Quantifying dynamic desorption of 3,5,6-trichloro-2-pyridinol in loamy farmland soils

Cyclodextrin Polymer-Loaded Micro-Ceramic Balls for Solid-Phase Extraction of Triazole Pesticides from Water

A citric acid cross-linked β-cyclodextrin (β-CD) polymer was synthesized and loaded on micro-ceramic balls to fabricate the solid-phase adsorbents (P-MCB) for adsorption and extraction of triazole pesticides from water. The stability of β-CD polymer and P-MCB was investigated in solutions with different pH values at different temperatures. The adsorption properties and the influence of kinetics, sorbent amount, pesticide concentration, and temperature on the adsorption capacity were evaluated. The results showed P-MCB had favorable adsorption of 15.98 mg/g flutriafol in 3.5 h. The equilibrium data followed the Freundlich equation, and the adsorption of flutriafol and diniconazole followed the second-order kinetics. The recovery rate of P-MCB for triazole pesticides in water was satisfactory, and the recovery rate was still 80.1%, even at the 10th cycle. The P-MCB had good stability, with a degradation rate of 0.2% ± 0.08 within 10 days, which could ensure extraction and recycling.

Experiment and Model Study on the Destination of 3,5,6-Trichloro-2-pyridinol in the Purple Soil of Southwestern China with a High Ratio of Biochar Applied

3,5,6-Trichloro-2-pyridinol (TCP), the main degradation production of the pesticide chlorpyrifos and the herbicide triclopyr, features anti-degradation and high water solubility that challenge the in situ prevention of the migration of TCP from soils to water bodies. Biochar is a widely used amendment, but previous studies focused on the low content of biochar application that restricted the off-site prevention. In this study, therefore, both experiments and models were employed to explore the destination of TCP in purple soil, an Entisol with low organic matter content, large pores, and high water conductivity in southwestern China with a high ratio of biochar applied. Soil columns were homogeneously packed by mixing biochar at 0, 1%, 2%, 3%, 4%, 5%, 7.5%, 10%, 15%, and 20%, then the impulsive input of the breakthrough curves was used to explore the adsorption and desorption process of TCP, and the release of adsorbed TCP was traced by Br−. Following the dynamic outflow during the adsorption processes was simulated using the cumulative distribution function of gamma distribution, and the release of TCP was simulated by coupling the mass balance equation and first-order decay kinetics equation. The results revealed that the adsorption ability of the soil increased exponentially with the content of mixed biochar, implying a much larger increment at high content. For the removal rate of 90%, e.g., the increment was about 20 mg/kg when the content of biochar was raised from 15% to 20%, while it was about 7 mg/kg when the content was raised from 0 to 5%. The dynamic release and the unreleasable TCP could be well simulated by the first-order decay kinetics equation and the logarithmic model, respectively. The releasable TCP showed an increase–decrease pattern, and the maximum was observed at a 5% biochar content. These results above will provide a systematic experimental scheme, model support, and data reference to control organic pollutants with high solubility, stability, and strong migration using biochar in an off-site pattern such as an ecological ditch system.