Nanocellulose based affinity membranes for water purification: Processing technologies for optimal adsorption of dyes and metal ions
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
The aim of current study was to fabricate high flux affinity membrane with mechanical stability, porosity and high functionality for capturing of contaminants (dyes and metal ions) from water. Cellulose nanocrystals (CNCSL) and cellulose nanofibers (CNFSL) as well as a special grade of cellulose nanocrystals (CNCBE) isolated following bioethanol pilot scale process were used for the membrane fabrication. To improve the functionality and adsorption capacity of the membranes, enzymatic phosphorylated CNCSL (PCNCSL) and in situ TEMPO functionalized CNCBE (TEMPO-CNCBE) membranes were adopted. The removal of water contaminants via adsorption on carboxyl, sulphonic and phosphoryl functional groups on nanocellulose based membranes was evaluated. Freeze-drying was used as one approach to fabricate CNCSL based hybrid membranes. In spite of high percentage removal of positively charges dyes, low water flux and mechanical stability was recorded. Very fast and effective process, viz. vacuum-filtration was further used to fabricate layered membranes with improved mechanical properties. CNFSL based support layer was coated with more functional nanomaterials (CNCSL and CNCBE) via dipping. The study showed that it was possible to tailor the specific surface area, pore sizes, water flux and wet strength of the membranes based on drying conditions (105 °C at a load of 100kN and 28 oC at ≈20N) and acetone treatment. This study was further extended to fabricate high flux bi-layered membrane having support layer of micro-sized cellulose sludge and top layer of CNCSL, CNCBE and PCNCSL within gelatin matrix for adsorption. The aim of this approach was to provide mechanical stability without decreasing the water flux significantly. In the final study, to increase the adsorption capacity of CNCBE layered membranes; in situ functionalization (TEMPO oxidation) of top layer was performed. Furthermore, CNFSL was introduced in support layer to understand the structural and functional behavior of CNFSL. All membranes were subjected to pollutants removal [dyes and Ag(I), Cu(II), Fe(II)/Fe(III) metal ions]. Remarkable increase in adsorption capacity towards metal ions was recorded after modification of nanocellulose (phosphorylation and in situ functionalization). The outstanding performance of nanocellulose reveals the possibility of next generation affinity membranes for water purification.
Place, publisher, year, edition, pages
Luleå tekniska universitet, 2016. , 50 p.
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
Research subject Wood and Bionanocomposites
IdentifiersURN: urn:nbn:se:ltu:diva-26165Local ID: cf195591-1217-4ced-bf7e-4a42f333cfc0ISBN: 978-91-7583-624-9ISBN: 978-91-7583-625-6 (PDF)OAI: oai:DiVA.org:ltu-26165DiVA: diva2:999324
Godkänd; 2016; 20160509 (zohkar); Nedanstående person kommer att disputera för avläggande av teknologie doktorsexamen. Namn: Zoheb Karim Ämne: Trä och bionanokompositer /Wood and Bionanocomposites Avhandling: Nanocellulose Based Affinity Membranes for Water Purification: Processing Technologies for Optimal Adsorption of Dyes and Metal Ions Opponent: Professor Monica Ek, Avd för träkemi och massateknologi, Skolan för kemivetenskap, Kungliga tekniska högskolan, Stockholm. Ordförande: Biträdande professor Aji Mathew, Avd för materialvetenskap, Institutionen för teknikvetenskap och matematik, Luleå tekniska universitet, Luleå. Tid: Torsdag 16 juni, 2016 kl 10.00 Plats: E632, Luleå tekniska universitet2016-09-302016-09-30Bibliographically approved