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|Title: ||Removal of metal ions from aqueous solutions using lecithin enhanced ultrafiltration|
|Authors: ||Kotzian, Roland|
|Issue Date: ||1998|
|Publisher: ||© Roland Kotzian|
|Abstract: ||This work is concerned with an alternative method for metal ion removal from
aqueous solutions - surfactant enhanced ultrafiltration. Surfactant monomers
aggregate above a certain concentration, specific to the surfactant, to form micelles.
Anionic surfactant micelles will attract and bind metal cations. Free metal ions and
surfactant monomers pass freely through an ultrafiltration membrane, but if the
micelle-metal ion complex is sufficiently large it is rejected.
Research reported in this thesis has been carried out on well defined aqueous solutions
containing only one type of metal ion together with the natural surfactant lecithin.
Lecithin is a food grade by-product of the soybean processing industry and it was
chosen because it is non-toxic, biodegradable, abundant and inexpensive. It has a high
molecular weight of about 750 Daltons and forms large size micelles. The main aim
was to identify the basic mechanisms which influence the permeate flux and rejection
levels of the process.
The project was carried out in three stages. Stage one was the characterisation of the
feed solution which included the determination of the critical micelle concentration
using surface tension measurements, measurement of micelle size and zeta potential
using a Malvern zeta sizer and visualisation of the micelle shape using scanning
electron microscopy of freeze fractured lecithin solution droplet.
In the second stage filtration experiments were carried out at a wide range of lecithin
concentrations, metal ion concentrations and operating conditions. The experiments
were run for 5 hours, by which stage a steady state condition was reached in all cases.
Permeate samples were taken after I, 3 and 5 hours. Permeate flux was monitored
throughout the experiment. The following properties were monitored for the feed
solution at the beginning and the end of each experiment and for all permeate
samples: lecithin concentration, copper concentration, pH, conductivity.
In the 3 stage Electron Dispersive Analysis by X-ray (EDAX), Scanning Electron
Microscopy (SEM) and a X-ray Photoelectron Spectrum Technique (XPS) were
employed to investigate any membrane feed solution interactions.
The results of the 3 stages were used to identify the basic mechanisms which control
the permeate flux levels and the extent of component rejection in lecithin enhanced
|Description: ||A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.|
|Appears in Collections:||PhD Theses (Chemical Engineering)|
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