Mechanistic insight into the adsorption of low concentrations of N-nitrosodiethylamine in water by functional MIL-96: Experiments and theoretical calculations

• Two novel MOFs adsorbents were synthesized to eliminate NDEA in low concentrations. • MOFs were first applied in the adsorption of NDEA. • The response surface methodology was adopted to investigated the variables. • Nucleophilic reactions play a dominant role in adsorption. N-nitrosodiethylamine (NDEA) is a disinfection by-product (DBP) and is classified as a probable carcinogen by the International Agency for Research on Cancer. Its concentration is lower but its toxicity is higher than other DBPs. Designing a new adsorbent with a high adsorption effect on low concentrations of NDEA instead of traditional materials will be useful. To the best of our knowledge, this is the first study to investigate metal-organic frameworks (MOFs) for the adsorption of NDEA. Two novel Al-based MOFs were synthesized by modifying MIL-96 with amino and thiol groups. Their adsorption performances at low concentrations of NDEA in water were compared using adsorption kinetics and isotherm models. It was observed that MIL-96 modified with thiol groups (MIL-96-M) followed the Langmuir and pseudo-second-order models and exhibited the best adsorption performance. Owing to the well-matched pore size and hydrophobicity, the Langmuir adsorption capacity of MIL-96-M for NDEA was achieved at 1004.71 μg/g. The parameters of the adsorption performance were investigated using the Box-Behnken response surface methodology, and on the basis of which, the performance under different conditions was predicted. The experimental data suggested that the increase in temperature and time was beneficial for the adsorption performance, whereas an increase in dosage was not beneficial. It was identified that the adsorption mechanism between MIL-96-M and NDEA involves van der Waals forces, electrostatic interactions, and nucleophilic reactions by characterization and density functional theory (DFT).