1
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Large-Scale Production of Size-Adjusted β-Cell Spheroids in a Fully Controlled Stirred-Tank Reactor. Processes (Basel) 2022. [DOI: 10.3390/pr10050861] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
For β-cell replacement therapies, one challenge is the manufacturing of enough β-cells (Edmonton protocol for islet transplantation requires 0.5–1 × 106 islet equivalents). To maintain their functionality, β-cells should be manufactured as 3D constructs, known as spheroids. In this study, we investigated whether β-cell spheroid manufacturing can be addressed by a stirred-tank bioreactor (STR) process. STRs are fully controlled bioreactor systems, which allow the establishment of robust, larger-scale manufacturing processes. Using the INS-1 β-cell line as a model for process development, we investigated the dynamic agglomeration of β-cells to determine minimal seeding densities, spheroid strength, and the influence of turbulent shear stress. We established a correlation to exploit shear forces within the turbulent flow regime, in order to generate spheroids of a defined size, and to predict the spheroid size in an STR by using the determined spheroid strength. Finally, we transferred the dynamic agglomeration process from shaking flasks to a fully controlled and monitored STR, and tested the influence of three different stirrer types on spheroid formation. We achieved the shear stress-guided production of up to 22 × 106 ± 2 × 106 viable and functional β-cell spheroids per liter of culture medium, which is sufficient for β-cell therapy applications.
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2
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Petry F, Salzig D. Impact of Bioreactor Geometry on Mesenchymal Stem Cell Production in Stirred‐Tank Bioreactors. CHEM-ING-TECH 2021. [DOI: 10.1002/cite.202100041] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- Florian Petry
- University of Applied Sciences Mittelhessen Institute of Bioprocess Engineering and Pharmaceutical Technology Wiesenstraße 14 35390 Giessen Germany
| | - Denise Salzig
- University of Applied Sciences Mittelhessen Institute of Bioprocess Engineering and Pharmaceutical Technology Wiesenstraße 14 35390 Giessen Germany
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3
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Liu D, Edraki M, Fawell P, Berry L. Improved water recovery: A review of clay-rich tailings and saline water interactions. POWDER TECHNOL 2020. [DOI: 10.1016/j.powtec.2020.01.039] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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4
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Revisiting and improving models for the breakup of compact dry powder agglomerates in turbulent flows within Eulerian–Lagrangian simulations. POWDER TECHNOL 2019. [DOI: 10.1016/j.powtec.2019.03.009] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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5
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Sung Ng W, Connal LA, Forbes E, Mohanarangam K, Franks GV. In situ study of aggregate sizes formed in chalcopyrite-quartz mixture using temperature-responsive polymers. ADV POWDER TECHNOL 2018. [DOI: 10.1016/j.apt.2018.04.027] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
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6
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Ng WS, Connal LA, Forbes E, Mohanarangam K, Franks GV. In situ investigation of aggregate sizes formed using thermo-responsive polymers: Effect of temperature and shear. J Colloid Interface Sci 2017; 494:139-152. [PMID: 28157632 DOI: 10.1016/j.jcis.2017.01.067] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Revised: 01/19/2017] [Accepted: 01/19/2017] [Indexed: 01/30/2023]
Abstract
Temperature-responsive flocculants, such as poly(N-isopropylacrylamide) (PNIPAM), induce reversible particle aggregation upon heating above a lower critical solution temperature (LCST). The aim of this work is to investigate the aggregation of ground iron ore using PNIPAM and conventional polyacrylamide (PAM) flocculants in a continuously-sheared suspension, through in situ chord length measurements using Focused Beam Reflectance Measurement techniques and real-time imaging of the particle aggregates. In the presence of uncharged PNIPAM, particle aggregation occurs only upon heating to the LCST, and the aggregates continue to grow with further heating. Subsequent cooling re-disperses the aggregates, and repeated heating causes reformation. Unlike uncharged PNIPAM, anionic PNIPAM produces aggregates at temperatures below the LCST due to the polymer chains binding to two different particles via attractive interactions between the acrylic acid groups and the hematite surfaces, and can be added at temperatures above the LCST due to the formation of charge-stabilised micelles. Under continuous shear, the flocculant most able to resist aggregate size reduction was anionic PAM, followed by PAM, anionic PNIPAM, PNIPAM (6MDa), and PNIPAM (122kDa). Reversible aggregate breakage was found with all samples, except with PNIPAM (6MDa) after being subjected to shear rates above 550s-1. Furthermore, heating of the PNIPAM-dosed suspensions at shear rates below 200s-1 produced larger and more breakage-resistant aggregates.
