Utjecaj pH vrijednosti na veličinsku raspodjelu pora RO/NF membrana

undergraduate thesis

• Title (english): Effect of pH on pore size distribution in RO/NF membranes
• Author: Nevena Milčić
• Mentor: Davor Dolar (mentor)
• Committee member: Davor Dolar (predsjednik povjerenstva)
• Committee member: Šime Ukić (član povjerenstva)
• Committee member: Dajana Kučić (član povjerenstva)
• Granter: University of Zagreb; Faculty of Chemical Engineering and Technology; Zagreb
• Defense date and country: 2016-09-16, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Chemical Engineering; Mechanical, Thermal and Separation Processes

Abstract

Reverzna osmoza (RO) i nanofiltracija (NF) su tlačni membranski procesi koji se primjenjuju u širokom spektru industrijskih djelatnosti. Membranska karakterizacija je nužna za povezivanje poroznosti sa separacijskim svojstvima membrane. Veličinska raspodjela pora (VRP krivulja) daje kvantitativni opis raspona veličina pora u određenoj membrani i time pruža informaciju o veličini čestica koja može biti zadržana. U ovom radu je ispitivan utjecaj pH vrijednosti 4, 7 i 10 na VRP krivulje komercijalno dostupnih RO (UTC-70HA, BW30, XLE) i NF (NF, NF90, NF270) membrana. Ispitivane su vrijednosti fluksa permeata i faktora zadržavanja odabranih referentnih tvari te su iz eksperimentalno određenih parametara pomoću „SF-PF“ modela izračunate pripadajuće VRP krivulje. Gusta NF90 i RO membrane imaju unimodalne VRP krivulje s maksimumom smještenim u rasponu 0,56 – 0,84 nm. Rahle NF i NF270 membrane imaju bimodalne VRP krivulje s glavninom pora smještenom u rasponu 0,72 – 0,82 nm i dodatnim pikom u rasponu 1,30 – 2,34 nm. U usporedbi s pH 4, pri pH vrijednostima 7 i 10 maksimumi VRP krivulja blago su pomaknuti prema manjim veličinama pora (za UTC-70HA, XLE, NF i NF90 membranu) i/ili postoji manji efektivni broj pora (za BW30, XLE i NF270 membranu). To se objašnjava sužavanjem pora pri višim pH vrijednostima do kojeg dolazi uslijed elektrostatskih odbijanja među istovrsno nabijenim funkcionalnim skupinama u površinskom selektivnom sloju membrana.

Abstract (english)

Reverse osmosis (RO) and nanofiltration (NF) are pressure-driven membrane processes which can be used in wide range of industrial activities. Membrane characterization is necessary for connecting porosity with membrane separation properties. Pore size distribution (PSD curve) gives quantitative description of membranes’ pore size range and provides information about the particle size that can be retained. In this work the effect of pH value 4, 7 and 10 on PSD curves of commercially available RO (UTC-70HA, BW30, XLE) and NF (NF, NF90, NF270) membranes was studied. Values of permeate flux and retention factor of selected markers were tested, and from the experimentally obtained parameters with “SF-PF” model related PSD curves were calculated. Dense NF90 and RO membranes have unimodal PSD curves, with a maximum located in a range from 0.56 – 0.84 nm. Loose NF and NF270 membranes have bimodal PSD curves, with the majority of the pores located in a range from 0.72 – 0.82 nm, with an additional peak in a range from 1.30 – 2.34 nm. In comparison with pH 4, at pH values of 7 and 10, peaks of PSD curves are slightly moved towards the smaller pores (for UTC-70HA, XLE, NF and NF90 membrane), and/or exists a lower effective number of the pores (for BW30, XLE and NF270 membranes). It can be explained by narrowing of the pores at higher pH values, occurring due to electrostatic repulsion between homogeneous charged functional groups in a surface active layer.

• Keywords: reverzna osmoza; nanofiltracija; VRP krivulje; veličina pora; pH vrijednost
• Keywords (english): reverse osmosis; nanofiltration; PSD curve; pore size; pH value
• Language: croatian
• URN:NBN: urn:nbn:hr:149:391055
• Study programme: Title: Environmental Engineering - Undergraduate study; Study programme type: university; Study level: undergraduate; Academic / professional title: sveučilišni/a prvostupnik/ prvostupnica (baccalaureus/baccalaurea) inženjer/inženjerka ekoinženjerstva (sveučilišni/a prvostupnik/ prvostupnica (baccalaureus/baccalaurea) inženjer/inženjerka ekoinženjerstva)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2018-02-06 12:38:34