Sugarcane juice clarifying and decoloring method based on alkaline calcium bentonite

Abstract

The invention relates to a sugarcane juice clarifying and decoloring method based on alkaline calcium bentonite, which comprises the following steps: mixing sugarcane juice and alkaline calcium bentonite, heating to 40-70 DEG C, keeping the temperature constant, adding a sulfurous acid solution / phosphoric acid solution into the sugarcane juice under the condition of stirring to react with the alkaline calcium bentonite, filtering, washing, and drying to obtain the sugarcane juice. Or continuously introducing sulfur dioxide gas / carbon dioxide gas to react with the alkaline calcium bentonite, and filtering after the reaction is finished to obtain the clarified and decolored cane juice. According to the method, alkaline calcium bentonite is used for replacing lime to serve as a clarifying agent, an existing cane juice clarifying process technology through a sulfurous acid method or a carbonic acid method is improved, the alkaline calcium bentonite and acidic substances such as sulfurous acid, phosphoric acid and carbonic acid are subjected to a neutralization reaction, and corresponding modified bentonite with high adsorption capacity is generated; further, the purpose of clarifying and decoloring the cane juice is achieved.

Description

Technical Field

[0001] The invention relates to a method for clarifying and decolorizing sugarcane juice, in particular to a method for clarifying and decolorizing sugarcane juice based on alkaline calcium-based bentonite. Background Art

[0002] The sugarcane sugar production process includes juice extraction, clarification, evaporation, crystallization, honey separation and drying. The mixed juice obtained after the sugarcane is squeezed and juiced (referred to as sugarcane juice or sugar juice). Sugarcane mixed juice has a very complex composition. In addition to a large amount of sucrose, it also contains various inorganic and organic non-sugar impurities. These impurities will undergo complex chemical changes during the sugar production process, reducing the purity and quality of the sugarcane juice. In order to produce high-quality white sugar products and obtain a higher sugar recovery rate, and to ensure the normal production process, the sugarcane juice must be clarified to remove these non-sugar impurities to the maximum extent. The clarification of sugarcane juice relies on the chemical and physicochemical effects of clarifiers and heating, and through the solid-liquid separation method, various non-sugar components in the mixed juice are removed as much as possible to obtain clarified juice with lower color value and higher purity.

[0003] Lime is an indispensable clarifier in sugarcane sugar factories. The sugarcane juice obtained by squeezing and extracting juice is slightly acidic and is prone to sucrose conversion and sugar loss. First of all, lime should be added in time to adjust the pH value and sterilize. Then other clarifiers need to be added for further clarification. The clarification methods of sugarcane juice can be divided into three types according to the different clarifiers added: lime method, sulfite method and carbonic acid method. The lime method only adds lime as a clarifier, and the clarification process removes less non-sugar components and pigments, which is suitable for the production of raw sugar. The sulfite method uses lime and sulfur dioxide as the main clarifiers, and uses lime and sulfur dioxide to react to generate calcium sulfite particles to absorb non-sugar components such as phenolic substances, colloids, proteins and pigments in the sugarcane juice to achieve the purpose of clarification; after the sugarcane juice absorbs sulfur dioxide, sulfurous acid is generated. Because of its reducing property, it can play a bleaching role and can temporarily reduce the pigment to a colorless substance. The carbonation method uses lime and carbon dioxide as the main clarifiers, and uses the good adsorption effect of a large number of calcium carbonate particles generated by the carbon dioxide saturation process on pigments, colloids and other non-sugar components to achieve the purpose of reducing the color value and improving the purity of the clear juice. It can be seen that the lime method, sulfite method and carbonation method all use lime as the basic clarifier, and then introduce carbon dioxide, sulfur dioxide, phosphoric acid, etc. to react with it to generate porous solids with adsorption characteristics to achieve the purpose of clarification and decolorization. Therefore, whether it is adjusting the pH in the juicing stage or the reaction in the clarification stage, lime is indispensable.

