Search

Vanadium is an important rare element and has been widely used in metallurgical industry, aerospace industry and chemical industry due to its special physical and chemical properties. In this work we explored the feasibility of using forward osmosis (FO) to concentrate the vanadium leaching solution (VLS) using saturated sodium chloride as the draw solution. The effluent draw solution can be directly reused as a raw material in the vanadium production process without the need for regeneration. The VLS concentration performance was evaluated using commercial thin film composite (TFC) and cellulose triacetate (CTA) FO membranes. It was found that the FO water flux decline was due to the coupled effects of VLS concentration and fouling. TFC membrane exhibited higher initial water flux but also experienced more severe fouling and faster flux decline. Importantly, this study observed an existence of a critical concentration factor (CF) during VLS concentration. Below the critical CF, membrane fouling was mainly caused by surface crystallization and flux decline was relatively milder; above the critical CF, severe bulk crystallization occurred in the feed VLS, which caused significant membrane scaling and dramatical flux decline. The critical CF concept was further used to guide the FO operation for VLS concentration in this study. While severe membrane fouling at a CF above the critical value could be removed by a brief water rinse, operating the FO below the critical CF is preferred for which cyclic VLS concentration process was demonstrated to be feasible without the need for periodic membrane cleaning. Overall, the results suggest that the FO can be a promising solution for highly efficient and low-energy VLS concentration. Image 1 • FO was used for energy-efficient concentration of vanadium leaching solution (VLS). • The existence of a critical concentration factor (CF) was observed for VLS concentration by FO. • Below the critical CF membrane fouling was caused by surface crystallization and flux decline was mild. • Above the critical CF membrane was severely fouled due to bulk crystallization and flux decline was dramatic. • Operating the FO concentration processes below the critical CF is preferred. [ABSTRACT FROM AUTHOR]

Direct preparation of dialysate from tap water based on osmotic dilution is beneficial for home hemodialysis which requires a defect-free forward osmosis (FO) membrane module. This report introduced a new vacuum-assisted interfacial polymerization (VAIP) process for optimal distribution of the aqueous phase and a well-controlled IP using dialyzer membranes. We demonstrated statistically that the vacuum-assisted process is beneficial for the preparation of integral FO modules with multiple fine fibers due to the good distribution of the aqueous phase. The as-prepared FO module displayed a low structural parameter (262 μm), an acceptable water flux (17.6 L m−2 h−1), and a low specific reverse salt flux (0.16 g/L) using deionized (DI) water as the feed and 1 M NaCl as the draw in AL-FS mode. Direct dialysate preparation from tap water using the FO module was presented and modeled with a good fit. The work showcases a new FO module based on dialyzer and its potential applications in the medical field. [Display omitted] • Tap water was used to directly dilute dialysis concentrate using dialyzer FO module. • Novel vacuum-assisted interfacial polymerization was employed to prepare the TFC HF FO membrane. • Hemodialysis is available at home using tap water and dialyzer FO module. [ABSTRACT FROM AUTHOR]

Preparation of dialysate for hemodialysis (or dialysis) requires dilution of the dialysis concentrate with purified water. Present practice contains two steps: first to purify water, and then water is transported to clinic to mix with the dialysate concentrate before treatment. As a new forward osmosis dialysis hybrid process, based on osmotic dilution, is evaluated for decentralized health care systems. A commercial cellulose triacetate (CTA) and a tailor-made thin film composite (TFC) polyamide FO membranes were examined. The rejection of salts in tap water by the FO membranes was investigated, and the real rejections of various ions as a function of permeate flux were well described by using a irreversible thermodynamic model. The hollow fiber TFC FO membrane showed higher water flux and lower reverse salt flux than the CTA membrane in diluting process. Both steric hindrance and electrostatic repulsion explained the rejection behavior of the membranes to the ions. Higher rejections of anions were obtained than cations, which was attributed to the anions selection characteristics of the membranes. No obvious foulings or scalings were observed in a relatively long time osmotic dilution process over 5 repeated cycles. The stable, high efficient osmotic dilution process in hemodialysis holds a strong promise in reducing the consumption of purified water or even eliminating the water purification step. This work provides a potentially new platform hemodialysis which can be portable and implementable away from major hospitals and major clinics. Image 1 • Tap water was used to dilute dialysis concentrate based on forward osmosis. • Ion rejections versus flux were fit well using irreversible thermodynamic model. • Low reverse diffusion of components in dialysis concentrate was found. • Very light fouling after long time osmotic dilution could be cleaned by rinsing with caustic. [ABSTRACT FROM AUTHOR]

Abstract In this paper, a forward osmosis (FO) process has been proposed to extract clean water from the micro-polluted feed containing heavy metal ions using biogas slurry as the draw solution, and then the diluted biogas slurry was directly utilized as a hydroponic solution to cultivate rice and leek without further treatment. In this process, the Cd2+ and Pb2+ ions, in the feed solution were effectively blocked by the FO membrane and the rejection coefficients were high to 98.5% and 97%, respectively. On basis of the high performance of FO membrane, the operation parameters of the FO process were optimized. Under the optimized conditions, the FO process can extract enough clean water to dilute the biogas slurry, and the diluted biogas slurry can promote rice and leek to grow. The growth of the rice and leek in the diluted biogas slurry confirmed that the use of FO process is an effective way in water recovery and reuse for agricultural processes. Graphical abstract Schematic diagram of Biogas slurry-drawn FO experimental apparatus. fx1 Highlights • Pollution-free biogas slurry was used as draw solution of forward osmosis. • The rejection coefficients of Cd2+ and Pb2+ were high to be 98.5% and 97%, respectively. • Rice and leek cultivated with diluted biogas slurry grew well. • The operation parameters of forward osmosis process were optimized. [ABSTRACT FROM AUTHOR]