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Affiliation(s)
- Wei Sung Ng
- Chemical and Biomolecular Engineering, University of Melbourne, Parkville, VIC 3010, Australia; CSIRO Mineral Resources, Clayton, VIC 3168, Australia.
| | - Luke A Connal
- Chemical and Biomolecular Engineering, University of Melbourne, Parkville, VIC 3010, Australia.
| | | | | | - George V Franks
- Chemical and Biomolecular Engineering, University of Melbourne, Parkville, VIC 3010, Australia.
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7
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Demoz A. Scaling inline static mixers for flocculation of oil sand mature fine tailings. AIChE J 2015. [DOI: 10.1002/aic.14958] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Alebachew Demoz
- Natural Resources Canada, CanmetENERGY-Devon, One Oil Patch Drive; Devon AB Canada T9G 1A8
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8
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Gaudreault R, Di Cesare N, van de Ven TGM, Weitz DA. Structure and Strength of Flocs of Precipitated Calcium Carbonate Induced by Various Polymers Used in Papermaking. Ind Eng Chem Res 2015. [DOI: 10.1021/acs.iecr.5b00818] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Roger Gaudreault
- Cascades Inc., Recherche et Développement, 471 Marie-Victorin, Kingsey Falls, Quebec Canada, J0A 1B0
- Pulp & Paper Research Centre, McGill University, 3420 University Street, Montreal, Quebec Canada, H3A 2A7
- Harvard University, Pierce Hall
231, 29 Oxford Street, Cambridge, Massachusetts 20138, United States
| | - Nicolas Di Cesare
- Cascades Inc., Recherche et Développement, 471 Marie-Victorin, Kingsey Falls, Quebec Canada, J0A 1B0
| | - Theo G. M. van de Ven
- Pulp & Paper Research Centre, McGill University, 3420 University Street, Montreal, Quebec Canada, H3A 2A7
| | - David A. Weitz
- Harvard University, Pierce Hall
231, 29 Oxford Street, Cambridge, Massachusetts 20138, United States
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9
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Guezennec AG, Michel C, Bru K, Touze S, Desroche N, Mnif I, Motelica-Heino M. Transfer and degradation of polyacrylamide-based flocculants in hydrosystems: a review. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2015; 22:6390-6406. [PMID: 25253053 DOI: 10.1007/s11356-014-3556-6] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2014] [Accepted: 09/03/2014] [Indexed: 06/03/2023]
Abstract
The aim of this review was to summarize information and scientific data from the literature dedicated to the fate of polyacrylamide (PAM)-based flocculants in hydrosystems. Flocculants, usually composed of PAMs, are widely used in several industrial fields, particularly in minerals extraction, to enhance solid/liquid separation in water containing suspended matter. These polymers can contain residual monomer of acrylamide (AMD), which is known to be a toxic compound. This review focuses on the mechanisms of transfer and degradation, which can affect both PAM and residual AMD, with a special attention given to the potential release of AMD during PAM degradation. Due to the ability of PAM to adsorb onto mineral particles, its transport in surface water, groundwater, and soils is rather limited and restricted to specific conditions. PAM can also be a subject of biodegradation, photodegradation, and mechanical degradation, but most of the studies report slow degradation rates without AMD release. On the contrary, the adsorption of AMD onto particles is very low, which could favor its transfer in surface waters and groundwater. However, AMD transfer is likely to be limited by quick microbial degradation.
