Simultaneous sulfate reduction and metal precipitation in an inverse fluidized bed reactor
Villa Gomez, D.K. - \ 2013
Wageningen University. Promotor(en): Piet Lens, co-promotor(en): Karel Keesman. - [S.l.] : S.n. - ISBN 9789461737410 - 194
wervelbedden - uitrusting - sulfaatreductie - chemische precipitatie - metalen - fluidized beds - equipment - sulfate reduction - chemical precipitation - metals
On-line estimation of the dissolved zinc concentration during ZnS precipitation in a continuous stirred tank reactor (CSTR)
Grootscholten, T.I.M. ; Keesman, K.J. ; Lens, P.N.L. - \ 2008
Water Science and Technology 57 (2008)10. - ISSN 0273-1223 - p. 1627 - 1633.
oppervlaktewater - afvalwaterbehandeling - zware metalen - zink - chemische precipitatie - verwijdering - sulfiden - selectiviteit - waterzuivering - surface water - waste water treatment - heavy metals - zinc - chemical precipitation - removal - sulfides - selectivity - water treatment - metals
In this paper a method is presented to estimate the reaction term of zinc sulphide precipitation and the zinc concentration in a CSTR, using the read-out signal of a sulphide selective electrode. The reaction between zinc and sulphide is described by a non-linear model and therefore classical observer theory cannot be applied directly, as this theory was initially developed for linear systems. However, by linear reparametrization of this non-linear system, the linear observer theory can be applied in an effective way. This is illustrated by a zinc sulphide example using real data.
Innovative developments in the selective removal and reuse of heavy metals from wastewaters
Veeken, A.H.M. ; Rulkens, W.H. - \ 2003
Water Science and Technology 47 (2003)10. - ISSN 0273-1223 - p. 9 - 16.
zware metalen - afvalwaterbehandeling - waterzuivering - chemische precipitatie - verwijdering - sulfiden - afvalwater - selectiviteit - heavy metals - waste water treatment - water treatment - chemical precipitation - removal - sulfides - waste water - selectivity - solubility
Sulphide precipitation of heavy metal containing wastewaters results in low effluent concentrations. However, sulphide precipitation is not widely applied in practice because the dosing of sulphide cannot adequately be controlled. A new process was developed where the combination of a sulphide-selective electrode (pS-electrode) and pH electrode controls the sulphide addition. Precipitation experiments were performed on a laboratory-scale in batch and continuous reactor systems with synthetic wastewaters containing Cd, Cu, Ni, Pb or Zn
Sulphide precipitation of heavy metal containing wastewaters results in low effluent concentrations. However, sulphide precipitation is not widely applied in practice because the dosing of sulphide cannot adequately be controlled. A new process was developed where the combination of a sulphide-selective electrode (pS-electrode) and pH electrode controls the sulphide addition. Precipitation experiments were performed on a laboratory-scale in batch and continuous reactor systems with synthetic wastewaters containing Cd, Cu, Ni, Pb or Zn. The response of the pS-electrode during precipitation was unique for each heavy metal and was directly related to the solubility product of the corresponding metal sulphide. The metals were removed to levels
Control of the sulfide (S2-) concentration for optimal zinc removal by sulfide precipitation in a continuously stirred tank reactor
Veeken, A.H.M. ; Akoto, L. ; Pol, L.W.H. ; Weijma, J. - \ 2003
Water Research 37 (2003)15. - ISSN 0043-1354 - p. 3709 - 3717.
