Ultrathin Alginate Coatings as Selective Layers for Nanofiltration Membranes with High Performance

Abstract

It is highly desirable to develop environmentally friendly processes for fabricating thin-film composite (TFC) nanofiltration membranes (NFMs) from natural materials. However, the nanofiltration performance of such TFC NFMs is not satisfactory for practical applications owing to the lack of efficient methods for constructing ultrathin, uniform, stable coatings as selective layers. In this study, a contra-diffusion strategy is used to fabricate TFC NFMs with ultrathin cross-linked alginate coatings as selective layers without the use of any organic solvents. The as-prepared NFMs show a water permeation flux that is nearly one order of magnitude higher than that of other alginate-based TFC NFMs with similar salt rejection, and represents the best performance among all TFC NFMs from natural materials. These NFMs also demonstrate excellent mono-/divalent ion selectivity, as well as good long-term operation stability and antifouling properties. Furthermore, this strategy maximizes the reactant usage rate, minimizes the waste discharge and provides new insight into environmentally friendly fabrication of TFC NFMs.

Harnessing Solar‐Driven Photothermal Effect toward the Water–Energy Nexus

“…In addition, their features of easy-to-integrate, portability, and low-cost/energy make it ideal to apply in open system like seas and rivers or remote off-grid areas. [150][151][152] Generally, high salinity would cause severe salt polarization phenomenon to greatly deteriorate the desalination performance, especially in those membrane-based desalination technologies, [153] while this solar-driven desalination can effectively avoid this obstacle. [114] Besides, the salinity of three artificial seawater like the Baltic sea (0.8 wt%), world ocean (3.5 wt%) and Dead Sea (10 wt%) after solar evaporation desalination was significantly decreased about four orders of magnitude.…”

“…Besides, the salinity of three artificial seawater like the Baltic sea (0.8 wt%), world ocean (3.5 wt%) and Dead Sea (10 wt%) after solar evaporation desalination was significantly decreased about four orders of magnitude . Recently, some reports have showed that the rejection of salt ions was up to 99.5% even under high original salt concentration (100 mg mL −1 ), which was even higher than that of various conventional desalination technologies . Generally, high salinity would cause severe salt polarization phenomenon to greatly deteriorate the desalination performance, especially in those membrane‐based desalination technologies, while this solar‐driven desalination can effectively avoid this obstacle.…”

Advanced functional polymer materials

“…It should be pointed out that the mussel-inspired selective layers can be formed on the porous substrates via direct deposition [649][650][651][652][653][654][655][656][657][658][659] or through the contradiffusion approach. [660][661][662] In the latter case, the fabricated mussel-inspired films usually showed lower thickness with narrow pore size distribution for achieving precise separation.…”

Preparation of lignosulfonate‐based nanofiltration membranes with improved water desalination performance

“…Taking these advantages, NF plays a critical role in water treatment and industrial fields because it selectively rejects multivalent ions and low molecular weight organic compounds [3–5]. Most commercial NF membrassnes are thin‐film composite (TFC) membranes fabricated with an ultrathin selective layer coating on a porous substrate, which can be fabricated through the coating, interfacial polymerization, photo‐grafting, and layer‐by‐layer (LbL) methods [6–9]. Among these TFC NF membranes fabrication methods, LbL is widely used owing to its tailorable thicknesses and surface charges of selective layers by varying polyelectrolytes, assembly layers, or other fabrication conditions [10].…”