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10
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Antunes E, Garcia FAP, Blanco A, Negro C, Rasteiro MG. Evaluation of the Flocculation and Reflocculation Performance of a System with Calcium Carbonate, Cationic Acrylamide Co-polymers, and Bentonite Microparticles. Ind Eng Chem Res 2015. [DOI: 10.1021/ie503342d] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- E. Antunes
- CIEPQPF,
Chemical Engineering Department, Coimbra University, Pólo
II, Pinhal de Marrocos, 3030-790 Coimbra, Portugal
| | - F. A. P. Garcia
- CIEPQPF,
Chemical Engineering Department, Coimbra University, Pólo
II, Pinhal de Marrocos, 3030-790 Coimbra, Portugal
| | - A. Blanco
- Chemical
Engineering Department, Faculty of Chemistry, Complutense University, 28040 Madrid, Spain
| | - C. Negro
- Chemical
Engineering Department, Faculty of Chemistry, Complutense University, 28040 Madrid, Spain
| | - M. G. Rasteiro
- CIEPQPF,
Chemical Engineering Department, Coimbra University, Pólo
II, Pinhal de Marrocos, 3030-790 Coimbra, Portugal
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11
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Ayoub GM, BinAhmed SW, Al-Hindi M, Azizi F. Coagulation of highly turbid suspensions using magnesium hydroxide: effects of slow mixing conditions. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2014; 21:10502-10513. [PMID: 24756673 DOI: 10.1007/s11356-014-2857-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2014] [Accepted: 03/31/2014] [Indexed: 06/03/2023]
Abstract
Laboratory experiments were carried out to study the effects of slow mixing conditions on magnesium hydroxide floc size and strength and to determine the turbidity and total suspended solid (TSS) removal efficiencies during coagulation of highly turbid suspensions. A highly turbid kaolin clay suspension (1,213 ± 36 nephelometric turbidity units (NTU)) was alkalized to pH 10.5 using a 5 M NaOH solution; liquid bittern (LB) equivalent to 536 mg/L of Mg(2+) was added as a coagulant, and the suspension was then subjected to previously optimized fast mixing conditions of 100 rpm and 60 s. Slow mixing speed (20, 30, 40, and 50 rpm) and time (10, 20, and 30 min) were then varied, while the temperature was maintained at 20.7 ± 1 °C. The standard practice for coagulation-flocculation jar test ASTM D2035-13 (2013) was followed in all experiments. Relative floc size was monitored using an optical measuring device, photometric dispersion analyzer (PDA 2000). Larger and more shear resistant flocs were obtained at 20 rpm for both 20- and 30-min slow mixing times; however, given the shorter duration for the former, the 20-min slow mixing time was considered to be more energy efficient. For slow mixing camp number (Gt) values in the range of 8,400-90,000, it was found that the mixing speed affected floc size and strength more than the time. Higher-turbidity removal efficiencies were achieved at 20 and 30 rpm, while TSS removal efficiency was higher for the 50-rpm slow mixing speed. Extended slow mixing time of 30 min yielded better turbidity and TSS removal efficiencies at the slower speeds.
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Affiliation(s)
- George M Ayoub
- Civil and Environmental Engineering Department, American University of Beirut, Beirut, Lebanon
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12
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Böl M, Ehret AE, Bolea Albero A, Hellriegel J, Krull R. Recent advances in mechanical characterisation of biofilm and their significance for material modelling. Crit Rev Biotechnol 2012; 33:145-71. [DOI: 10.3109/07388551.2012.679250] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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13
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Zong Y, Yang X, Dai G. Design Simulation of Glass-Fiber-Loaded Flow in an Internally Spout-Fluidized Bed for Processing of Thermoplastic Composites. I. Flow Characterization. Ind Eng Chem Res 2011. [DOI: 10.1021/ie102509z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Yuan Zong
- State Key Laboratory of Chemical Engineering, East China University of Science and Technology, Shanghai 200237, China
| | - Xiaogang Yang
- Institute of Arts, Science and Technology, Glyndŵr University, Wrexham LL11 2AW, United Kingdom
| | - Gance Dai
- State Key Laboratory of Chemical Engineering, East China University of Science and Technology, Shanghai 200237, China
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14
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Frappier G, Lartiges BS, Skali-Lami S. Floc cohesive force in reversible aggregation: a Couette laminar flow investigation. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:10475-10488. [PMID: 20515055 DOI: 10.1021/la9046947] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
A simple theoretical model is proposed to describe the limiting size of aggregates attained at steady state under given shear conditions. The stable size is assumed to be the result of a dynamic equilibrium between simultaneous aggregate growth and breakup that are represented as first-order processes. The theory establishes that the evolution of steady-state aggregate size versus shear rate is written as the sum of two exponential laws. The validity of the model is verified by direct observation of the coagulation behavior of latex particles in the stagnant plane of a counter-rotating Couette reactor. The influence of latex elementary particle size, initial particle volume fraction, and inner gap spacing of Couette reactor, are investigated. In all cases, the model shows good agreement with the experimental results. Aggregate growth proceeds with a monomodal size distribution that exhibits a scaling behavior. Such monomodal distribution evolves toward broad and even bimodal steady-state distributions at both low and high shear rates, whereas a narrow monomodal pattern is observed at intermediate shear gradients. The aggregate cohesive force F(C) can be calculated from the critical shear rate of dislocation defined by the model. In contrast to the broadly accepted view that larger flocs should be more fragile than smaller aggregates, we find that F(C) scales as D(3/2) where D is the aggregate characteristic diameter. The latter relationship may be derived by assuming linear elasticity of aggregates.
