Recovery by membranes

The enzyme has a monomer weight of 30 kDa and a Km and Vmax for L-pan-tolactone of 7 mM and 30 U mg-1, respectively. X-ray fluorescence spectroscopy of crystals, and renaturation of urea/EDTA-denatured Lph in the presence of Zn2+, Mn2+, Co2+, or Ni2+ indicated Lph to be a Zn2+-hydrolase. Kinetic resolution of rac-pantolactone proceeds similarly to the fungal process mentioned above except that L-pantolactone is hydrolyzed and D-pantolactone is left behind. Repeated batches with isolated Lph and enzyme recovery by membrane filtration give d-pantolactone with 50% yield and 90-95% ee over 6 days. 

Because caffeine extraction is an important industrial application of SC CO2 technology, different studies have been recently conducted on solvent recovery by membrane separation. As the molecular weight (MW) (194 g moP ) of caffeine is higher than CO2 (44 g moP ), classical suitable membrane for this application needs to reject caffeine while letting CO2 cross through the membrane. Thus, pure CO2 can be obtained on permeate side and recycled. 

Tomaszewa, M., Gryta, M., and Morawski, A.W. The influence of salt in solutions on hydrochloric acid recovery by membrane distillation, Sep. Purif. TechnoL, 14, 183, 1998. 

Hydrogen recovery by membrane processes by pressure swing adsorption Hyperfiltration, see Reverse osmosis... 

Alternatively, solvent recovery by membranes could be carried out after degumming the micelle using the UF process so as to obtain hexane-free degununed oil. According to Snape and Nakajima [3], the oil/hexane micelle, previously degummed by UF, could be sent for the NF process in order to maximize solvent recovery, the rest being separated by distillation (Figure 23.13). 

New approaches to catalyst recovery and reuse have considered the use of membrane systems permeable to reactants and products but not to catalysts (370). In an attempt to overcome the problem of inaccessibility of certain catalytic sites in supported polymers, some soluble rho-dium(I), platinum(II), and palladium(II) complexes with noncross-linked phosphinated polystyrene have been used for olefin hydrogenation. The catalysts were quantitatively recovered by membrane filtration or by precipitation with hexane, but they were no more active than supported... 

Lokhandwala et al. [6] have already provided costs for the membrane-based upgrading of tail gas for recycle to a liquefaction process. They showed that recovery of 228 kg h-1 (1915 tonnes per annum) of chlorine from a 20% (v/v) tail gas should provide a pay-out time of about 14 months. Other comparisons made by Membrane Technology and Research, Inc. [11] for an 800 tonnes per day plant shown in Table... 

Table 7.4 Incremental recovery of chlorine by membranes (800 tonnes day 1 plant liquefaction conditions — 18°C and 450 kPa).

Schlosser, S., Kertesz, R. and Martak, J. (2005) Recovery and separation of organic acids by membrane-based solvent extraction and pertraction - An overview with a case study on recovery of MPCA. Separation and Purification Technology, 41, 237. 

Frenzel, I., Holdik, H., Stamatialis, D.F., Pourcelly, G., and Wessling, A. (2005) Chromic acid recovery by electro-electrodialysis -1. Evaluation of anion-exchange membrane. J. Membr. Sci., 261 (1-2), 49-57. 

System design plays a role in determining acceptable recovery by an RO. Flow rates per pressure vessel, recovery per module, and BETA values must all be taken into account when considering acceptable recovery by the RO system (see Chapters 9.4, 9.5, and 9.6). The higher the recovery of the RO system, the closer concentrate flow rates and individual module recoveries come to reaching limits recommended by membrane manufacturers. 

Recovery of lactic acid is complicated by the high solubility of its salt. The traditional method of recovering calcium lactate is being replaced by membrane, electrodialysis, or... 

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