[0004] The essence of the sulfite process for clarifying sugarcane juice is to use sulfur dioxide to react with lime milk to generate calcium sulfite precipitate particles. The newly formed calcium sulfite absorbs non-sugar components such as phenols, amino acids, pigments, proteins and pectin in the sugarcane juice during the formation, coagulation and flocculation sedimentation process to achieve the clarification of the sugarcane juice; at the same time, the reducing property of sulfur dioxide is used to inhibit enzymatic browning, non-enzymatic browning and reduce unsaturated double bonds in pigment molecules to reduce the color value of the sugarcane juice. In order to strengthen flocculation, phosphoric acid is added at the same time, and lime and phosphoric acid are reacted to generate a network of calcium phosphate with stronger flocculation ability. The clarification process of the sulfite process includes: pre-ashing, heating, adding phosphoric acid, sulfur fumigation and neutralization. Because of its simple process, low production cost, and product quality that can meet relevant standards, it is widely used by sugar factories. The principle of carbonation method clarification is mainly to use the good adsorption of a large number of calcium carbonate particles generated by the saturation process reaction on colloids, pigments and other non-sugar components to achieve the purpose of reducing color value and improving the purity of clear juice. The quality of sucrose produced by the carbonation method is better than that by the sulfite method. However, due to the large consumption of quicklime (about 8-10 times that of the sulfite method) and the large amount of alkaline sludge produced, it causes serious environmental pollution. In addition, the process flow of the carbonation method is much more complicated than that of the sulfite method, and the operating technology requirements are high and difficult, so the carbonation method is difficult to promote.

[0005] The quality of sucrose produced by the sulfite process is worse than that produced by the carbonate process. The main problems are high color value and high sulfur dioxide residue. At the same time, the sulfite process also has the defects of consuming sulfur, quicklime, phosphoric acid and producing a large amount of filter mud. It faces many challenges in terms of product quality, food safety and environmental protection. Therefore, improving the sulfite process has always been an important topic in the field of sugar science and engineering. According to domestic and foreign literature reports, the research on improving the sulfite process mainly focuses on equipment, process technology and additives. The main purpose is to reduce the consumption of quicklime and sulfur dioxide, improve the clarification effect, and ensure product quality.

[0006] 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 or the carbonation method and are therefore limited in their promotion.

[0007] In the current public literature, there are some technical solutions for applying bentonite to sugarcane juice clarification, but there are still problems such as relatively complex process flow and inability to effectively combine with sulfite method and carbonation method. Summary of the invention

[0008] The technical problem to be solved by the present invention is to provide a method for clarifying and decolorizing sugarcane juice based on alkaline calcium-based bentonite. The method uses alkaline calcium-based bentonite instead of lime as a clarifier, improves the existing sulfite method or carbonate method sugarcane juice clarification process technology, and makes the alkaline calcium-based bentonite react with acidic substances such as sulfurous acid, phosphoric acid, and carbonic acid to generate corresponding modified bentonite with strong adsorption capacity, thereby achieving the purpose of clarifying and decolorizing sugarcane juice.

[0009] The technical solution for solving the above technical problems is: a method for clarifying and decolorizing sugarcane juice based on alkaline calcium bentonite, wherein 0.5-8g of alkaline calcium bentonite is added to 100mL of sugarcane juice, the sugarcane juice and the alkaline calcium bentonite are mixed, heated to 40-70°C and kept at a constant temperature, and sulfurous acid solution is added to the sugarcane juice under stirring to react with the alkaline calcium bentonite, and the reaction is continued for 1.5-3.5 hours after the addition; or phosphoric acid solution is added to react with the alkaline calcium bentonite, and the reaction time is 2-15 minutes starting from the addition of the phosphoric acid solution, or sulfur dioxide gas / carbon dioxide gas is continuously introduced to react with the alkaline calcium bentonite for 0.3-2.5 hours, and after the reaction is completed, the clarified and decolorized sugarcane juice is filtered to obtain.

