Preparation method of clarifying agent modified bentonite for clarifying and decoloring sugar juice

Abstract

The invention relates to a preparation method of clarifying agent modified bentonite for clarifying and decolorizing sugar juice, which comprises the following steps: mixing ethanol with alkaline calcium bentonite, heating to 30-70 DEG C, keeping the temperature constant, adding a sulfurous acid solution / phosphoric acid solution into the ethanol under the condition of stirring to react with the alkaline calcium bentonite, timing from the time when the solution is added, and reacting for 0.5-5.5 hours; or continuously introducing sulfur dioxide gas / carbon dioxide gas to react with the alkaline calcium bentonite for 0.5-3.5 hours, filtering to obtain a filter cake after the reaction is finished, washing the filter cake with ethanol, and drying to obtain the modified bentonite. The inorganic acid bentonite is prepared by reacting the alkaline calcium bentonite with the inorganic acid (sulfurous acid, phosphoric acid or carbonic acid), and the inorganic acid bentonite can be used as a clarifying agent for clarifying and decoloring sugar juice and has the advantages of good clarifying and decoloring effects and simplicity and convenience in operation.

Description

Technical Field

[0001] The invention relates to a method for preparing clarifier-modified bentonite for sugar juice clarification and decolorization. Background Art

[0002] The color value of white sugar is the most important and technically difficult quality indicator of white sugar. There are many and complex types of colored substances in sugar products, including two categories: those originally contained in sugarcane and those generated during the production process. The pigments originally contained in sugarcane are mainly fat-soluble and water-soluble. The former coexists with lipids in sugarcane juice and is basically insoluble in water. Most of them can be removed during heating. Water-soluble pigments are mainly various polyphenols, which are the main reason for the color of white sugar and various sugar products. On the other hand, in the sugar production process, in addition to the clarification treatment to remove some colored substances, new colored substances are constantly generated, and the original colorless or light-colored substances become darker substances. Therefore, to reduce the color value of white sugar, it is necessary to start from the clarification link to inhibit or avoid the generation of new colored substances in the sugar production process.

[0003] In order to improve the adsorption and flocculation ability of clarifiers on sugarcane juice, many researchers have tried to introduce porous and large specific surface materials as sugarcane juice clarifiers, such as activated carbon, macroporous resin, clay, bentonite, activated white clay, porous magnesium oxide, etc. Many scholars have also synthesized porous composite materials for sugarcane juice clarification, such as BAC-bentonite, activated carbon-loaded chitosan, porous magnesium silicate, porous inorganic / polymer composite materials, etc. Although these adsorption clarifiers have good sugarcane juice clarification effects, they are difficult to combine with the sulfite method and are therefore limited in their promotion.

[0004] Alkaline calcium-based bentonite is obtained by modifying activated clay with lime. It has the same properties as alkaline clay (also known as activated clay loaded with calcium hydroxide) (the only difference is the preparation method, one is a wet method and the other is a semi-dry method). It has a large number of -OH groups between its layers and on its surface, making it strongly alkaline in water, and it also has a developed pore structure and strong adsorption properties. Chinese invention patent CN200710027154.X discloses an organic acid bentonite and a preparation method thereof, wherein different types of organic acids (one of carboxylic acid, hydroxy acid, amino acid and benzenesulfonic acid) and alkaline bentonite raw materials are used, and alkaline calcium-based bentonite reacts with organic acid in an organic dehydrating solvent to prepare a series of organic acid bentonites with different functions; the structure of the organic acid bentonite is still a layered structure of bentonite material, and the calcium ions between the layers are combined with organic acid radicals in an ionic bond manner; the application scope of the organic acid bentonite mainly includes the following three aspects: first, using its traditional hydrophobic and lipophilic properties, it is used for thickening or anti-settling of organic solutions or emulsions; second, protecting organic acids with poor stability, after the organic acids are fixed between bentonite layers, their heat resistance, antioxidant and UV resistance are greatly improved; third, it is used to prepare various organic / bentonite nanocomposites.

