CN100510727C - Method for measuring clay dispersion average binding free energy and adsorption free energy to cation - Google Patents
Method for measuring clay dispersion average binding free energy and adsorption free energy to cation Download PDFInfo
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- CN100510727C CN100510727C CNB2006100390489A CN200610039048A CN100510727C CN 100510727 C CN100510727 C CN 100510727C CN B2006100390489 A CNB2006100390489 A CN B2006100390489A CN 200610039048 A CN200610039048 A CN 200610039048A CN 100510727 C CN100510727 C CN 100510727C
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Abstract
This invention relates to one method to test earth anode ion even combination free energy and absorptive free energy, which comprises the following steps: a, processing the anode saturation earth adhThis invention relates to one method to test earth anode ion even combination free energy and absorptive free energy, which comprises the following steps: a, processing the anode saturation earth adhesive particles with radium less than 2 mu m and then using ion remove water or stilled water to match earth hanging liquid; b, putting the earth hanging liquid into field less than 15kV.cm<-1> to graesive particles with radium less than 2 mu m and then using ion remove water or stilled water to match earth hanging liquid; b, putting the earth hanging liquid into field less than 15kV.cm<-1> to gradually form field intensity to test each conductivity rate to get the relation ship curve between earth hanging liquid and field intensity; c, according to math formula to compute particles anode ion dually form field intensity to test each conductivity rate to get the relation ship curve between earth hanging liquid and field intensity; c, according to math formula to compute particles anode ion even combination free energy and absorptive free energy, wherein, Delta G<bo>=RTln(2CEC.Cp.lambada /EC0) (4); Delta G<ad>=RTln(EC/EC0) with R for gas constant; T for thermal temperature and CEC for even combination free energy and absorptive free energy, wherein, Delta G<bo>=RTln(2CEC.Cp.lambada /EC0) (4); Delta G<ad>=RTln(EC/EC0) with R for gas constant; T for thermal temperature and CEC for anode ion exchange volume and Cp for particle concentration. anode ion exchange volume and Cp for particle concentration.
Description
Technical field
The invention belongs to a kind of new technology of plant nutrient chemistry and environmental protection technical field, relate to a kind of glutinous grain of soil of measuring to cationic average new method in conjunction with free energy and average adsorption free energy, the basis of its technology is the Wien effect in the soil supension.
Background technology
Can infer guarantor accumulation of energy power and the nutrient availability of soil to cationic on average in conjunction with free energy and average adsorption free energy, the difficulty or ease of the activity of contaminated ion and detoxifcation measure in the soil by measuring the glutinous grain of soil to the nutrient ion.So, provide the glutinous grain of soil to ion on average in conjunction with effective assay method of free energy and average adsorption free energy, be the pedologist always, the workers of especially fertility regulation and control, soil remediation and field of environment protection want the problem that solves.
Marshall (1950) proposes kation for a long time on average in conjunction with the free energy notion, in order to the binding energy between expression grogs and kation, and has provided and calculates kation on average in conjunction with the formula of free energy.Chinese scholar was measured Na in the soil supension with ion-selective electrode afterwards
+, K
+When activity, the formula that provides according to Marshall have been calculated latosol, red soil with the different pH of yellowish soil to the binding energy of sodion and potassium ion.Yet, because the ion activity in the soil supension is difficult to measure, this is because single ion activity is not measurable on thermodynamics on the one hand, the aspect is because of the usual method of measuring ion activity with ion-selective electrode two weakness to be arranged in addition, because the obligate difference of indicator electrode causes the ion activity indeterminacy,, contrast electrode make activity measurement introduce error owing to existing unsettled liquid junction potential; Moreover, also there is not practical obligate electrode at present for multivalent ion.So it is very few that this so far method adopts.Nineteen fifty-nine Blanchet sticks the energy of adsorption (desorb merit) of grain to potassium ion with simple chemical gauging.But want the expensive time owing to calculate the measurement of the required adsorption isothermal of energy of adsorption, and this method only can be measured several univalent cations (as K
+And Na
+) energy of adsorption, this method is not adopted by afterwards researcher.
Half a century has gone over, and the measuring of soil and interionic energy relationship is still inreal to solve.Over past ten years, applicant of the present invention is by the research of soil-aqueous systems highfield DC conductance, the method of the Wien effect in a kind of measured soil suspension has been proposed, and calculate soil and interionic according to conductivity-field intensity curve on this basis on average in conjunction with free energy and average adsorption free energy, further proposed this kind and measured soil and interionic simply and effectively on average in conjunction with the inventive method of free energy with average adsorption free energy.
