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|Title: ||Natural organic matter removal by nanofiltration: effects of solution chemistry on retention of low molar mass acids versus bulk organic matter|
|Authors: ||Schäfer, Andrea|
Fane, Anthony G.
Waite, T. D.
|Issue Date: ||2004|
|Citation: ||Schäfer, A.I. ; Pihlajamäki, A. ; Fane, A.G. ; Waite, T.D. ; Nyström, M. (2004) Natural organic matter removal by nanofiltration: effects of solution chemistry on retention of low molar mass acids versus bulk organic matter, Journal of Membrane Science, 242, 1-2, 73-85|
|Abstract: ||The main emphasis of this study is the difference in behaviour between those two organic types. Stirred
cell experiments were used to investigate charge and size effects in the rejection behaviour of bulk
natural organics as well as low molecular mass (LMM) acids by nanofiltration membranes.
To distinguish between size and charge effects thorough characterisation of membrane, natural
organics and ionic environment was carried out. Membrane zeta potential was determined as a function
of the ionic environment and the intrinsic membrane rejection was measured with dextran, ionic
solutions and synthetic surface water.
The behaviour of three thin film composite (TFC) and one cellulose acetate (CA) membranes was
studied as a function of solution chemistry (pH, ionic composition and strength, calcium concentration,
and organic type). Rejections of DOC, UV254nm, as well as the cations calcium and sodium were
measured. Natural organics in selected feed and permeate samples were also characterised using liquid
chromatography organic carbon detection (LC-OCD) which allows the characterisation of the organic
fractions in the low concentration permeates and hence give insight into the rejection of low molecular
mass (LMM) organics. The retention of such LMM compounds is important due to their impact on the
microbiological regrowth potential of the product water
The results emphasised that charge and size are both important for cations and low molecular mass
acids. While the bulk of the natural organics are retained due to size exclusion that is independent on
solution chemistry for the membranes investigated, the retention of LMM acids follows different
mechanisms. The analysis of organic fraction in the permeates showed that the rejection of low
molecular mass acids is strongly pH, and thus charge, dependent while this effect of solution chemistry
on the LMM acids was masked when only bulk organic rejection was measured.|
|Keywords: ||Membrane zeta potential|
Natural organic matter
|Appears in Collections:||Membrane Technology Research Group publications|
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