화학공학소재연구정보센터
Energy & Fuels, Vol.33, No.6, 5766-5776, 2019
Surface-Modified Multi-lumen Tubular Membranes for SAGD-Produced Water Treatment
The extraction of bitumen from oil sands using steam-assisted gravity drainage (SAGD) produces a considerable amount of oily process water that must be recycled. Ceramic membranes are well suited for this task, but membrane fouling remains a significant barrier to their widespread application. Bituminous clays in produced water are heavily charged and interact with the charged surfaces of ceramic membranes in a way that reduces membrane performance. To address this problem, the surfaces of commercially available multi-lumen tubular ceramic membranes were chemically modified using several charge-neutral polyethylene oxide (PEO)-based organosilanes. Membranes with a pore size of 10 nm and selective layers of either gamma-Al2O3 or TiO2 were modified based on protocols previously used on small-scale ceramic membrane disks and challenged with SAGD-produced water. Results indicate that the modification leads to an improvement in membrane performance. Modification of gamma-Al2O3 membranes by a 30% solution of straight-chain PEO-silane increased permeate flux by factors as high as 2.9. Modification of TiO2 membranes also improved permeate flux. Flux recovery factors upon backflushing increased from 1.3 to 1.6. Furthermore, flux values for gamma-Al2O3 membranes ranged between 50 and 150 Lmh and increased over time, while flux values for TiO2 membranes ranged between 220 and 350 Lmh and declined slightly over time. This indicates that gamma-Al2O3 is a stronger adsorbent for bituminous foulants than TiO2, with foulants being adsorbed quickly and subsequently released during filtration and backflushing. Finally, the decline in performance when switching to a SAGD feed, with a higher pH, total organic carbon and alkalinity, was significantly less severe for modified TiO2 membranes compared to unmodified counterparts. Based on these results, surface modification of tubular ceramic membranes with PEO-based silanes was successful in improving the rejection of bituminous foulants from the membrane surface.