A novel concept of Vertical Up-Flow Forward Osmosis reactor: Design, performance and evaluation

Performance evaluation of deep eutectic solvent as a draw solute and vertical up-flow forward osmosis module for desalination of seawater

Forward osmosis (FO) has gained prominence in recent years particularly in desalination due to its ability to operate at low or no hydraulic pressure, with relatively limited membrane fouling and high-water recovery. However, pre-treatment of seawater is required to reduce membrane fouling caused by the presence of suspended solid particles. Also, a significant area of research in forward osmosis is still finding a suitable draw solute (DS) with the ideal characteristics. In this study, a novel deep eutectic solvent (DES) draw solute was used and able to extract water after the 500% dilution of DS. This signifies it as the potential candidate for the ideal DS. A comparative study of plate and frame and vertical up-flow forward osmosis (VUF) FO modules has been evaluated to eliminate the drawbacks associated with FO in terms of membrane fouling and draw solute. In addition, the performance of a novel DES as reline (choline chloride-urea) has been tested in both the modules. In VUF module, significantly less fouling was observed than in the plate and frame module. The initial water flux in plate and frame module was 2.30 LMH with seawater (without pre-treatment) as feed. However, it dropped to 1 LMH after 26 h of run. However, initial water flux in VUF was 1.90 LMH, and it was maintained to 1.50 LMH after 89 h of run. Regeneration of draw solute was carried out using a phase separation method and it was observed that phase separation was only observed for 10% dilution of DES.

Synthesis and characterization of porous reduced graphene oxide based geopolymeric membrane with titanium dioxide coating for forward osmosis application

Forward Osmosis (FO) is a promising separation technology with a wide range of applications in water and wastewater treatment. FO membrane is the core of the forward osmosis process. Recently, the organic membrane has been widely used for forward osmosis applications even though inorganic membrane has excellent mechanical properties, decent chemical resistance, high durability, high porosity, and good hydrophilicity. Nevertheless, the utilization of inorganic membrane is hindered by the heat-intensive steps involved in its fabrication and the use of expensive source material. Geopolymerization provides a cost-effective technique for the preparation of inorganic membranes because of its sintering-free steps and utilization of fly ash as source material. Herein, we present a sintering-free, environmentally friendly, and cost-effective synthesis of geopolymeric membrane for application in forward osmosis. Fly ash was mixed with alkaline activator solution and porous reduced graphene oxide (PRGO) to prepare geopolymer slurry. The hydrogen peroxide and egg albumen were used as foaming agent and surfactant, while the membrane surface was coated with titanium dioxide to enhance the hydrophilicity of the membrane surface. The PRGO content improved the mechanical properties of the geopolymeric membrane. The average maximum flux recorded was 21 L/m² h with geopolymer substrate having a pore size of 1.8 μm and hydrophilic coated layer pore size of 0.25 μm. The varying concentrations of PRGO control the substrate's mechanical properties and pore size, as well as provide new insights for future studies. These preliminary results show that low-cost geopolymer material is a promising candidate for FO membrane fabrication.