Influence of Calcium Concentrations on Cadmium Uptake by the Freshwater Mussel Ellptio complanata

1993 ◽  
Vol 50 (12) ◽  
pp. 2591-2596 ◽  
Author(s):  
Y. Wang ◽  
R. D. Evans
Keyword(s):  
Calcium Ions ◽  
Laboratory Experiments ◽  
Freshwater Mussel ◽  
Cadmium Uptake ◽  
Molar Ratio ◽  
Strong Impact ◽  
Uptake Rates

The effect of calcium ions on the uptake of cadmium by the freshwater mussel Ellptio complanata was studied in controlled laboratory experiments. Radioactive 45Ca and 109Cd were used as tracers. The experiments were designed to minimize geochemical differences between treatments so that the physiological interactions of the two ions could be studied. Uptake of Cd was correlated with concentration of Cd in the experimental tanks. However, the concentrations of Ca also had a strong impact on uptake rates. When uptake of Cd was expressed as a function of the molar ratio of Cd to Ca, greater than 96% of the variation could be explained.

Optimization of phosphorus precipitation from swine manure slurries to enhance recovery

2003 ◽  
Vol 48 (1) ◽  
pp. 139-146 ◽  
Author(s):  
R.T. Burns ◽  
L.B. Moody ◽  
I. Celen ◽  
J.R. Buchanan
Keyword(s):  
Reaction Time ◽  
Laboratory Experiments ◽  
Swine Manure ◽  
High Strength ◽  
Recovery Process ◽  
Molar Ratio ◽  
Swine Waste ◽  
High Concentration ◽  
Low Concentration ◽  
Addition Rate

Laboratory experiments were conducted using magnesium chloride (MgCl2·6H2O, 64% solution) to force the precipitation of phosphorus and reduce the concentration of soluble phosphorus (PO43-) in two swine wastes. One of the swine wastes tested contained a high concentration of PO43- (initially ≈1,000 mg/L), and the other swine waste tested contained a low concentration of PO43- (initially ≈230 mg/L). The precipitation reactions were performed to determine the required reaction time, pH, magnesium addition rate and seed material for future precipitate recovery work. For the high and low concentration waste, a 10-minute reaction time at a pH of 8.6 was sufficient to remove 98 and 96% of the PO43- from solution. A molar ratio of Mg2+:PO43- of 1.6:1 was determined to be effective for PO43- removal from both the low and high strength wastes. At a molar ratio of 1.6:1, the PO3- in the high concentration waste was reduced from 590 to 12 mg/L. In the low concentration waste, the PO43- concentration was reduced from 157 to 15 mg/L. Seeding the reaction did not significantly enhance the recovery process.

Substitution of Lipids with Bile Salts in the Formation of Thrombin

1969 ◽  
Vol 22 (01) ◽  
pp. 013-027 ◽  
Author(s):  
Monika Barthels ◽  
W. H Seegers
Keyword(s):  
Calcium Ions ◽  
Bile Salts ◽  
Thrombin Generation ◽  
Sodium Deoxycholate ◽  
Sodium Cholate ◽  
Phosphatidyl Serine ◽  
Molar Ratio ◽  
Platelet Factor ◽  
Analytical Reagents ◽  
Autoprothrombin C

SummaryThe generation of thrombin was studied in an activating system consisting of purified thrombin zymogens, purified autoprothrombin C, purified Ac-globulin, lipid or bile salts, and calcium chloride. With the concentration of calcium ions and pH fixed, the effect of varying the other three procoagulants was studied. Bile salts were effective substitutes for lipids in a concentration where micelles form. The approximate effectiveness from highest to lowest was: conjugated sodium salt of taurocholic acid, sodium cholate, sodium deoxycholate. Sodium dehydrocholate was ineffective. Autoprothrombin C is the enzyme for thrombin formation. For accelerating its activity best results were obtained with the simultaneous presence of optimal concentrations of calcium ions, Ac-globulin and lipids or bile salts. Reducing any one of the three to zero concentration decreased the rate and yield of thrombin generation.The form in which the zymogen is used was found to be important. Prothrombin complex, DE AE-prothrombin and prethrombin were studied. Each substrate has its peculiar requirements for yielding thrombin. Prothrombin complex and DEAE-pro-thrombin activated far more rapidly and required 10 times less autoprothrombin C than prethrombin. The yield of thrombin from these substrates was also higher than from prethrombin. DE AE-prothrombin required the least amount of lipid. For the bile salts the required concentrations were nearly always the same from one substrate to another. To a certain extent Benadryl could also be substituted for lipids. In association with rapid thrombin generation from DE AE-prothrombin the Ac-globulin and autoprothrombin C Avere represented in approximately a 6:1 molar ratio. As compared with the weight of the enzyme large amounts of Ac-globulin and cholate were required.DE AE-prothrombin was readily made refractory to the two-stage analytical reagents with purified platelet factor 3 and calcium ions. Combinations of sodium cholate and phosphatidyl serine were also effective, but either one alone was ineffective.