[0010] Furthermore, the amount of sulfurous acid solution added is calculated based on 0.2 to 2 g of sulfurous acid per 100 mL of sugarcane juice.

[0011] Furthermore, the added sulfurous acid solution has a mass concentration of 1 to 10%, the reaction time is 2 to 3 hours, and the amount of alkaline calcium-based bentonite added is calculated as 4 to 6 g of alkaline calcium-based bentonite per 100 mL of sugarcane juice.

[0012] Furthermore, the amount of phosphoric acid solution added is calculated as 0.2 to 6 g of phosphoric acid per 100 mL of sugarcane juice.

[0013] Furthermore, the mass concentration of the added phosphoric acid solution is 15-35%, the reaction time is 5-10 minutes, and the amount of alkaline calcium-based bentonite added is calculated as 4-6 g of alkaline calcium-based bentonite added to 100 mL of sugarcane juice.

[0014] Furthermore, the speed of introducing carbon dioxide gas is 2-10 mL / min, the reaction time is 25-35 min, and the amount of alkaline calcium-based bentonite added is calculated as 0.5-3.5 g of alkaline calcium-based bentonite added to 100 mL of sugarcane juice.

[0015] Furthermore, the speed of introducing sulfur dioxide gas is 2-10 mL / min, the reaction time is 1-2 hours, and the amount of alkaline calcium-based bentonite added is calculated as 4-6 g of alkaline calcium-based bentonite added to 100 mL of sugarcane juice.

[0016] Furthermore, the sugarcane juice is a mixed juice obtained by squeezing and extracting sugarcane.

[0017] Furthermore, the pH value of the sugarcane juice is 4-11.

[0018] The principle of the present invention is: my country has abundant reserves of bentonite. Bentonite can be activated with acid to obtain activated clay, which can then be prepared with lime by semi-dry or wet method to prepare alkaline calcium-based bentonite. It can be seen that alkaline calcium-based bentonite is widely available and inexpensive. The preparation of alkaline calcium-based bentonite (Bent-CaOH) uses activated clay, quicklime (calcium oxide) and water as raw materials. Through the reaction of hydroxide ions with hydrogen ions between activated clay layers, Ca(OH)+ is introduced into the interlayer, so that there are exchangeable hydroxides between the layers, which has anion exchange function and increases the interlayer distance; it also shows that calcium hydroxide is highly dispersed on the surface and between the layers of bentonite, which is conducive to the efficient use of lime.

[0019] Since alkaline calcium-based bentonite has strong adsorption capacity, large alkali capacity, and active and exchangeable hydroxide groups between layers, alkaline calcium-based bentonite is used as a clarifier instead of lime and added to the sulfite method or carbonate method sugarcane juice clarification process. Alkaline calcium-based bentonite reacts with the added acidic substances such as sulfurous acid (sulfur dioxide dissolved in water), phosphoric acid, and carbonic acid (carbon dioxide dissolved in water) to generate modified bentonite with stronger adsorption capacity, and then the strong adsorption capacity of the newly modified bentonite is used to achieve the purpose of sugarcane juice clarification.

[0020] The reaction process of alkaline calcium bentonite with sulfurous acid, phosphoric acid and carbonic acid 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 bentonite is used to replace lime in the pre-liming process of sugarcane juice clarification. The layered porous structure of alkaline calcium bentonite has a strong adsorption effect on non-sugar components in sugarcane juice. In the sulfur fumigation stage, the -OH on the surface and between the layers of alkaline calcium bentonite reacts with SO2 to generate sulfite-modified bentonite in situ. Alkaline calcium bentonite is unstable under strong acidic conditions (pH <3), but in the sulfite method of sugarcane juice clarification process, the pH value of the neutralized juice is generally controlled between 6.8-7.1, and is often even controlled under weak alkaline conditions (pH 8.0±0.2) to improve the quality of finished sugar and sugar recovery rate. Therefore, as long as the pH value is strengthened, the structure of alkaline calcium bentonite will not be destroyed during the reaction of alkaline calcium bentonite with sulfite in sugarcane juice.

