Facile fabrication of high performance nanofiltration membranes for recovery of triazine-based chemicals used for H2S scavenging

Abstract

The synthesis of tailormade thin-film composite (TFC) nanofiltration (NF) membranes produced by interfacial polymerization is presented for the separation of unspent (MEA-triazine) and spent (DTZ) H2S scavengers obtained from an oil and gas wastewater from an offshore installation in the North Sea. The physicochemical properties, thermal stability, and hydrophilicity of the synthesized TFC membranes were investigated using SEM, FTIR, XRD, TGA, and contact angle. Filtration layer thicknesses from 25 to 400 µm were investigated and the optimal value (100 µm) was determined, based on the efficiency in the separation and the water permeability. Operating at 50% permeate recovery, rejections for MEA-triazine and monoethanolamine of 62% and 82%, respectively, were obtained, with zero rejection for DTZ. In 24 h batch recirculation tests, the water permeability remained stable at 6 L/(m2·h·bar), indicating insignificant fouling with 13 times higher compared to the 0.45 L/(m2·h·bar) achieved by the commercial NF270 membrane under comparable conditions. The results indicate that the NF of mixtures of spent/unspent H2S scavengers using tailored membranes is a promising strategy for recovering MEA-triazine, thus reducing costs for offshore oil and gas operators, while reducing the environmental impact associated to the discharge of this wastewater.