afvalwaterbehandeling - zink - verwijdering - chemische precipitatie - sulfiden - sulfaat reducerende bacteriën - waste water treatment - zinc - removal - chemical precipitation - sulfides - sulfate reducing bacteria - sulfate-reducing bacteria - crystal precipitation - particle formation - sphalerite zns - solubility - mechanism
Precipitation of Zn2+ with S2− was studied at room temperature in a continuously stirred tank reactor of 0.5 l to which solutions of ZnSO4 (800–5800 mg Zn2+/l) and Na2S were supplied. The pH was controlled at 6.5 and S2− concentration in the reactor was controlled at set point values ranging from 3.2x10−19 to 3.2x10−4 mg l−1, making use of an ion-selective S2− electrode
Precipitation of Zn2+ with S2- was studied at room temperature in a continuously stirred tank reactor of 0.51 to which solutions of ZnSO4 (800-5800 mg(-1) Zn2+) and Na2S were supplied. The pH was controlled at 6.5 and S2- concentration in the reactor was controlled at set point values ranging from 3.2 x 10(-19) to 3.2 x 10(-4) mg l(-1), making use of an ion-selective S2- electrode. In steady state, the mean particle size of the ZnS precipitate decreased linearly from 22 to 1 mum for S2- levels dropping from 3.2 x 10(-4) to 3.2 x 10(-18) mg l(-1). At 3.2 x 10(-11) Mg l(-1) of S2-, the supplies of ZnSO4 and Na2S solutions were stoichiometric for ZnS precipitation. At this S2- level, removal of dissolved zinc was optimal with effluent zinc concentration <0.03 mg l(-1) while ZnS particles formed with a mean geometric diameter of about 10 mum. Below 3.2 x 10(-11) mg l(-1) of S2- insufficient sulfide was added for complete zinc precipitation. At S2- levels higher than 3.2 x 10(-11) mg l(-1) the effluent zinc concentration increased due to the formation of soluble zinc sulfide complexes as confirmed by chemical equilibrium model calculations. (C) 2003 Elsevier Science Ltd. All rights reserved.
Physico-chemical and functional properties of potato proteins
Koningsveld, G.A. van - \ 2001
Wageningen University. Promotor(en): P. Walstra; A.G.J. Voragen; M.A.J.S. van Boekel; H. Gruppen. - S.l. : S.n. - ISBN 9789058084446 - 147
aardappelen - aardappeleiwit - chemische precipitatie - oplosbaarheid - chemische structuur - schuimen - emulgering - potatoes - potato protein - chemical precipitation - solubility - chemical structure - foaming - emulsification
Key words: potato proteins, patatin, protease inhibitors, solubility, structure, pH, temperature, ethanol, ionic strength, phenolic compounds, foams, emulsions
In potato starch manufacture an aqueous byproduct remains that is called potato fruit juice (PFJ). On a dry matter basis PFJ contains about 20-25 % protein and amino acids, 15 % sugars, 20 % minerals, 14 % organic acids and other components, such as phenolic compounds. Potato protein has a relatively high nutritional quality, comparable to that of whole egg, and it therefore has high potential for utilization in food applications. Protein recovery from industrial PFJ is presently achieved through heat coagulation by steam injection after pH adjustment. This method is very efficient in removing protein from solution. However, it leads to protein precipitates that exhibit a poor solubility, which hampers potential food applications.
An economic method to efficiently recover soluble potato protein would considerably increase its possibilities for use in food and add to its commercial value. Therefore, the important question resulting in this study was: can potato proteins be recovered from PFJ in such a way that they retain their functional properties, most importantly their solubility? This recovery method should be applicable at a large scale and result in a high yield. Potato protein recovery was expected to be complicated by the presence of and the interactions with non-protein components in PFJ. The objective in this study was to examine how extrinsic factors like pH, ionic strength and temperature would influence the structure of potato proteins, this in relation to the functionality of the proteins in making and stabilizing foams and emulsions.
Three groups of potato proteins can be distinguished in PFJ. Patatin, the major potato tuber protein, comprises 38 % of the protein in PFJ from cultivar Elkana . The protease inhibitors make up about 50 % and other proteins up to 12 % of total protein in PFJ from cultivar Elkana .
In Chapter 2 the effects of pH and various additives on the precipitation and (re)solubility at pH 7 of potato proteins from industrial PFJ are studied. Addition of various strong and weak acids caused the same extent of protein precipitation, which comprised at the most 60 % of total protein at pH 3. The use of weak acids, however, resulted in an increase in the resolubility of the precipitates at pH 7, as compared to strong acids. At pH 5 addition of FeCl 3 or ZnCl 2 increased both precipitation and resolubility. The largest increase in precipitation and resolubility was achieved by using organic solvents, resulting in a maximum precipitation (pH 5) of 91 % of total protein and a maximum resolubility of 91 % of precipitated protein. The results described in Chapter 2 lead to the hypothesis that precipitation and resolubilization of potato proteins from PFJ is not so much determined by their isoelectric pH but by their interactions with low molecular weight components.
