ITMI991010A1 - A METHOD FOR THE TREATMENT OF INDUSTRIAL WASTE WITH A HIGH CONTENT OF POLLUTANTS - Google Patents

Description

A METHOD FOR THE TREATMENT OF HIGH INDUSTRIAL WASTE

CONTENT OF POLLUTANTS

Description

The present invention relates to a new method for the treatment of industrial wastewater with a high content of pollutants, in particular of aqueous or hydroorganic solutions of organic chemical substances with a high molecular weight,

the method of the present invention allows to selectively separate the monovalent from the polyvalent between the inorganic salts present in the wastewater, in such a way as to be able to reduce the quantity of inorganic substances sent to the discharges.

It is known that the excess of inorganic substances constitutes an important pollutant of industrial waste and their limitation is necessary.

By hydroorganic solutions we mean solutions of organic substances in mixtures of water and solvents selected from the following group: alcohols containing from 1 to 5 carbon atoms, linear or branched; polyethers; cellosolvi; aliphatic ketones; aliphatic amides derived from acetic acid, organic acids with a number of carbon atoms from 1 to 3. Particularly preferred among these are: methanol, retando, n-butanol, 2-butanol, tert-butanol, n -pentanol, 2-pentanol, dimethylacetamide, dimethylformamide, acetic acid, 2-hydroxypropionic acid, 2-acetoxylactic acid, dìglyme and methylcellosolve, methylethylketone.

The organic substances dissolved in said solutions are present in concentrations ranging from 90% to 0% by weight and are organic molecules having a molecular weight greater than 150 Dalton.

The method of the present invention can be applied to various classes of organic molecules; among these preferred are: aromatic compounds optionally halogenated or containing carboxylic or phenolic groups with one or more aromatic rings.

Preferred are contrast media for radiography and magnetic resonance imaging.

X-ray contrast media are characterized by having an aromatic ring or more, replaced as much as possible by iodine groups, which are responsible for opacification under X-rays. The most modern contrast media, that is, those of the non-ionic type in which there are no free acid groups, they are derivatives from 2,4,6-triiode-1,3-benzendicarboxylic acid.

Instead the contrast media for magnetic resonance are linear or cyclic complexes of polyamine carboxylic acids with paramagnetic metal ions, in particular the Gadolinium ion.

The process of the present invention is particularly suitable for the following contrast media: lopamidol, lomeprol, lohexol, 5-amino-2,4,6-triiodobenzendicarboxylic acid; Gadoteridol, gadolinium complex of the acid N- [2 - [{2-aminoethyl) -amino] ethyl]] - 0-benzyl-DL-serine salified with meglumine;

as well as for the intermediates of their production and products of their degradation: potassium salt of 3-benzoxyl-2-chloro-propanoic acid, 3,6,9-triaza-12-oxa-3,6,9-tricarboxymethylene acid 10-carboxy-13-phenyl-tridecanoic; derivatives (amides and esters with serinol, 1-amino-2,3-propanediol, dimethylamine, methanol, ethanol, 1-butanol) of 5-hydroxyisophthalic acid or its salts, derivatives (esters and amides with ethanol, methanol, 1- butanol, serinol, 1-amino-2,3-propandiol, dimethylamine) of 5-aminoisophthalic acid or its salts.

The method, object of the present invention, consists of five fundamental operations: 1. Alkalization of the wastewater at pH greater than 12 by adding alkali in solution at 30-50% by weight or solid and adding metallic copper or its salts in a minimum quantity of 1000 ppm;

2. Concentration at about one third of the initial weight, distilling the solvents present, and maintaining the temperature of at least 105 ° C for a minimum of six hours. 3. Cooling and filtration of the salts present.

4. Permeate and retentate separation by nanofiltration treatment using water to diafilter.

5. The retentate is concentrated at about a quarter of the initial weight. The residue can be sent to the activated sludge treatment plant or to external disposal.

Through the synergy of the five operations it is possible to completely remove the bi and polyvalent anions present in industrial waste, reduce the amount of chlorides, significantly reduce the amount of pollutant by increasing the biodegradability of the discharges, carry out, when possible, recoveries of useful substances to the production cycles.

Finally, we surprisingly found that this method is able to separate highly polluting substances with high molecular weight that are not easily biodegradable from other less polluting low molecular weight substances, which can be further treated by using activated sludge plants, obtaining a significant reduction. of the pollutant load.