[0021] Adsorption and removal of non-sugar components are the essence of the sugarcane juice clarification process. Typical non-sugar components in sugarcane juice include colloids, phenolic substances, pigments, amino acids, proteins, etc. The morphology and structure of the adsorption clarifier generated in situ in the sulfite process have a clarifying effect on sugarcane juice, which is essentially the macroscopic effect of the adsorption clarifier on the adsorption and separation of the above non-sugar components. Adsorption and flocculation are the key to the clarification of sugarcane juice by calcium sulfite particles. In the sulfite process, the calcium sulfite particles generated in situ in the sulfur fumigation and neutralization stage first adsorb the non-sugar substances in the sugarcane juice and condense, and then react with the flocculant to flocculate and settle through mechanisms such as bridging, netting, and sweeping, thereby achieving clarification, decolorization, and impurity removal of the sugarcane juice and improving the sucrose purity of the sugarcane juice. A large number of literatures have confirmed that the morphology and structure of the newly generated calcium sulfite particles are closely related to the adsorption and flocculation properties and mechanism of non-sugar substances in sugarcane juice, and have an important influence on the clarification of sugarcane juice; by effectively regulating the morphology and structure of the clarifier particles, the efficiency of the sugar production process by the sulfite process can be improved. Obviously, the in-situ generated modified bentonite composite can adsorb and remove colored substance molecules, and its morphology and structure will also have an important influence on the clarification of sugarcane juice.

[0022] After clarification, the mixed sugarcane juice is filtered to achieve clarification and decolorization of the sugarcane juice at a lower temperature. During the filtration process, the porous bentonite becomes a good filtration aid, making the filtration process of the viscous and difficult-to-filter sugarcane juice very easy. The filter cake is bentonite rich in organic matter, which is an excellent raw material for producing organic fertilizers.

[0023] The present invention has the following beneficial effects: (1) Clarification is carried out at a lower temperature, the sugarcane juice does not need to be heated to a high temperature, there are fewer side reactions, and the energy consumption is low.

[0024] (2) Using alkaline calcium-based bentonite with porous layered structure to replace lime for clarification of sugarcane juice by sulfite or carbonation can not only adjust the pH of sugarcane juice, but also strengthen the adsorption of the system, and can further react with sulfurous acid or carbonic acid to form a complex with stronger adsorption capacity in situ. The alkaline calcium-based bentonite clarifier has an adsorption effect on non-sugar impurities in both the pre-liming stage and the sulfur fumigation stage, so it can be organically combined with the sulfite or carbonation process. Since the [Ca(OH)+] group in the alkaline calcium-based bentonite is highly dispersed between the bentonite layers and on the surface, this method can effectively improve the problem of poor dissolution of lime in sugarcane juice in the traditional method, improve the utilization efficiency of lime, reduce the amount of lime, and help reduce carbon emissions. At the same time, it also reduces the consumption of sulfur dioxide or carbon dioxide, reduces the risk of environmental pollution caused by sulfur dioxide in the sulfite process, and significantly reduces the filter mud of the carbonation process; this method does not change the sulfite or carbonation process, only needs to update the clarifier, which greatly reduces the investment cost of technical transformation, and can be used as the most convenient and green way to improve the sulfite / carbonation clarification process.

[0025] (3) Bentonite is a porous layered material, so it can be used as a good filtration aid. Conventional filtration methods can be used to achieve liquid-solid separation, thus overcoming the problem that sugarcane juice is difficult to filter directly due to its high viscosity.

[0026] (4) Short process and easy operation.

[0027] (5) The bentonite rich in organic matter in the filter cake can be used as organic fertilizer and is a good soil conditioner.

