In this study, a thin-film composite membrane based on hydrophilized polyamide was synthesized for the concentration of an aqueous fructose solution using a forward-osmosis (FO) technique. The membrane was prepared by the addition of excess mphenylenediamine along with a small quantity of dipolar aprotic dimethyl sulfoxide solvent in the aqueous reaction bath followed by excess trimesoyl chloride in an organic bath with a longer time provided for interfacial polymerization to minimize fructose losses. The effect of operating parameters such as draw NaCl concentration, cross-flow velocity, and temperature on FO performance was evaluated. Membrane characterization was performed using scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction to study the physicochemical properties. A coupled model based on molecular modeling and computational fluid dynamics was developed to study the diffusion behavior and concentration profiles of the two solutions within the process. A detailed economic estimation for the production of crystalline fructose sugar is presented. The study reveals the significant potential of FO as an economical process for concentration of sugar solutions using brine as the draw solution. V C 2016 Wiley Periodicals, Inc. J.Appl. Polym. Sci. 2017, 134, 44649.
Global supply of commercial reverse osmosis (RO) membranes is growing exponentially due to rapid population growth, industrialization, and urbanization. The continuous demand for enormous quantity of drinking water has brought about process improvements and technological advancements in membrane preparation. The transformation of used RO membranes into nanofiltration (NF) and ultrafiltration membranes by opening up the pores using chemical treatment by inexpensive oxidizing agents could be one of the cost-effective options. The present study investigates the chemical oxidation of the indigenously synthesized RO membrane using aqueous sodium hypochlorite (NaOCl). The performance of the membrane was evaluated by conducting experiments under varying operating conditions of operating time, feed pressure, and total dissolved solids (TDS) in raw water for calculation of flux and salt rejection (%). From an initial flux of 25.2 L/m2 h and TDS rejection of 97.5% for original RO membrane, the values reached 80 L/m2 h and 25.5%, which is in NF range, after a reaction time of 780 min with 4000 ppm concentration of NaOCl oxidizing agent. Further extension of treatment time to 900 min enhanced the flux to 130 L/m2 h with salt rejection lowering to 5.67%. Membrane cleaning was performed efficiently using an advanced technique in which chlorine dioxide (ClO2) was used in combination with citric acid. This combination ensured rapid cleaning with restoration of water flux and % salt rejection. The process was scaled up to pilot plant level using RO membranes modified to NF range of pore size. Permeate water enriched with minerals was further packed using an indigenously designed semi-automatic bottling unit. The studies revealed that the indigenously developed RO membranes are easy to alter into high-performance NF membranes. Overall, the process for production of packaged drinking water was cost-effective, easy to operate, and environmentally friendly.
2-Hydroxypropionic acid, commonly known as lactic acid (LA), is a valuable chemical widely used for the manufacture of green solvents such as ethyl lactate and biodegradable polymers such as poly(lactic acid) (PLA). LA is manufactured by fermentation molasses and whey. Isolation of LA from aqueous broths by conventional methods is energy intensive. Reactive extraction through membranes using specific reagents could prove to be a cost-effective alternative for LA recovery. This study focuses on reactive separation of LA using a novel indigenously developed hydrophobic H-beta zeolite/polyvinylidene fluoride (PVDF) mixed matrix membrane. Experiments were conducted using a stirred cell assembly consisting of two bell shaped glass pipe reducers containing aqueous LA separated by the membrane from an organic solution of tri-n-octylamine (TOA) carrier in alcoholic medium. Effects of experimental parameters such as the concentration of TOA in organic phase and zeolite loading on the rate of acid extraction were evaluated by increasing the TOA concentration from 206 to 620 mol/m3 and the extent of zeolite loading from 1 to 25% (w/w) of (PVDF) polymer. SEM analysis was carried out to oversee zeolite distribution on the PVDF surface, whereas TGA was used to determine the maximum operating temperature. XRD study was done to investigate the influence of zeolite loading on intersegmental spacing in the polymer, while FT-IR helped in the identification of interactions between the inorganic filler and organic polymer. A mass transfer correlation was deduced by taking into account all possible reactions involved in formation of the complexes. An optimum extraction of nearly 34% was obtained using 25% zeolite loading, 206 mol/m3 TOA in 1-octanol, and 100 mol/m3 acid concentration, at a stirring rate of 400 rpm over a processing time of 1 h. Continuous separation of LA by a membrane contactor could help improve the fermentation yield of the acid by preventing the inhibition of lactate dehydrogenase enzyme, which is affected by the product itself. Such reactive extractions by membrane contactors could be successfully scaled up using a hollow fiber modular configuration.
Nanofiltration (NF) is a membrane-based separation process having significant potential for the treatment of industrial effluents to enable water reuse. It has the ability to remove low molecular weight trace contaminants from water, which cannot be separated by conventional treatment methods. In the present investigation, a thin film composite polyamide membrane was synthesized by interfacial polymerization technique and evaluated for the treatment of biscuit industrial effluent. The synthesized membrane was characterized using Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, and scanning electron microscopy to elucidate structure and intermolecular interactions, crystallinity, thermal stability and cross-sectional morphology, respectively. The influence of operating parameters such as feed pressure 0-21 kg/cm 2 and total dissolved solids (TDS) of 3160 ppm on water flux and impurity rejection was determined. An average flux of 11.63 L/m 2 h was obtained at a constant pressure of 21 kg/ cm 2 . The TDS, chemical oxygen demand (COD), and biochemical oxygen demand (BOD) rejections were found to be 53.62, 80, and 74%, respectively, at a water recovery of 65%. A statistical mechanical model was used to validate the experimental data. Based on this study, a detailed economic estimation for processing biscuit effluent of 1 m 3 /h feed capacity using commercial NF system is presented. The study revealed that the synthesized NF membrane could be an effective alternative for the treatment of various industrial effluents as well as to reduce the load on reverse osmosis process for desalination of seawater and effluent treatment through high degree of COD and BOD separation.
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