Biological additives for improved mechanical dewatering of fuel-grade peat

Cooper, David G.; Pillon, D. W.; Mulligan, Catherine N.; Sheppard, John D.

doi:10.1016/0016-2361(86)90016-5

Cited by 16 publications

(10 citation statements)

References 8 publications

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“…Surfactin has been shown to produce ion-selective channels in arti®cial lipid membranes 17 and can free water that is bound by an organic colloid such as peat. 18 The mechanism of action of the surfactants on enzyme yield in this system has not been determined. However, since both the synthetic and biosurfactants produce positive effects, it can be surmised that the mechanism is related to an interfacial phenomenon occurring between the microbial cells and the starch substrate.…”

Section: Resultsmentioning

confidence: 98%

Effect of surfactants on α-amylase production in a solid substrate fermentation process

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Sheppard

1999

J. Chem. Technol. Biotechnol.

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Solid substrate fermentation (SSF) is a process where the substrate is a moist solid, which is insoluble in water but not suspended in water. In this study SSF of Bacillus subtilis (ATCC 21556) was used to produce an enzyme of commercial importance, a-amylase, using as a substrate potato peel. To enhance the production of this enzyme, two nonionic synthetic surfactants were used, Tween 80 and Tween 20, one anionic surfactant, SDS at concentrations of 0.05% and 0.10% (v/w) and a biosurfactant produced by Bacillus subtilis (ATCC 21332), known as surfactin, at concentrations of 0.003%, 0.007%, 0.013% and 0.03% (w/w). The results have shown that surfactants signi®cantly increase the production of a-amylase. Tween 80 at 0.10% and surfactin at 0.013% provided the highest enzyme activity when compared with the control.

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Section: Resultsmentioning

confidence: 98%

Effect of surfactants on α-amylase production in a solid substrate fermentation process

Goes

Sheppard

1999

J. Chem. Technol. Biotechnol.

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“…By a reduction of the electrostatic interactions, the suspended particles adhere to the peat matrix and thus a much increased permeability results. The electrostatic interactions can be modified, mainly by changing the pH [1][2][3][4][5][6] or by adding ionic surfactant [1,5,6,[8][9][10][11], polymer [1][2][3][4][5]12] and/or inorganic electrolyte [13][14][15]. Besides the compressibility and permeability studies, the mechanism is supported by changes in turbidity observed on adding metal ions of different valency and on changing the pH [4].…”

Section: Resultsmentioning

confidence: 99%

“…In order to better master peat dewatering *) Dedicated to Professor Dr. Dr. h. c. Armin Weiss on the occasion of his 60th birthday. GL 330 by a number of techniques it seems very important to understand the colloidal properties of peat and how these can be modified [1][2][3][4][5][6]. With this as a starting point we have chosen to investigate different physicochemical properties of peat and how they are modified by chemical additives.…”

Section: Introductionmentioning

confidence: 99%

Surface and colloid chemistry of peat and peat dewatering. Electrostatic effects

Andreasson

Jönsson²,

Lindman³

1988

Colloid & Polymer Sci

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A study of the potentiometric titration and metal ion binding properties of peat is reported. Peat is found to behave as a typical polyelectrolyte system which, especially at high pH's, can be very highly charged. One difference between peat and commonly investigated polyelectrolyte systems (like poly(acrylate)) is that a very broad spectrum of pKa values is required for the description of the titration characteristics of peat. The prime reason for this is assigned to the presence of humic acids, formed during decomposition of plant parts. The humic acids constitute a rather badly defined group of polyelectrolytes built up inter alia of carboxylic, phenolic and sugar groups. The presence of different length segments of conjugated double bonds provides conditions for light absorption at a broad range of wave-lengths, hence the black or brown colour of these compounds, as well as the stabilisation of resonance structures including carboxylate and phenolate groups. Because of large differences in double-bond segment lengths, a broad range of pKa values results.For the analysis of potentiometric titrations, a theoretical model is developed which has the following characteristics:1. The titratable groups are assumed to be evenly distributed on the peat surfaces. 2. The surfaces are assumed to be planar and no consideration of curvature effects is made.3. Only monovalent and divalent counterions and monovalent colons are assumed to be present in the aqueous medium.4. Counterions can bind to peat electrostatically in the counterion layer as well as specifically to different groups on the peat surface.5. The electrostatic potential on the surface is calculated using the Poisson-Boltzmann equation.By means of this theoretical model, a very good description of the titration characteristics of peat is obtained if peat is assumed to contain titratable surfaces with a continuous spectrum of pKa values in the interval 1-11.

