Flotation as a separation technology for recovering pulp fines and sustainable nanocellulose production

Wriju Kargupta; Christine Browne; Luis Verdugo; Ian Hunt; Karen Stack; Warren Batchelor; Joanne Tanner

doi:10.1016/j.seppur.2021.118810

Flotation as a separation technology for recovering pulp fines and sustainable nanocellulose production

Wriju Kargupta
, Christine Browne
, Luis Verdugo
, Ian Hunt
, Karen Stack
, Warren Batchelor
, Joanne Tanner

Research output: Contribution to journal › Article › peer-review

12 Citations (Scopus)

Abstract

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.

Original language	English
Article number	118810
Number of pages	11
Journal	Separation and Purification Technology
Volume	270
DOIs	https://doi.org/10.1016/j.seppur.2021.118810
Publication status	Published - 1 Sept 2021
Externally published	Yes

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10.1016/j.seppur.2021.118810

https://doi.org/10.1016%2Fj.seppur.2021.118810

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@article{cc0abf621a6c47a2be231348a05a3724,

title = "Flotation as a separation technology for recovering pulp fines and sustainable nanocellulose production",

abstract = "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. ",

author = "Wriju Kargupta and Christine Browne and Luis Verdugo and Ian Hunt and Karen Stack and Warren Batchelor and Joanne Tanner",

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doi = "10.1016/j.seppur.2021.118810",

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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

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.

U2 - 10.1016/j.seppur.2021.118810

DO - 10.1016/j.seppur.2021.118810

M3 - Article

VL - 270

JO - Separation and Purification Technology

JF - Separation and Purification Technology

M1 - 118810

ER -

Flotation as a separation technology for recovering pulp fines and sustainable nanocellulose production

Abstract

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