SU950681A1 - Method for purifying effluents containing dispersed impurities - Google Patents

Description

The invention relates to the purification of disperse systems: suspensions, emulsions and other colloidal solutions containing particles of various sizes and nature, and can be used in food, pharmaceutical, chemical, petroleum refining industries for the separation of real dispersions and the separation of valuable substances with the aim of recycling as well as for cleaning various liquids. There is a method of clarifying wastewater by treating them with electric current fl. According to this method, the cleaning of solutions is carried out due to the bulk coagulation of impurities that occur in the direct current field under the interaction of iron ions. The electrical treatment of the dispersion being cleaned is carried out in five stages, increasing the field strength from the previous, stage to the next. The disadvantages of this method are the low efficiency of separation of highly dispersed systems with significant energy consumption, the need for the consumption of soluble electrodes {or reagents) for electrocoagulation of the impurity. by passing the solution through a sorbent placed in an electric field 2. According to this method, the sorbent is placed in the middle chamber of a three-chamber hydrochloric electrolytic cell is applied to the electrodes of a constant electric field, and cleaning solution is passed at a certain speed. At the same time, the impurity particles present in the solution are deposited on the sorbent in an amount that considerably exceeds its absorption capacity. The disadvantages of this method include the need for significant power consumption, since it provides for the cleaning of dispersed systems / regardless of their composition at maximum electric fields. In addition, when cleaning real rastorors containing polydisperse impurities, the specified purification effect is not achieved due to the primary coagulation of large and medium-sized impurity particles and insufficient removal of small-sized impurities in connection with this. The purpose of the invention is to increase the degree of purification and reduce energy consumption for the process. The goal is achieved by the fact that wastewater treatment is carried out by passing them through a layer of sorbent placed in an electric current field, moreover, cleaning is carried out cyclically with a stepwise increase in the intensity of the electric field from cycle to cycle in the range from 1 to 100 V / cm purified water through a layer of sorbent: (5-7) 10 m / s. In addition, the intensity of the electric current from cycle to cycle is increased by 5-25 V / cm. Within the specified limits of the field, complete coagulation and retention of impurity particles takes place, covering in size the entire colloidal dispersion region (lO lOcM) for each dispersion (e.g., suspension, emulsion, solution of colored substances) differing from each other in their fractional composition, there is a limit to the strength of the electric field, which ensures the complete removal of impurities from the solution. Studies show that for jpacTBopOB colored substances with a particle size of 1-0.5 nm, it is necessary to create an electric field with a strength of up to 100 V / cm with an increase interval from cycle to cycle of 15-25 V / cm, which provides an increase in the cleaning effect by 10 -15%. For separation — of such dispersed systems as, for example, montmorillonite suspension, consisting of particles with a size of 250-200 nm, it is necessary to create electric fields with a strength of up to 20 V / cm with an interval of increasing the intensity of the field from cycle to cycle of 5-7 V / cm The flow rate of the solution has a significant impact on the efficiency of the electro-cleaning process of dispersed systems. To implement the method, an electrolytic cell divided by ion-exchange membranes into three chambers is used: cathode, middle and anodic. Electrodes are graphite or platinum plates. A sorbent is placed in the middle chamber (silica gel or granulated clay calcined at). Electrolyte solution (Na.SOj.) Is passed through the electrode chambers at a speed of 0.03-0-0.05 m / s. Electrodes are supplied with a constant electric current with a minimum voltage ensuring that impurities of maximum sizes are kept in the sorbent layer. The separation is carried out "in static or dynamic conditions at a flow rate of the plant no more than 7-KG m / s. The residence time of the dispersion in the sorbent layer is determined by the rate of onset of the equilibrium state of the system and must be at least 2.5 minutes. After the completion of the cleaning cycle, determined by the stabilization of the impurity concentration in the solution (under static conditions) and by increasing the concentration - from the minimum value - at the exit from the cell (under dynamic conditions), stop the flow of the solution, carefully pour it out of the cell, supply water to the layer, turn off the electric current. In this case, the sediment consisting of impurity particles of a certain size is destroyed and carried away by the flow of water from the intergranular space. Then a higher voltage current is supplied to the electrodes and the previously purified solution containing particles of smaller diameter is passed through and the cycle is repeated. The intensity of the field increases from cycle to cycle, and a precipitate consisting of impurity particles of various sizes is obtained. PR and measure 1. A dispersion system, which is an aqueous solution of colored substances - products of thermal decomposition of sucrose, with an impurity concentration of 5 g / l is passed through the middle chamber of an electrolytic cell, 20x30x300 mm in size (thickness, height, width), granules