RU2198927C2 - Method of treatment of acrylamide aqueous solution prepared by biotechnological method from biocatalyst slime - Google Patents

Abstract

FIELD: chemical technology. SUBSTANCE: method involves addition of cation-active flocculant solution and finely-dispersed mineral addition from dioxide in the amount 0.0002-0.02 wt.-% and 0.05-1.0 wt.-%, respectively, to acrylamide aqueous solution obtained with bacterial biocatalyst in concentration of acrylamide from 5 to 50% that is carried out before filtration at stirring. This allows to remove biocatalyst slime with the enhanced efficiency that results to increase of filtration rate and to alleviate precipitate removal from filter. EFFECT: improved method of treatment, simplified process. 1 tbl, 8 ex

Description

 The invention relates to biotechnology and relates to a method for cleaning aqueous solutions of acrylamide from biocatalyst sludge.

 In the last decade, the development of biotechnology has allowed the organization of large-scale production of acrylamide solutions, which are widely used to obtain polymer materials. One of the main requirements for the quality of acrylamide solutions obtained by the biotechnological method is the high degree of purification of acrylamide solutions from the spent bacterial mass.

 Known methods for cleaning aqueous solutions of acrylamide from biocatalyst sludge using activated carbon. In this case, divalent copper ions [1] are preliminarily added to the solutions or saturated with oxygen [2] to inhibit the polymerization of acrylamide.

A significant drawback of the above methods is the low speed of cleaning aqueous solutions of acrylamide (not more than 8 dm ³ / h) and the need to dispose of spent activated carbon and wastewater generated after regeneration of activated carbon.

 The closest in technical essence is the "Method of purification of aqueous solutions of acrylamide obtained by microbiological transformation of acrylate nitrile from bacterial mass" [3]. In this method, the purification is carried out by filtration with pre-treatment of the solution with aluminum sulfate and acrylamide polymer.

This method is as follows. In a reactor with a volume of up to 250 dm ³ , containing a solution of acrylamide with a concentration of from 6 to 30% with a bacterial mass, 0.005-0.02 wt.% Aluminum sulfate and 0.0005 ÷ 0.001 wt.% Acrylamide polymer are successively loaded with stirring, after which filtered. The acrylamide copolymer may contain from 70 to 99% of acrylamide units and from 1 to 30% of sodium acrylate units. The method extends to the use of a biocatalyst based on microorganisms belonging to Rhodococcus rhodochrous M8.

 The disadvantages of this method include the relatively low average filtration rate and fast clogging of the filter material, which requires frequent regeneration of the latter, and also makes it difficult to remove the bacterial mass from the filter with a scraper due to the small thickness of the sediment layer. This method purifies solutions of acrylamide with a concentration of only up to 30 wt.%, Although a number of industries require a concentration of solutions of acrylamide up to 40-50%. It should be noted that the above method only applies to acrylamide solutions obtained using microorganisms belonging to Rhodococcus rhodochrous M8.

 The objective of the invention is to increase the filtration rate, the duty cycle between regenerations of the filter material, facilitate the removal of sediment from the filter, reduce the number of reagents used.

 The problem is solved due to the fact that in the known method of purification of an aqueous solution of acrylamide obtained by a biotechnological method from the biocatalyst sludge by filtration, before filtering into an aqueous solution of acrylamide with a concentration of 5 to 50% with stirring, a solution of a cationic flocculant and a finely divided mineral dioxide additive are sequentially introduced silicon in the amount of 0.0002 ÷ 0.02 wt.% and 0.05 ÷ 1.0 wt.%, respectively. The invention consists in the following. 0.0002 ÷ 0.02 wt.% Cationic flocculant solution and 0.05 ÷ 1.0 wt.% Finely dispersed silicon dioxide additive are introduced into the reactor containing a 5 ÷ 50% solution of acrylamide obtained using microorganisms, and filtered. Filtration is carried out by known methods using a suction filter, a press filter, a drum filter. As the filter material use non-woven material, belting, nylon, etc.