Summary of the invention
The purpose of this invention is to provide a kind of average method of measuring kation at soil surface in conjunction with free energy and average adsorption free energy simple and efficiently.The glutinous grain of soil to cationic on average in conjunction with free energy and average adsorption free energy data, can be and judge guarantor accumulation of energy power and the nutrient availability of soil the nutrient ion, and in the soil contaminated ion activity and the detoxifcation measure difficulty or ease important information is provided, and these information be up to now other measuring method can't provide.
The present invention utilize strong electric field condition measure the glutinous grain of soil to cationic on average in conjunction with free energy and average adsorption free energy, promptly calculate cationic on average in conjunction with free energy and adsorption free energy by measuring conductivity-electric field intensity curve.
The present invention proposes on the basis of following result of study:
The theory of electrolytic conductance of electrolyte solution points out, because the interaction between the ion, the conductivity of effects of ion is low during than its individualism.20,000 volts/centimetre of highfields (〉) in, because the weakening or disappear of relaxation effect and electrophoretic effect, the electricity of solution is led and can be become to reaching maximal value, is called Wien (Wien) effect.
In soil-aqueous systems, the interaction except between effects of ion, also have the conductive capability of a prior factor affecting ion, promptly the soil of surface charging lotus is to the suction-operated of ion.Because this absorption, the ion that can participate in conduction in the solution only accounts for the fraction of total ion concentration.Therefore the Wien effect in the soil supension is than then much bigger in the solution (Li etc., 2002).And by sticking, the way that can add different-energy makes it free to these ions with different energy of adsorptions, participates in conduction.Like this, might disclose grogs and the interactional mechanism of interionic, grogs and interionic interaction are provided quantizating index by the measurement of soil supension Wien effect in highfield.This interaction is the core of soil chemistry, and this interactional quantitative expression is the most important thing in soil chemistry research and the application thereof.
On average in conjunction with free energy
, after being mixed with suspension, being adsorbed on the lip-deep kation of grogs and can partly dissociating in the aqueous solution by the glutinous grain of the saturated electronegative soil of kation, increase the conductivity of suspension with distilled water.The measurement result of Wien effect shows in the soil supension, make the suspension conductivity increase by 5%, and it is 35～155kVcm that the required beginning shows electric field intensity
-1, that is to say, than extra electric field intensity (about 15kVcm of minimum
-1) much bigger, when electric field intensity is increased to 15kVcm by 0
-1The time suspension conductivity be constant basically.Therefore, can take it is conductivity when not having extra electric field as in the suspension conductivity of minimum extra electric field ionization meter.
Electrophoretic mobility (0.023 * 10-4～0.15 * 10 of the glutinous grain of soil (＜2 μ m)
-4Cm
2/ SV) than general cationic mobility (5.2 * 10
-4～7.6 * 10
-4Cm
2/ SV) much smaller.This show grogs move than ion slowly many.In addition, under thin electrostatic double layer condition, even grogs moves quite soon, opposite sign movement of electric charges aggregate is electroneutral because negative charge grogs band on every side, so the suspension electricity is led not contribution.Therefore, can suppose, at low electric field (15kVcm
-1) down the grogs swimming contribution of suspension conductivity is compared with the ionization kation is negligible.According to DC conductance mechanism, the suspension electricity lead second half must cause by negative ion.These negative ion are produced by near the complicated fast response in the soil liquid and the electrode surface.These rapid reactions and the anion species that is produced thereof are also not really clear at present.But can suppose that the contribution that kation and these negative ion are led the total electricity of suspension is similarly, that is to say that the cationic contribution of ionization should be suspension conductivity (EC under low electric field
0) half.If the unsaturated cationic on grogs surface all dissociates, corresponding conductivity (EC
u) should be:
EC
u＝2CEC·C
p·λ(Sm
-1) (1)
CEC is cation exchange capacity (CEC) (Eq kg in the formula
-1), C
pBe glutinous grain concentration (kg L in the suspension
-1), λ is cationic equivalent conductance (the S m that dissociates
-1Eq
-1L
-1).Therefore, the dissociation degree of unsaturated cationic or active mark can calculate with following formula:
f
0＝EC
0/EC
u＝EC
0/(2CEC·C
p·λ) (2)
Calculating kation on average in conjunction with the Marshall formula of free energy is:
ΔG
bo＝RTln(C
i/α
i)＝RTln(1/f
0) (3)
R is gas law constant (8.314Jmol in the formula
-1K
-1), T is a thermodynamic temperature, α
iBe cationic activity, C
iBe this cationic total concentration in the suspension, f
0Be active mark, it equals activity coefficient (α
i/ C
i).For clarity sake, all binding energy and energy of adsorption are all represented with positive sign herein.
