Application of theoretical alkali dosage in paper deacidification

Abstract

The invention provides an application of theoretical alkali dosage in the aspect of paper deacidification, which comprises the following steps: acquiring an extraction liquid of to-be-tested paper by using an extraction method, testing the pH value of the to-be-tested paper, and recording the corresponding hydrogen ion concentration as H1; diluting the extraction liquid of the paper to be measured, measuring the pH value of the extraction liquid again, and recording the corresponding hydrogen ion concentration as H2; calculating acid reserves and ionization equilibrium constants by using the pH measured before and after dilution; and setting target alkali reserves after deacidification, and calculating the amount of needed deacidified alkali. According to the application of the theoretical alkali dosage in the aspect of paper deacidification, the alkali application principle in the deacidification process is defined, the thought of theoretical simulation calculation is given, and the method can be popularized to deacidification theoretical alkali dosage scenes of different pieces of paper.

Description

Technical Field

[0001] The invention relates to the field of paper processing, and in particular to an application of a theoretical alkali dosage in paper deacidification. Background Art

[0002] During the manufacturing, storage and use of paper, it is often affected by various factors and gradually acidifies. At the same time, acidification will promote the hydrolysis reaction of cellulose in the paper, making it brittle and powdery, and affecting the strength and durability of the paper. In the long-term preservation of precious paper materials such as ancient books, archives, documents, calligraphy and paintings, paper deacidification provides an important guarantee for extending the life of paper and maintaining the integrity of the collection. Existing deacidification technology can be divided into gas phase deacidification and liquid phase deacidification according to the physical state of the deacidifier. The basic purpose is to neutralize the original acidic substances in the paper and deposit a certain alkaline reserve on this basis. However, the current deacidification method does not have a clear numerical estimate of the amount of alkalinity used in the actual deacidification process, and it is impossible to directly give the amount of deacidification and alkali used for the sample to be deacidified; there is no direct numerical estimate of the alkaline reserve after deacidification is completed, and the alkaline reserve needs to be measured again by standard titration after deacidification is completed. Summary of the invention

[0003] The object of the present invention is to provide an application of a theoretical alkali dosage in paper deacidification.

[0004] To achieve the above object, the present invention provides an application of a theoretical alkali dosage in paper deacidification, comprising the following steps:

[0005] Use the extraction method to obtain the extraction liquid of the paper to be tested and test the pH of the paper to be tested, and the corresponding hydrogen ion concentration is recorded as H1;

[0006] Dilute the extracted liquid of the paper to be tested and measure its pH again. The corresponding hydrogen ion concentration is recorded as H2;

[0007] Using the pH measured before and after dilution, calculate the acid reserve and ionization equilibrium constant;

[0008] Set the target alkali reserve after deacidification and calculate the required deacidification alkali dosage.

[0009] Preferably, the extraction liquid of the paper to be tested is diluted 10 times.

[0010] Preferably, the required deacidification and alkali dosage or the target pH after deacidification is calculated, and the calculation of the alkaline reserve is divided into two parts:

[0011] The first part is the alkali consumed to neutralize the acid capacity of paper; the second part is the additional alkaline reserve added to prevent acidification. The source of this part of the alkaline reserve is the alkali produced by the hydrolysis of the added alkali and the weak acid radicals after neutralization.

[0012] Preferably, the acid reserve is:

[0013]

[0014] The source of acid reserves is approximately regarded as a monobasic weak acid, and the ionization equilibrium constant of this monobasic weak acid is:

[0015]

[0016] The hydrolysis equilibrium constant of the acid radical of this monoprotic weak acid is:

[0017]

[0018] Preferably, the target alkali reserve after deacidification is set, and the required deacidification alkali dosage is calculated, including

[0019] Set the target pH after deacidification, and record the corresponding hydrogen ion concentration as H3. Calculate the required deacidification and alkali dosage, where the deacidification and alkali dosage is calculated in terms of MgCO3 as follows:

[0020]

[0021] The alkali reserve calculation in the formula includes two parts. The first part is the alkali consumed to neutralize the acid capacity of paper. The second part is an additional alkaline reserve added to prevent acidification The alkalinity reserve in this part comes from the addition of alkali The base produced by hydrolysis of the neutralized weak acid radical

[0022] Preferably, MgCO3 is used as the calculation of alkali reserves, and sodium borate, sodium carbonate, and sodium bicarbonate can also be used to replace MgCO3.

[0023] Therefore, the present invention adopts the above-mentioned theoretical alkali dosage in the application of paper deacidification, and the technical effects are as follows:

[0024] (1) The reserve acid in paper is regarded as a monobasic weak acid HA, so that its theoretical acid reserve and ionization equilibrium constant can be measured by extraction and dilution, which simplifies the calculation model for neutralizing the acid content in paper.