 The proposed method purifies 5 ÷ 50% aqueous solutions of acrylamide obtained by hydrolysis of acrylic acid nitrile using microorganisms containing the nitrile hydratase enzyme and having an excess negative charge on the cell surface.

 Cationic flocculants are polymers containing in the chain primary, secondary and tertiary nitrogen atoms, capable of protonation in aqueous solutions; polymers containing quaternary phosphorus atoms or tertiary sulfur atoms in the main chain; Quaternary salts of vinyl pyridines, aminoethyl esters of acrylic and methacrylic acids, quaternized aminoalkyl (meth) acrylamides. For example, Praestol 854, Praestol 852 (TU 2216-001-40910172-98), VPK-101 (TU 6-05-231-140-81), VPK-402 (TU 6-05-231-188-77), Sedipur CL. The cationic flocculant is introduced in the form of an aqueous solution with a concentration of 0.1: 0.4 wt.%.

 Fine-dispersed silicon dioxide mineral additive - Aerosil (TOST 14922-77), Novakulit, white soot (GOST 18307-78), quartz flour, perlite (TU 2131-44-82).

 The cleaning efficiency and quality of the resulting acrylamide solutions were determined on a photocolorimeter. The presence of microorganism cells at a wavelength of 540 nm, the residual flocculant content after processing the solution with butanol at 400 nm. The cell thickness is 5 cm. The optical density of the purified acrylamide solutions at λ = 540 nm is 0.055.

 The table shows the cleaning conditions and the quality of the purified solutions of acrylamide according to examples of specific performance.

Example 1. In a reactor with a capacity of 0.5 m ³ containing 0.35 m ^{3 of a} 50% solution of acrylamide obtained using microorganisms Brevibacterium sp. GT, is introduced with stirring sequentially with an interval of 5 minutes, 17.5 dm ^{3 of a} 0.4% (0.02 wt.%) Solution of the cationic flocculant Praestol 854 and then 3.5 kg (1.0 wt.%) Aerosil. After 10 minutes, the solution is filtered at a speed of 16.0 m ³ / h • m ² . Filtration is carried out on a suction filter with a filtration area of 0.05 m ² .

Example 2. In a reactor with a capacity of 1.0 m ³ containing 0.75 m ^{3 of a} 40% solution of acrylamide obtained using the microorganisms Bacillus cereus B5, 18.75 dm ^{3 of} 0.4% (0 , 01 wt.%) Solution of cationic flocculant Praestol 852 and then 3.0 kg (0.4 wt.%) Perlite. After 10 minutes, the solution is filtered at a speed of 15.2 m ³ / h • m ² . Filtration is carried out on a drum filter with a filtration area of 0.05 m ² .

Example 3. In a reactor with a capacity of 0.5 m ³ containing 0.35 m ^{3 of a} 30% solution of acrylamide obtained using microorganisms Rhodococcus rhodochrous M33, it is introduced with stirring sequentially with an interval of 5 minutes 1.75 dm ³ 0.2% (0.001 wt.%) a solution of cationic flocculant VPK-101 and then 0.7% kg (0.2 wt.%) of novaculite. After 10 minutes, the solution is filtered at a speed of 15.3 m ³ / h • m ² . Filtration is carried out on a suction filter with a filtration area of 0.05 m ² .

Example 4. In a reactor with a capacity of 1.0 m ³ containing 0.75 m ^{3 of a} 20% solution of acrylamide obtained using microorganisms Rhodococcus rhodochrous M8, it is introduced with stirring sequentially with an interval of 5 minutes 1.5 dm ³ 0.1% (0 , 0002 wt.%) Solution of cationic flocculant VPK-402 and then 0.75 kg (0.1 wt.%) Of quartz flour. After 10 minutes, the solution is filtered at a rate of 12.7 m ³ / h • m ² . Filtration is carried out on a press filter with a filtration area of 0.05 m ² .

Example 5. In a reactor with a capacity of 1.0 m ³ containing 0.75 m of a 5% solution of acrylamide obtained using the microorganisms Bacillus cereus B5, 18.75 dm ³ 0.4% is introduced with stirring sequentially with an interval of 5 minutes (0, 01 wt.%) Solution of the cationic flocculant Cedipur CL and then 0.375 kg (0.05 wt.%) Of white carbon black. After 10 minutes, the solution is filtered at a speed of 9.4 m ³ / h • m ² . Filtration is carried out on a drum filter with a filtration area of 0.05 m ² .