Struvite crystallization versus amorphous magnesium and calcium phosphate precipitation during the treatment of a saline industrial wastewater

2011 ◽  
Vol 64 (12) ◽  
pp. 2460-2467 ◽  
Author(s):  
D. Crutchik ◽  
J. M. Garrido
Keyword(s):  
Wastewater Treatment ◽  
Calcium Ions ◽  
Industrial Wastewater ◽  
Wastewater Treatment Plants ◽  
Calcium Phosphates ◽  
Treated Wastewater ◽  
Molar Ratio ◽  
Struvite Precipitation ◽  
Struvite Crystallization ◽  
Calcium Phosphate Precipitation

Struvite crystallization (MgNH4PO4·6H2O, MAP) could be an alternative for the sustainable and economical recovery of phosphorus from concentrated wastewater streams. Struvite precipitation is recommended for those wastewaters which have high orthophosphate concentration. However the presence of a cheap magnesium source is required in order to make the process feasible. For those wastewater treatment plants (WWTP) located near the seashore magnesium could be economically obtained using seawater. However seawater contains calcium ions that could interfere in the process, by promoting the precipitation of amorphous magnesium and calcium phosphates. Precipitates composition was affected by the NH4+/PO43− molar ratio used. Struvite or magnesium and calcium phosphates were obtained when NH4+/PO43− was fixed at 4.7 or 1.0, respectively. This study demonstrates that by manipulating the NH4+/PO43− it is possible to obtain pure struvite crystals, instead of precipitates of amorphous magnesium and calcium phosphates. This was easily performed by using either raw or secondary treated wastewater with different ammonium concentrations.

Thermodynamic Modelling of the Sorption of Radioelements onto Cementitious Materials

1995 ◽  
Vol 412 ◽  
Author(s):  
T. G. Heath ◽  
D. J. Ilett ◽  
C. J. Tweed
Keyword(s):  
Surface Chemistry ◽  
Calcium Ions ◽  
Cementitious Materials ◽  
Molar Ratio ◽  
Iodide Ions ◽  
Zeta Potentials ◽  
High Calcium ◽  
Cement Based Materials ◽  
Calcium Silicon ◽  
Modelling Approach

AbstractA model has been developed for the sorption of radioelements onto cementitious materials based on the diffuse-layer modelling approach. The model assumes that silicon sites (>SiOH) and calcium sites (>CaOH) dominate the surface chemistry and the sorption of radioelements onto the cementitious materials. Both types of site may undergo surface protonation and deprotonation reactions. Cement-based systems vary greatly in their chemistry depending on their calcium-tosilicon molar ratio, and the corresponding variation in the surface chemistry has been incorporated by allowing sorption of calcium ions onto silicon sites. This process results in a change from a silica-type surface, at very low calcium-silicon ratios, to a calcium hydroxide-type surface for high-calcium cement-based materials. The predicted variation in the surface chemistry is consistent with literature data on measured zeta potentials of cements. The model has been applied successfully to describe the sorption of simple caesium and iodide ions at varying calciumsilicon ratios. In a Nirex repository for low and intermediate level wastes, a high-calcium cementitious backfill would be specified. This model has allowed a consistent interpretation of experimental data for sorption of key radioelements, including uranium and plutonium, onto the backfill, under saline and non-saline conditions.

scholarly journals Modeling bromide effects on the speciation of trihalomethanes formation in chlorinated drinking water

2013 ◽  
Vol 7 (1) ◽  
pp. 1-16
Keyword(s):  
Laboratory Experiments ◽  
Reactivity Ratio ◽  
Chlorine Concentration ◽  
Molar Ratio ◽  
Chlorination Rate ◽  
Incubation Periods ◽  
Local Plant ◽  
Chlorinated Drinking Water ◽  
Model Equations ◽  
Trihalomethanes Formation

Speciation behavior of trihalomethanes formation in chlorinated waters due to the effects of bromide is mathematically modeled by a three-tier scheme. Equations for the mole fractions of the mono-, di-, and trihalo-intermediates at each tier level in terms of the initial bromide to chlorine molar ratio are derived and verified by comparison with results of other theoretical studies based on an assumption of constant bromination to chlorination reaction reactivity ratio. It is identified that the usage of applied chlorine concentration or available chlorine concentration for calculation of the relative initial bromide to chlorine concentration would yield different reactivity ratio and should be used consistently. The model equations are also tested by laboratory experiments done with source water at a local plant. It is found that equations with an overall bromination to chlorination rate constant ratio of 18.66 can capture the THM speciation behavior of all four tested incubation periods well.

scholarly journals Cadmium uptake rates in freshly hatched zebrafish (Danio rerio) larvae in the presence of two dissolved organic matter (DOM) isolates

2007 ◽  
Vol 24 (1) ◽  
pp. 110-111
Author(s):  
T. Meinelt ◽  
B. K. Burnison ◽  
M. Pietrock ◽  
E. Zwirnmann ◽  
A. Wienke ◽  
...  
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Danio Rerio ◽  
Cadmium Uptake ◽  
Uptake Rates
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