[0005] At present, there is no relevant technical solution for preparing inorganic acid bentonite by reacting alkaline calcium-based bentonite with inorganic acid (such as sulfurous acid, phosphoric acid, etc.) for application in the field of sugarcane juice clarification and decolorization. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a method for preparing a clarifier-modified bentonite for sugar juice clarification and decolorization, wherein alkaline calcium-based bentonite is reacted with an inorganic acid (sulfite, phosphoric acid or carbonic acid) to prepare inorganic acid bentonite, which can be used as a clarifier for sugar juice clarification and decolorization, and has the advantages of good clarification and decolorization effect and simple operation.

[0007] The technical solution to solve the above technical problems is: a preparation method of a clarifier modified bentonite for sugar juice clarification and decolorization, according to which 4-11g of alkaline calcium-based bentonite is added to 100mL of ethanol, ethanol and alkaline calcium-based bentonite are mixed, heated to 30-70°C and kept at a constant temperature, and sulfurous acid solution / phosphoric acid solution is added to the ethanol under stirring to react with the alkaline calcium-based bentonite, and the reaction time is 0.5-7 hours from the time the solution is added, or sulfur dioxide gas / carbon dioxide gas is continuously introduced to react with the alkaline calcium-based bentonite for 0.5-3.5 hours. After the reaction is completed, a filter cake is obtained by filtering, and the filter cake is washed with ethanol and dried to obtain modified bentonite.

[0008] Furthermore, the mass concentration of the ethanol is 25.0-99.8%.

[0009] Furthermore, the amount of sulfurous acid solution added is calculated by adding 0.05 to 0.5 g of sulfurous acid to 100 mL of ethanol.

[0010] Furthermore, the added sulfurous acid solution has a mass concentration of 1 to 5%, the reaction time is 1 to 3 hours, and the amount of alkaline calcium-based bentonite added is calculated by adding 4 to 6 g of alkaline calcium-based bentonite to 100 mL of ethanol.

[0011] Furthermore, the amount of phosphoric acid solution added is calculated by adding 0.1 to 5 g of phosphoric acid to 100 mL of ethanol.

[0012] Furthermore, the mass concentration of the added phosphoric acid solution is 2-20%, the reaction time is 3-5 hours, and the amount of alkaline calcium-based bentonite added is calculated as 4-6 g of alkaline calcium-based bentonite per 100 mL of ethanol.

[0013] Furthermore, the speed of introducing carbon dioxide gas is 80-120 mL / min, the reaction time is 2.5-3.5 hours, and the amount of alkaline calcium-based bentonite added is calculated by adding 5-10 g of alkaline calcium-based bentonite to 100 mL of ethanol.

[0014] Furthermore, the speed of introducing sulfur dioxide gas is 80-120 mL / min, the reaction time is 1-2 hours, and the amount of alkaline calcium-based bentonite added is calculated by adding 4-6 g of alkaline calcium-based bentonite to 100 mL of ethanol.

[0015] The principle of the present invention is: The relatively active hydroxide -OH on the surface and interlayer of alkaline calcium-based bentonite reacts with acidic substances such as sulfurous acid (SO2 dissolved in water), phosphoric acid, and carbonic acid (CO2 dissolved in water) to generate corresponding modified bentonite. The newly generated modified bentonite has a strong adsorption capacity and can be used for sugarcane juice clarification. The reaction formula is as follows: Bent-Ca-OH + H2SO3→ Bent-Ca-O-SO3 + H2O Bent-Ca-OH + H2PO4→ Bent-Ca-O-PO4 + H2O Bent-Ca-OH + H2CO3→ Bent-Ca-O-CO3 + H2O Alkaline calcium clay is not very stable under strong acidic conditions (pH < 3), but by gradually adding the reaction dropwise in an ethanol-water solution, the reaction process with the acid is slow, ensuring that the structure is not destroyed.

[0016] The modified bentonite prepared by the present invention is used as a clarifier in sugar juice clarification and decolorization, which has the following beneficial effects: (1) Clarification can be performed at a relatively low temperature. Sugarcane juice does not need to be heated to a high temperature. There are fewer side reactions and energy consumption is low. The process is short and the operation is simple.

[0017] (2) The color value of the treated sugar juice is low, so the color value of the finished white sugar is low and the product quality is high. The color value of white sugar is affected by the quality of syrup and operating conditions, so the color value of the sugar juice directly affects the color value of white sugar. The decolorization rate of the decolorized sugar juice reaches 88%-96%, which greatly reduces the color value of the sugar juice and improves the quality of white sugar.

