Synthesis and Characterization of Modified (PVA) Membranes

1. Synthesis and Characterization of Modified (PVA) Membranes 1Textile Metrology Lab., National Institute for Standards, Giza, Egypt 2 Central lab of the Ministry of Electricity, Cairo, Egypt. 3Textile Division, National Research Centre, Dokki, Cairo, Egypt Ferial M. Tera1 , A.I. Shehata2 , E.A. Al-Alfy3, S. H. Samaha1, and Elkhradly, A.E.3

2. Abstract This work dealt with synthesis and characterization of modified polyvinyl membrane cross – linked on polyester fabric by using three different aldehyde solutions namely: formaldehyde, acetaldehyde and gluteraldyhyed. Scanning electron microscope and transition microscope were used to study the surface morphology of the produced membranes and to follow membrane structure changes due to changing cross-linking agents. The obtained results showed that optimum conditions of aldehyde cross-linking concentrations of the membranes are those prepared by using 10% formaldehyde with 1.5% gluteraldehyde. These conditions gave the prepared membranes excellent mechanical properties and also good results in the filtration of waste water containing high amounts of organic matter and some elements. Key words Aldehyde, Filtration, Membrane, Polyester, PVA, Waste water.

3. Experimental Materials • Polyvinyl alcohol M.W app. (1, 25,000, Glutaraldehyde solution CH2 (CH2. CHO)2 , formaldehyde supplied by Loba Chemie Pvt. India • Acetaldehyde supplied by, Riedel-de Haen A.G.D.3016 seelzel. • Examined water sample was obtained from industrial zone at west Cairo, Egypt.

4. Preparation of P.V.A. membranes: 1- 6% P.V.A. aqueous solution cast on glass plate was dried in the air at 25°C to obtain (10-20µm) thickness film. The film then thermally compressed on a partially wet polyester fabric. The product was cut into 20cm x 15cm pieces.

5. 2- An acidic solution of concentrated sodium sulphate containing 10% formaldehyde, was prepared and divided into four portions, (0.5, 1, 1.5 and 2%) glutaraldehyde solutions were added successively to form four different mixtures. 3- Four film pieces were soaked in the formaldehyde solution for 24hours. Another four pieces were soaked in 10% acetaldehyde . 4- The produced membranes were washed several times, and soaked in distilled water.

6. Testing Mechanical properties: • Tensile strength and elongation % at break determined by using tensile strength tester; Shimmadzu Autograph S-500. • Abrasion resistant was determined using rubtester; Universal Rotary • Flat Abrasion Tester Type: FF-25 computext textilpari, Muszeres, Inc. Morphological structure: This was investigated using: • Jeol JSM-T200S Electron Scanning Microscope. • Transmission Optical Microscope Versamet-2 union 7609. Thickness • This was measured using thickness gauge micrometer.

7. Permeation of water • Permeation measurements were performed using Osmonics SEPA CF membrane cell. Water analysis • The following series of examinations were carried out according to the standard method of testing [1]. • Turbidity was measured in nephelometric turbidity units (N.T.U) using Helige Digital Direct Reading Turbidimeter. • pH was determined by Accumet pH meter model 810, Fisher scientific. • Mn, Cu, Al, Ni, Zn were measured by using atomic absorption 5000, Spectrophotometer Perkin Elmer. [1] Arnold, E.; Greenberg; Lenore, S.; Clesceri and Andrew, D.; Eaton, In "Standar methods for the examination of water and waste water". 18th edition, American Public Health Association, American Water Works Association & Water Invironment Federation, (1992)

8. Water analysis • Total Silical was measured using plasma 400 ICP Spectrometer Perkin Elmer. • The soluble silica expressed as (SiO2) was measured by spectrophotometry using Baush & Lamb, Spectronic 2000 Spectrophotometer. • The colloidal silica was determined by deducting the soluble silica from the total silica. • The total organic matter (T.O.M.) of industrial water was measured by evaporating adequate sample and measuring the loss in weight after ashing in muffle furnace at 500˚C for 1 hour [2]. [2]. Stewart E. Allen, "Chemical Analysis of Ecological Materials" Blackwell Scientific Publication (1974). Oxford, London, (1953).

9. Results and discussion • Treatment of (P.V.A.) with aldehyde solution in the presence of sulfuric acid as a catalyst, render the (P.V.A.) insoluble in water due to the blocking of two adjacent (OH) groups of (P.V.A) and few cross-links occurs between (OH) groups of two or more neighboring chains. While the presence of saturated solution of sodium sulfate prevents the dissolving of membrane during the treatment over 24 hours. • This treated (P.V.A.) has higher water absorption, and also found to posses excellent dimensional stability, resistance to abrasion and remarkable tensile strength, elongation and water permeation.

10. Characterization of porous membrane Mechanical properties When using membrane in ultra, nano, micro filtration techniques, it works under severe conditions and suffers greatly some factors: 1- It is subjected to high pressure. 2- Abrasion resulting from friction between membrane surface and liquid with its impurities, especially when the flow is parallel to membrane surface 3- It is subjected to a great tension on using.

13. Morphological structure of porous membrane Transmission Photomicrographs Of P.V.A. Membranes Prepared in Formaldehyde at Different Concentrations of Gluatraldehyde: (a) 0,5% (b) 1% (c) 1.5% (d) 2%

14. Transmission Photomicrographs Of P.V.A. Membranes Prepared in acetaldehyde at Different Concentrations of Gluatraldehyde: (a) 0,5% (b) 1% (c) 1.5% (d) 2%

15. Scanning electron micrograph (SEM) Of P.V.A. Membranes Prepared in formaldehyde at Different Concentrations of Gluatraldehyde” (a) 0,5% (b) 1% (c) 1.5% (d) 2%

16. Scanning electron microscope (SEM) of P.V.A. Membranes Prepared in acetaldehyde at Different Concentrations of Gluatraldehyde (a) 0,5% (b) 1% (c) 1.5% (d) 2%.

17. Characterization of Treated Water

19. Conclusion • The water insoluble (P.V.A) membrane prepared on polyester fabric, possesses an excellent mechanical stability, water permeation and filtration when used in the treatment of industrial waste water. • The experimental results, indicate that the membranes prepared by 10% formaldehyde, 1.5% glutaraldehyde and that by 10% acetaldehyde, 1% glutaraldehyde were found to be stable through the period of testing.

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