investigate the sorption and desorption characteristics of GA on aquifer media. The results demonstrated special sorption characteristic of GA on ferrihydrite compared to goethite, hematite, montmorillonite, and kaolinite, where the sorption kinetics of GA on ferrihydrite was fitted well with the pseudo-second-order, Elovich, and intra-particle diffusion models. The sorption kinetics of GA on ferrihydrite indicated an initial high sorption rate followed by a slow reaction process. The initial high GA sorption rate may be related to electrostatic sorption and surface complexation reactions on the outer surfaces and at the macropore entrances of ferrihydrite. While the slow step was controlled by GA diffusion into mesopore of ferrihydrite. Analysis of the desorption hysteresis indicated a high hysteresis index (HI) ranging from 0.68 to 17.32, and a low desorption percentage ranging from 18 to 48%. After sufficient desorption, the calculated maximum residual GA quantity due to surface complexation reactions with the ferrihydrite coordinated unsaturated sites was 9.05 ± 0.12 mg g. The calculated maximum quantity of GA trapped within the mesopore was 16.23 ± 0.91 mg g. Graphical Abstract Schematic overview of GA sorption and desorption on five minerals in groundwater.

Role of Pond Sediments for Trapping Pesticides in an Agricultural Catchment (Auradé, SW France): Distribution and Controlling Factors

“…The sediment texture was a less significant controlling factor for tebuconazole, probably due to a multitude of factors, as presented before [66,68,71] masking or inhibiting this effect as observed by Gao et al [72]. As mentioned above, sediments present a complex mineralogical composition [73]; potentially, they include a great amount of oxides which might induce favourable conditions for tebuconazole sorption in this compartment [74]. Surprisingly, boscalid was also associated to the coarser particles such as the coarse silts (coefficient of determination: R 2 bosc = 0.67, if we excluded the outliers PM, AM2 and AV1, Figure 6B) and to sands in deep sediments (Figure 4C, r s = 0.93, p-value < 0.01, Figure S4).…”

Different binding characteristics of ciprofloxacin to iron mineral surfaces: Thermodynamic evidence and site energy distribution analysis

“…(2012) pointed out that for the system with higher ∆ S (absolute value), more energy was needed to regain its original entropy state, and thus desorption was more difficult. At the same time, the inner‐sphere complexes were more difficult to desorb than the outer‐sphere complexes (Yeasmin et al., 2014; Zhang et al., 2017). The above statements were in accordance with our findings.…”