In Chapter 3 it was shown, using DSC and both far-UV and near-UV CD spectroscopy, that potato proteins unfold between 55°C and 75°C. Increasing the ionic strength from 15 to 200 mM generally caused an increase in denaturation temperature. It was concluded that the dimeric protein patatin unfolds either in its monomeric state or that its monomers are loosely associated and unfold independently. Thermal unfolding of the protease inhibitors was correlated with a decrease in protease inhibitor activities and resulted in an ionic strength dependent loss of protein solubility. Potato proteins were best soluble at neutral and strongly acidic pH. At mildly acidic pH the overall potato protein solubility was dependent on ionic strength and the presence of unfolded patatin.
In Chapter 4 a protein isolate with a high solubility at neutral pH prepared from industrial PFJ by precipitation at pH 5 in the presence of ethanol is described. The effects of ethanol itself and the effects of its presence during precipitation on the properties of various potato protein fractions were examined. The presence of ethanol significantly reduced the denaturation temperature of potato proteins, indicating that preparation of this potato protein isolate should be done at low temperature to retain a high solubility. In the presence of ethanol the thermal unfolding of the tertiary and the secondary structure of patatin were shown to be almost completely decoupled. Even at 4°C precipitation of potato proteins in the presence of ethanol induced significant conformational changes. These changes did, however, only result in minor changes in the solubility of the potato protein preparations.
In Chapter 5 foam forming and stabilizing properties of potato proteins are described; whipping or sparging was used to make foam. The performed whipping tests showed that less foam could be formed from untreated patatin than from the protease inhibitors, but also that patatin foam was much more stable against coalescence, Ostwald ripening and drainage. The foam forming properties of patatin could be strongly improved by partial unfolding of the protein. Whipping tests, at both low (0.5 mg/ml) and high (10 mg/ml) protein concentrations, also indicated that foams made with an ethanol precipitated protein isolate (PPI) were more stable against Ostwald ripening and drainage than those made withβ-casein andβ-lactoglobulin. More generally it was concluded that when proteins are used as a foaming agent, a high concentration is required, because the available protein is inefficiently used. Also, the different methods used to make foam, result in changes in the mutual differences in foaming properties between the various protein preparations and may induce different instabilities to become apparent in foams made at the same conditions.
In Chapter 6 emulsions made with various potato protein preparations were characterized with respect to average droplet size, plateau surface excess and the occurrence of droplet aggregation. The average droplet size of the emulsions made with potato proteins appeared to be determined by the lipolytic release of surface active fatty acids and monoglycerides from the tricaprylin oil phase during the emulsification process. It was concluded that only trace amounts of patatin, the lipase activity of which has been strongly underestimated in literature, sufficed to liberate significant amounts of these surfactants. The plateau surface excess of emulsions made with patatin was found to be 2.6 mg/m 2 , while emulsion droplets made with protease inhibitors showed a significantly smaller surface excess. Of the various solvent conditions and treatments applied only heat treatment resulted in a significant increase in surface excess. Droplet aggregation in emulsions made with potato protein preparations other than patatin, could in contrast to at pH 5 and at pH 7 be prevented at pH 3.
In Chapter 7 the relations between potato protein structure, solubility and foam and emulsion forming and stabilizing properties are discussed. Also, the different mechanisms by which phenolic compounds may affect protein solubility are discussed in relation to the solubility and resolubility behavior of potato proteins in PFJ and when separated. A summary of the most important differences in the properties of patatin and protease inhibitors is also given.
Impact of location of CaCO3 precipitation on the development of intact anaerobic sludge
Langerak, E.P.A. van; Ramaekers, H. ; Wiechers, J. ; Veeken, A.H.M. ; Hamelers, H.V.M. ; Lettinga, G. - \ 2000
Water Research 34 (2000)2. - ISSN 0043-1354 - p. 437 - 446.
