TY - JOUR
T1 - Flotation as a separation technology for recovering pulp fines and sustainable nanocellulose production
AU - Kargupta, Wriju
AU - Browne, Christine
AU - Verdugo, Luis
AU - Hunt, Ian
AU - Stack, Karen
AU - Batchelor, Warren
AU - Tanner, Joanne
N1 - Funding Information:
We wish to thank Australian Paper Maryvale for providing Bleached Eucalyptus pulp. Wriju Kargupta thanks Monash University for CF-MGS scholarship. The authors would like to acknowledge the facilities used with Monash Center for Electron Microscopy. We would also like to acknowledge the financial support from the Australian Research Council, Australian Paper, Norse Skog, Opal and Visy through the Processing Advanced Lignocellulosics Industry Transformation Research Hub grant (IH130100016). A special thanks to Dr Sonita Singh, at University of Tasmania, Hobart for demonstrating the laboratory flotation set up and her cooperation to facilitate our research.
Publisher Copyright:
© 2021 Elsevier B.V.
Copyright:
Copyright 2021 Elsevier B.V., All rights reserved.
PY - 2021/9/1
Y1 - 2021/9/1
N2 - Nanocellulose has great potential in the pulp and paper industry, but current nanocellulose production methods require high energy. One way to achieve energy efficient production of nanocellulose is to develop a large-scale process of separating small fibers (fines) from large fibers. In this study, a laboratory mill was used to produce moderately refined (30.8% fines) and highly refined (81.8% fines) Bleached Eucalyptus Kraft (BEK) pulp. Refined samples were subjected to flotation separation, and separation efficiency was quantified by fines recovery and fines enrichment ratio. At high pH (11.9), with a surfactant concentration of 0.15 mM, the surface tension of the air–water interface was 44 mN/m and the Sauter mean diameter of the bubbles in the froth was 0.948 mm. These conditions provide the required froth stability and low bubble size to achieve selective separation of fines. Maximum recoveries of 80.4% and 43.0% were achieved at pH 11.9 and 1.0 wt% for moderately refined and highly refined pulp, respectively. Maximum enrichment ratios of 4.33 and 4.37 were observed for moderately refined and heavily refined pulp at pH 11.9 and 1.5 wt%, respectively. The aspect ratio of float fibers increased by 14% and 18% for moderately and highly refined BEK, respectively. Flotation was shown to be controlled by the viscosity and surface charge of the pulp suspension. Viscosity and zeta potential values were maximised at pH 11.9 and 1.0–1.5 wt% pulp solids, promoting agglomeration of long fibers and enhanced fines separation. Experimental results were found to be statistically significant via ANOVA. Fines were shown to have analogous properties to commercial nanocellulose. This study demonstrates that size-selective fiber flotation is governed by pulp suspension rheology and fluid flow hydrodynamics, and that flotation represents a promising technology for fines separation and production of a sustainable nanocellulose substitute.
AB - Nanocellulose has great potential in the pulp and paper industry, but current nanocellulose production methods require high energy. One way to achieve energy efficient production of nanocellulose is to develop a large-scale process of separating small fibers (fines) from large fibers. In this study, a laboratory mill was used to produce moderately refined (30.8% fines) and highly refined (81.8% fines) Bleached Eucalyptus Kraft (BEK) pulp. Refined samples were subjected to flotation separation, and separation efficiency was quantified by fines recovery and fines enrichment ratio. At high pH (11.9), with a surfactant concentration of 0.15 mM, the surface tension of the air–water interface was 44 mN/m and the Sauter mean diameter of the bubbles in the froth was 0.948 mm. These conditions provide the required froth stability and low bubble size to achieve selective separation of fines. Maximum recoveries of 80.4% and 43.0% were achieved at pH 11.9 and 1.0 wt% for moderately refined and highly refined pulp, respectively. Maximum enrichment ratios of 4.33 and 4.37 were observed for moderately refined and heavily refined pulp at pH 11.9 and 1.5 wt%, respectively. The aspect ratio of float fibers increased by 14% and 18% for moderately and highly refined BEK, respectively. Flotation was shown to be controlled by the viscosity and surface charge of the pulp suspension. Viscosity and zeta potential values were maximised at pH 11.9 and 1.0–1.5 wt% pulp solids, promoting agglomeration of long fibers and enhanced fines separation. Experimental results were found to be statistically significant via ANOVA. Fines were shown to have analogous properties to commercial nanocellulose. This study demonstrates that size-selective fiber flotation is governed by pulp suspension rheology and fluid flow hydrodynamics, and that flotation represents a promising technology for fines separation and production of a sustainable nanocellulose substitute.
KW - Fines enrichment ratio
KW - Fines recovery
KW - Flotation
KW - Level of refining
KW - Nanocellulose
KW - pH
KW - Pulp rheology
UR - http://www.scopus.com/inward/record.url?scp=85105054381&partnerID=8YFLogxK
U2 - 10.1016/j.seppur.2021.118810
DO - 10.1016/j.seppur.2021.118810
M3 - Article
AN - SCOPUS:85105054381
SN - 1383-5866
VL - 270
JO - Separation and Purification Technology
JF - Separation and Purification Technology
M1 - 118810
ER -