[0028] The technical features of the method for clarifying and decolorizing sugarcane juice based on alkaline calcium-based bentonite of the present invention are further described below in conjunction with embodiments. DETAILED DESCRIPTION

[0029] Alkaline calcium-based bentonite is obtained by modifying activated clay with lime. Similar products include alkaline clay (also known as calcium hydroxide-loaded activated clay). The former is prepared by semi-dry method and the latter by wet method. Because it has more -OH between layers and on the surface, it is strongly alkaline in water and has a developed pore structure, so it has strong adsorption performance. Taking advantage of this characteristic, it can replace lime for sugarcane juice clarification, which can not only adjust the pH of sugarcane juice, but also enhance the adsorption capacity of the system. After reacting with sulfurous acid, phosphoric acid and carbonic acid, a composite with strong adsorption capacity can be obtained. Therefore, it can be organically combined with the sulfite method and the carbonic acid method to further reduce the consumption of quicklime, sulfur dioxide and carbon dioxide and improve the clarification effect of sugarcane juice.

[0030] Operation steps: weigh the alkaline calcium-based bentonite and put it into a three-necked flask, then measure the sugarcane juice and add it into the flask, under heating and stirring conditions, use a dropping funnel to drop sulfurous acid (sulfur dioxide dissolved in water) / phosphoric acid / carbonic acid (carbon dioxide dissolved in water) solution to react with the alkaline calcium-based bentonite, and continue the reaction after the addition is complete; after the reaction is completed, filter the filtrate, use an ultraviolet spectrophotometer and an Abel refractometer to measure the absorbance and sugarcane juice brix data, correct the relevant data, and then calculate the decolorization rate using the sugar juice decolorization rate calculation formula.

[0031] Example 1: 5.0 g of alkaline calcium-based bentonite was put into a three-necked flask, and 100 mL of sugarcane juice was added thereto. Under the condition of heating to a constant temperature of 50° C. and continuous stirring, a 2% sulfuric acid solution was added dropwise with a dropping funnel to react with the alkaline calcium-based bentonite. After the addition of 15 mL, the reaction was continued for 3 h. After the reaction was completed, the solution was filtered, and the absorbance was measured and the brix calibration was performed according to the literature. The decolorization rate of the obtained clear juice was 97.48%. The finished white sugar was obtained by evaporation, concentration, crystallization and honey separation.

[0032] Example 2: 5.0 g of alkaline calcium-based bentonite was put into a three-necked flask, and 100 mL of sugarcane juice was added thereto. Under the condition of heating to a constant temperature of 50°C and continuous stirring, a 3% sulfuric acid solution was added dropwise with a dropping funnel to react with the alkaline calcium-based bentonite. After the addition of 25 mL, the reaction was continued for 3 h. After the reaction was completed, the solution was filtered, and the absorbance was measured and the brix calibration was performed according to the literature. The decolorization rate of the obtained clear juice was 97.83%. The finished white sugar was obtained by evaporation, concentration, crystallization and honey separation.

[0033] Example 3: 5.0 g of alkaline calcium-based bentonite was put into a three-necked flask, and 100 mL of sugarcane juice was added thereto. Under the condition of heating to a constant temperature of 50°C and continuous stirring, a 3% sulfuric acid solution was added dropwise with a dropping funnel to react with the alkaline calcium-based bentonite. After the addition of 20 mL, the reaction was continued for 2 h. After the reaction was completed, the solution was filtered, and the absorbance was measured and the hammer calibration was performed according to the literature. The decolorization rate of the obtained clear juice was 99.01%. The finished white sugar was obtained by evaporation, concentration, crystallization and honey separation.

[0034] Example 4: 5.0 g of alkaline calcium-based bentonite was put into a three-necked flask, and 100 mL of sugarcane juice was added thereto. Under the condition of heating to a constant temperature of 50°C and continuous stirring, a 3% sulfuric acid solution was added dropwise with a dropping funnel to react with the alkaline calcium-based bentonite. After adding 25 mL, the reaction was continued for 2 h. After the reaction was completed, the solution was filtered, and the absorbance was measured and the brix calibration was performed according to the literature. The decolorization rate of the obtained clear juice was 97.71%. The finished white sugar was obtained by evaporation, concentration, crystallization and honey separation.