If our supposition, the active mark of Marshall is equal to the cationic degree of dissociation of absorption, and we can will obtain a formula with formula (2) substitution formula (3), can be used for calculating kation to grogs on average in conjunction with free energy (Δ G
Bo):
ΔG
bo＝RTln(2CEC·C
p·λ/EC
0) (4)
Average adsorption free energy
Introduce a kind of method of how calculating energy of adsorption now according to the measurement of Wien effect E C (E).According to the chemical thermodynamics principle, when the next soil supension of constant temperature and pressure changed to state (2) by state (1), the variation of kation free energy in the suspension (Δ G) can be represented by the formula:
ΔG＝RTln(α
2/α
1) (5)
α in the formula
2And α
1Be respectively the activity of kation when state (2) and state (1) in the suspension.There is the class same sex owing to dissociate under the test condition between cationic activity and suspension conductivity, can gets following equation:
α
2/α
1＝EC
2/EC
1 (6)
EC in the formula
2And EC
1Be respectively the conductivity of suspension when state (2) and state (1).So cationic average adsorption free energy (Δ G
Ad) can be expressed as:
ΔG
ad＝RTln(EC
2/EC
1) (7)
If we are defined as state under weak electric field and highfield respectively with the state (1) of suspension and (2), formula (7) can be rewritten into:
ΔG
ad＝RTln(EC/EC
0) (8)
EC and EC in the formula
0Represent the suspension conductivity under highfield and the weak electric field respectively.When extra electric field when 0 is increased to E, this formula can make us can calculate the cationic average adsorption free energy that dissociates from grogs; And when this formula is applied to a series of Wien effect measurement value, can provide a kation absorption power spectrum.The increase of cationoid activity is to be caused by the adhesion institute work that extra electric field overcomes the glutinous intergranular of kation and soil in the suspension.The energy of adsorption that calculates with formula (8) obviously is positive, and this shows that extra electric field does work to the suspension system.
According to above-mentioned result of study, the invention provides a kind of strong electric field condition that utilizes and measure the glutinous grain of soil cationic average method in conjunction with free energy and average adsorption free energy, this method comprises the following steps:
A. prepare particle diameter＜2 μ m and, be mixed with soil supension with deionized water or distilled water then by the glutinous grain of the saturated soil of kation;
B. soil supension is placed initial electric field intensity≤15kVcm
-1Electric field under, and progressively increase electric field intensity, measure the conductivity of soil supension under each electric field intensity respectively, obtain the relation curve of soil supension conductivity and electric field intensity;
C. respectively according to following mathematical derivation formula calculate the glutinous grain of soil to metal cation on average in conjunction with free energy and average adsorption free energy:
ΔG
bo＝RTln(2CEC·C
p·λ/EC
0) (4)
ΔG
ad＝RTln(EC/EC
0) (8)
In the formula, R is gas law constant 8.314Jmol
-1K
-1T is a thermodynamic temperature, and its unit is K; CEC is a cation exchange capacity (CEC), and its unit is Eq kg
-1, C
pBe the glutinous grain of the soil in suspension concentration, its unit is kg L
-1, λ is the cationic equivalent conductance of dissociating, its unit is S m
-1Eq
-1L
-1EC
0Be electric field intensity≤15kVcm
-1Electric field under the suspension conductivity, its unit is mS cm
-1EC is an electric field intensity〉15kVcm
-1Electric field under the suspension conductivity, its unit is mS cm
-1
In one embodiment, comprise also between step a and the step b soil supension carried out ultrasonic dispersing that every day, the constant temperature vibration was 1～2 time, and 7～10 days treatment step of balance.
In this embodiment, described kation can be sodion, potassium ion, ammonium ion, calcium ion, magnesium ion or heavy metal ion etc.Concentration (the C of described suspension colloid
p) scope can be 1～50gL-1.
In another embodiment, step b is by soil supension being placed conductance cell, apply the pulse voltage that progressively increases at the conductance cell two ends, measuring to produce the electric field that progressively strengthens.
The scope of described pulse voltage is 0～30000 volt; Pulse width is 5～50 μ S; The measurable range of conductance cell resistance is 1～20k Ω.
Described initial electric field intensity is about 15kVcm
-1, and the variation range of described electric field intensity is 15kVcm
-1～200kVcm
-1, this is enough concerning holard suspension.
