The mechanisms involved into the inhibitory effects of ionic liquids chemistry on adsorption performance of ciprofloxacin onto inorganic minerals

Effects of surfactants on the adsorption of norfloxacin onto ferrihydrite: comparison between anionic and cationic surfactants

There is little information on how widespread surfactants affect the adsorption of norfloxacin (NOR) onto iron oxide minerals. In order to elucidate the effects of various surfactants on the adsorption characteristics of NOR onto typical iron oxides, we have explored the different influences of sodium dodecylbenzene sulfonate (SDBS), an anionic surfactant, and didodecyldimethylammonium bromide (DDAB), a cationic surfactant, on the interactions between NOR and ferrihydrite under different solution chemistry conditions. Interestingly, SDBS facilitated NOR adsorption, whereas DDAB inhibited NOR adsorption. The adsorption-enhancement effect of SDBS was ascribed to the enhanced electrostatic attraction, the interactions between the adsorbed SDBS on ferrihydrite surfaces and NOR molecules, and the bridging effect of SDBS between NOR and iron oxide. In comparison, the adsorption-inhibition effect of DDAB owning to the adsorption site competitive adsorption between NOR and DDAB for the effective sites as well as the steric hindrance between NOR-DDAB complexes and the adsorbed DDAB on ferrihydrite surfaces. Additionally, the magnitude of the effects of surfactants on NOR adsorption declined with increasing pH values from 5.0 to 9.0, which was related to the amounts of surfactant binding to ferrihydrite surfaces. Moreover, when the background electrolyte was Ca2+, the enhanced effect of SDBS on NOR adsorption was caused by the formation of NOR-Ca2+-SDBS complexes. The inhibitory effect of DDAB was due to the DDAB coating on ferrihydrite, which undermined the cation-bridging effect. Together, the findings from this work emphasize the essential roles of widely existing surfactants in controlling the environmental fate of quinolone antibiotics.

Sorption of ciprofloxacin and enrofloxacin on alkaline cropland soil in semiarid regions: Roles of pH, ionic strength, and ion type

Animals manure and chemical fertilizers are widely applied to agricultural soils to mitigate soil fertility decline resulting from intensive farming practices. However, the use of antibiotics such as ciprofloxacin (CIP) and enrofloxacin (ENR) in these manures introduces certain environmental risks. The sorption of CIP and ENR in soil is influenced by various factors. Soil cations (i.e., Na+, K+, Mg2+, and Ca2+) and artificially introduced ions (NH4+) can affect the sorption behavior of CIP and ENR in alkaline agricultural soils through mechanisms such as ion exchange and competitive sorption. To investigate the effects of ionic strength and ion type on the sorption of antibiotics in alkaline agricultural soil, batch equilibrium experiments were conducted in this study. The results showed that the affinity of alkaline farmland soil to CIP and ENR was poor, and Kd was only 159 L/kg and 89 L/kg, respectively. Increases in temperature and pH inhibited CIP and ENR sorption on soil. Mineral elements in the soil strongly inhibited CIP and ENR sorption. Conversely, NH4+ promoted the Kd values of CIP and ENR by 46% and 221%, respectively. Additionally, under different influencing factors, both the sorption affinity (Kd) and sorption amount of ENR were lower than those of CIP. These findings indicate that ENR has a greater migration potential and poses a greater environmental risk in agricultural soils. Alkaline soil and mineral elements increase the migration potential of CIP, ENR, but the introduction of NH4+ in agricultural production can weaken the migration potential of them.

Assessing sorption of fluoroquinolone antibiotics in soils from a Kd compilation based on pure organic and mineral components

The presence of fluoroquinolone (FQ) antibiotics in soils may cause a threat to human health due to overexposure and the generation of antibiotic resistance genes. Understanding their sorption behavior in soils is important to predict subsequent FQ (bio) availability. Here, FQ sorption in pure soil organic (i.e., humic substances) and mineral (i.e., metal oxides; phyllosilicates) components is evaluated through a solid-liquid distribution coefficient (Kd (FQ)) dataset consisting of 243 entries originated from 80 different studies, to elucidate their respective contribution to the overall Kd (FQ) in bulk soils. First, different factors affecting FQ sorption and desorption in each of these soil phases are critically discussed. The strong role of pH in Kd (FQ), due to the simultaneous effect on both FQ speciation and surface charge changes, encouraged the derivation of normalized sorption coefficients for the cationic, zwitterionic and anionic FQ species in humic substances and in different phyllosilicates. Kd (FQ) in metal oxides revealed a key role of metal nature and material specific surface area due to complexation sorption mechanisms at neutral pH. Cumulative distribution functions (CDF) were applied to each dataset to establish a sorption affinity range for each phase and to derive best estimate Kd (FQ) values for those materials where normalized sorption coefficients to FQ species were unavailable. The data analysis conducted in the different soil phases set the basis for a Kd (FQ) prediction model, which combined the respective sorption affinity of each phase for FQ and phase abundance in soil to estimate Kd (FQ) in bulk soils. The model was subsequently validated with sorption data in well characterized soils compiled from the literature.