[0035] Example 5: 5.0 g of alkaline calcium-based bentonite was put into a three-necked flask, and 100 mL of sugarcane juice was added thereto. Under the condition of heating to a constant temperature of 50°C and continuous stirring, a 6.5% sulfuric acid solution was added dropwise using a dropping funnel to react with the alkaline calcium-based bentonite. After adding 25 mL, the reaction was continued for 2 h. After the reaction was completed, the solution was filtered, and the absorbance was measured and the brix calibration was performed according to the literature. The decolorization rate of the obtained clear juice was 99.15%. The finished white sugar was obtained through evaporation, concentration, crystallization and honey separation.

[0036] Example 6: 100 mL of sugarcane juice (pH about 5.38) was added to a 500 mL three-necked flask, and 5 g of alkaline calcium-based bentonite was weighed and put into the flask. Under the condition of heating to a constant temperature of 40°C and continuous stirring, a phosphoric acid solution with a mass concentration of 20% was added dropwise using a dropping funnel to react with the alkaline calcium-based bentonite. After the addition of 25 mL, the reaction was continued for 10 min (starting from the time when the phosphoric acid solution was added). After the reaction was completed, the sugarcane juice in the flask was filtered, and the decolorization rate was determined and calculated. The decolorization rate was 97.69%.

[0037] Example 7: 100 mL of sugarcane juice (pH about 5.38) was added to a 500 mL three-necked flask, and 5 g of alkaline calcium-based bentonite was weighed and put into the flask. Under the condition of heating to a constant temperature of 40°C and continuous stirring, a phosphoric acid solution with a mass concentration of 20% was added dropwise using a dropping funnel to react with the alkaline calcium-based bentonite. After the addition of 25 mL, the reaction was continued for 5 min (starting from the time when the phosphoric acid solution was added). After the reaction was completed, the sugarcane juice in the flask was filtered, and the decolorization rate was determined and calculated. The decolorization rate was 99.13%.

[0038] Example 8: 100 mL of sugarcane juice (pH about 5.38) was added to a 500 mL three-necked flask, and 0.5 g of alkaline calcium-based bentonite was weighed and put into the flask. Under the condition of heating to a constant temperature of 40°C and continuous stirring, a phosphoric acid solution with a mass concentration of 20% was added dropwise using a dropping funnel to react with the alkaline calcium-based bentonite. After the addition of 1.5 mL, the reaction was continued for 5 minutes (the timing started from the addition of the phosphoric acid solution). After the reaction was completed, the sugarcane juice in the flask was filtered, and the decolorization rate of the filtered juice was determined and calculated, and the decolorization rate was 98.82%.

[0039] Example 9: 100 mL of sugarcane juice (pH about 5.38) was added to a 500 mL three-necked flask, and 5 g of alkaline calcium-based bentonite was weighed and put into the flask. Under the condition of heating to a constant temperature of 40°C and continuous stirring, a phosphoric acid solution with a mass concentration of 30% was added dropwise using a dropping funnel to react with the alkaline calcium-based bentonite. After the addition of 1.5 mL, the reaction was continued for 5 min (starting from the addition of the phosphoric acid solution). After the reaction was completed, the sugarcane juice in the flask was filtered, and the decolorization rate was determined and calculated. The decolorization rate was 99.28%.

[0040] Example 10: 100 mL of sugarcane juice (pH about 5.38) was added to a 500 mL three-necked flask, and 6.5 g of alkaline calcium-based bentonite was weighed and put into the flask. Under the condition of heating to a constant temperature of 40°C and continuous stirring, a phosphoric acid solution with a mass concentration of 30% was added dropwise using a dropping funnel to react with the alkaline calcium-based bentonite. After the addition of 1.5 mL, the reaction was continued for 5 minutes (starting from the time when the phosphoric acid solution was added). After the reaction was completed, the sugarcane juice in the flask was filtered, and the decolorization rate was determined and calculated. The decolorization rate was 99.37%.