afvalwaterbehandeling - anaërobe behandeling - calciumcarbonaat - chemische precipitatie - biofilms - modellen - slib - waste water treatment - anaerobic treatment - calcium carbonate - chemical precipitation - biofilms - models - sludges
The development of intact anaerobic granular sludge was studied in UASB reactors under varying conditions of CaCO3 precipitation and biomass yield. Varying precipitating quantities were obtained using different calcium concentrations in the influent and different biomass yields were obtained by feeding with completely or partly acidified substrate. Four reactors were operated at a constant organic loading rate of 13
Control of calcium carbonate precipitation in anaerobic reactors
Langerak, E.P.A. van - \ 1998
Agricultural University. Promotor(en): G. Lettinga. - S.l. : Van Langerak - ISBN 9789054859239 - 112
anaërobe behandeling - afvalwater - calcium - calciumcarbonaat - neerslag - anaërobe omstandigheden - chemische precipitatie - rioolslib - biomassa - fosfaat - kristallisatie - anaerobic treatment - waste water - calcium - calcium carbonate - precipitation - anaerobic conditions - chemical precipitation - sewage sludge - biomass - phosphate - crystallization
Anaerobic treatment of waste waters with a high calcium content may lead to excessive precipitation of calcium carbonate. So far, no proper methods were available to predict or reduce the extent of precipitation in an anaerobic treatment system. Moreover, it also was not clear to what extent precipitation in an anaerobic reactor can be tolerated because adequate knowledge on the structure and quality of methanogenic sludges with high calcium carbonate content was lacking. In this thesis, the feasibility of anaerobic treatment of waste waters with a high calcium content was investigated.
The development of high ash content anaerobic sludges was studied under varying conditions of biomass yield, precipitating quantities of CaCO 3 and particle size of the seed sludge. The location of CaCO 3 precipitation, within the aggregates or in the bulk solution, appeared to be an important factor determining the quality of high ash content sludges. Precipitation in the bulk solution is considered as favourable for the development of these sludges and can in example be stimulated by seeding with the smallest possible granules or by maintaining the phosphate concentration as low as possible. Operating a reactor containing heavy sludge is often problematical because the crystals will tend to agglomerate, resulting in cementation of the sludge bed. This cementation can be retarded by decreasing the degree of pre-acidification.
Two different options can be distinguished to reduce the extent of calcium carbonate precipitation in an anaerobic reactor. It was found that phosphate, in concentrations of 0.5 - 5 mgP.l -1, can drastically reduce the quantity of calcium carbonate precipitation. Additives that only inhibit the formation of calcite and not that of aragonite (e.g. iron) are not suitable, because in that case aragonite, of which the solubility is only slightly lower than of calcite, will accumulate in the reactor. The second option is to remove calcium from the influent in a crystallization reactor reusing the anaerobic effluent alkalinity.
The amount of calcium carbonate precipitation in an anaerobic reactor can be estimated with equilibrium models as developed in this dissertation, which take into account kinetic factors that influence the apparent solubility of calcium carbonate, being the influent composition, the hydraulic retention time and the value of the crystallization rate constant.
In this dissertation, insights have been provided for the design and application of integrated anaerobic-physical-chemical technologies which enable the control of the calcium carbonate precipitation in the anaerobic treatment of waste water with a high calcium content, which appear e.g. in the waste-paper and food processing industries.
Mest indikken met zonne-energie
Wagenberg, V. van; Hendriks, J. - \ 1996
Praktijkonderzoek varkenshouderij 10 (1996)4. - ISSN 1382-0346 - p. 20 - 22.
rundveedrijfmest - chemische precipitatie - energie - vloeibare meststoffen - mest - varkens - straling - zonne-energie - opslagloodsen - mestoverschotten - mestverwerking - cattle slurry - chemical precipitation - energy - liquid manures - manures - pigs - radiation - solar energy - stores - manure surpluses - manure treatment
Om mestafzetkosten te verlagen kan de mest op het varkensbedrijf ingedikt worden. Mestsilo's kunnen hiertoe voorzien worden van een zonlichtdoorlatende afdekking. Hierbij wordt de verdamping gestimuleerd.
|CORRELACI : identification of traditional and air pollution related stress factors in a douglas fir ecosystem : the aciforn stands : a correlative evaluation of monitoring data on the carbon, nutrient and water cycles
Evers, P.W. ; Bouten, W. ; Grinsven, J.J.M. van - \ 1991
Wageningen : De Dorschkamp (Rapport / De Dorschkamp Research Institute for Forestry and Urban Ecology nr. 623) - 202
bosbouw - bomen - bosschade - chemische precipitatie - luchtverontreiniging - zouten - depositie - zure regen - plantenfysiologie - statistiek - wiskundige modellen - pseudotsuga menziesii - forestry - trees - forest damage - chemical precipitation - air pollution - salts - deposition - acid rain - plant physiology - statistics - mathematical models - pseudotsuga menziesii
|Canopy interactions in a Douglas fir forest. Estimating dry deposition from canopy wetness, throughfall and wet deposition.