[0018] (3) White sugar has a low sulfur content. Decolorizing the mixed juice with sulfurous acid / phosphoric acid / carbonic acid modified bentonite will greatly reduce the sulfur fumigation intensity required for sulfur fumigation neutralization, and even eliminate the need for sulfur fumigation. Decolorizing the clear juice or syrup with modified bentonite can eliminate secondary sulfur fumigation (syrup sulfur bleaching). Both of the above situations can reduce the amount of SO2 added to the juice and also reduce the amount of SO3 remaining in the juice. 2- The amount of sulfur in white sugar is greatly reduced (reduced by more than 30%), thereby reducing the sulfur content in white sugar.

[0019] (4) The purity of white sugar is improved. During the crystallization process of sucrose, although most of the colored substances (pigments) in the syrup are not easy to enter the crystals, the high molecular weight colored substances in the syrup will enter the white sugar or raw sugar crystals in a large proportion and become the main pigments of white sugar or raw sugar. By treating the sugar juice with modified bentonite, the pigment molecules in the sugar juice are adsorbed by the modified bentonite and can no longer condense into colored substances, thereby reducing the total colored substances in the sugar juice and greatly reducing the pigment molecules in the crystals, thereby improving the purity of white sugar.

[0020] (5) Low cost. By treating sugar juice with modified bentonite, the amount of sulfur (used to produce SO2) and lime (used to produce Ca(OH)2) can be reduced. More importantly, the sugar juice phosphorus flotation method, which requires large investment and high operating costs, can be eliminated, greatly reducing investment and operating costs, while also reducing the loss of sucrose.

[0021] The technical features of the method for preparing a clarifier-modified bentonite for sugar juice clarification and decolorization of the present invention are further described below in conjunction with the accompanying drawings and examples. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a scanning electron microscope image of alkaline calcium bentonite.

[0023] Figure 2 This is a scanning electron microscope image of sulfite-modified bentonite in Example 3 of the present invention.

[0024] Figure 3 This is a scanning electron microscope image of the phosphoric acid-modified bentonite of Example 6 of the present invention.

[0025] Figure 4 This is a scanning electron microscope image of the carbonate-modified bentonite of Example 9 of the present invention. DETAILED DESCRIPTION Example 1

[0026] 5.0 g of alkaline calcium-based bentonite was added to 100 mL of 75% ethanol, the reaction temperature was 30°C, 5 mL of 2% sulfurous acid solution was added dropwise, and the reaction time was 3 h. After the reaction was completed, the filter cake was filtered and washed repeatedly three times with 70% ethanol. The obtained filter cake was placed in a forced air drying oven at 50°C and dried for more than 12 hours to obtain modified bentonite.

[0027] The modified bentonite was crushed into powder, 0.50 g was weighed and added into a beaker containing 50 mL of sugarcane juice, and stirred at a constant temperature of 50 °C for 30 min for adsorption decolorization, then filtered, and the absorbance and sugarcane juice brix data of the clear liquid were measured by ultraviolet spectrophotometer and Abel refractometer, the relevant data were corrected, and the decolorization rate was calculated to be 95.12% by the sugar juice decolorization rate calculation formula. Example 2

[0028] 5.0 g of alkaline calcium-based bentonite was added to 100 mL of 75% ethanol, the reaction temperature was 60°C, 5 mL of 2% sulfurous acid solution was added, and the reaction time was 1 h. After the reaction was completed, the filter cake was filtered and washed three times with 70% ethanol. The obtained filter cake was placed in a forced air drying oven at 50°C and dried for more than 12 hours to obtain modified bentonite.

[0029] The modified bentonite was crushed into powder. 0.50 g was weighed and added to a beaker containing 50 mL of sugarcane juice, and stirred at 50 °C for 30 min for adsorption decolorization, and then filtered. The absorbance and brix data of the clear liquid were measured by UV spectrophotometer and Abel refractometer, and the relevant data were corrected. The decolorization rate was calculated by the sugar juice decolorization rate calculation formula to be 95.83%. Example 3

[0030] 5.0 g of alkaline calcium bentonite was added to 100 mL of 99.7% ethanol, the reaction temperature was 30°C, 5 mL of 2% sulfurous acid solution was added, and the reaction time was 1 h. After the reaction was completed, the filter cake was filtered and washed three times with 70% ethanol. The obtained filter cake was placed in a forced air drying oven at 50°C and dried for more than 12 hours to obtain modified bentonite.

