RU2142848C1 - Catalyst for oxidation of inorganic and organic compounds in biological sewage purification stage - Google Patents

Abstract

FIELD: chemical industry. SUBSTANCE: method comprises, wt %: microsphere of fly ash from thermal electric station, 25-30; and the polychlorovinyl balance. During aeration operation, catalyst is distributed uniformly over entire depth of catalytic zone. EFFECT: greater efficiency of purification.

Description

 The invention relates to the production of heterogeneous catalysts for the intensification of the oxidative neutralization of inorganic and organic toxic impurities in wastewater at the stage of biological treatment and can be used in the petrochemical, oil refining, chemical, pulp and paper industries, as well as any other industrial enterprise having biological treatment facilities.

It is known to use activated carbon to intensify the biological treatment of wastewater. Dusty poly-fractional activated carbon is introduced into the aeration tank in the amount of 1 g of coal per 10 g of dry sludge, at a pH of 8.8, a temperature of 24 ^o C and a COD of 20,000 mg / l. In this case, COD after cleaning is reduced to values of 190 mg / l / Avt.sv. N 947084 /.

 Activated carbons in the process of biooxidation play the role of oxygen carriers, i.e., along with the adsorption properties, they also perform a catalytic function.

The disadvantages of using active carbon in the biological treatment process are:
- low catalytic activity in the oxidation of inorganic components, due to the high sorption ability of organic compounds;
- clogging the pores of activated carbon with activated sludge fragments and mechanical impurities leads to the deactivation of activated carbon as a sorbent and as a catalyst;
- the need for mandatory wastewater filtration and the additional introduction of activated carbon in the effluent treatment process increases economic costs.

 The closest to the proposed invention according to the achieved result and technical essence is a catalyst for the oxidation of sulfur compounds, in particular sulfite-containing solutions, natural and waste waters, containing a microsphere of fly ash - TPP, chromium oxide and a polymer binder (Patent RU. 2067496).

The disadvantages of using the known catalyst in the biological treatment process are:
- the use of chromium oxide, which is a poison for activated sludge [N. G. Rybalsky, O.L. Zhaketov, A.E. Ulyanova, N.P. Shepelev. Environmental aspects of the examination. - Reference book of VNIIIPI. - Moscow. - 1989 year]. The appearance of chromium in wastewater will lead to the fact that microorganisms adapted to petroleum products will begin to respond to a new pollutant and the treatment of petroleum products will be disrupted;
- leaching of chromium oxide under intensive bubbling conditions leads to a decrease in the pH of wastewater, which may be accompanied by a violation of the biological regime of treatment facilities;
- the use of the above catalyst is proposed at the stage of biological treatment for the oxidation of only sulfur compounds, in particular sulfite-containing, while not taking into account the nature of other pollutants and microflora of biological treatment;
- the use of polyethylene as a binder component allows to obtain a heterogeneous catalyst with a density of 0.9 - 0.89 g / cm ³ . When using such a catalyst in bubbling processes, the catalyst floats to the surface of the liquid phase and the catalyst only partially participates in the oxidation of harmful components.

To eliminate the above disadvantages, to intensify the process at the stage of biological treatment, an active, stable, mechanically strong, heterogeneous catalyst is proposed containing a microsphere and a polymer binder in the following ratio of components, wt.%:
Microsphere of fly ash TPP - 25 - 30
Polymer Binder - Else
The microsphere is an integral part of fly ash of thermal power plants and is gas-filled aluminosilicates with a smooth outer surface. The main components of the microspheres are glass phase, mullite, quartz, hematite, magnetite, calcium oxide. The composition of the microspheres includes, wt.%: Al ₂ O ₃ - 23.8; Fe ₃ O ₄ - 6.2; FeO - 1.37: TiO ₂ - 0.53; CaO - 3.6; MgO - 3.4; SiO ₂ - the rest.

 The catalytic activity of the microsphere is due to the high dispersion on the surface of the microsphere of metal oxides of variable valency. Due to their high sorption properties, aluminosilicate balls retain oxygen on the surface of the catalyst, ensuring stable operation of the microspheres as a catalyst.

The content of the active component up to 30% gives the catalyst hydrophilic properties and prevents the likelihood of fouling with biomass. The density of the catalytic spheres is 1 - 0.97 g cm ³ , which allows the catalyst under uniform aeration conditions to be evenly distributed throughout the catalysis zone. If microspheres get into wastewater, biological treatment is not disturbed, because microsphere balls will float to the surface of the water, their number will be insignificant, but even in this case, the microsphere will serve as a catalytic component that improves biological treatment.

