The Effects And Mechanism Of Activated Carbon And Biochar On The Freely Dissolved Fipronil And Ethiprole

This paper focused on the freely dissolved concentration(Cfree) of fipronil and ethiprole to go on for a series of work. Firstly, we have developed negligible depletion–solid phase microextraction(nd-SPME) and polyoxymethylene(POM) techniques to determine Cfree of fipronil and ethiprole. Secondly, we investigated the sorption behavior of activated carbon to Cfree of fipronil and ethiprole in water. Moreover, the sorption characteristics of humic acid on activated carbon was studied. Thirdly, the effects of biochar on the Cfree in the sediment were investigated. In addition, we studies the influence of the different pyrolytic temperature of biochar, addition doses, aging time and different sediments on the sorption of biochar to Cfree of target compounds. This reseach provides the technical support and theoretical basis for the ecological environment safety evaluation and environmental pollution of fipronil and ethiprole. Main results are listed as follows:1. The kinetics data were well fit with the first order kinetics model with R2 > 0.90. The equilibrium time for fipronil and ethiprole on polyacrylate(PA) fiber and POM were 192 h and 28 d,respectively. The depletion for target compounds by the nd-SPME fibers was less than 0.1%.Sorption isotherm experiment demonstrated that the PA-water partition coefficients for fipronil and ethiprole were 6877.0 and 390.5, the POM-water partition coefficients for fipronil and ethiprole were 365.5 and 26.3, respectively.2. Activated carbon contained a high sorption capacity to fipronil and ethiprole. Cfree of fipronil and ethiprole in water has been greatly reduced with the increase of activated carbon addition. Humic acid in the water did not exert obvious influence on the Cfree. The reduction of free fraction of the target analytes was no more than 10.2% with humic acid ranged from 1% to 20%. However,humic acid decreased the sorption of activated carbon to fipronil and ethiprole. And the free fraction of the compounds augmented with the increase of humic acid. This was caused by the competitive sorption of humic acid and target compounds to the activated carbon.3. The biochars with different pyrolytic temperature shows different sorption capacity to fipronil and ethiprole with nonlinearity. The sorption capacity and nonlinearity augmented with pyrolytic temperature increasing from 300 ℃ to 700 ℃.Sorption mechanisms of biochars were electron-donor acceptor(EDA) interaction, partitioning effect, micropore-filling effect and hydrogen bonds.4. Biochar contained a high sorption capacity to fipronil and ethiprole in the sediments. The reduction of Cfree of fipronil and ethiprole ranged from 34.9% to 81.1% with the addition of 5% biochars prepared under different temperatures(BC300, BC500 and BC700). And the reduction increased with the augment of biochar doses. Besides, sediments with different characteristics have different effects on the Cfree of fipronil and ethiprole. The Cfree of the target compounds in Sediment 1 with higher organic matter was significantly greater than that in Sediment 2. The aging time between sediments and biochars exerted great influence on the Cfree of fipronil and ethiprole. The Cfree of target compounds significantly decreased with the increase of the aging time. Sediment aging times would increase the chance for target compounds in the sediment to biochars, and the resistance to desorption. Thus fipronil and ethiprole were strongly adsorbed to the biochars.