Enhanced adsorption removal performance of UiO-66 by rational hybridization with nanodiamond

In the present work, a series of nanohybrids based on UiO-66 as a physicochemical stable metal-organic framework (MOF) and different amounts of thermally oxidized nanodiamond (OND) (0.5-10 wt%) were synthesized and used as adsorbents for anionic (methyl red, MR, and methyl orange, MO) and cationic (malachite green, MG, and methylene blue, MB) dyes from contaminated water in single and binary dye solutions. The single adsorbents and their nanohybrids were characterized by FESEM, FTIR, XRD,TGA, BET, and zeta potential measurements. The experimental adsorption results displayed that the synthesized nanohybrids presented higher adsorption capacity for anionic dyes compared to cationic dyes in both single and binary dye solutions. It was deduced that the electrostatic interactions and hydrogen bonding between anionic dye molecules and adsorbents were the main mechanisms for selective adsorption of these dyes onto synthesized nanohybrids. Additionally, the results suggested that the maximum improvement in dye adsorption was achieved at certain concentration of OND in the nanohybrid, e.g. at 3 wt% OND named OND-UiO-3, which was associated to its microstructure. OND-UiO-3 nanoparticles displayed an increase of 532% in MR adsorption capacity and a four-order-of-magnitude increase, in removal rate compared to parent UiO-66 nanoparticle.