Department of Chemical and Environmental Engineering , Yale University , New Haven , Connecticut 06511 , United States.
Nanosystems Engineering Research Center for Nanotechnology Enabled Water Treatment (NEWT) , Yale University , New Haven , Connecticut 06520 , United States.
Environ Sci Technol. 2018 Dec 18;52(24):14311-14320. doi: 10.1021/acs.est.8b03967. Epub 2018 Dec 5.
Enhancing the chemical and physical properties of the polyamide active layer of thin-film composite (TFC) membranes by surface coating is a goal long-pursued. Atomic layer deposition (ALD) has been proposed as an innovative approach to deposit chemically robust metal oxides onto membrane surfaces due to its unique capability to control coating conformality and thickness with atomic scale precision. This study examined the potential to coat the surface of TFC reverse osmosis (RO) and nanofiltration (NF) membranes via ALD of TiO. Our results suggest that the optimal ALD conditions, the film growth kinetics, and the depth of deposition are different for RO and NF membranes due to the different diffusive transport of ALD precursors through the membrane pores. The TiO coating mainly located at the surface of the RO membrane; in contrast, the TiO coating extended to the depth of the NF membrane. The TiO coating degraded membrane water permeability and salt rejection beyond 10 cycles of ALD, the condition commonly employed in previous ALD-based membrane modification studies. Instead, this study showed that with fewer than 10 cycles, the TiO coating of RO membrane increased the membrane surface charge without negatively impacting water permeability and salt rejection. For the NF membranes, the coating of TiO inside their pores led to the tuning of pore sizes and increased the rejection of selected solutes.
通过表面涂层来提高薄膜复合（TFC）膜聚酰胺活性层的化学和物理性质是长期追求的目标。原子层沉积（ALD）因其独特的能力，可以以原子级精度控制涂层的一致性和厚度，被提议作为在膜表面沉积化学稳定的金属氧化物的创新方法。本研究考察了通过 ALD 沉积 TiO 来涂覆 TFC 反渗透（RO）和纳滤（NF）膜表面的可能性。我们的结果表明，由于 ALD 前体通过膜孔的扩散传输不同，RO 和 NF 膜的最佳 ALD 条件、薄膜生长动力学和沉积深度不同。TiO 涂层主要位于 RO 膜的表面；相比之下，TiO 涂层延伸到 NF 膜的深度。TiO 涂层在超过 10 次 ALD 循环后降低了膜的水透过率和盐截留率，这是以前基于 ALD 的膜改性研究中常用的条件。相反，本研究表明，在少于 10 次循环的情况下，RO 膜的 TiO 涂层增加了膜表面电荷，而不会对水透过率和盐截留率产生负面影响。对于 NF 膜，TiO 涂层在其孔内会导致孔径的调整，并增加对选定溶质的截留率。
