Synthesis of a Carboxyl Enriched Microporous Organic Network and Its Application in Rapid Adsorption and Removal of Benzotriazoles in Water

KeyWord:microporous organic network  ?benzotriazoles  ?adsorption  ?removal  ?environmental contaminants

Abstract:

      A carboxyl enriched microporous organic network£¨MON-2COOH£© with large surface area £¨720.2 m2¡¤g-1£©£¬good solvent and thermal stability£¨280 ¡æ£© was synthesized with carboxyl-contained monomers for rapid adsorption and efficient removal of benzotriazoles in water£®The synthesized MON-2COOH was characterized by solid-state?13C nuclear magnetic spectroscopy£¬N2 adsorption - desorption£¬Fourier transform infrared spectroscopy£¬thermogravimetric analysis£¬scanning electronic microscopy and water contact angle analysis.The adsorption isotherms£¬kinetics and thermodynamics£¬effects of ionic strength£¬pH and humic acid of MON-2COOH for 1H-benzotriazole £¨BTri£© and 5-tolyltriazole £¨5-TTri£© were also investigatied in detail.The adsorption equilibriums of BTri and 5-TTri £¨100 mg¡¤L-1£© were realized within 10 min on MON-2COOH£¬showing the extremely fast adsorption kinetics of MON-2COOH for benzotriazoles£®The pseudo-second-order kinetics plots showed good linearity for all three initial concentrations of BTri and 5-TTri£¬and the adsorption capacity values calculated from the pseudo-second-order model were all close to the experimental ones£¬both suggesting the well-fitting of pseudo-second-order kinetic model for BTri and 5-TTri on MON-2COOH£®The good linearity of the Langmuir adsorption plots revealed the good plotting of Langmuir adsorption model and the monolayer adsorption process for BTri and 5-TTri on MON-2COOH£®The MON-2COOH gave the large maximum adsorption capacities of 251.3 and 369.0 mg¡¤g-1 for BTri and 5-TTri£¬respectively£¬which were larger than many reported adsorbents.The MON-2COOH gave relatively stable adsorption capacity for BTri and 5-TTri in the pH range of 2.0 - 7.0£¬but decreased adsorption capacity of BTri and 5-TTri from 8.0 to 11.0£¬which suggested the alkaline condition was unfavorable for the adsorption of BTri and 5-TTri on MON-2COOH.Moreover£¬the adsorption capacity of BTri and 5-TTri was independent under NaCl concentration lower than 100 mg¡¤g-1 and humic acid concentration less than 40 mg¡¤g-1£®The MON-2COOH also owned good reusability and reproducibility£®In addition£¬MON-2COOH was successfully applied to the adsorption and removal of BTri and 5-TTri in real lake and river water samples£®The mechanisms studies revealed the important roles of ¦Ð - ¦Ð£¬hydrophobic and hydrogen bonding interaction during the adsorption£®This work provided a promising way to design and synthesize efficient adsorbents for benzotriazoles£¬which may also promote the application of functionalized MONs in environmental contaminants analysis and elimination£®