Process for bentonite obtaining

Description:

The invention refers to a process for obtaining bentonite which can be used in the wine industry, for the manufacture of juices, etc.

It is known that the clarification of wines, juices and other liquids is very successful by using the clay mineral - bentonite. It has been established that the increased sorption capacity of this mineral is determined, first of all, by its high degree of dispersion, the structure of the crystalline network and the ion exchange capacity.

It is also known that in the wine, juice and other industries, it is usually preferred to use alkaline bentonites which are characterized by higher sodium content than calcium content. The content of sodium and calcium in bentonite varies depending on how it is treated.

Usually, in order to increase efficiency, natural bentonite is subject to activation. The process of activation of bentonite with ammonia is known [1]. The disadvantage of the process is the reduced organoleptic properties of the products subjected to activation with this sorbent.

Also known is the bentonite activation process, which allows satisfactory results, including: bentonite crumbling, water softening (quantitative ratio 1: 3), menstruation for 24 hours for swelling, activation with 5% sodium carbonate solution ( quantitative ratio 10 kg bentonite to 100 kg solution), washing activated bentonite with water, filtering, drying, crushing and packing the dry product [2].

Closer to the requested process is the activation process of bentonite with sulfuric acid (less hydrochloric acid) of 15 .25%, the other steps of the process being similar to the previous process [3].

The main disadvantages of the process consist of the corrosion of the machines, the need for the total elimination of chlorine (in case of activation with hydrochloric acid), the use of aggressive solutions that produce the disturbance of the ecological security, the high consumption of water for washing. Thus, for example, at 100 kg of clay, 50 kg of 25% sulfuric acid solution and 150 kg of water are consumed. In the subsequent washing process that follows after acid treatment, it consumes about 800 ... 1000 kg of water, 60 kg of steam, etc.

The problem solved by the invention is the elaboration of a process for obtaining bentonite with efficient sorbfunctional properties, reducing the corrosion of the machine, protecting the environment, reducing the preface of the finished product.

The process according to the invention removes the disadvantages mentioned in that it provides for the activation of natural bentonite (from the deposit near Lărguța village) with small quantities of acetic and citric acids in different quantitative ratios and the subsequent activation with sodium carbonate.

Bentonite extracted from the deposit near Lărguța village is characterized by the greasy chemical composition,%: SiO₂ 60.3 ... 55.0, A1₂A₃ 13.8 ... 13.1, TiO₂'1.0 ... 0.9, F₂A₃ 5.3 ... 4.9, CaO 3.5 ... 2.2, MgO

3.2 .. .2.8, K₂O 1.6 ... 0.9, Na₂O 0.2 ... 0.1, other foreign inclusions 17.7 ... 13.9. X-ray and diffractometric analyzes showed that the main component of the aforementioned bentonite is the montmorillonite mineral that represents alumosilicate with a stratified structure capable of swelling. Good quality of bentonite is mentioned - ion exchange capacity, clarification of wines, juices, oils [7].

The proposed process includes: softening of bentonite with water from the aqueduct in the quantitative ratio bentonite: water 1: 3, maintaining the suspension within 24 hours for swelling, chemical activation of bentonite in three stages, in the first step the treatment of bentonite suspension with solution 5 % of acetic acid (in the quantitative ratio bentonite suspension: 1: 1 acetic acid solution), the activation time constitutes 6 ... 8 h while stirring, washing the bentonite suspension with 3 volumes of distilled or softened water with subsequent filtration, in the second step - treating with citric acid solution (2.5 .. .5.0 kg citric acid per 1000 kg bentonite) with agitation within 1 .. .2 h and meninges within 24 h and in the third stage - treatment with sodium carbonate solution (50 ... 100 kg sodium carbonate per 1000 kg bentonite) for 72.. 120 h, drying at a temperature of

120 .. .150 ° C, bentonite crumbling.

Table 1 shows the dynamics of the modification of the calcium content in natural bentonite, the pH of the water (contact time with acetic acid - 0 hours) and the 5% acetic acid solutions contacting bentonite for different periods of time. The results of three series of experiments are presented. Samples of 100 g bentonite were taken in 100 ml acetic acid solution.

