Polyacrylic acid pore-filled microporous membranes and their use in membrane-mediated synthesis of nanocrystalline ferrihydrite
作者:
Françoise M Winnik,
André Morneau,
Alicja M Mika,
Ronald F Childs,
Anna Roig,
Elies Molins,
Ronald F Ziolo,
期刊:
Canadian Journal of Chemistry
(NRC Available online 1998)
卷期:
Volume 76,
issue 1
页码: 10-17
ISSN:0008-4042
年代: 1998
DOI:10.1139/v97-210
出版商: NRC Research Press
数据来源: NRC
摘要:
A series of cation-exchange membranes were obtained by photoinitiated grafting of acrylic acid onto a polypropylene microporous support having 0.2 µm diameter pores. The poly(acrylic acid) was shown to be contained within the pores of the membrane. The ion-exchange capacities of these "pore-filled" membranes ranged from 65 to 80% of the theoretical values calculated on the basis of their measured graft yields, with water contents ranging from 72 to 77%. The membranes exhibited a chemical valve effect of flux as a function of pH. Treatment of a poly(acrylic acid) grafted membrane with a solution containing ferrous ions resulted in a large uptake of iron (>24% by weight of iron with a membrane containing 152% graft yield of poly(acrylic acid)). Subsequent alkaline (pH 14) oxidation at 70°C with either oxygen or hydrogen peroxide led to the formation of a superparamagnetic nanocrystalline form of ferrihydrite, 5Fe2O3·9H2O. The oxide was identified by temperature-dependent Mössbauer spectroscopy recorded from 300 K to 4.2 K. TEM micrographs of sectioned membranes that were treated with H2O2revealed the presence of two iron oxide morphologies, disk-shaped particles 3-4 nm in diameter and needle-like particles about 4 nm wide and 50 nm long. Only disk-shaped particles were observed in membranes treated with O2. Magnetization measurements indicate that the membranes are superparamagnetic above 50 K with a room temperature magnetization of 3.3 emu g-1at 20 kOe.Key words: membrane, poly(acrylic acid); iron oxide, magnetic, Mössbauer spectroscopy; magnetization, photografting
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