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Polyethyleneimine-coated magnetic iron oxide nanoparticles for improvement of flow assurance

Fyllingsnes, Regina Lopez
Master thesis
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http://hdl.handle.net/11250/2472624
Utgivelsesdato
2017
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  • Institutt for kjemisk prosessteknologi [1425]
Sammendrag
This thesis aims to gain further insight into how the naphthenic acids

(NA), which cause different problems with respect to flow assurance, can

be removed from the water phase. The main objective has been to test

how effective the polyethyleneimine functionalized magnetic iron oxide

nanoparticles are to remove phenylacetic acid, which functioned as model

naphthenic acid from water.

The first part of the experimental work was concerned with the adsorp-

tion of polyethyleneimine onto the nanoparticle surface. The zeta potentials

as function of pH were determined for both the iron oxide nanoparticles

and the polymer. From superimposing the isoelectric points for both syn-

thesised and purchased iron oxide nanoparticles and comparing them to the

zeta potentials for polyethyleneimine, pH 8 was chosen.

Since the confidence for the true mean of the zeta potential was low

for the functionalized iron (II, III) oxide core, using shaking overnight, the

functionalization was done again with iron (III) oxide as core. In a new

approach the polyethyleneimine was added to the supernatant of iron (III)

oxide after centrifugation followed by sonication.

The new functionalized nanoparticles gave a high confidence for the

zeta potentials and were attracted to an external magnetic field. The spe-

cific surface area for the functionalized iron (III) oxide nanoparticles was

iiidetermined to be 62.5 ± 0.2 with 95% confidence, using gas adsorption.

The composition with respect to mass was determined to be 6 wt% from

running a thermogravimetric analysis. Hence, the surface excess of poly-

ethyleneimine was calculated to be 0.9 mg/m 2 .

In the second part of the experiments, test adsorptions of the model

acid were conducted using the polyethyleneimine coated iron (III) oxide

nanoparticles. At pH 8 the adsorption of the phenylacetic acid was negli-

gible. A new calibration curve was made at pH 4.5. Two different values

for the surface excess were obtained. When concentration of the bulk acid

prior to the adsorption was estimated from the calibration curve, the surface

excess was calculated to be 0.16 mg/m 2 , whereas 0.28 mg/m 2 was procured

using the value from the balance.

Since previous research has indicated that the chain length of the poly-

mer determines the adsorption and the surface excess is independent of the

chain length, it was concluded to continue using polyethyleneimine in the

functionalization of iron (III) oxide, but with a lower average molecular

weight.
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