Adsorption of sodium dodecyl benzene sulfonate on zeolitic imidazolate framework-8 synthesized using surfactant-free microemulsion as template

While surfactants created great convenience for the development of society, the abuse use of surfactants also brought about severe challenges, such as contamination to the environment and life, inactivation and degradation of nanomaterials due to the blockage of active sites. To this end, a surfactant-free microemulsion (SFME) was utilized here for the first time to prepare nanoscale zeolitic imidazolate framework-8 (ZIF-8) material for surfactant removal from wastewater. The results demonstrated that SFME can effectively control the crystal size of ZIF-8 nanoparticles, just like surfactant-based microemulsion (SBME) system, with a uniform particle size distribution from 20 to 40 nm, smaller and more integral than that was obtained by conventional solvothermal method. Nano ZIF-8 material can efficiently remove surfactant from the wastewater by adsorption, especially for anionic surfactants (sodium dodecyl benzene sulfonate (SDBS)). The adsorption of SDBS on nano ZIF-8 well fitted the pseudo-second order kinetic model and Langmuir adsorption model, with the highest adsorption capacity of 548 mg/g at 318 K. Compared with ZIF-8 based on SBME, ZIF-8 based on SFME showed higher adsorption capacity to SDBS, because of larger surface area and pore volume. The data of zeta potential, FT-IR, XPS and SEM-EDS revealed that the adsorption of SDBS on ZIF-8 not only involves the electrostatic attraction but also hydrophobic interaction including π-π and dispersion force interactions. The current study provides a simple, energy-efficient, green and sustainable route of synthesizing nano ZIFs, without worrying about the secondary pollution, and the as-synthesized can be used as a high-efficient adsorbent to remove the pollutant from water.