Versluis, A.H. ; Vermetten, A.W.M. ; Bouten, N. ; Maas, R. van der; Hofschreuder, P. - \ 1991
In: CORRELACI : identification of traditional and air pollution related stress factors in a douglas fir ecosystem : the aciforn stands : a correlative evaluation of monitoring data on the carbon, nutrient and water cycles / Evers, P.W., Bouten, W., van Grinsven, J.J.M., - p. 85 - 118.
bosbouw - bomen - bosschade - chemische precipitatie - luchtverontreiniging - zouten - depositie - kroon - kroondak - stamafstroming - regen - interceptie - neerslag - zure regen - zure depositie - pseudotsuga menziesii - forestry - trees - forest damage - chemical precipitation - air pollution - salts - deposition - crown - canopy - stemflow - rain - interception - precipitation - acid rain - acid deposition - pseudotsuga menziesii
|Netto zuurbelasting van de bodem door atmosferische depositie
Loman, H. - \ 1989
Haren (Gr.) : IB (Nota / Instituut voor Bodemvruchtbaarheid 207) - 44
bodem ph - bodemaciditeit - bosschade - chemische precipitatie - luchtverontreiniging - zouten - depositie - neerslag - chemische eigenschappen - zuurgraad - zure regen - soil ph - soil acidity - forest damage - chemical precipitation - air pollution - salts - deposition - precipitation - chemical properties - acidity - acid rain
|Qualitative and quantitative research on the relation between ectomycorrhiza of Pseudotsuga menziesii, vitality of the host and acid rain.
Jansen, A.E. ; Vries, F.W. de - \ 1988
Wageningen [etc.] : Agricultural University [etc.] - 73
bosbouw - bomen - bosschade - chemische precipitatie - luchtverontreiniging - zouten - depositie - mycorrhizae - achteruitgang, bossen - levensvatbaarheid - pseudotsuga menziesii - ectomycorrhiza - zure regen - nederland - forestry - trees - forest damage - chemical precipitation - air pollution - salts - deposition - mycorrhizas - forest decline - viability - pseudotsuga menziesii - ectomycorrhizas - acid rain - netherlands
Gezonde mycorrhiza, gezonde bossen
Smits, W.T.M. - \ 1984
Nederlands Bosbouwtijdschrift 56 (1984)4. - ISSN 0028-2057 - p. 92 - 96.
luchtverontreiniging - chemische precipitatie - depositie - bosschade - bosbouw - mycorrhizae - zouten - air pollution - chemical precipitation - deposition - forest damage - forestry - mycorrhizas - salts
Aandacht voor de rol van mycorrhiza in verband met het afsterven van bossen en het gebruik van mycorrhiza als middel tegen beschadiging van bomen door zure depositie en luchtverontreiniging
|De gevoeligheid van bomen voor strooizout
Burg, J. van den; Kopinga, J. - \ 1981
Wageningen : De Dorschkamp (Bericht / Rijksinstituut voor Onderzoek in de Bos- en Landschapsbouw "De Dorschkamp" nr. 103)
bosschade - chemische precipitatie - luchtverontreiniging - zouten - depositie - bosbouw - groene zones - heggen - straatbomen - houtachtige planten als sierplanten - forest damage - chemical precipitation - air pollution - salts - deposition - forestry - green belts - hedges - street trees - ornamental woody plants
|Bomen op zoute gronden, zoutschade, resistentie
Anonymous, - \ 1971
Wageningen : [s.n.] (Literatuurlijst / Centrum voor landbouwpublikaties en landbouwdocumentatie no. 3322)
luchtverontreiniging - bibliografieën - chemische precipitatie - oogstschade - depositie - bosschade - bosbouw - verbetering - houtachtige planten als sierplanten - verzilting - zouten - natrium - bodem - bodemverontreiniging - bodemzoutgehalte - bodemkunde - bodemgiftigheid - air pollution - bibliographies - chemical precipitation - crop damage - deposition - forest damage - forestry - improvement - ornamental woody plants - salinization - salts - sodium - soil - soil pollution - soil salinity - soil science - soil toxicity