[0031] The modified bentonite was crushed into powder. 0.50 g was weighed and added to a beaker containing 50 mL of sugarcane juice, and stirred at 50 °C for 30 min for adsorption decolorization, and then filtered. The absorbance and brix data of the clear liquid were measured by UV spectrophotometer and Abel refractometer, and the relevant data were corrected. The decolorization rate was calculated by the sugar juice decolorization rate calculation formula to be 96.11%. Example 4

[0032] Weigh 5 g of alkaline calcium-based bentonite, add it to 100 mL of 75% ethanol, slowly drop 5 mL of 2% phosphoric acid solution, and react at 50°C for 3 hours. After the reaction is completed, filter the filter cake and wash it repeatedly with 70% ethanol three times. Place the obtained filter cake in a forced air drying oven at 50°C and dry it for more than 12 hours to obtain modified bentonite.

[0033] The modified bentonite was crushed into powder. 0.50 g was weighed and added to a beaker containing 50 mL of sugarcane juice. The mixture was stirred at 50 °C for 30 min for adsorption and decolorization. The supernatant was then filtered and the absorbance and brix data of the sugarcane juice were measured using an ultraviolet spectrophotometer and an Abel refractometer. The relevant data were corrected and the decolorization rate was calculated to be 88.32% using the sugar juice decolorization rate calculation formula. Example 5

[0034] Weigh 5 g of alkaline calcium-based bentonite, add it to 100 mL of 75% ethanol, set the reaction temperature to 50°C, slowly add 25 mL of 20% phosphoric acid solution, and the reaction time is 3 hours. After the reaction is completed, filter the filter cake and wash it repeatedly with 70% ethanol three times. The obtained filter cake is placed in a forced air drying oven at 50°C and dried for more than 12 hours to obtain modified bentonite.

[0035] The modified bentonite was crushed into powder. 0.50 g was weighed and added to a beaker containing 50 mL of sugarcane juice. The mixture was stirred at 50 °C for 30 min for adsorption and decolorization. The supernatant was then filtered and the absorbance and brix data of the sugarcane juice were measured using an ultraviolet spectrophotometer and an Abel refractometer. The relevant data were corrected and the decolorization rate was calculated to be 92.35% using the sugar juice decolorization rate calculation formula. Example 6

[0036] Weigh 5 g of alkaline calcium-based bentonite, add it to 100 mL of 50% ethanol, set the reaction temperature to 50°C, slowly drop 25 mL of 20% phosphoric acid solution, and the reaction time is 5 hours. After the reaction is completed, filter the filter cake and wash it repeatedly with 70% ethanol three times. The obtained filter cake is placed in a forced air drying oven at 50°C and dried for more than 12 hours to obtain modified bentonite.

[0037] The modified bentonite was crushed into powder. 0.50 g was weighed and added to a beaker containing 50 mL of sugarcane juice, and stirred at a constant temperature of 50 ° C for 30 min for adsorption decolorization, and then filtered. The absorbance and sugarcane juice brix data of the clear liquid were measured by ultraviolet spectrophotometer and Abel refractometer, and the relevant data were corrected. The decolorization rate was calculated by the sugar juice decolorization rate calculation formula to be 93.42%. Example 7

[0038] 5.0 g of alkaline calcium-based bentonite was added to 100 mL of 50% ethanol solution, and carbon dioxide gas (purity 99.00-99.99%) was introduced into the ethanol solution at a flow rate of 100 mL / min for 10 min. The reaction temperature was controlled at 50°C for 3 hours. After the reaction was completed, the filter cake was filtered and washed repeatedly with 70% ethanol three times. The obtained filter cake was placed in a blast drying oven at 50°C and dried for more than 12 hours to obtain modified bentonite.