To evaluate the effectiveness of the method of the present invention, the COD (Chemical Oxygen Demand, quantity of oxygen necessary to transform the carbon of organic molecules into carbon dioxide), expressed in mg / L, determined in the laboratory by analyzing some type discharges of the substances mentioned above:

diglyme grinding residue containing 5-amino-2,4,6-triiodoisophthalic acid, 2% other unknown organic products and 10% diglyme: 52500.

crystallization residue of lopamidol from 2-butanol containing 8% of lopamidol and its side and 12% of 2-butanol: 960000.

crystallization mother liquors containing 2% of the sodium salt of S-5 - [[2- (acetyloxy) -1-oxopropyl) amino] -2,4,6-triiodo-benzendicarboxylic acid 1% of tertbutanol and 6 % of by-products in unknown composition derived from lactic acid and acetic acid. 237000

residue from dodecane purification treatment containing 90% sulfuric acid and 6% aliphatic substances: 480600.

The COD values obtainable at the end of the treatment with our method can range from 2000 to 7000.

Operation 1 is performed to ensure the successful demolition and mineralization of the organic molecules present.

The quantity of copper catalyst must be defined according to the characteristics of the wastewater to be treated, and it is the task of the technician skilled in the art who will be able, through some preliminary tests, to easily define the necessary quantity, which must be greater than 1000 ppm. The use of this catalyst makes it possible to transform, in the presence of oxygen, the aromatic nuclei into phenolic compounds which in some cases will transform into substances of the quinonic type, in accordance with what was already published in the Journal of the American Chemical Society in 1984, you. 106, 2121; also in Journal of the American Chemical Society in 1988, you. 110, 5020 and in Journal of Organic Chemistry in 1988, vol. 53, 296.

It is important to ensure that during the entire duration of operation 2 the pH is greater than 12 units, preferably 13 units

In step 2, the duration of the concentration must be such that the wastewater remains at a temperature greater than or equal to 105 ° C for at least six hours; if the concentration at one third of the weight is finished before the completion of the six hours it will be necessary to keep the wastewater in reflux conditions. If the quantity of solvent is greater than two thirds by weight of the wastewater, it will be necessary to add water in such a way as to have an aqueous solution. The temperature increase must be guaranteed by the presence of inorganic salts, therefore, if they are not sufficient, it will be necessary to add sodium sulfate, sodium phosphate or sodium carbonate or similar salts to ensure the ebullioscopic rise.

The choice of these salts depends on their poor solubility at 20 ° C and therefore at the end of the concentration they will be removed through the filtration step 3. Furthermore, some of these salts present, at pH higher than 12, divalent or trivalent anions which will remain in the nanofiltration retentate and therefore separated from the low molecular weight substances. Additions of monovalent ion salts such as sodium chloride are however not recommended because they will increase the amount of chlorides at the discharge of the nanofiltration permeate. Some data on the solubility of sodium sulphate decahydrate and some sodium phosphates are reported in the table. Data was taken from Handbook of Chemistry and Physics 44th edition.

The choice of salts will eventually depend on the type of unwanted interactions, such as for example dangerous reactions, which could occur with the substances present in the wastewater. In particular, you can choose to use phosphates, if there is a need to add a phosphorus content to the subsequent treatment with activated sludge, in this case it will be important to adjust the pH at the end of filtration in order to cause precipitation or maintenance in solution of the go up according to the above data.

Operation 3 provides for the filtration of the precipitated salts. In general, under these conditions a part of the sodium chloride present by effect of the common ion co-precipitates.

This operation must be carried out in such a way that the crystalline form of the easily filterable precipitate, if appropriate, can germinate.

The solution obtained will show a significant decrease in the pollutant load with an increase in biodegradability. For example, in a production waste of lopamidol starting from a COD of 265000 mg / L and a BOD5 (Biological Oxygen Demand, represents the demand for biological oxygen, therefore the biodegradability of the molecule). of 1500 mg / L of starting it is possible to obtain a solution at the end of mineralization with COD 7000 and a BOD5 of 3500. This reduction is due both to the possible elimination of solvents and to the partial demolition of the aromatic molecules.

