Selective denitrification of simulated oily wastewater by oxidation using Janus-structured carbon nanotubes

The intense industrial development has resulted in several consequences for human and environmental health, including the increased discharge of oily products in water bodies. Oily products are widely used in industry, often bearing an associated high cost. Finding alternatives to treat oily wastewater aiming at recovering oily and water phases is an approach allowing recovery of products of economic interest. In this work, Janus-like carbon nanotubes (CNTs) were synthesized by varying the feed time of acetonitrile and ethylene, respectively, as nitrogen/carbon and carbon precursors in a chemical vapor deposition (CVD) approach. The CVD approach allowed the synthesis of completely undoped, completely doped and partially doped CNTs with a Janus structure. The CNTs were then tested as catalysts for the selective oxidation of 4-nitrophenol (4-NP) contained in a simulated oily wastewater (2,2,4-trimethylpentane/water (O/W) = 1:9, volume basis) by catalytic wet peroxide oxidation (CWPO). The CWPO experiments were conducted for 24 h, 80 °C, 2.5 g L−1 of catalyst, and the stoichiometric concentration of H2O2 (3.6 g L−1) for the degradation of 4-NP (1 g L−1). The same conditions were kept for experiments conducted under a biphasic system. The catalysts bearing a Janus-like structure were demonstrated to be more effective in CWPO experiments in aqueous-only and biphasic systems for the abatement of 4-NP. [Display omitted] •Janus-like materials containing undoped and N-doped sections were synthesized.•The materials were tested for the selective oxidation of 4-NP in oily wastewater.•Rate of H2O2 decomposition is related to pyridinic N in aqueous and biphasic runs.•Emulsion formation depends on the material, and it affects reaction rate.•E1A19 resulted in lower droplet sizes and higher TOC abatement in biphasic runs.