Example 6. In a reactor with a capacity of 0.5 m ³ containing 0.35 m of a 40% solution of acrylamide obtained using the microorganisms Brevibacterium sp GT, it is introduced with stirring successively with an interval of 5 minutes 0.35 dm 0.1% (0.0001 wt.%) solution of cationic flocculant Praestol 854 and then 0.035 kg (0.01 wt.%) Aerosil. After 10 minutes, the solution is filtered at a speed of 4.2 m ³ / h • m ² . Filtration is carried out on a suction filter with a filtration area of 0.05 m ² .

Example 7. In a reactor with a capacity of 0.5 m ³ containing 0.35 m ^{3 of a} 20% solution of acrylamide obtained using the microorganisms Rhodococcus rhodochrous M33, 35.0 dm ^{3 of} 0.5% (0 , 04 wt.%) Solution of the cationic flocculant Praestol 852 and then 5.25 kg (1.5 wt.%) Of novaculite. After 10 minutes, the solution is filtered at a speed of 16.0 m ³ / h • m ² . Filtration is carried out on a suction filter with a filtration area of 0.05 m ² .

Example 8 (comparative). 0.75 m ^{3 of a} 30% solution of acrylamide obtained by the transformation of acrylonitrile in the presence of microorganisms Rhodococcus rhodochrous M8 is introduced into a reactor with a capacity of 1 m ³ . With stirring, 7.5 dm ^{3 of a} 2% solution of aluminum sulfate and 3.75 dm ^{3 of a} 0.25% solution of anionic flocculant containing 70% acrylamide and 30% sodium acrylate are successively added. The costs of the coagulant and flocculant are 0.02 and 0.001 wt.%, Respectively. Filtration rate 3 m ³ / h • m ² with a filtration area of 1 m ² .

 The addition of a cationic flocculant allows you to bind negatively charged biomass cells, which leads to an increase in the filtration speed and performance, to an increase in the adhesion of cell agglomerates, and to the addition of a finely dispersed mineral additive from silicon dioxide having a negative charge on its surface. As a result, the precipitate becomes more durable and resistant to the action of the flow of the filtered acrylamide solution, which, in turn, leads to an increase in the filtration rate and the working cycle between clogging of the filter material, improves the quality of the filtrate, and reduces the amount of wash water during filter regeneration. Wash water is used either at the acrylamide synthesis stage or at the (co) polymerization of acrylamide.

 The addition of a finely dispersed mineral additive of silicon dioxide of less than the claimed amount of 0.05 wt.% Dramatically reduces the filtration rate, shortens the duty cycle, worsens the removal of sediment, and also reduces the quality of the filtrate. The use of a finely dispersed mineral additive of silicon dioxide of more than the claimed amount of 1.0 wt.%, Practically without changing the cleaning efficiency, leads to an overuse of the material.

 The use of a cationic flocculant of less than the claimed amount of 0.0002 wt.% Does not allow to obtain the filtrate of the required quality, and if it is added to the claimed amount of 0.02 wt.%, An increased consumption of materials occurs without increasing the cleaning efficiency.

Sources of information
1. US patent 4248968, cl. C 12 P 13/02, 1987

 2. US patent 4701558, CL C 12 P 13/02, 1987

 3. RF patent 2029739, cl. C 12 P 13/02. The method of purification of an aqueous solution of acrylamide obtained by microbiological transformation of acrylonitrile from the bacterial mass.

Claims (1)

 The method of purification of aqueous solutions of acrylamide obtained by a biotechnological method from the biocatalyst sludge by filtration, characterized in that before filtering into an aqueous solution of acrylamide with a concentration of 5 to 50%, a cationic flocculant and a finely divided silica mineral additive in an amount of 0.0002 are sequentially introduced with stirring -0.02 wt.% And 0.05-1.0 wt.%, Respectively.

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