Combination Of Pervaporation Research Articles

Evaluation of membrane-assisted hybrid processes for the separation of a tetrahydrofuran-methanol-water mixture

The combination of pervaporation (PV) and distillation provide considerable potential for the separation of azeotropic multicomponent mixtures. However, only a proper techno-economic evaluation of these processes compared to a reference process enables a reliable evaluation of benefits. Within this work, the potential of a PV-assisted distillation process is evaluated for the mixture of tetrahydrofuran methanol and water compared to a heat-integrated pressure-swing distillation process. Since initial evaluations reveal a significant potential of the PV-assisted processes regarding the required energy demand, experimental investigations of three polymeric and two inorganic membranes were conducted. A detailed characterization of the most promising membranes PERVAP™ 4155–40 and Hybrid Silica HybSi® AR was performed, and the latter one provided the highest permeance and selectivity. Based on the derived flux models, an economical optimization was performed. Despite the energy-benefits of the PV-assisted processes, the reference process was still evaluated more favorable under the considered framework, mainly caused by high investment and cooling costs. The current study illustrates the benefits of a tight integration of model-based process design and experimental investigations. Despite possible energy savings and promising performance metrics of the membrane, an assessment of the techno-economic performance of these processes is of major importance to identify applications.

A novel system for zero-discharge treatment of high-salinity acetonitrile-containing wastewater: Combination of pervaporation with a membrane-aerated bioreactor

High-salinity acetonitrile (ACN)-containing wastewater is a typical chemical wastewater with high salinity, high volatility, high toxicity and nitrogen-rich organic matter. To efficiently treat high-salinity ACN wastewater without generating secondary pollution, a novel zero-discharge treatment system was developed based on the combination of pervaporation (PV) with a membrane-aerated bioreactor (MAB). Integrated (IMABS) and separate (SMABS) MAB systems were constructed and compared. In these two systems, the ACN was separated from the high-salinity ACN wastewater by PV. The separated ACN entered the MAB for biodegradation, and the high-salinity water remaining after separating ACN was reused for industrial production. The effects of the hydraulic retention time (HRT), salt content of the feed liquid, initial ACN concentration of the feed liquid, and aeration pressure on the process performance were investigated. The ACN separation and removal by SMABS were superior to those by IMABS. With an initial feed liquid ACN concentration of 2000 mg/L and salt content (as NaCl) of 5 wt%, ACN was not detected in the feed liquid of SMABS over an 8-day operation, and the high-salinity water remaining after ACN separation satisfied the requirements for reuse. The corresponding ACN permeation flux and ACN removal rate at 8 days were 0.131 g/(m2·h) and 98.75%, respectively. This research shows that the zero-discharge treatment of high-salinity ACN wastewater can be realized by the combination of PV with an MAB.

Novel Polyheteroarylene Membranes for Separation of Methanol\u2012Hexane Mixture by Pervaporation

Polymer membranes with improved transport properties are required for effective separation of organic mixtures (such as methanol‒hexane system) by combination of pervaporation and azeotropic distillation. The present work is devoted to comparative study of two types of membranes based on poly(amidoimide acid) with 2,2′-biquinoline-6,6′ units in the backbone; the objects were prepared (i) from the initial polymer and (ii) from the polymer-metal complex (with Cu(I)). Thermo-mechanical and mass spectrometric investigations demonstrated good operational properties of the samples. Density measurements and SEM analysis revealed that the structure formed in polymer-metal complex is more compact as compared to that of the pure polymer membrane. Mass transfer processes of methanol and hexane through both kinds of membranes were studied by sorption, desorption and pervaporation tests. The values of equilibrium sorption degree, the Flory–Huggins parameter, and diffusion coefficient were determined for the obtained membranes. The pervaporation data allowed calculating permeability and selectivity of membranes in addition to the flux and the separation factor. The membrane based on polymer-Cu(I) complex allowed separating the methanol‒hexane azeotropic mixture with a separation factor of 980 and pervaporation separation index equal to 66.6; therefore, this process is significantly more effective than separation procedures involving other known membranes.

Pervaporation Membrane System for the Removal of Ammonia from Water

Regenerated cellulose and chitosan membranes were studied for the pervaporation separation of an aqueous solution of urine component (ammonia, uric acid or creatinine). The permeation rate of water increased with increase of the temperature of feed solution induced into the upstream side of membrane module. Uric acid, creatine and creatinine were not found in the permeate through the all membranes investigated. Selective permeation of water and ammonia depends on membrane. The removal of ammonia through the chitosan membrane was from 57% to 59%. Adsorption of ammonia from the downstream vapor by silica gels was carried out. And desorption of ammonia from the adsorbents by heating under the reduced pressure to regenerate the capacity of adsorption was also confirmed. In the case of new pervaporation system, the combination of pervaporation and adsorption/desorption process, ammonia was almost completely removed, and finally the pure condensed water was obtained in the cold trap.