FI69572C - FOERFARANDE FOER RENING AV AVFALLSVATTEN - Google Patents

Abstract

1. Process for preparing an anion exchanger, especially for the waste water treatment, comprising the treatment of cellulose derivatives with polyethylene imine in an aqueous reaction medium and recovery of the ion exchanger from the reaction mixture, characterized in that as cellulose derivative bark treated first with caustic alkali and subsequently with sulfuric acid is used and the treatment is carried out at a pH value of from 2 to 6.

Description

69572

Method for waste water treatment

The invention relates to a process for the treatment of waste water using an anion exchanger.

5 The treatment of domestic and industrial effluents is a growing problem due to the ever-increasing demands on the purity of effluents. There are only methods for wastewater treatment that are good in efficiency and can be applied relatively cheaply, 10 applied in practice. It must therefore be possible to produce the substances used for the treatment of waste water at the lowest possible cost.

According to its origin, wastewater mainly contains high molecular weight proteins, low molecular weight poly-15 peptides and amino acids, lipids, and sugars. To date, special coagulation methods have been used to remove nitrogenous compounds from wastewater, in which substances capable of flocculating with contaminants are added to the wastewater, whereby the formed vapors precipitate to form a precipitate, after which they can be separated from the water. Examples of such flocculants are lignin sulfonic acid and dodecylbenzenesulfonic acid. These compounds are able to flocculate with high molecular weight proteins, but not with low molecular weight nitrogenous compounds such as polypeptides and amino acids. Thus, industrial effluents, such as effluents from fish processing plants or slaughterhouses, cannot thus be treated with such flocculants to such an extent that effluents could be discharged.

Wastewater treatment with ion exchangers is known, but the method has not been economically viable so far. Known ion exchangers based on cellulose consist of cellulose phosphate esters or cellulose sulfate esters prepared by reacting cellulose with SO 2 gas. However, the manufacture of these ion exchangers is too expensive to start their production for wastewater treatment.

The invention relates to a process for the treatment of waste water, wherein the waste water is contacted with an anion exchanger 5 prepared by treating a cellulosic material with a polyethyleneimine solution. The process is characterized in that an anion exchanger prepared by treating a bark or a modified bark with a polyethyleneimine solution having a pH of 10 to 6, preferably 4 to 5, is used. The ion exchanger used in the process of the invention is efficient and can be prepared inexpensively. This ion exchanger removes anionic organic compounds such as proteins and nitrogen compounds from wastewater. It must be possible to regenerate the ion exchanger in order to minimize the removal problems of the spent ion exchanger, and this is achieved by the ion exchanger used in the process according to the invention.

Recovery of the ion exchanger from the reaction mixture can be accomplished by decantation, filtration, or some other separation method, and after separation from the reaction mixture, the ion exchanger can be washed and / or dried. However, it is appropriate to treat the ion exchanger without washing or drying and to wash it with water only immediately before use.

The reaction between the bark or modified bark and the polyethyleneimine can take place at ambient temperature, however, in order to shorten the reaction time and increase the yield, it is expedient to work at elevated temperatures, preferably in the range 40-90 ° C and especially in the range 60-70 ° C.

The pH of the reaction mixture is preferably adjusted to a range of about 4-5, which can be done with an acid, preferably hydrochloric acid. The reaction time depends on other reaction conditions, in particular whether the reaction takes place with or without stirring. The reaction time is relatively long and is usually between two hours and four days.

69572

The reaction rate depends on the concentration of the polyethyleneimine solution. This concentration must therefore be at least 1% by weight, but preferably at least 2% by weight, which can be achieved by using a 5-40% by weight solution.

The polyethyleneimine solution can be used several times, because after the first use and also after several other uses, it still contains enough polyethyleneimine to be used in the next reaction. Generally, 5-10% of polyethyleneimine is consumed in the manufacture of an ion exchanger.

In order to achieve good activation of the material and binding of a sufficient amount of polyethylene to the bark or modified bark, the reaction time is suitably between 1 and 4 days.