[0025] (2) The two parts of the calculation of the amount of alkali used for deacidification are given, and the reasonable sources of the theoretical alkali dosage are sorted out. In the subsequent practical application scenarios, the formula can be adjusted according to the specific conditions of the two parts.

[0026] (3) By setting the goal after deacidification, the theoretical alkali dosage formula for deacidification is given, which can guide the idea of ​​paper deacidification in actual work. DETAILED DESCRIPTION

[0027] The technical solution of the present invention is further illustrated by the following examples.

[0028] Unless otherwise defined, technical or scientific terms used in the present invention shall have the common meanings understood by one having ordinary skills in the field to which the present invention belongs.

[0029] Embodiment 1

[0030] The present invention provides an application of a theoretical alkali dosage in paper deacidification, comprising the following steps:

[0031] Step 1. Use the extraction method to obtain the extraction liquid of the handmade paper to be tested and test the pH of the paper to be tested

[0032] Cut the sample that has not been touched by hand into 5-10 mm pieces. 2 2g of sample was weighed accurately (accurate to 0.1g) and extracted with 100mL of cold distilled water for 1h. The pH value was measured to be 5, and the corresponding hydrogen ion concentration was recorded as H1=10 -5 mol L -1 ;

[0033] Step 2. Dilute the extracted liquid of the paper to be tested ten times and measure its pH again. The pH value is 5.6, and the corresponding hydrogen ion concentration is recorded as H2=10 -5.6 mol L -1 .

[0034] Step 3. Calculate the acid reserve and ionization equilibrium constant using the pH values ​​measured before and after dilution. Consider the reserve acid in the paper as a monoprotic weak acid HA, and the acid reserve is:

[0035]

[0036] The ionization constant of this monoprotic weak acid and the hydrolysis equilibrium constant of the corresponding acid radical are:

[0037]

[0038] The acid in the paper is considered as a monoprotic weak acid. The application condition of this approximation is that the difference in the ionization equilibrium constants between the mixed acids in the extract is within one to two orders of magnitude, that is, there is no obvious ionization difference between the acids.

[0039] The approximate rationality is that the acid in acidified paper mainly comes from carboxylic acid formed after cellulose breaks and oxidizes, and its pK a Around 4-5, pK b Around 9-10, such as the K of acetic acid a 1.8*10 -5 , K of formic acid a 1.8*10 -4 The K of the simulated monobasic weak acid HA obtained at this time is a=2.4*10 -6 This is consistent with the dissociation constant of general carboxylic acids.

[0040] Step 4. Set the target pH after deacidification to 9, and the corresponding hydrogen ion concentration is recorded as H3 = 10 -9 mol L -1 , calculate the required amount of deacidification and alkali. The deacidification and alkali dosage is calculated based on MgCO3, which is completely double hydrolyzed in aqueous solution to generate Mg(OH)2:

[0041]

[0042] m(MgCO3)=1.8×10 -4 g (5);

[0043] The conditions for the validity of formula (4) and formula (5) are that the paper reaches a weak alkaline state after deacidification, and at this time Mg(OH)2 has not reached the precipitation-dissolution equilibrium. SP =1.8*10 -11 :

[0044] When pH = 9, H3 = 10 -9 When c(Mg)<0.18mol L -1 Complete dissolution can be achieved when

[0045] When pH = 9.5, H3 = 10 -9.5 When c(Mg)<0.018mol L -1 It is obvious that when the amount of MgCO3 added is 1.8×10 -4 g, c(Mg) meets the above requirements.

[0046] Embodiment 2

[0047] The present invention provides an application of a theoretical alkali dosage in paper deacidification, comprising the following steps:

[0048] Step 1. Use the extraction method to obtain the extraction liquid of the handmade paper to be tested and test the pH of the paper to be tested

[0049] Cut the sample that has not been touched by hand into 5-10 mm pieces. 2 2g of sample was weighed accurately (accurate to 0.1g) and extracted with 100mL of cold distilled water for 1h. The pH value was measured to be 5, and the corresponding hydrogen ion concentration was recorded as H1=10 -5 mol L -1 ;

[0050] Step 2. Dilute the extracted liquid of the paper to be tested ten times and measure its pH again. The pH value is 5.6, and the corresponding hydrogen ion concentration is recorded as H2=10-5.6 mol L -1 .

[0051] Step 3. Calculate the acid reserve and ionization equilibrium constant using the pH values ​​measured before and after dilution. Consider the reserve acid in the paper as a monoprotic weak acid HA, and the acid reserve is:

[0052]

[0053] The ionization constant of this monoprotic weak acid and the hydrolysis equilibrium constant of the corresponding acid radical are:

[0054]

[0055] The acid in the paper is considered as a monoprotic weak acid. The application condition of this approximation is that the difference in the ionization equilibrium constants between the mixed acids in the extract is within one to two orders of magnitude, that is, there is no obvious ionization difference between the acids.