[0041] Example 11: 100 mL of sugarcane juice (pH about 5.38) was added to a 500 mL three-necked flask, and 0.5 g of alkaline calcium bentonite was weighed and put into the flask. Under the conditions of constant temperature of 50°C and stirring, 5 mL / min of carbon dioxide was introduced to react with the alkaline calcium bentonite for 30 min. After the reaction, the sugarcane juice in the flask was filtered, and the decolorization rate of the filtered juice was measured and calculated. The decolorization rate was 91.5%.

[0042] Example 12: 100 mL of sugarcane juice (pH about 5.38) was added to a 500 mL three-necked flask, and 3.0 g of alkaline calcium-based bentonite was weighed and put into the flask. Under the conditions of a constant temperature of 70°C and stirring, 5 mL / min of carbon dioxide was introduced to react with the alkaline calcium-based bentonite for 30 min. After the reaction, the sugarcane juice in the flask was filtered, and the decolorization rate of the filtered juice was determined and calculated. The decolorization rate was 98.4%.

[0043] Example 13: 100 mL of sugarcane juice (pH about 5.38) was added to a 500 mL three-necked flask, and 3.0 g of alkaline calcium-based bentonite was weighed and put into the flask. Under the conditions of a constant temperature of 70°C and stirring, 5 mL / min of carbon dioxide was introduced to react with the alkaline calcium-based bentonite for 20 min. After the reaction, the sugarcane juice in the flask was filtered, and the decolorization rate of the filtered juice was determined and calculated. The decolorization rate was 98.5%.

[0044] Example 14: Take 100 mL of sugarcane juice (pH about 5.38), adjust the pH of the sugarcane juice to 7 with sodium hydroxide solution, add it into a 500 mL three-necked flask, and then weigh 3.0 g of alkaline calcium-based bentonite and put it into it. Under the conditions of constant temperature of 70°C and stirring, pass 5 mL / min of carbon dioxide to react with the alkaline calcium-based bentonite for 30 minutes; after the reaction, the sugarcane juice in the flask is filtered, and the filtrate obtained by filtration is subjected to the absorption and decolorization rate determination and calculation, and the decolorization rate is 96.9%.

[0045] Example 15: 5.0 g of alkaline calcium-based bentonite is placed in a three-necked flask, and 100 mL (pH about 5.38) of sugarcane juice is added thereto. While heating to a constant temperature of 50°C and stirring continuously, 5 mL / min of sulfur dioxide is introduced to react with the alkaline calcium-based bentonite for 1 hour. After the reaction is completed, suction filtration is performed, and after the suction filtration, the absorbance is measured and the hammer calibration is performed according to the literature. The decolorization rate of the obtained clear juice is 95.18%. The finished white sugar is obtained through evaporation, concentration, crystallization and honey separation.

[0046] Example 16: 5.0 g of alkaline calcium-based bentonite is placed in a three-necked flask, and 100 mL (pH about 5.38) of sugarcane juice is added thereto. While heating to a constant temperature of 70°C and stirring continuously, 5 mL / min of sulfur dioxide is introduced to react with the alkaline calcium-based bentonite for 1 hour. After the reaction is completed, suction filtration is performed, and after the suction filtration, the absorbance is measured and the hammer correction is performed according to the literature. The decolorization rate of the obtained clear juice is 97.58%. The finished white sugar is obtained through evaporation, concentration, crystallization and honey separation.

