RU2060953C1 - Method for purification of sewage which contains formaldehyde resins - Google Patents

Abstract

FIELD: purification of sewage. SUBSTANCE: sewage is allowed to stand, then resin and resin supernatant fractions are separated from it. Clay mineral being activated by sulfuric acid is added into resin supernatant fraction, its quantity being 30-40 kg per 1 m³. Thus obtained mixture is allowed to stand within 18-30 min and crystalline ammonium carbonate is added into it, its quantity being 14-16 kg per 1 m³ of resin supernatant water. After sustaining within 3-5 min liquid phase is separated and removed in sewer system. EFFECT: improves efficiency of method.

Description

 The invention relates to chemistry and can be used in the woodworking industry as environmental measures aimed at the treatment of wastewater from formaldehyde.

A known method of wastewater treatment from formaldehyde with ammonia water [1]
The products of the interaction of formaldehyde with ammonia are non-toxic. However, the ammonia used refers to toxic substances, the work with which requires additional protective measures and sophisticated equipment. It should be noted that the daily average concentration of ammonia is: MAC = 0.04 mg / m ³ .

Known methods for wastewater treatment of the pulp and paper industry by using ammonium sulfate, and the technology involves the use of oxygen [2] Flocculants are also used for the purification of these waters, for example a copolymer of vinyl pyrolidone with vinyl glycine diester of ethylene glycol [3] oligopeptide-2-aminoethyl vinyl ether [4] ]
However, these methods are multistage and require expensive solutions.

 A known adsorption method for treating wastewater from formaldehyde with granular activated carbons from lignin, which requires preliminary wastewater treatment by aeration with compressed air [5], this method is the closest in technical essence to the proposed invention.

 The disadvantage of this method is the presence of high energy costs for producing lignin activated carbon, lower mechanical strength of this coal in comparison with activated carbons, the multi-stage process of wastewater treatment, which complicates and increases the cost of the cleaning process.

 Both the known and the proposed method involve processing and then the use of an adsorbent.

 The main task posed and resolved in this invention is the development of a cheap and safe way to reduce the toxicity of wastewater from a woodworking enterprise formed in the production of urea-formaldehyde resins and their use. The amount of urea-formaldehyde resin in these wastewater reaches 20%. The treatment of wastewater from formaldehyde is carried out with the aim of discharging it into the sewer, rather than generally taking it to a dump out of town, since the formaldehyde content in the wastewater without preliminary treatment varies from 1000 to 30000 mg / l, which significantly exceeds the permissible concentration of formaldehyde in sewage water (1000 mg / l).

To solve this problem, wastewater containing formaldehyde resins is settled until they are separated into tar and tar fractions, then an adsorbent is introduced into the tar water, they are kept, the liquid phase is separated as a final product, and activated sulfuric acid is first introduced into the tar water as an adsorbent acid clay mineral in an amount of 30-40 kg per 1 m ³ tar water, the mixture was allowed to stand for 18-30 minutes, then the crystalline ammonium carbonate in an amount of 14-16 kg per 1 m ³ of water and re-tar vyde alive for 3-5 minutes.

The preparation of the adsorbent consists in mixing clay and sulfuric acid at the rate of 58.8 g of Н ₂ SO ₄ per 100 g of clay mineral, its heat treatment at 98 ^о С for 6 hours.

 The concentration of formaldehyde in wastewater was determined by the complex sulfite-potentiometric method.

 As a result of the introduction of activated clay into waste water, formaldehyde is adsorbed on its surface. The residual formaldehyde reacts with crystalline ammonium carbonate added to the tar water after the adsorption process.

 Wastewater can be almost completely purified from formaldehyde by adding ammonium carbonate in the absence of activated clay. At the same time, 5 times more crystalline ammonium carbonate is consumed. Despite the equal efficiency of wastewater treatment from formaldehyde with ammonium salts (carbonate, thiocyanate, chloride), ammonium carbonate was chosen as a neutralizer due to the formation of non-toxic reaction products of formaldehyde with this salt of water, carbon dioxide and urotropine (hexamethylenetetramine). The latter is used in many industries and medicine.

 The method is as follows.

Wastewater is maintained in an appropriate volume until it is divided into two fractions: tar (solid) and tar (liquid). Usually it takes 1.5-2.0 hours. The resinous part is removed, and the clay mineral activated with sulfuric acid in the amount of 30-40 kg per 1 m ^{3 is} added to the suprasmal part. The mixture is kept for 18-20 minutes, then crystalline ammonium carbonate is added in an amount of 14-16 kg per 1 m ^{3 of} tar resin and re-aged for 3-5 minutes, the liquid fraction suitable for discharge into the sewer is separated.

 PRI me R 1. Prepared six solutions of tar resin with different contents of activated clay mineral (see table. 1).

100%
Исходя из данных табл. 1 наиболее высокая степень очистки сточной воды от формальдегида наблюдается при введении в надсмольную воду от 30 до 40 кГ активированной глины на 1 м³ сточной воды.The degree of wastewater treatment (%) is determined by the difference in the concentrations of formaldehyde in the wastewater before the clay mineral is introduced into the wastewater and after the clay contacts the wastewater
η

one hundred%
Based on the data table. The 1 highest degree of formaldehyde wastewater treatment is observed when activated clay from 30 to 40 kg of activated clay per 1 m ^{3 of} wastewater is introduced into the tar water.

PRI me R 2. Prepared six solutions of tar resin with a constant amount of activated clay 40 kg / m ³ . The contact time of clay with wastewater varies from 0.2 to 0.6 hours. The data obtained are given in table. 2.

 Thus, the optimal range of contact of clay with wastewater is 0.3-0.5 hours

PRI me R 3. Prepared six solutions of tar resin, each placed 40 kg / m ^{3 of} activated clay and a certain mass of crystalline ammonium carbonate in kg per 1 m ^{3 of} tar resin for its purification from formaldehyde. The data are presented in table. 3.

Almost complete neutralization of formaldehyde occurs when 14-16 kg of ammonium carbonate is added in 1 m ^{3 of} tar resin.

PRI me R 4. Prepared six solutions of tar resin, each placed 16 kg of ammonium carbonate per 1 m ³ tar resin. 40 kg of activated clay (per 1 m ^{3 of} waste water) were introduced into these solutions. The contact time of this salt with wastewater is small. The optimal time range is given in table. 4. It is 3-5 minutes.

Thus, with the sequential introduction of 30-40 kg / m ^{3 of} clay activated with sulfuric acid and after 0.3-0.5 h of 14-16 kg / m ^{3 of} crystalline ammonium carbonate, the tar waters are almost completely purified from formaldehyde (taking into account the sensitivity of the determination method formaldehyde), which allows the discharge of tar water into the sewer network. All of the above proves the achievement of the goal.

Claims (1)

The method of purification of wastewater containing formaldehyde resins for discharge into the sewer, including their treatment with the subsequent introduction of adsorbent into the water, maintaining and separating the liquid phase in the form of the final product, characterized in that the wastewater is treated by settling until two fractions of tar are formed and-tar, a resin fraction was removed, and water-tar as the adsorbent is first introduced sulfuric acid activated clay mineral in an amount of 30 to 40 kg per 1 m ^3, the mixture was incubated for 18 30 minutes, then Adds crystalline ammonium carbonate in an amount of 14 to 16 kg per 1 m ³ tar water and aged again for 3 5 minutes.

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