[0039] The modified bentonite was crushed into powder. 0.50 g was weighed and added to a beaker containing 50 mL of sugarcane juice, and stirred at 50 °C for 30 min for adsorption decolorization, and then filtered. The absorbance and brix data of the clear liquid were measured by UV spectrophotometer and Abel refractometer, and the relevant data were corrected. The decolorization rate was calculated to be 89.8% by the sugar juice decolorization rate calculation formula. Example 8

[0040] 5.0 g alkaline calcium-based bentonite, 100 mL mass concentration 50% ethanol solution, reaction temperature at 30 °C reaction time 3 hours, flow rate of 100 mL / min carbon dioxide gas for 10 min. After the reaction is completed, filter the filter cake and wash it repeatedly with 70% ethanol three times. The obtained filter cake is placed in a forced air drying oven at 50 °C and dried for more than 12 hours to obtain modified bentonite.

[0041] The modified bentonite was crushed into powder. 0.50 g was weighed and added to a beaker containing 50 mL of sugarcane juice, and stirred at 50 °C for 30 min for adsorption decolorization, and then filtered. The absorbance and brix data of the clear liquid were measured by UV spectrophotometer and Abel refractometer, and the relevant data were corrected. The decolorization rate was calculated to be 89.9% by the sugar juice decolorization rate calculation formula. Example 9

[0042] 5.0 g of alkaline calcium-based bentonite was added to 50 mL of 50% ethanol solution, the reaction time was 3 hours, the reaction temperature was 30 °C, and the flow rate of carbon dioxide gas was 100 mL / min for 10 min. After the reaction was completed, the filter cake was filtered and washed repeatedly with 70% ethanol three times. The obtained filter cake was placed in a forced air drying oven at 50 °C and dried for more than 12 hours to obtain modified bentonite.

[0043] The modified bentonite was crushed into powder. 0.50 g was weighed and added to a beaker containing 50 mL of sugarcane juice, and stirred at a constant temperature of 50 ° C for 30 min for adsorption decolorization, and then filtered. The absorbance and sugarcane juice brix data of the clear liquid were measured by ultraviolet spectrophotometer and Abel refractometer, and the relevant data were corrected. The decolorization rate was calculated by the sugar juice decolorization rate calculation formula to be 93.9%. Example 10

[0044] 5.0 g of alkaline calcium-based bentonite was added to 100 mL of 75% ethanol, the reaction temperature was 30°C, and sulfur dioxide gas (purity 99.00-99.99%) was introduced at a flow rate of 100 mL / min for 1 hour. After the reaction, the filter cake was filtered and washed repeatedly with 70% ethanol three times. The obtained filter cake was placed in a forced air drying oven at 50°C and dried for more than 12 hours to obtain modified bentonite.

[0045] The modified bentonite was crushed into powder. 0.50 g was weighed and added to a beaker containing 50 mL of sugarcane juice, and stirred at 50 ° C for 30 min for adsorption decolorization, and then filtered. The absorbance and sugarcane juice brix data of the clear liquid were measured by ultraviolet spectrophotometer and Abel refractometer, and the relevant data were corrected. The decolorization rate was calculated by the sugar juice decolorization rate calculation formula to be 94.21%. Embodiment 11

[0046] 5.0 g of alkaline calcium-based bentonite was added to 100 mL of 75% ethanol, the reaction temperature was 60°C, and the flow rate of sulfur dioxide gas was 100 mL / min for 1 hour. After the reaction was completed, the filter cake was filtered and washed repeatedly three times with 70% ethanol. The obtained filter cake was placed in a forced air drying oven at 50°C and dried for more than 12 hours to obtain modified bentonite.

[0047] The modified bentonite was crushed into powder. 0.50 g was weighed and added to a beaker containing 50 mL of sugarcane juice, and stirred at 50 ° C for 30 min for adsorption decolorization, and then filtered. The absorbance and sugarcane juice brix data of the clear liquid were measured by ultraviolet spectrophotometer and Abel refractometer, and the relevant data were corrected. The decolorization rate was calculated by the sugar juice decolorization rate calculation formula to be 95.18%. Example 12

[0048] 5.0 g of alkaline calcium-based bentonite was added to 100 mL of 99.7% ethanol, the reaction temperature was 60°C, and the flow rate of sulfur dioxide gas was 100 mL / min for 2 hours. After the reaction was completed, the filter cake was filtered and washed repeatedly three times with 70% ethanol. The obtained filter cake was placed in a forced air drying oven at 50°C and dried for more than 12 hours to obtain modified bentonite.