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Affiliation(s)
- G Frappier
- Nancy University-LEM-ENSG/INPL-CNRS, BP 40 54501 Vandoeuvre Cedex, France
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15
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Colbert MJ, Raegen AN, Fradin C, Dalnoki-Veress K. Adhesion and membrane tension of single vesicles and living cells using a micropipette-based technique. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2009; 30:117-121. [PMID: 19777278 DOI: 10.1140/epje/i2009-10514-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2009] [Accepted: 07/25/2009] [Indexed: 05/28/2023]
Abstract
The fundamental study of the adhesion of cells to each other or to a substrate is a key research topic in cellular biophysics because cell adhesion is important to many biological processes. We report on the adhesion of a model cell, a liposome, and a living HeLa cell to a substrate measured with a novel experimental technique. The cells are held at the end of a micropipette mounted on a micromanipulator and brought into contact with a surface. The adhesion energy and membrane tension are measured directly using the deflection of the micropipette when binding or unbinding the cell from the substrate. Since the force applied on the cells is known throughout the experiment, the technique presented enables the measurement of dynamics such as changes in the adhesion, elasticity, and membrane tension with time.
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Affiliation(s)
- M-J Colbert
- Department of Physics & Astronomy and the Brockhouse Institute for Materials Research, McMaster University, Hamilton, ON, Canada
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16
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Jarvis P, Parsons SA, Henderson R, Nixson N, Jefferson B. The Practical Application of Fractal Dimension in Water Treatment Practice–the Impact of Polymer Dosing. SEP SCI TECHNOL 2008. [DOI: 10.1080/01496390801974506] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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17
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Zeidan M, Xu BH, Jia X, Williams RA. Simulation of Aggregate Deformation and Breakup in Simple Shear Flows using a Combined Continuum and Discrete Model. Chem Eng Res Des 2007. [DOI: 10.1205/cherd06149] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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18
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Zeidan M, Xu B, Jia X, Williams R. Simulation of Aggregate Deformation and Breakup in Simple Shear Flows Using a Combined Continuum and Discrete Model. Chem Eng Res Des 2007. [DOI: 10.1016/s0263-8762(07)73208-2] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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19
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Gray S, Ritchie C. Effect of organic polyelectrolyte characteristics on floc strength. Colloids Surf A Physicochem Eng Asp 2006. [DOI: 10.1016/j.colsurfa.2005.08.020] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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20
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McFarlane A, Bremmell K, Addai-Mensah J. Improved dewatering behavior of clay minerals dispersions via interfacial chemistry and particle interactions optimization. J Colloid Interface Sci 2006; 293:116-27. [PMID: 16038921 DOI: 10.1016/j.jcis.2005.06.034] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2005] [Revised: 06/04/2005] [Accepted: 06/11/2005] [Indexed: 11/17/2022]
Abstract
Orthokinetic flocculation of clay dispersions at pH 7.5 and 22 degrees C has been investigated to determine the influence of interfacial chemistry and shear on dewatering and particle interactions behavior. Modification of pulp chemistry and behavior was achieved by using kaolinite and Na-exchanged (swelling) smectite clay minerals, divalent metal ions (Ca(II), Mn(II)) as coagulants and anionic polyacrylamide copolymer (PAM A) and non-ionic polyacrylamide homopolymer (PAM N) as flocculants. The pivotal role of shear, provided by a two-blade paddle impeller, was probed as a function of agitation rate (100-500 rpm) and time (15/60 s). Particle zeta potential and adsorption isotherms were measured to quantify the interfacial chemistry, whilst rheology and cryogenic SEM were used to investigate particle interactions and floc structure and aggregate network, respectively. Osmotic swelling, accompanied by the formation of "honeycomb" particle network structure and high yield stress, was produced by the Na-exchanged smectite, but not kaolinite, dispersions. Dispersion of the clay particles in 0.05 M Ca(II) or Mn(II) solution led to a marked reduction in particle zeta potential, complete suppression of swelling, honeycomb network structure collapse and a concomitant reduction in shear yield stress of smectite pulps. Optimum conditions for improved, orthokinetic flocculation performance of negatively charged clay particles, reflecting faster settling flocs comprised (i) coagulation, (ii) moderate agitation rate, (iii) shorter agitation time, and (iv) anionic rather than non-ionic PAM. The optimum dewatering rates were significantly higher than those produced by standard, manual-mixing flocculation techniques (plunging and cylinder inversion) commonly used in industry for flocculant trials. The optimum flocculation conditions did not, however, have a significant impact on the final sediment solid content of 20-22 wt%. Further application of shear to pre-sedimented pulps improved consolidation by 5-7 wt% solid. Higher shear yield stresses and greater settling rates were displayed by PAM A based than PAM N based pulps and this is attributed to the former's more expanded interfacial conformation and greater clay particles bridging ability. It appears that the intrinsic clay particles' physico-chemical properties and interactions limit compact pulp consolidation.