The solution after mineralization, concentration and filtration is purified by nanofiltration, step 4. Nanofiltration is a well known process that separates molecules based on molecular weight and charge, through filtration through particular types of membranes. We speak of permeate to define the solution filtered by the membranes, while the retentate is the residue that does not pass through the membranes.

This operation is carried out in three phases:

1. Preliminary nanofiltration of the solution.

2. Diafiltration, adding water.

3. Concentration of the retentate.

In this case, the purified solution to be sent directly to the activated sludge treatment is the permeate, which may contain in the specific case of discharges from the production of lopamidol, for example sodium iodide, sodium chloride and low molecular weight organic substances such as for example acetic acid and traces of lactic acid.

The retentate contains sodium sulfite, sodium sulfate, sodium phosphate and high molecular weight organic substances.

Diafiltration begins when the osmotic pressure generated by the salts is equivalent to about 30 bar, in these conditions the permeation is zero. At this point water will be added to allow low molecular weight substances and monovalent salts to permeate.

The choice of prolonging this operation will depend on the type of subsequent treatment and the characteristics of the substances present in the retentate. In fact, if you have a biodegradable retentate or you do not want to remove the residual sulphates or phosphates, this operation can be limited to a concentration of the retentate or to the removal of part of the low molecular weight substances, in such a way as to obtain a wastewater at low pollutant content and another more concentrated.

If sodium iodide is present in a significant quantity in the wastewater, it will be advisable to prolong this operation in such a way as to recover the iodide in the permeate to be sent for a specific recovery. The retentate will then be concentrated until a residue is obtained which will not produce permeate.

The membranes that can be used for this operation are thin film membranes specific for this technique capable of rejection of bi and polyvalent ions and of substances with a molecular weight greater than 150 Dalton.

Among these are preferred DESAL 5, PERSP or similar type capable of operating between pH between 1 and 11.5, the choice of materials and dimensions will depend on the type of plant in use, while the characteristics of the construction material will depend on the type of operating pH and the characteristics of the wastewater in relation to the quantity of residual solvents present, polyamides and polymers containing fluorine are preferred for their chemical resistance.

Operation 5 will allow to concentrate at 50% of the initial weight. Through this operation it is possible to remove even more inorganic salts through a simple filtration and obtain a residue that, in some cases, is biodegradable and therefore can be sent to the purification plant, otherwise it can be sent to specific treatments at external companies. .

In this way it is possible to easily separate bi and polyvalent salts and substances with a high molecular weight (greater than 150 Dalton), generally poorly biodegradable, from other substances with greater biodegradability and, consequently, reduce the pollutant content in the industrial discharges of a chemical-pharmaceutical or fine chemical manufacturing company.

Other techniques, such as combustion, could seem equally effective, but they are difficult to industrialize due to problems of pollution generated in the form of gaseous emissions and, consequently, require special authorizations from the competent authorities, as well as specific abatement systems that nullify the benefits of the process. combustion.

Other treatments, such as the use of anodic oxidation cells, have the drawback of being very specific with respect to the process proposed by us which is difficult to use due to the risk of generating chlorine or chlorine oxides which can develop by anodic oxidation if they are present. of chlorides. This limitation makes their use uninteresting.

The following examples are intended to illustrate the best experimental conditions for implementing the process, object of the invention.

Experimental Part

Example 1

300 kg of mixture of effluents from the production of lopamidol, containing about 4% (w / w) of organic solvents (2-butanol, butyl acetate, diglime, tert-butanol, dodecane) and 0.4% (w / w ) about 2,4,6-triiode-5-amino-1,3-benzenedicarboxylic acid and about 0.9% of lopamidol and its side (COD 190000 mg / L) are brought to pH 13 with 30% NaOH (w / p). 50 g of CuS04 · 5 HzO are added and it is concentrated at ambient pressure to a weight equal to 80% of the initial weight; the reaction mixture is then kept under reflux to complete the mineralization, so that the overall distillation and reflux time is 6 hours.

The solution is concentrated to 30% by weight of the initial solution using a 2000 L enamelled reactor equipped with a development tube, condenser and collection tank with drain connected to the purification plant.

The reactor is loaded in portions of 1500 L each.

At the end of the concentration it is cooled and buffered to pH 9.5 with 50% H2S04 (w / w) and then subjected to filtration.

About 15 kg of salts are separated by filtering on a pressure filter which, when analyzed, have the following composition:

75% sodium sulfate decahydrate

10% sodium chloride

2% sodium iodide

13% water.