[0056] The approximate rationality is that the acid in acidified paper mainly comes from carboxylic acid formed after cellulose breaks and oxidizes, and its pK a Around 4-5, pK b Around 9-10, such as the K of acetic acid a 1.8*10 -5 , K of formic acid a 1.8*10 -4 The K of the simulated monobasic weak acid HA obtained at this time is a =2.4*10 -6 This is consistent with the dissociation constant of general carboxylic acids.

[0057] The target alkali reserve after deacidification is set at 0.5%, and the deacidification alkali dosage is calculated as MgCO3:

[0058]

[0059] m(MgCO3)=2.0×10 -2 g (10);

[0060] It is necessary to assume that MgCO3 is completely double hydrolyzed in aqueous solution to generate Mg(OH)2; and after setting the deacidification target alkali reserve to 0.5%, the alkali produced by the hydrolysis of weak acid radicals after neutralization is ignored.

[0061] Furthermore, the pK of the corresponding acid radical of this monobasic weak acid is b =8.4. When the hydroxide concentration in the solution is high, the hydrolysis of the acid radical is greatly inhibited. In the second part (additional alkaline reserve added to prevent acidification), it can be determined that the alkaline reserve is completely derived from the presence of the added alkali. Since MgCO3 is also added during the neutralization in the first part, it is obvious that Mg in the solution 2+ More than OH- concentration, then for Mg(OH)2, K SP =1.8*10 -11 ,exist:

[0062] Q sp =c(Mg 2+ )*c(OH - ) 2 >1.2×10 -3 ×(2.4×10 -3 ) 2 =6.9×10 -9 >K sp (11);

[0063] At this time, Mg(OH)2 has reached precipitation-dissolution equilibrium.

[0064] Embodiment 3

[0065] The present invention provides an application of a theoretical alkali dosage in paper deacidification, comprising the following steps:

[0066] Step 1. Use the extraction method to obtain the extract liquid of the newsprint to be tested and test the pH of the paper to be tested

[0067] Cut the sample that has not been touched by hand into 5-10 mm pieces. 2 2 g of the sample was weighed accurately (accurate to 0.1 g) and extracted with 100 mL of cold distilled water for 1 h. The pH value was measured to be 4.7, and the corresponding hydrogen ion concentration was recorded as H1=10 -4.7 molL -1 ;

[0068] Step 2. Dilute the extracted liquid of the paper to be tested ten times and measure its pH again. The pH value is 5.4, and the corresponding hydrogen ion concentration is recorded as H2=10 -5.4 mol L -1 .

[0069] Step 3. Calculate the acid reserve and ionization equilibrium constant using the pH values ​​measured before and after dilution. Consider the reserve acid in the paper as a monoprotic weak acid HA, and the acid reserve is:

[0070]

[0071] The ionization constant of this monoprotic weak acid and the hydrolysis equilibrium constant of the corresponding acid radical are:

[0072]

[0073] The acid in the paper is considered as a monoprotic weak acid. The application condition of this approximation is that the difference in the ionization equilibrium constants between the mixed acids in the extract is within one to two orders of magnitude, that is, there is no obvious ionization difference between the acids.

[0074] The approximate rationality is that the acid in acidified paper mainly comes from carboxylic acid formed after cellulose breaks and oxidizes, and its pK a Around 4-5, pK b Around 9-10, such as the K of acetic acid a 1.8*10 -5 , K of formic acid a 1.8*10 -4 The K of the simulated monobasic weak acid HA obtained at this time is a =1.2*10 -5 This is consistent with the dissociation constant of general carboxylic acids.

[0075] Step 4. Set the target pH after deacidification to 9.5, and the corresponding hydrogen ion concentration is recorded as H3=10 -9.5 mol L -1 , calculate the required amount of deacidification and alkali. The amount of deacidification and alkali is calculated based on Mg(OH)2:

[0076]

[0077] m(Mg(OH)2)=2.4×10 -3 g (16);

[0078] The conditions for the validity of formula (15) and formula (16) are that the paper reaches a weak alkaline state after deacidification, and at this time Mg(OH)2 has not reached the precipitation-dissolution equilibrium. SP =1.8*10 -11 :

[0079] When pH = 9, H3 = 10 -9 When c(Mg)<0.18mol L -1 Complete dissolution can be achieved when

[0080] When pH = 9.5, H3 = 10 -9.5 When c(Mg)<0.018mol L -1 Complete dissolution can be achieved.

[0081] Obviously, when the amount of Mg(OH)2 added is 2.4×10 -3 g, c(Mg) meets the above requirements.