of prebaked clay (bentonite) with an average size of 2, b mm are placed in it beforehand, the flow rate is maintained at about 5f lO M / s. 0.1 and a solution of N32.50400 at a speed of 0.035 m / s are pumped through the electrode chambers. The distance between the electrodes is 30 mm. A voltage is applied to the electrodes to provide a field strength in the sorbent layer of 5 + 0.1 V / cm. The field strength control is carried out using reference electrodes installed in the middle cell of the cell and a high-resistance potentiometer. The temperature is maintained within 25 C. The solution is passed through a layer of sorbent .10 minutes Then the supply of the solution is stopped, the rest of it is carefully drained from the cell, the electric current is turned off, water is supplied, and the residue is poured into a separate container. After this, the experiment is repeated, returning the solution purified in the first cycle to the second cycle. The intensity of the floor is increased to 12.5 V / cm. A repetition of the experiments and an increase in the intensity of the field to a given value, a fraction of precipitates with different particle sizes is obtained. The mass of the fractions obtained is determined by drying by a gravimetric method. The size of particles of colored substances is determined by the Fürth microdiffusion method based on the determination of the diffusion coefficient. . The results of the experiments are presented in table. 1, from which it can be seen that, by increasing the intensity of the field, it becomes possible to separate individual fractions from the same solution of colored substances, which is a polydisperse system, differing in the size of the impurity particles. The larger the radius of the particles, the less the field strength is required for their deposition on the sorbent. EXAMPLE 2. A dispersed system containing substances - products of the thermal decomposition of sucrose a-montmorillonite with a concentration of 1 g / l of each substance, is placed in an average cell of an electrical cell, size .20x30x300 mm, prefilled with granular clay granules of 2-3 mm, and exposed to a constant electric current of 2.5 minutes at 25 ° C. 0.1 g solution is pumped through the electrode chambers, separated from the middle ion-exchange membrane. A voltage is applied to the electrodes to provide a voltage field in the middle chamber of 1 V / cm. After a predetermined time (system equilibrium time) has elapsed, the solution is drained, the current is turned off, and the sorbent is washed with distilled water. The cycles are then repeated, gradually increasing the field strength to 100 V / cm and returning the solution cleaned in the previous cycle to clean it in the next cycle. In the obtained fractions, the concentration of colored substances — calorimetric substances and suspensions — are determined by the gravimetric method. Taty studies are given in Table. 2, from the data table. 2 it can be seen that each of the impurities contained in the solution has its maximum strength, the electric field, the magnitude of which is determined by the nature and size of particles retained on the sorbent fraction. For small values of the field strength and the actual low power consumption is removed, mainly a- montmorillonite, whose particles reach 200-250 nm, with large values of the floor, are colored substances with an average size of fractions of O, 82, 2 nm. With a gradual increase in the voltage of the electric field, it is possible to achieve complete separation of the dispersed system and almost 100% purification. Example 3. A dispersed system containing colored substances, products of caramelization of sucrose and dispersions of a-montmorillonite with a concentration of a substance of 5 g / l, is purified under static conditions in an electrolytic cell according to the method described in Example 2. In parallel. (by a known method) with the same maximum mode parameters. In the course of the experiments, the concentration of the impurity in the solutions, the current density, the voltage across the electrodes, and the intensity of the electric field in the middle working chamber of the cell are determined. In tab. Figure 3 shows the calculated values of the power consumption by the cleaning steps of the proposed method and the total cleaning effect after each step. As can be seen from the table. 3, the total energy consumption per cleaning cycle with a duration of 1.6 minutes according to the proposed method is 0.01774 kWh, while the prototype at the same condition is 0.0668 kWh, i.e. almost 4 times less. The cleaning effect of the proposed method is 2.5 times greater than that known and is 74.3%. With an increase in the number of stages, the solution can be almost completely purified from impurities that are contained. Table 1

37.5

4 5 50.0

75.0

b 100.0 7

39.3

12.8 55.3 16.0

73.5

, 18.2 89.0

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Claims (2)

1. The method of purification of wastewater, 2. The method according to p. 1, about tl 1 and h a-. containing dispersed impurities, y and u with the fact that the intensity including passing them through a layer. electric field from cycle to cycle a sorbent placed in a constant n-5 field is increased by 5-25 V / cm, of an electric current, characterized in that, for the purpose of the sources of information, increase the degree of purification and reduce taken into account in the examination of energy consumption for the process, 1. USSR author's certificate cleaning lead cyclically with step-10 346237, class. C 02 F 1/46, 1970. by increasing the intensity of the elec- ture. 2. USSR author's certificate cycle from cycle to cycle in pre-number 470503, cl. C 02 F 1/46, 1972 (about cases from 1 to 100 V / cm with a speed type). sorbent (5-7).