 The following examples illustrate the invention.

Example 1
The microsphere of fly ash of combustible coal is taken at the place of ash pulp discharge into a slag storage unit with a specific gravity <1 t / m ³ , dried in an oven at 105 ^o C to a residual moisture content of 7 - 9 wt.%.

To prepare the catalyst, the microsphere of the composition, wt.%: Al ₂ O ₃ - 23.8: Fe ₃ O ₄ - 6.24; FeO - 1.37; TiO - 0.35; MgO - 3.44; CaO - 3.4; SiO ₂ - the rest is introduced into the polymer melt and spherical catalyst granules with a diameter of 6 - 8 mm are formed on the injection molding machine. Polyvinyl chloride is used as the polymer binder.

 Catalysts containing a microsphere and a polymeric binder are prepared in a similar manner in various weight ratios by mixing the corresponding components.

Example 2
200 ml of a model solution containing 1 g / dm ³ sodium sulfide, the rest of the water, pH 10 - 12 is oxidized in the presence of 20 g of the catalyst prepared according to example 1. The catalyst, in the form of regular balls, is loaded into a batch glass reactor with a disperser plate in the bottom parts of the reactor for air supply.

 Air is supplied from the unit through the gearbox, the dosage is carried out using a hydrometer at the outlet of the reactor. Flue gases are passed through a system of absorbers for monitoring hydrogen sulfide.

Sulfide-containing solutions are oxidized in a static mode at a temperature of 20 ^o C, atmospheric pressure for 40 minutes with an air supply of 5 liters per 1 liter of oxidizable solution.

 Evaluation of the catalytic activity of the prepared catalysts of example 1 is carried out with a catalyst for the oxidation of sulfur compounds with a microsphere of fly ash TPP, chromium oxide and high pressure polyethylene (prototype).

 The residual concentration of sulfide ions in the oxidized solution is determined by standard methods (Yu. Lurie, A. I. Rybnikova. Chemical analysis of industrial wastewater. - Chemistry. - 1974).

 Data on catalytic activity are presented in table 1.

Example 3
200 ml of real industrial wastewater entering biological treatment with COD - 239 mg / dm ³ , oil content of 8.4 mg / dm ³ , sulfides - 36 mg / dm ^{3 are} oxidized according to example 2 in the presence of a catalyst prepared according to example 1. In parallel carry out experiments with a known catalyst.

 Analysis of wastewater for the content of sulfides, petroleum products and COD is carried out after 40, 60, 120 and 240 minutes. The initial and residual concentration of petroleum products and COD in wastewater is determined by methods (Yu. Lurie, AI Rybnikova. Chemical analysis of industrial wastewater. - Chemistry. - 1974). The concentration of sulfide sulfur is determined by potentiometric titration according to GOST - 22985 - 75.

 The test results are shown in table 2.

Example 4
1000 ml of real industrial wastewater composition see table. 2 pour in a vessel with activated sludge adapted to petroleum products. 100 g of the catalyst prepared according to Example 1 are placed there. The catalyst is in a free-floating state. Air is supplied through a system made in the form of perforated tubes. Air consumption was 5 m ³ / m ³ drains.

 At the same time in a parallel vessel under similar conditions was a catalyst - a prototype.

 Sewage analysis is carried out after 40, 80, 120 and 240 minutes.

 The test results are shown in table 3.

 From the above data it follows that the effectiveness of the neutralization of harmful impurities during biological treatment in the presence of the proposed catalyst is not limited to the oxidation of sulfur compounds, there is a decrease in COD by 50%, the content of petroleum products by 60%, the pH of the water being purified does not change after 4 hours of catalyst operation, while in the presence of a known catalyst, the pH of the treated effluents decreases to 5.8, which leads to a disruption of the function of activated sludge.

 The proposed catalyst during aeration is distributed evenly over the entire depth of the catalytic zone, while the known catalyst floated to the surface and was almost 50% outside the catalysis zone.

 The use of the proposed catalyst at the stage of biological treatment will increase the efficiency of treatment, increase the volume of wastewater, which will significantly reduce the economic costs of treatment facilities.

Claims (1)

A catalyst for the oxidation of inorganic and organic compounds at the stage of biological wastewater treatment, including a microsphere of fly ash of thermal power plants and a polymer binder, characterized in that it contains polyvinyl chloride as a polymer binder in the following ratio of components, wt.%:
Microsphere of fly ash TPP - 25 - 30
Polyvinyl chloride - Other

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