Polyvinyl alcohol recovery

Lopez Garcia et al. [2] have described a rapid and sensitive spectrophotometric method for the determination of boron complex anions in plant extracts and waters which is based on the formation of a blue complex at pH 1 - 2 between the anionic complex of boric acid with 2,6-dihydroxybenzoic acid and crystal violet. The colour is stabilised with polyvinyl alcohol. At 600 nm the calibration graph is linear in the range 0.3-4.5 xg boron per 25 ml of final solution, with a relative standard deviation of 2.6% for xg/l of boron. In this procedure to determine borate in plant tissues, the dried tissue is treated with calcium hydroxide, then ashed at 400 °C. The ash is digested with 1N sulfuric acid and heated to 80 °C, neutralized with cadmium hydroxide and then treated with acidic 2,6-dihydroxybenzoic acid and crystal violet, and the colour evaluated spectrophotometrically at 600 nm. Most of the ions present in natural waters or plant extracts do not interfere in the determination of boron complex anions by this procedure. Recoveries of boron from water samples and plant extracts were in the range of 97 -102%. 

A chloroplast suspension was mixed with native ferredoxln plus ferredoxin-NADP resuctase which were freshly prepared and co-immoblllzed with polyvinyl alcohol (PVA-117). The resulting film reduced NADP upon illumination as 0.64 vmole per mg chlorophyll per hr, about 1% yield of recovery. They applied the film to a photovoltaic cell,... 

Inhibition of animal cell cultures by ammonia has been overcome by either passing oxygen through a porous poly(tetrafluoroethylene) membrane into the culture or by continuous removal through a membrane of the same material (0.2-Jum pores) to aqueous phosphoric acid on the other side.245 Urea was removed by an anion-exchange membrane clamped over an insolubilized polyvinyl alcohol membrane containing urease.246 No ammonium ion returned back into the feed solution. A urease in poly(ethy-lene-co-vinyl acetate) converted urea on one side to ammonia for recovery on the other.247... 

Polyvinyl Alcohol Size Recovery. A textile mill washes the PVA size from wovea fahric in a conniereurrem washer giving 2% PVA in hot water. PVA is required upslrenm al 14% tctal solids io tmet warp thread before weaving. An ulliafilter is employed to recover both lha PVA concentrate and the hot water (Fig. 18.1-3)... 

FIGURE 18.I-3 Schematic diagram of process using UF for recovery of polyvinyl alcohol size. 

Mechanical properties and control of particle size are the main drawbacks of CLEAs. Particles are compressible and shear sensitive and size is usually small so that recovery of the biocatalyst may pose a problem for conventional reactor configurations (see Chapter 5). To solve that problem, basket-type bioreactors can be used or else the biocatalyst can be modified. An interesting approach is the encapsulation of CLEAs within polymer gels, as shown in Fig. 4.4c. Entrapment of CLEAs within polyvinyl alcohol lens-shaped gel particles (LentiKats) produced very robust biocatalysts of a convenient size to be easily recovered (Wilson et al. 2004c). 

Hydrolysis methyl acetate + water = methanol + acetic acid ion-exchange resin bags recovery of acetic acid and medianol in polyvinyl alcohol (PVA) and terephthalic acid (PTA) manufacture [26, 27]... 

A grass roots facility to produce polyvinyl alcohol (PVOH) is being constructed in a chemical complex on the U S. Gulf Coast. Your design team will complete the process engineering for the unit which produces polyvinyl acetate (PVAC). PVAC is further reacted in another part of the facility to produce the PVOH final product. The polyvinyl acetate unit includes the polymerization reactor system and the downstream recovery process. Your design must be capable of an annual production rate of 100 MMlb of PVAC intermediate. 

U.S. production of vinyl acetate is over 1 3 Mt, while western Europe and Japan each produce over half a million tonnes. In the U.S. and Europe, polymers are used mainly for adhesives (e.g. plywood) and paints. In Japan, however, nearly 70% of vinyl acetate polymer is hydrolysed to polyvinyl alcohol (with recovery of acetic acid), for use in fibres. 

Kumar, M., Tripathi, B. R, and Shahi, V. K. (2009). Cross-linked chitosan/polyvinyl alcohol blend beads for removal and recovery of Cd(II) from waste v/ater. Journal of Hazardous Materials 172(2-3), 1041 8. 

A good AEM should fulfill stringent mechanical, thermal, and chemical properties as mentioned in Section 11.2. Historically, the first AEM material was developed by researchers from the Toknyama Soda Company. They introduced quaternary ammonium groups to the divinylbenzene-cross-linked polychloropropene polymer matrix via trimethylamine. Since then, several membrane-associated companies explored various kinds of AEMs and pushed them to commercial market most of them were based on cross-linked polystyrene, polyvinyl alcohol, low (or high)-density polyethylene, and other aliphatic polymers through irradiation-grafting method. The primary objective of developing these materials was for applications in the fields such as electrodialysis, desalination, selective electrode, and waste acid recovery. However, they showed performance in AEM fuel cells far below practical... 

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