The preferred starting material is a mixture obtained by treating the bark in separate steps with alkali liquor and sulfuric acid. The compounds present in such a starting material have not been defined, but it is nevertheless clear that they contain sulfur-containing, strongly acidic groups, such as acid sulfate ester groups or sulfonic acid groups, as well as carboxylic acid groups and hydroxyl groups.

This starting material is prepared according to purpose-25 by first treating a finely ground bark with an average particle diameter of 0.5-5 mm, preferably 1-3 mm, with an alkali liquor, in particular sodium hydroxide solution, of at least 5% by weight, preferably 20-40% by weight. , the material is then washed with water, suitably to a pH of less than 9, then treated with 50 to 65% by weight of sulfuric acid and finally washed again with water, preferably to a pH of more than 4. The treatment time with alkaline liquor is between 0.5 and 20 hours, preferably between 3 and 10 hours and the treatment with sulfuric acid is between 0.5 and 8 hours, preferably between 1 and 6 hours.

4,69572

In particular, when using an ion exchanger prepared by reaction with polyethyleneimine for wastewater treatment, it is expedient to mix activated clay soil, preferably 5 Al 2 O 3, with a mixing ratio between the ion exchanger and the activated clay soil, suitably between 2: 1 and 1: 4, e.g. 1: 2. This last value is especially relevant when the mixture is used for municipal wastewater treatment.

10 Clay soils can be conveniently activated by treatment with nitric acid, although other activated clay soils are also possible.

The ion exchanger used in the process of the invention is highly efficient in wastewater treatment, with a particularly high selectivity for proteins, polypeptides, amino acids, dyes, humic acids, inorganic anions such as chromate ions or phosphate ions and other compounds found in economic, plant and industrial effluents. The method according to the invention 20 can thus be used, for example, in the treatment of municipal waste water, as well as waste water from textile dyeing plants, electroplating plants, slaughterhouses and fish factories, waste water from kitchens and laundries and waste water from soybean mills and the like.

If the anion exchanger is mixed with a cellulose cation exchanger and an activated clay soil such as clinoptilolite in a ratio of 2: 2: 1 to 1: 1: 4, the method can also be applied to the recycling of water from fish farms. Because clinoptilolite is capable of removing ammonium, it is possible to achieve complete removal of nitrogen compounds from water from fish processing plants using this mixture.

The anion exchanger used in the process of the invention can be easily regenerated, if necessary, by eluting with sodium hydroxide solution or an aqueous solution containing a mixture of sodium hydroxide solution and common salt. Regenerator

After activation of It 69572, reactivation can be performed by treatment with polyethyleneimine.

Example A mixture of cellulose derivatives 5 used as a starting material was prepared as follows. Using a cutting machine, a bark of pine wood was chopped to a particle size of 0.5-5 mm. 2 M sodium hydroxide solution was poured into the comminuted bark in a reaction vessel until the bark was covered. The reaction mixture was allowed to stand for 7 hours. The sodium hydroxide solution 10 was then removed and the treated bark was washed with water to pH 9. The bark was then covered with 65% sulfuric acid and the mixture was allowed to stand for 4 hours. The sulfuric acid was then removed and the solid reaction product was washed several times with tap water until the pH was greater than 4.

The pH of the approximately 7% polyethyleneimine solution was adjusted to 4.5 with hydrochloric acid. The starting material prepared as described above was covered with this solution, and the reaction mixture was heated at 70 ° C for 5 hours and then allowed to stand at room temperature for 3 days. The resulting product was then removed by filtration and the filtrate could be reused.

Immediately before use, the wet ion exchanger thus obtained was washed several times with water.

To determine the selectivity factors, solutions of azo dyes, dodecylbenzene sulfonate (DBS), humic acid, and potassium chromate were prepared and applied to an anion exchange column. A 2.5 cm diameter glass column packed with an anion exchanger was used. The layer thickness was 30 cm and the flow rate was 15 meters in 30 hours. Removal from the column was analyzed every 500 ml.