MD 1966 G2 2002.07.31

Table 1

<td>Nr. sample</td><td>Contact time with 5% acetic acid solution, h</td><td>Calcium content, mg / 100 g bentonite</td><td>pH of solutions after contact with bentonite</td>

<td rowspan="4">I</td><td> 0</td><td> 1698</td><td> 8,23</td>

<td> 4</td><td> 456</td><td> 3,68</td>

<td> 8</td><td> 340</td><td> 4,02</td>

<td> 24</td><td> 315</td><td> 4,06</td>

<td rowspan="4">II</td><td> 0</td><td> 1468</td><td> 8,40</td>

<td> 4</td><td> 478</td><td> 3,92</td>

<td> 8</td><td> 432</td><td> 4,52</td>

<td> 24</td><td> 308</td><td> 4,63</td>

<td rowspan="4">III</td><td> 0</td><td> 917</td><td> 8,33</td>

<td> 4</td><td> 424</td><td> 3,55</td>

<td> 8</td><td> 288</td><td> 4,00</td>

<td> 24</td><td> 235</td><td> 4,03</td>

As shown in Table 1, in practice, during the first 8 hours of contact with acetic acid solution of bentonite, the о amount of calcium is eliminated, which is smaller than the amount of calcium eliminated in 24 hours. That is the difference between the results obtained in if the contact of the bentonite with the acetic acid solution is 8 hours and the ones obtained if the contact takes place 24 hours is not considerable. This allows the conclusion that the activation time with acetic acid can be reduced up to 8 h.

Table 2

Modification of some characteristics of bentonite samples depending on the activation process

<td rowspan="2">index</td><td colspan="2">Bentonite activated with citric acid + sodium carbonate</td><td colspan="2">Bentonite activated with acetic acid + citric acid + sodium carbonate</td>

<td> 1</td><td> 2</td><td> 1</td><td> 2</td>

<td>Inflation degree,%</td><td> 316</td><td> 315</td><td> 350</td><td> 350</td>

<td>Protein adsorption,%</td><td> 41,8</td><td> 40,8</td><td> 51,9</td><td> 53,3</td>

<td>Reduction of the optical density of the methylene blue solution, a.</td><td> 0,60</td><td> 0,65</td><td> 1,30</td><td> 1,35</td>

<td>Calcium content, mg / 100 g bentonite</td><td> 1290</td><td> 734</td><td> 404</td><td> 378</td>

Note: position 1 corresponds to the quantitative ratio 2.5 kg citric acid and 50 kg sodium carbonate per 1000 kg bentonite, position 2 - the reagent quantities are 2 times higher than 1 at the same amount of bentonite.

The obtained results correspond to the requirements of PT MD 67-38971808-001: 2000 "Bentonites for the wine industry" and do not yield the results characteristic of foreign bentonites.

Table 3

<td colspan="3">Bentonite Bentogram Indexes (France) and Askangel (Georgia)</td>

<td>index</td><td>Askangel</td><td>Bentogram</td>

<td>Inflation degree,%</td><td> 400</td><td> 390</td>

<td>Protein adsorption,%</td><td> 56</td><td> 48</td>

<td>Reduction of the optical density of the methylene blue solution, a.</td><td> 1,5</td><td> 1,5</td>

<td>Calcium content, mg / 100 g bentonite</td><td> 48</td><td>ИЗО</td>

Bentonite activated by the proposed process has demonstrated a pronounced thixotropic capacity, it has quality and indices comparable to those of known bentonites and can be successfully used to stabilize and clarify wines, juices, other liquid systems.

According to the data in tab.l - 3 it can be deduced that the result of the invention consists in:

MD 1966 G2 2002.07.31

1. Obtaining high quality bentonite;

2. Minimizing corrosion of equipment and machinery;

3. Essential reduction of water consumption for washing;

4. Reduce the use of aggressive media;

5. Environmental protection;

6. Reduce the cost of the finished product.

Example. The 120 g bentonite sample (due to the fact that 100 g bentonite equals 20 g foreign inclusions) is crumbled. Above it water of aqueduct in the quantitative ratio bentonite: water = 1: 3. The mixture is stirred well and left for 24 hours for swelling. Over 24 hours the top layer of water is poured. The clay suspension is passed through the sieve (0.25) to remove the sand and coarse particles. The suspension is then treated with 5% acetic acid solution in the 1: 1 quantitative ratio when stirring. The activation time is 8 hours.

After this, the clay suspension is washed with 3 volumes of distilled water (compared to the volume of the suspension) or softened and filtered in order to eliminate the calcium ions, which tree in solution.

The clay thus treated is subjected to activation with citric acid. For this, 0.5 g of citric acid is dissolved in a small amount of water (about 25 ml). The obtained solution is mixed with clay under intense stirring for 2 hours and left for 24 hours. The next step is the activation with sodium carbonate. For this purpose, the solution containing 5.0 g of sodium carbonate in 50 ml of water is prepared, which is stirred with bentonite suspension and left for 72 h, then filtered.

Activated bentonite is dried at 120 ° C (up to 10% humidity) and crumbled.