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Affiliation(s)
- Angus McFarlane
- Ian Wark Research Institute, University of South Australia, Mawson Lakes, Adelaide, SA 5095, Australia
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21
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Blanco A, Negro C, Fuente E, Tijero J. Effect of Shearing Forces and Flocculant Overdose on Filler Flocculation Mechanisms and Floc Properties. Ind Eng Chem Res 2005. [DOI: 10.1021/ie050870v] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Angeles Blanco
- Department of Chemical Engineering, Faculty of Chemistry, Complutense University of Madrid, Avda Complutense S/N, 28040 Madrid, Spain
| | - Carlos Negro
- Department of Chemical Engineering, Faculty of Chemistry, Complutense University of Madrid, Avda Complutense S/N, 28040 Madrid, Spain
| | - Elena Fuente
- Department of Chemical Engineering, Faculty of Chemistry, Complutense University of Madrid, Avda Complutense S/N, 28040 Madrid, Spain
| | - Julio Tijero
- Department of Chemical Engineering, Faculty of Chemistry, Complutense University of Madrid, Avda Complutense S/N, 28040 Madrid, Spain
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22
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Jarvis P, Jefferson B, Gregory J, Parsons SA. A review of floc strength and breakage. WATER RESEARCH 2005; 39:3121-37. [PMID: 16000210 DOI: 10.1016/j.watres.2005.05.022] [Citation(s) in RCA: 312] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2004] [Revised: 05/06/2005] [Accepted: 05/18/2005] [Indexed: 05/03/2023]
Abstract
The main focus of the paper is to review current understanding of floc structure and strength. This has been done by reviewing current theoretical understanding of floc growth and breakage and an analysis of different techniques used for measuring floc strength. An overview has also been made of the general trends seen in floc strength analysis. The rate of floc formation is a balance between breakage and aggregation with flocs eventually reaching a steady-state size for a given shear rate. The steady-state floc size for a particular shear rate can, therefore, be a good indicator of floc strength. This has resulted in the development of a range of techniques to measure floc size at different applied shear levels using a combination of one or more of the following tools: light scattering and transmission; microscopy; photography; video and image analysis software. Floc strength may be simply quantified using the initial floc size for a given shear rate and the floc strength factor. More complex techniques have used theoretical modelling to determine whether flocs break by large-scale fragmentation or smaller-scale surface erosion effects, although this interpretation is open to debate. Impeller-based mixing, ultrasound and vibrating columns have all been used to provide a uniform, accurate and controllable dissipation of energy onto a floc suspension to determine floc strength. Other more recent techniques have used sensitive micromanipulators to measure the force required to break or compress individual flocs, although these techniques have been limited to the measurement of only a few hundred flocs. General trends emerge showing that smaller flocs tend to have greater strength than larger flocs, whilst the use of polymer seems to give increased strength to only some types of floc. Finally, a comparison of the strength of different types of floc (activated sludge flocs, organic matter flocs, sweep flocs and charge neutralised flocs) has been made highlighting differences in relative floc strength.
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Affiliation(s)
- P Jarvis
- School of Water Sciences, Cranfield University, Cranfield, Bedfordshire MK40 0AL, UK
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23
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Lu C, Pelton R. Flocculation with poly(ethylene oxide)/tyrosine-rich polypeptide complexes. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2005; 21:3765-3772. [PMID: 15835935 DOI: 10.1021/la047519j] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
New insights into the mechanism for the flocculation of aqueous colloids by the sequential addition of a water-borne phenolic polymer, called cofactor, followed by very high molecular poly(ethylene oxide) (PEO) are presented. It is proposed that PEO/cofactor complexes form in the aqueous phase and adsorb onto the surfaces of the target colloidal particles. Flocculation will occur if PEO/cofactor complex on one particle will bind to adsorbed complex on a second particle; i.e., if the complexes are sticky. The proposed mechanism was illustrated by flocculation experiments with precipitated calcium carbonate, very high molecular weight PEO, and a polypeptide cofactor called PEY1 which was a 1:1 random copolymer of l-glycine and l-tyrosine. Independent measurements of the PEO/PEY1 complex properties, in the absence of calcium carbonate, were used to support the mechanism. In order for PEO/PEY1 complexes to be sticky, they must simultaneously have unbound PEY1 and polymer segments. With time the complexes deactivate (i.e., lose their stickiness) by a reconfiguration process which results in elimination of either unbound PEY1 or PEO segments.