The solution is sent to the nanofiltration, using a system composed of 10 modules containing Separem membranes mod.Desal5 and at an operating pressure of 25-30 bar it concentrates up to 80 kg. It is diafiltered by adding water, keeping the volume of the retentate approximately constant (about 50 L of H20 are added).

The permeate, about 60 L, containing 4% sodium chloride, 1% sodium iodide and 1% acetic acid with a COD of 6000 mg / L is sent to the iodine recovery treatment.

The retentate, 80 kg, is concentrated to 50% and then about 20 kg of inorganic salts (about 100% sodium sulphate) are filtered and 20 kg of solution with COD 15000 and BOD 7500 mg / discharged to the purification plant. L.

Example 2

A 40 kg of mixture (COD 45000 mg / L) of effluents deriving from the hydrogenation of 5-nitroisophthalic acid, containing about 7% of amino-isophthalic, 15% of sodium sulphate, 7% of sodium chloride and other substances unknown organic compounds of low molecular weight, 6 g of CuS04 · 5 HzO are added and solid sodium hydroxide is added. It is sent to a pilot plant for treatment, it concentrates at ambient pressure at a weight equal to 30% of the initial weight; the reaction mixture is then kept under reflux to complete the demolition, so that the overall distillation and reflux time is 8 hours. The concentrated solution is left to cool at 15 ° C for 2 hours and the precipitated salts are filtered on a porous septum.

The solution is buffered at pH 7 with 50% H2S04 (w / w) and subjected to nanofiltration, using a Separem membrane mod. DesaIS (DK2521T) with an operating pressure of 25-30 bar. It is diafiltered, keeping the volume of the retentate constant (about 18 L of H20 are added) 'in order to completely remove the chlorides and low molecular weight substances present in the starting mixture or produced by demolition. The average COD of the permeate is measured, obtaining values around 5000 mg / L. The retentate, 12 kg, has a COD of 9400 mg / L and a BOD of 500 mg / L. This retentate is concentrated to 3 kg using a 20 L reactor equipped with stirrer and heating system. Salts precipitate which are filtered and sent to external treatment (mainly sodium sulphate decahydrate) The distilled water is sent to the purification plant while the residue with COD 40000 mg / L is sent to an external company for treatment.

Example 3

A 40 kg of mixture (COD 450 000 mg / L) of effluents from various industrial discharges containing 2% 5-nitroisophthalic acid, 7% amino isophthalic, 7% sodium chloride, 0.8% N- [2- [(2-aminoethyl) amino] ethyl]] - 0-benzyl-DL-serine trichlorhydrate, potassium salt of 3-benzoxyl-2-chloro-propanoic acid and other unknown organic substances of low molecular weight are added 6 g of CuS04 · 5 H20 and 0.5 kg of sodium phosphate dihydrate, concentrates at ambient pressure to a weight equal to 30% of the initial weight; the reaction mixture is then kept under reflux to complete the demolition, so that the overall distillation and reflux time is 8 hours. After concentration, pH 4.5 is brought by adding 50% sulfuric acid.

the concentrated solution is left to cool at 15 ° C for 2 hours and any precipitated salts are filtered on a porous septum. In this way it is obtained to have mainly the monosodium phosphate which will remain in solution.

The solution is subjected to nanofiltration, using a Separem membrane mod. Desal5 (DK2521T) with an operating pressure of 25-30 bar. It is diafiltered, keeping the volume of the retentate constant (about 18 L of H20 are added) in order to completely remove the chlorides and low molecular weight substances present in the starting mixture or produced by demolition. The average COD of the permeate is measured, obtaining values around 5000 mg / L. The retentate, 12 kg, has a COD of 9400 mg / L and a BOD of 500 mg / L. This retentate is brought to pH12 and concentrated at 30%. Salts precipitate, mainly sodium phosphate hydrate and sodium sulphate decahydrate which are dissolved with water and sent to the purification plant, the 3.8 kg residue with COD 350000 is sent for external treatment.