The selectivity coefficients observed indicate the percentage of substance that preferentially binds to the ion exchanger relative to sodium chloride when the ion-35 exchanger is treated with a solution in which the solute contains 50% of the substance in question and 50% of sodium chloride.

69572 The following selectivity factors were obtained for the different substances:

Table 1 5 25 mg / l In the treated Selectivity solution to be treated pH value of the solution

Red azo dye 6.8-7.2 67

Yellow azo dye 6.8-7.2 35 10 DBS 6.8-7.2 50

Humic acid 6.0-6.5 100

Cr04 6.5-6.8 19

The ion exchanger prepared as described above was mixed with the activated Al 2 O 2 material in such a proportion that the mixture contained 2/3 of the activated Al 2 O 2 and 1/3 of the ion exchanger. This mixture was used to study the phosphate removal from aqueous solution. The mixture was placed in a test apparatus with a diameter of 15 cm and a height of 2 m 20 and a layer thickness of 1 m. The activated clay soil is able to bind orthophosphate, while the ion exchanger removes polyphosphate and organic phosphate. A flow rate of 10 bed volumes per hour was used, corresponding to about 175 liters of wastewater per hour. Wastewater was passed up through 25 columns.

After the column was saturated, it was regenerated as follows: washing with 35 liters of water, elution with 25 liters of 0.5 M NaOH, washing with 70 liters of water.

The following wastewaters were treated in a pilot plant: 30 I. Wastewater from a biological filter with a total phosphorus content of 9.6 mg / liter.

II. Wastewater from a chemical precipitation plant with a total phosphorus content of 0.61 mg / liter.

III. Overflow from a rainwater basin with a total phosphorus content of 1.08 mg / liter.

The column and eluent were used 4 times to perform the experiment presented here. Samples from column I! 69572 of incoming fluid was taken once an hour and analyzed. The results are shown in the following Tables 2 and 3.

Table 2 5 Feed Capacity Sludge 3 3

Material volume m x) 1 1 / m wastewater I 320 5.5 5 0.90 II 2200 38.4 5 0.13 III 1811 31.6 5 0.16 10 was removed 0.1 m "corresponding to 0.1 wash water

Table 3 15 Sample P.. P,. . Ortho-P Soluble Soluble J tot soluble (average) organic polyphosphate

P

Input I 9.6 7.3 6.1 0.7 0.5 20 Deletion I 0.95 0.95 0.57 0.2 0.2

Input II 0.61 0.37 0.25 0.05 0.05

Depreciation II 0.06 0.06 0.01 0.03 0.02

Input III 1.08 0.51 0.38 0.11 0.04

Depreciation III 0.10 0.10 0.03 0.03 0.04 25

Tables 2 and 3 show that the capacity corresponds to about 90% phosphate removal.

Claims (6)

69572 A method for treating wastewater, comprising contacting the wastewater with an anion exchanger prepared by treating a cellulosic material with a polyethyleneimine solution, characterized in that an anion exchanger prepared by treating a bark or a modified bark with a polyethylene imine solution of pH 2 is used. -6, preferably 4-5. Process according to Claim 1, characterized in that the anion exchanger is prepared by treating the bark or modified bark with a polyethyleneimine solution at a temperature of 40 to 90 ° C, preferably 60 to 70 ° C. Process according to Claim 1 or 2, characterized in that the anion exchanger is prepared by carrying out the treatment over a period of 2 hours to 4 days. Process according to one of the preceding claims, characterized in that the anion exchange and is prepared using a 1% polyethyleneimine solution. Process according to Claim 1, characterized in that the anion exchanger is made of wood bark which has been modified in separate treatments with alkali liquor and sulfuric acid. Process according to Claim 1, characterized in that the anion exchanger is used mixed with clay soil in a weight ratio of 2: 1 to 1: 4. Il