Study On Hydroxyapatite-based Material For Removal And Analysis Of Benzoylurea Insecticides From Environmental Water

Objectives Pesticides pollution in environmental water induced by their wide application on agriculture has posed great ecosystem and human health risk.For the removal and exposure evaluation of pesticides,the required adsorbents generally have difficulty in cost,selectivity and generation of secondary pollutants.Hydroxyapatite（HAP）is a kind of calcium phosphate compound,which has been applied for the removal of heavy metal ions,fluoride,antibiotics and dyes due to its simple preparation and environmental friendliness.To develop novel and efficient adsorbent and explore the application of HAP in the field of pesticides adsorption,HAP was fabricated via facile hydrothermal method and applied for effective,fast and selective removal of benzoylurea pesticides（BUs）in environmental water.In addition,magnetic HAP（HAP/Fe3O4）adsorbent was constructed by in-situ growth and explored for magnetic solid-phase extraction（MSPE）of BUs from environmental water.Methods 1 HAP core-shell adsorbent was fabricated via hydrothermal reaction using Ca CO3 as both calcium source and nucleation,Na3PO4 as phosphorous source.The effect of solution p H was investigated.The prepared HAP was characterized by Fourier-transform infrared spectrometry（FT-IR）,X-ray diffractometry（XRD）,scanning electron microscopy（SEM）,nitrogen adsorption-desorption and solvent stability experiments.2 HAP was developed as an adsorbent for removal of diflubenzuron,chlorfluazuron,lufenuron and hexaflumuron in environmental water.The factors such as p H,ionic strength,adsorption time and temperature were optimized.The conditions of desorption of BUs,regeneration and reusability of HAP were studied and the adsorption kinetics,isotherms,thermodynamics and selectivity were explored.3 HAP/Fe3O4 was prepared by in-situ growth and characterized by FT-IR,XRD,SEM and vibrating sample magnetometry.4 HAP/Fe3O4 was applied as an adsorbent in MSPE,and the main experimental parameters,including adsorbent amount,adsorption time,p H,ionic strength,elution solvent and its volume,were investigated.HAP/Fe3O4-based MSPE followed by high performance liquid chromatography-variable wavelength detector（HPLC-VWD）was developed for determination of BUs in environmental water.Linear range,limit of detection,limit of quantification,accuracy and precision were evaluated.Reusability and enrichment factor of adsorbent were also studied.Results 1 Both FT-IR and XRD results proved the successful fabrication of HAP.SEM images revealed that the morphology of HAP were controlled by the solution p H.HAP exhibited micro-mesoporous structure and possessed remarkable solvent stability in both acid/basic,polar/non-polar and aqueous/organic solvents.2 HAP was applied for removal of BUs in environmental water.The adsorption equilibrium was achieved in 20 min using0.1 g.L^-1 of HAP at 25°C when p H was 6.0.HAP was regenerated with 2 m L of acetonitrile.Relative standard deviation（RSD）of maximum adsorption capacity of chlorfluazuron for20 cycles was less than 11%.The adsorption of BUs on HAP followed the pseudo-second-order kinetics（R²≥0.963）and Langmuir adsorption models（R²≥0.992）,and it was an endothermic process.HAP showed high adsorption selectivity for the BUs containing fluorine,and gave the maximum adsorption capacity of 114.7-294.2 mg.g^-1.3 For HAP/Fe3O4,all characteristic peaks of HAP and Fe3O4 were observed on FT-IR spectra and XRD pattern of HAP/Fe3O4,which confirmed the successful preparation of HAP/Fe3O4.SEM images indicated that HAP/Fe3O4 exhibited good dispersibility and uniform particle size.The saturation magnetization value of HAP/Fe3O4 was 27.1 emu.g^-1.4 The prepared HAP/Fe3O4 was developed for MSPE of BUs from environmental water.The adsorption of BUs was accomplished within 10 min using 20 mg of adsorbent,and 1 m L×2 of acetonitrile was selected as elution solvent.The method of HAP/Fe3O4-based MSPE followed by HPLC-VWD gave linear ranges of 0.70-800 ng.m L^-1（r=0.9996）and limits of detection of 0.20-0.25 ng.m L^-1.The recoveries ranged from 81.7%-102%with intra-day and inter-day precisions≤8.1%.Enhancement factors were found to be 40.9-51.0 when the loading volume was fixed at 10 m L.HAP/Fe3O4 was stable enough for 10 cycles of adsorption/desorption with RSDs of recoveries≤10.3%.Conclusions 1 HAP was fabricated via hydrothermal reaction using Ca CO3 as both calcium source and nucleation,and Na3PO4 as phosphorous source for the effective,fast and selective removal of BUs in environmental water.The prepared HAP was environmentally friendly and cost-effective,which had great potential in the field of removal of organic compounds.2 HAP/Fe3O4 was constructed via in-situ growth and applied for MSPE of BUs from environmental water prior to HPLC-VWD.The proposed method was accurate,convenient and economic which not only provided a novel strategy for analysis of pesticide pollutants in environmental water,but also expanded the application of HAP in the field of the sample pretreatment techniques.Figure 26;Table 10;Reference 124...