[0049] The modified bentonite was crushed into powder. 0.50 g was weighed and added to a beaker containing 50 mL of sugarcane juice, and stirred at 50 ° C for 30 min for adsorption decolorization, and then filtered. The absorbance and brix data of the clear liquid were measured by ultraviolet spectrophotometer and Abel refractometer, and the relevant data were corrected. The decolorization rate was calculated by the sugar juice decolorization rate calculation formula to be 96.40%.

[0050] The sugarcane juice described in the embodiments of the present invention is a mixed juice obtained by squeezing and extracting sugarcane.

[0051] Table 1 shows the changes in BET specific surface area of ​​the modified bentonite used in Examples 3, 6 and 9 of the present invention.

[0052]

[0053] After using modified bentonite for decolorization, the specific surface area of ​​the decolorization filter cake decreased many times, indicating that a lot of pigments and colloids were adsorbed on the surface and inside. The specific surface area of ​​the sample increased after roasting because the high temperature burned away the organic matter of sugarcane juice adsorbed on the surface, and the specific surface area returned to its original level, indicating that the modified bentonite can be reused.

Claims

1. A method for preparing a clarifier-modified bentonite for sugar juice clarification and decolorization, characterized in that: According to the calculation that 4-11 g of alkaline calcium bentonite is added to 100 mL of ethanol, the ethanol and the alkaline calcium bentonite are mixed, heated to 30-70° C. and kept at a constant temperature, and sulfurous acid solution / phosphoric acid solution is added to the ethanol under stirring to react with the alkaline calcium bentonite. The reaction time is 0.5-7 hours from the time when the solution is added, or sulfur dioxide gas / carbon dioxide gas is continuously introduced to react with the alkaline calcium bentonite for 0.5-3.5 hours. After the reaction is completed, a filter cake is obtained by filtering, and the filter cake is washed with ethanol and dried to obtain modified bentonite.

2. The method for preparing a clarifier-modified bentonite for sugar juice clarification and decolorization according to claim 1, characterized in that: The mass concentration of the ethanol is 25.0-99.8%.

3. The method for preparing a clarifier-modified bentonite for sugar juice clarification and decolorization according to claim 1 or 2, characterized in that: The amount of sulfurous acid solution added is calculated by adding 0.05-0.5 g of sulfurous acid to 100 mL of ethanol.

4. The method for preparing a clarifier-modified bentonite for sugar juice clarification and decolorization according to claim 3, characterized in that: The mass concentration of the added sulfurous acid solution is 1-5%, the reaction time is 1-3 hours, and the amount of alkaline calcium-based bentonite added is calculated by adding 4-6g of alkaline calcium-based bentonite to 100mL of ethanol.

5. The method for preparing a clarifier-modified bentonite for sugar juice clarification and decolorization according to claim 1 or 2, characterized in that: The amount of phosphoric acid solution added is calculated by adding 0.1 to 5 g of phosphoric acid to 100 mL of ethanol.

6. The method for preparing a clarifier-modified bentonite for sugar juice clarification and decolorization according to claim 5, characterized in that: The mass concentration of the added phosphoric acid solution is 2-20%, the reaction time is 3-5 hours, and the amount of alkaline calcium-based bentonite added is calculated as 4-6g of alkaline calcium-based bentonite per 100mL of ethanol.

7. The method for preparing a clarifier-modified bentonite for sugar juice clarification and decolorization according to claim 1 or 2, characterized in that: The speed of introducing carbon dioxide gas is 80-120 mL / min, the reaction time is 2.5-3.5 hours, and the amount of alkaline calcium-based bentonite added is calculated by adding 5-10 g of alkaline calcium-based bentonite to 100 mL of ethanol.

8. The method for preparing a clarifier-modified bentonite for sugar juice clarification and decolorization according to claim 1 or 2, characterized in that: The speed of introducing sulfur dioxide gas is 80-120 mL / min, the reaction time is 1-2 hours, and the amount of alkaline calcium-based bentonite added is calculated by adding 4-6 g of alkaline calcium-based bentonite to 100 mL of ethanol.

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