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Affiliation(s)
- Chen Lu
- Department of Chemical Engineering, McMaster University, 307-1710 Main Street West, Hamilton, Ontario L8S 1G6, Canada
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24
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Carissimi E, Rubio J. The flocs generator reactor-FGR: a new basis for flocculation and solid–liquid separation. ACTA ACUST UNITED AC 2005. [DOI: 10.1016/j.minpro.2004.08.021] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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25
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Rahmani NH, Dabros T, Masliyah JH. Evolution of asphaltene floc size distribution in organic solvents under shear. Chem Eng Sci 2004. [DOI: 10.1016/j.ces.2003.10.017] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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26
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Hopkins DC, Ducoste JJ. Characterizing flocculation under heterogeneous turbulence. J Colloid Interface Sci 2003; 264:184-94. [PMID: 12885534 DOI: 10.1016/s0021-9797(03)00446-6] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
This study investigated the impact of turbulent heterogeneity in a flocculation reactor on particle aggregation and breakup. In particular, the influence of average characteristic velocity gradient (G), particle concentration, and coagulation mechanism (sweep floc vs charge neutralization) on the floc growth, steady-state size, and variance was analyzed. Experiments were performed in a bench-scale reactor with a low-shear axial-flow impeller using a photometric dispersion analyzer (PDA). Results indicated that as G increased, floc growth increased while the mean size and variance in the floc size distribution decreased. In addition, floc growth, mean size, and variance increased with increasing primary particle concentration and when the coagulation mechanism was switched from charge neutralization to sweep floc. Lastly, floc growth, mean size, and variance were found to vary spatially in the reactor at low G values with larger floc size and growth rate in the bulk region and a larger variance in the impeller discharge region.
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Affiliation(s)
- D Cory Hopkins
- Department of Civil Engineering, North Carolina State University, 208 Mann Hall, Raleigh, NC 27695-7908, USA
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Maes A, Vreysen S, Rulyov NN. Effect of various parameters on the ultraflocculation of fine sorbent particles, used in the wastewater purification from organic contaminants. WATER RESEARCH 2003; 37:2090-2096. [PMID: 12691894 DOI: 10.1016/s0043-1354(02)00551-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
A sorbent (Organosorb) is used in the wastewater purification from organic contaminants, here simulated by tetradecane. A short hydrodynamic treatment in a rather intense hydrodynamic field (G>10(3)) (called ultraflocculation) is applied to the sorbent suspension to which a flocculant is added. The efficiency of removal of the sorbent is studied. The sorbent concentration, the flocculant concentration, the treatment time, the organic pollutant (which has to be sorbed by the sorbent), the detergent (used for the emulsification of the pollutant), the pH and the calcium concentration of the water all influence the flocculation efficiency (E) of the sorbent particles. For each set of these parameters there exists an optimum intensity of the hydrodynamic treatment at which maximum flocculation efficiency is reached. An increase in the optimum intensity of the hydrodynamic field corresponds to an increased floc break-up, and consequently a lower maximum flocculation efficiency.
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Affiliation(s)
- André Maes
- Laboratory of Colloidchemistry, Katholieke Universiteit Leuven, Kasteelpark Arenberg 23, 3001 Heverlee, Belgium.
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Yeung A, Dabros T, Masliyah J, Czarnecki J. Micropipette: a new technique in emulsion research. Colloids Surf A Physicochem Eng Asp 2000. [DOI: 10.1016/s0927-7757(00)00509-4] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Gibbs A, Pelton R, Cong R. The influence of dextran derivatives on polyethylene oxide and polyacrylamide-induced calcium carbonate flocculation and floc strength. Colloids Surf A Physicochem Eng Asp 1999. [DOI: 10.1016/s0927-7757(99)00160-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Goto S, Pelton R. The influence of phenolic cofactors on the properties of calcium carbonate flocs formed with PEO. Colloids Surf A Physicochem Eng Asp 1999. [DOI: 10.1016/s0927-7757(98)00780-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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