[0082] Embodiment 4

[0083] The present invention provides an application of a theoretical alkali dosage in paper deacidification, comprising the following steps:

[0084] Step 1. Use the extraction method to obtain the extraction liquid of the archival paper to be tested and test the pH of the paper to be tested

[0085] Cut the sample that has not been touched by hand into 5-10 mm pieces. 2 2 g of the sample was weighed accurately (accurate to 0.1 g) and extracted with 100 mL of cold distilled water for 1 h. The pH value was measured to be 4.9, and the corresponding hydrogen ion concentration was recorded as H1=10 -4.9 molL -1 ;

[0086] Step 2. Dilute the extracted liquid of the paper to be tested ten times and measure its pH again. The pH value is 5.6, and the corresponding hydrogen ion concentration is recorded as H2=10 -5.6 mol L -1 .

[0087] Step 3. Calculate the acid reserve and ionization equilibrium constant using the pH values ​​measured before and after dilution. Consider the reserve acid in the paper as a monoprotic weak acid HA, and the acid reserve is:

[0088]

[0089] The ionization constant of this monoprotic weak acid and the hydrolysis equilibrium constant of the corresponding acid radical are:

[0090]

[0091] The acid in the paper is considered as a monoprotic weak acid. The application condition of this approximation is that the difference in the ionization equilibrium constants between the mixed acids in the extract is within one to two orders of magnitude, that is, there is no obvious ionization difference between the acids.

[0092] The approximate rationality is that the acid in acidified paper mainly comes from carboxylic acid formed after cellulose breaks and oxidizes, and its pK a Around 4-5, pK b Around 9-10, such as the K of acetic acid a 1.8*10 -5 , K of formic acid a 1.8*10 -4 The K of the simulated monobasic weak acid HA obtained at this time is a =7.6*10 -6 This is consistent with the dissociation constant of general carboxylic acids.

[0093] The target alkali reserve after deacidification is set at 0.5%, and the deacidification alkali consumption is calculated as Na2CO3:

[0094]

[0095] m(Na2CO3)=2.0×10 -2 g (21);

[0096] After setting the deacidification target alkali reserve to 0.5%, the alkali produced by the hydrolysis of weak acid radicals after neutralization can be ignored.

[0097] Furthermore, the pK of the corresponding acid radical of this monobasic weak acid is b =8.9, and CO3 2- pK b =3.7, obviously the hydrolysis of this monobasic weak acid radical is greatly inhibited. In the second part (additional alkaline reserve added to prevent acidification), it can be determined that the alkaline reserve is completely derived from the presence of the added base.

[0098] Therefore, the present invention adopts the above-mentioned theoretical alkali dosage for the deacidification of paper, clarifies the principle of applying alkali in the deacidification process, and provides an idea of ​​theoretical simulation calculation, which can be extended to the theoretical alkaline dosage scenarios for deacidification of different papers.

[0099] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. An application of a theoretical alkali dosage in paper deacidification, characterized in that: The following steps are involved: Use the extraction method to obtain the extraction liquid of the paper to be tested and test the pH of the paper to be tested, and the corresponding hydrogen ion concentration is recorded as H1; Dilute the extracted liquid of the paper to be tested and measure its pH again. The corresponding hydrogen ion concentration is recorded as H2; Using the pH measured before and after dilution, calculate the acid reserve and ionization equilibrium constant; Set the target alkali reserve after deacidification or the target pH after deacidification, and calculate the required deacidification alkali dosage.

2. The use of a theoretical alkali dosage in paper deacidification according to claim 1, characterized in that: Dilute the extraction liquid of the paper to be tested 10 times.

3. The use of a theoretical alkali dosage in paper deacidification according to claim 1, characterized in that: Calculate the amount of deacidification and alkali required, and divide the calculation of alkaline reserves into two parts: The first part is the alkali consumed to neutralize the acid capacity of the paper; the second part is the additional alkaline reserve added to prevent acidification, and the source of the alkaline reserve is the alkali produced by the hydrolysis of the added alkali and the weak acid radicals after neutralization.

4. The use of a theoretical alkali dosage in paper deacidification according to claim 1, characterized in that: Acid reserves are: The ionization equilibrium constant of this monoprotic weak acid is: The hydrolysis equilibrium constant of the acid radical of this monoprotic weak acid is:

5. The use of a theoretical alkali dosage in paper deacidification according to claim 1, characterized in that: Set the target alkali reserve after deacidification and calculate the required deacidification alkali dosage, including Set the target pH after deacidification, and record the corresponding hydrogen ion concentration as H3. Calculate the required deacidification and alkali dosage, where the deacidification and alkali dosage is calculated in terms of MgCO3 as follows:

6. The use of a theoretical alkali dosage in paper deacidification according to claim 1, characterized in that: When using MgCO3 as the calculation of alkali reserves, sodium borate, sodium carbonate, sodium bicarbonate, calcium carbonate, and hydroxide can also be used to replace MgCO3.

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