Description of drawings
Fig. 1 is the determinator synoptic diagram of Wien effect;
Fig. 2 shows with the saturated glutinous grain of yellowish soil suspension (the 10g L of the different kations of quilt of distilled water preparation
-1, ＂ Na ＂ is 5g L
-1) conductivity to the dependence of electric field intensity;
Fig. 3 shows with the saturated glutinous grain of the black earth suspension (10gL of the different kations of quilt of distilled water preparation
-1, ＂ Na ＂ is 5g L
-1) conductivity to the dependence of electric field intensity.
Embodiment
The invention will be further described below in conjunction with accompanying drawing and example.
The preparation of pedotheque and suspension
Extract the glutinous grain of soil of particle diameter＜2 μ m with sedimentation, with conventional method the glutinous grain of soil is prepared into respectively to the saturated sample of different kations then, dry, grind, use for the preparation suspension.Take by weighing a certain amount of above-mentioned soil sample, being mixed with concentration range with deionized water is 1～50g L
-1(as concentration is 10g L
-1) suspension, after the ultrasonic dispersing, every day, constant temperature vibration was 1～2 time, balance is made the Wien effect measurement after 7～10 days.
Measurement mechanism
The device that is used for measuring soil supension Wien effect is made up of a variable high-voltage DC power supply of pulsed and a conductance cell, and the DC voltage of output is up to 30kV; Pulse width is for counting μ S to tens of μ S; The measurable range of conductance cell resistance is 1～20k Ω.
Measuring method
Measurement mechanism is placed in the constant temperature enclosure, under constant temperature (25 ℃), the soil supension of balance is poured in the conductance cell, from minimum impressed voltage (about 1.5kV), till the output voltage that promotes measurement mechanism step by step sparkles between electrode in electricity is led, the resistance value of the interior soil supension of conductance cell under the different voltages is read in survey, and calculates its conductivity value.
The optimal operating parameter of this measuring method is:
Output voltage: 0～30000 volt,
Pulse width: 5～50 μ S
The measurement range of conductance cell resistance: 1～20k Ω
Device is as shown in Figure 1 placed in the constant temperature enclosure, the glutinous grain of the soil suspension of above-mentioned preparation is poured in the Wien effect measurement conductance cell 1, open switch 4, Closing Switch 6 is opened the pulse power, click pulse switch, make the of short duration energising in loop, open switch 6, Closing Switch 4, use universal electric meter to measure the resistance value at electrode 2,3 two ends.The output voltage that promotes measurement mechanism step by step repeats above-mentioned steps till 2,3 of conductance electrodes sparkle, survey the resistance value of reading the interior soil supension of conductance cell under the different voltages.
Fig. 2 has described respectively by different kations saturated yellowish soil and the conductivity of the glutinous grain of black earth suspension and the graph of a relation of electric field intensity with Fig. 3, as can be seen from the figure along with the progressively increase of electric field intensity, no matter be on the yellowish soil or in the glutinous grain of black earth suspension, the conductivity of soil supension all increases along with the progressively increase of electric field intensity, and the degree of its increase is different because of kation.We have carried out quantitative description according to above-mentioned formula of deriving to the phenomenon among Fig. 2 and Fig. 3, have calculated average free binding energy and the average free energy of adsorption of several cation at two kinds of soil surfaces respectively, see Table 1.
Several metal ion species of table 1 are at the average free binding energy and the average free energy of adsorption of soil surface
Annotate: Ui: ionic mobility; Up: glutinous grain mobility; CEC: cation exchange capacity (CEC); Cp: glutinous grain concentration; λ: equivalent conductance; f
0: weak electric field (15kVcm
-1) under the dissociated ion mark; EC
0: weak electric field (15kVcm
-1) under the suspension conductivity; EC:100kVcm
-1Under the suspension conductivity; Δ Gbo:100kVcm
-1Under the average free binding energy of Gibbs; Δ Gad:100kVcm
-1Under the average free energy of adsorption of Gibbs.
As can be seen from Table 1, the binding energy of bivalent cation is greater than univalent cation, and different cationic binding energy are Na＜K＜Ca＜Cd in proper order.When suspension concentration is 10g L
-1The time, can increase to 8.2 kilojoules/grammol from 4.7 in the cationic binding energy scope.Under test condition, bivalent cation to the binding energy of black earth than high about 1 kilojoule of yellowish soil person/grammol; And univalent cation will be lower than yellowish soil to the binding energy of black earth.Can find out that also greater than univalent cation, the variation range of kation energy of adsorption is 0.7 to 2.3 kilojoules/grammol to the energy of adsorption of bivalent cation for yellowish soil and black earth.A little more than the yellowish soil person, univalent cation is then just opposite to the energy of adsorption of black earth for bivalent cation.