Example 4

An industrial production plant produces four high pollutant content wastewater in the following weekly quantities:

Discharge 1. 214275 kg / week CODmedi060000 mg / L

Discharge 2: 57235 kg / week CODmedl052000 mg / L

Discharge 3: 11850 kg / week COD average 960000 mg / L

Discharge 4 78155 kg / week CODm (! Dio43330 mg / L

A pilot plant for the treatment of these effluents was tested by operating continuously over 24 hours, feeding a mixture of these effluents at a flow rate of 2500-3000 kg / hour.

Sodium hydroxide at 30% was added continuously at a flow rate of 35-40 kg / hour in order to maintain the pH greater than 13 units. A 10% solution of copper sulphate pentahydrate was charged continuously at 4 L / hour.

The wastewater was treated with a tube concentrator, in order to obtain an outgoing wastewater flow rate of between 1000 and 1500 kg / hour.

The exhaust was treated with a pair of 8000 liter reactors, which alternately concentrate a volume of 6000 liters once collected. The concentration is carried out in such a way as to obtain approximately 5000-5400 L residues every six hours.

It is cooled to 20 ° C and the salts are filtered using a pair of press filters (2m diameter 4 m3) obtaining 720 kg of salts every six hours containing 40% of the initial sulphates and 8% of the chlorides.

The solution brought to pH 9 with 50% sulfuric acid feeds a nanofiltration unit composed of 10 modules containing Separem membranes of the DESAL 5 type with an active area of 32.5 m2 each.

Four identical operations are carried out in 24 hours, nanofiltering about 5300 L of solution, adding about 15000 of industrial water to diafilter.

A permeate with an average COD of 2000-2500 mg / L and a retentate of approximately 5000 L will be obtained. The retentate is concentrated to 1250 L by distilling 2500 L of water and separating 900 kg of salts (presently sodium sulphate decahydrate) by filtration. The residue has a COD of approximately 30,000 mg / L and BOD 3,000 mg / L is sent along with the salts to a company for specialized processing.

Claims (1)

Claims A method for treating industrial waste with a high pollutant content, including the following steps: 1. Alkalization of the wastewater at pH greater than 12 by adding alkali in solution at 30-50% by weight or solid and adding metallic copper or its salts in a minimum quantity of 1000 ppm; 2. Concentration at about one third of the initial weight, distilling the solvents present, and maintaining the temperature of at least 105 ° C for a minimum of six hours; 3. Cooling and filtration of the salts present; 4. Permeate and retentate separation by nanofiltration treatment using water to diafilter; 5. The retentate is concentrated at about a quarter of the initial weight. A method according to claim 1, wherein the effluents are aqueous or hydroorganic solutions of organic chemicals in concentrations ranging from 90% to 0% by weight and are organic molecules having a molecular weight greater than 150 Dalton. A method according to claim 2, wherein the organic substances are X-ray or magnetic resonance contrast media. A method according to claim 3, in which the solvents present in the hydroorganic solutions are selected from the group consisting of: alcohols containing from 1 to 5 carbon atoms, linear or branched; polyethers; cellosolvi; aliphatic ketones; aliphatic amides derived from acetic acid, organic acids with a number of carbon atoms from 1 to 3. A method according to claim 4, in which the solvents present in the hydroorganic solutions are selected from the group consisting of methanol, ethanol, n-butanol, 2-butanol, tert-butanol, n-pentanol, 2pentanol , dimethylacetamide, dimethylformamide, acetic acid, 2-hydroxypropionic acid, 2-acetoxylactic acid, diglyme and methylcellosolve, methylethylketone. 6. A method according to claim 5, wherein the effluents are aqueous or hydroorganic solutions of organic chemical substances selected as a whole consisting of: lopamidol, lomeprol, lohexol, 5-amino-2,4,6-triiodobenzendicarboxylic acid; Gadoteridol, gadolinium complex of N- [2 - [(2-aminoethyl) amino] ethyl]] - 0-benzyl-DL-serine salified with meglumine, potassium salt of 3-benzoxyl-2-chloro-propanoic acid , 3,6,9-triaza-12-oxa-3,6,9-tricarboxymethylene-10-carboxy-13-phenyl-tridecanoic acid; derivatives (amides and esters with serinol, 1-amino-2,3-propanediol, dimethylamine, methanol, ethanol, 1-butanol) of 5-hydroxyisophthalic acid or its salts, derivatives (esters and amides with ethanol, methanol, 1- butanol, serinol, 1-amino-2,3-propandiol, dimethylamine) of 5-aminoisophthalic acid or its salts.