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The structure parameter of the forward osmosis membrane has been defined as the characteristics of the support membrane, not related to the separation layer. Therefore, studies for improving the performance of the forward osmosis (FO) membranes have been focused on the optimization of the support structure. This study demonstrates that the separation thin-film polyamide (PA) layer has a strong impact on the performance of the FO membrane thus the structure parameters (S). We intentionally utilized a polyethersulfone hollow fiber substrate and two types of active separation skin were prepared at the inner surface: the first MPD/TMC and the second by adding triethylamine (TEA) into the aqueous phase during the interfacial polymerization (IP). By adding TEA, a rough PA layer with a leaf-like structure and a high crosslinking degree was obtained followed with high FO flux and low reverse salt flux attributed to the increased effective filtration area and crosslinking degree. The structure parameter of the FO membrane was reduced from 0.78 mm (for MPD/TMC system) to 0.45 mm (for MPD-TEA/TMC system). The result indicated that for the same substrate, lower structure parameter corresponded to the skin layer with higher permeance and rejection. This study confirmed that the structure parameter is more an inherent property of the entire TFC FO membrane than the character of the porous substrate. Future design for FO membranes needs to regulate the substrate, but more importantly to optimize the separation layer. • An approaching ratio (α) was designed as a simple guideline for control the structure parameter of FO membranes. • Diethylene glycol was used as the nonsolvent to control the approaching ratio. • Lowest structure parameter and highest FO performance were obtained at α = 50 %. • The optimized TFC membrane is of practical interest for lithium concentration. [ABSTRACT FROM AUTHOR]

Forward osmosis has been widely used due to its advantages such as low energy consumption and low membrane fouling. Conventional treatment of vegetable industry wastes leaving the liquor an additional puzzle. The objective of this study is to evaluate the feasibility of reducing energy consumption by using forward osmotic membrane technology to concentrate vegetable liquor. In this research, the suitable draw solutes' condition was investigated, results showed 1 M ammonium sulphate could reach 7.21 LMH water flux and it was chosen as the draw solution for concentrating vegetable liquor, then the long-term FO performance was compared with theoretical water flux showing that the difference of water flux decrease is caused by the organic matter. Further identification of the major foulant via a control variable method using simulated vegetable liquor leads to anthocyanins as the major foulant. This novel application of the fertilizer drawn FO process provided an environmentally friendly solution to the vegetable industry, which would potentially transform an industry into a sustainable cyclic economy. [ABSTRACT FROM AUTHOR]

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]

Hemodialysis is one of the therapies for patients with kidney failure. Hemodialysis requires large amounts of pure water, and is one of the most water-hungry medical procedures, and thus represents a clear opportunity where improvements should be made concerning the consumption and wastage of water. In this paper, we explored the potential of forward osmosis (FO) membrane for recycling the spent dialysate using the dialysis concentrate as the draw solution. Partially diluted dialysis concentrate could be further diluted with pure water to form dialysate for further dialysis process. Using commercial cellulose triacetate (CTA) FO membranes, the water recovery of approximately 64% was achieved and the final volume of the partially diluted dialysis concentrate was about four times the initial volume. Flux decline of the FO process was observed, mainly due to concentration of synthetic spent dialysate and dilution of dialysis concentrate, while membrane scaling had little impact on the flux decline. The urea rejection was found to be relatively low owing to the small size and electroneutral nature of the urea molecule. Obvious membrane scaling was observed after three FO cycles. The energy dispersive spectroscopy analysis of the scaling layer indicated that the scalants were phosphates and carbonates. The scaling was removed via osmotic backwash and almost completely recovery of FO flux was obtained. Economic analysis showed that the centralized treatment of spent dialysate in a dialysis center using the proposed osmotic dilution process could greatly save water resources and cost. Improving the urea rejection of FO membrane was identified as an important research focus for future research on the potential application of FO technology for recycling the spent dialysate in hemodialysis. Image 1 • Osmotic dilution was used for recycling spent dialysate of hemodialysis. • Decrease in osmotic pressure gradient mainly led to flux decline. • Membrane scaling occurred, but was cleaned by osmotic backwash. • Urea rejection of the FO membrane should be improved. • Centralized treatment of spent dialysate by FO could greatly save water resources and cost. [ABSTRACT FROM AUTHOR]

• A novel process for the treatment of N ,N- dimethylformamide (DMF) wastewater was proposed. • Chloroform was selected for the extraction of DMF in the wastewater. • Kerosene was used to extract the dissolved chloroform in the raffinate. • High purity DMF could be recovered and the water quality improved greatly after treatment. • Total annual cost of the novel process is significantly lower than conventional distillation. Toxic N,N- dimethylformamide (DMF) is extensively used as a versatile solvent in various processes and thus released in large quantities in many industrial effluents. Low degradability requires effective treatment of DMF wastewater. A novel process combining extraction, distillation, and reverse osmosis (RO) was proposed. After screening, chloroform was selected as the solvent for DMF extraction. The extraction process conditions, namely phase ratio and the number of counter-current theoretical stages were determined by calculation and batch simulation. Kerosene was then used for the extraction of the dissolved chloroform in the wastewater after DMF extraction. The distillation columns for the separation and recovery of DMF and extractants were designed by Aspen Plus. The simulation results showed that more than 99.8% of DMF could be recovered with a purity of 99%. The salinity of the wastewater was reduced to a much lower level through RO process, and the quality of the wastewater improved greatly. Economic analysis showed that a significant reduction of 72.74% in the total annual cost (TAC) can be obtained by using the proposed process. [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]

Hemodialysis consumes significant amounts of pure water and produces large amounts of spent dialysate. Recovering water from spent dialysate is a new attempt in medical industries to save water and costs. The recent proposal of using forward osmosis (FO) to concentrate the spent dialysate showed economic viability. However, there is still one key concern of potentially extended hemodialysis duration because commercial FO membranes have limited urea rejection, which would reduce the urea concentration gradient during hemodialysis. In this paper, a model was developed to quantify the effect of incomplete urea rejection in FO on subsequent hemodialysis duration. The impacts of average urea rejection, water recovery, and the number of hemodialysis sessions were systematically analyzed. Counter-intuitively, the results indicated that relatively low urea rejection of FO membranes actually has little impact on hemodialysis duration. Low urea concentration in the spent dialysate, partial urea rejection by the FO membrane, and further dilution of pre-diluted dialysis concentrate, largely reduces this impact. The result further supports the viability of FO in spent dialysate reuse. Although FO membrane with 100% rejection is expected, the present work indicates that commercial FO membranes with a low rejection of neutral matters are of practical utility in certain applications. • Osmotic dilution was used for recycling spent dialysate of hemodialysis. • A model was developed to evaluate the effect of several factors in the osmotic dilution on the hemodialysis duration. • A relatively low urea rejection of an FO membrane has a minor impact on the subsequent hemodialysis duration. • The reasons for the counter-intuitive result in recycling the spent dialysate by FO were revealed. [ABSTRACT FROM AUTHOR]