The beneficial effect of the inventive method is: the application of the invention method can be by simple analysis just Can directly obtain cation at Mean free binding energy and the Mean free adsorption energy of soil surface, disclose Various cations develop soil colloid electric double layer model in the regularity of distribution on glutinous grain surface, and this is in the past The soil chemistry method can't obtain; Quantitatively summarize grogs and interionic from the energy relationship aspect Interact, it is many, direct to change in for a long time soil chemistry research energy relationship aspect mediate inference Measure few situation; Can quantitatively calculate the shared ratio of the ion of different binding strengths. By Measure grogs to cationic Mean free binding energy and Mean free adsorption energy, can infer soil pair Guarantor's accumulation of energy power and the nutrient availability of nutrient ion, the activity of contaminated ion and detoxifcation measure in the soil Difficulty or ease. For drafting of fertility regulation and control, soil remediation and environmental protective measure provides authentic communication.
Claims (7)
1. measure glutinous average method in conjunction with free energy and average adsorption free energy to metal cation of soil for one kind, this method comprises the following steps:
A. prepare particle diameter＜2 μ m and, be mixed with soil supension with deionized water or distilled water then by the glutinous grain of the saturated soil of metal cation;
B. soil supension is placed initial electric field intensity≤15kVcm
-1Electric field under, and progressively increase electric field intensity, measure the resistance of soil supension under each electric field intensity respectively, obtain the relation curve of soil supension conductivity and electric field intensity;
C. respectively according to following mathematical derivation formula calculate the glutinous grain of soil to metal cation on average in conjunction with free energy and average adsorption free energy:
ΔG
bo＝RTln(2CEC·C
p·λ/EC
0)
ΔG
ad＝RTln(EC/EC
0)
In the formula, R is a gas law constant; T is a thermodynamic temperature; CEC is a cation exchange capacity (CEC); C
pBe the glutinous grain of the soil in suspension concentration, λ is the cationic equivalent conductance of dissociating; EC
0Be electric field intensity≤15kVcm
-1Electric field under the suspension conductivity; EC is an electric field intensity〉15kVcm
-1Electric field under the suspension conductivity.
2. method according to claim 1 is characterized in that, also comprises between described step a and the step b soil supension is carried out ultrasonic dispersing, and every day, the constant temperature vibration was 1～2 time, and 7～10 days treatment step of balance.
3. method according to claim 1 is characterized in that, described metal cation is sodion, potassium ion, ammonium ion, calcium ion, magnesium ion or heavy metal ion.
4. method according to claim 1 is characterized in that the range of concentrations of described suspension colloid can be 1～50g L
-1
5. method according to claim 1 is characterized in that, described step b is by soil supension is placed conductance cell, applies at the conductance cell two ends that the pulse voltage that progressively increases measures with the electric field that produces electric field intensity and progressively increase.
6. method according to claim 5 is characterized in that, the scope of described pulse voltage is 0～30000 volt; Pulse width is 5～50 μ S; The measurable range of conductance cell resistance is 1～20k Ω.
7. method according to claim 1 is characterized in that, the variation range of described electric field intensity is 15kVcm
-1～200kVcm
-1
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| RU2640754C1 (en) * | 2016-09-12 | 2018-01-11 | Федеральное государственное бюджетное образовательное учреждение высшего образования "Брянский государственный аграрный университет" | Method for determining activation energy of desorption of soil exchangeable ions |
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| CN101603892B (en) * | 2009-07-17 | 2011-11-30 | 中国科学院武汉岩土力学研究所 | Rock sample/earth sample saturation device by chemical solution |
| CN102175834B (en) * | 2011-01-24 | 2014-07-09 | 华南农业大学 | Device for stimulating nutrient absorption of plant root system and using method of device |
| CN102590471B (en) * | 2012-01-17 | 2014-09-17 | 南京大学 | Method for determining dissolving state and adsorption state of Cd (II) in mineral soil |
| RU2649074C2 (en) * | 2016-09-19 | 2018-03-29 | Федеральное государственное бюджетное образовательное учреждение высшего образования "Брянский государственный аграрный университет" | Method of express-evaluation of composition of exchange ions of soil on their energy of activation of desorbtion |
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| CN101042361A (en) | 2007-09-26 |
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