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“…The cations with large organic portions, including surfactants, have an augmented adsorption to the particle surface because of the hydrophobic effect. The amount of water removed in the pressing stage is paramount to the efficiency of the process and may be enhanced by chemically or thermally pretreating the peat before pressing (Cooper et al, 1985(Cooper et al, , 1986Glass et al, 1987;Ayub and Sheppard, 1986). Protons are very effective because they can actually neutralize the net charge on the particle surface by forming covalent bonds with the acid functions.…”

mentioning

confidence: 99%

“…charged additives to peat, heat pretreatment of peat. The amount of water removed in the pressing stage is paramount to the efficiency of the process and may be enhanced by chemically or thermally pretreating the peat before pressing (Cooper et al, 1985(Cooper et al, , 1986Glass et al, 1987;Ayub and Sheppard, 1986). However, there is 89-95% water in crude peat which presents a large obstacle in the development and commercialization of peat as an energy source (Bettinger, 1983;Gallo et al, 1981).…”

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confidence: 99%

The effect of charged additives and heat pretreatment on the dewatering of fuel‐grade peat

1988

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The addition of salt, mineral acid or polyelectrolyte or the preheating of fuel-grade peat results in significant improvement of the amount of water released during mechanical pressing.The charged species all act by suppressing the charge on the colloidal particles and, for different reasons, organic salts, protons and polyelectrolytes are all more effective than simple inorganic salts. The cations with large organic portions, including surfactants, have an augmented adsorption to the particle surface because of the hydrophobic effect. The polyelectrolytes are strongly associated with the particles because of the chelate effect. Protons are very effective because they can actually neutralize the net charge on the particle surface by forming covalent bonds with the acid functions.The mechanism by which heat pretreatment improves dewatering is not caused by suppression of the surface charge. The effect could be due to melting or softening of peat waxes causing alterations of surface features which improve water release. It is also possible that heating provides sufficient energy to overcome the energy barrier keeping the particles apart. L'addition de sel, d'acide mineral ou de polyklectrolyte, ou le prkchauffement de tourbe combustible permettent une amelioration importante de la quantite d'eau libCree au cours du pressage mkcanique.Toutes les esp2ces chargees agissent en supprimant la charge sur les particules colloidales et, pour diffkrentes raisons, les sels organiques les protons et les polyelectrolytes sont tous plus efficaces que les sels inorganiques simples. Les cations avec de larges portions organiques, y compris les surfactants, ont une adsorption augmentee la surface en raison de I'effet hydrophobe. Les polyelectrolytes sont fortement associes aux particules en raison de I'effet chelate. Les protons sont plus efficaces du fait qu'ils peuvent effectivement neutraliser la charge nette sur la surface des particules en formant des liaisons covalentes avec les fonctions acides.Le mecanisme par lequel le pretraitement a la chaleur amkliore la deshydratation n'est pas cause par la suppression de la charge de surface. Cet effet pourrait &tre dfi la fusion ou au ramollissement des cires de tourbe causant des alterations des caracteristiques de surface qui amiliorent la liberation de I'eau. I1 est Cgalement possible que le Cchauffenient fournisse suffisamment d'energie pour depasser la barrikre d'energie gardant les particules a I'ecart.Keywords: peat dewatering. charged additives to peat, heat pretreatment of peat. eat is geologically considered as a young fossil fuel, the P first step in the formation of coal (Tibbetts, 1981; Farnham, 1981). However, there is 89-95% water in crude peat which presents a large obstacle in the development and commercialization of peat as an energy source (Bettinger, 1983;Gallo et al., 1981). The use of peat as fuel requires a reduction of the moisture content to at least 50% due to the considerable energy that would otherwise be expended in vapourization of water (Punwani, 198...

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Biological additives for improved mechanical dewatering of fuel-grade peat

Cited by 16 publications

References 8 publications

Effect of surfactants on α-amylase production in a solid substrate fermentation process

Effect of surfactants on α-amylase production in a solid substrate fermentation process

Surface and colloid chemistry of peat and peat dewatering. Electrostatic effects

The effect of charged additives and heat pretreatment on the dewatering of fuel‐grade peat

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