[0047] Example 17: 5.0 g of alkaline calcium-based bentonite is placed in a three-necked flask, and 100 mL (pH about 5.38) of sugarcane juice is added thereto. While heating to a constant temperature of 70°C and stirring continuously, 5 mL / min of sulfur dioxide is introduced to react with the alkaline calcium-based bentonite for 2 hours. After the reaction is completed, suction filtration is performed, and after the suction filtration, the absorbance is measured and the hammer calibration is performed according to the literature. The decolorization rate of the obtained clear juice is 98.15%. The finished white sugar is obtained through evaporation, concentration, crystallization and honey separation.

[0048] The sugarcane juice described in the embodiments of the present invention is a mixed juice obtained by squeezing sugarcane.

[0049] Table 1 shows the changes in BET specific surface area of ​​the alkaline calcium-based bentonite used in Examples 4, 10 and 12 of the present invention.

[0050]

[0051] After using alkaline calcium-based 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 caused the organic matter of sugarcane juice adsorbed on the surface to burn away, and the specific surface area returned to its original level, indicating that the modified bentonite can be reused.

Claims

1. A method for clarifying and decolorizing sugarcane juice based on alkaline calcium-based bentonite, characterized in that: The sugarcane juice and the alkaline calcium bentonite are mixed, heated to 40-70°C and kept at a constant temperature, and sulfurous acid solution is added to the sugarcane juice under stirring to react with the alkaline calcium bentonite, and the reaction is continued for 1.5-3.5 hours; or phosphoric acid solution is added to the alkaline calcium bentonite to react, and the reaction time is 2-15 minutes starting from the addition of the phosphoric acid solution; or sulfur dioxide gas / carbon dioxide gas is continuously introduced to react with the alkaline calcium bentonite for 0.3-2.5 hours, and after the reaction is completed, the clarified and decolorized sugarcane juice is filtered.

2. The method for clarifying and decolorizing sugarcane juice based on alkaline calcium bentonite according to claim 1, characterized in that: The amount of sulfurous acid solution added is calculated based on 0.2 to 2 g of sulfurous acid per 100 mL of sugarcane juice.

3. The method for clarifying and decolorizing sugarcane juice based on alkaline calcium bentonite according to claim 2, characterized in that: The mass concentration of the added sulfurous acid solution is 1-10%, the reaction time is 2-3 hours, and the amount of alkaline calcium-based bentonite added is calculated as 4-6g of alkaline calcium-based bentonite added to 100mL of sugarcane juice.

4. The method for clarifying and decolorizing sugarcane juice based on alkaline calcium bentonite according to claim 1, characterized in that: The amount of phosphoric acid solution added is calculated based on 0.2 to 6 g of phosphoric acid per 100 mL of sugarcane juice.

5. The method for clarifying and decolorizing sugarcane juice based on alkaline calcium bentonite according to claim 4, characterized in that: The mass concentration of the added phosphoric acid solution is 15-35%, the reaction time is 5-10 minutes, and the amount of alkaline calcium-based bentonite added is calculated by adding 4-6g of alkaline calcium-based bentonite to 100mL of sugarcane juice.

6. The method for clarifying and decolorizing sugarcane juice based on alkaline calcium bentonite according to claim 1, characterized in that: The speed of introducing carbon dioxide gas is 2-10 mL / min, the reaction time is 25-35 min, and the amount of alkaline calcium-based bentonite added is calculated as 0.5-3.5 g of alkaline calcium-based bentonite per 100 mL of sugarcane juice.

7. The method for clarifying and decolorizing sugarcane juice based on alkaline calcium-bentonite according to claim 1, characterized in that: The speed of introducing sulfur dioxide gas is 2-10 mL / min, the reaction time is 1-2 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 sugarcane juice.

8. The method for clarifying and decolorizing sugarcane juice based on alkaline calcium bentonite according to claim 1, characterized in that: The sugarcane juice is a mixed juice obtained by squeezing and extracting sugarcane.

9. The method for clarifying and decolorizing sugarcane juice based on alkaline calcium-bentonite according to claim 1, characterized in that: The pH value of the sugarcane juice is 4-11.

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