Process for water purification from hydrogen sulfide and sulfides

The invention relates to a process for the purification of hydrogen sulphide and sulphide water and can be used in communal households, fisheries, public aquariums, autonomous filters, as well as for the purification of groundwater.

About 50% of the total amount of groundwater in the territory of the republic is characterized by an increased confinement of different pollutants (hydrogen sulphide, nitrates, fluorine, heavy metals). Sulfur compounds (hydrogen sulphide, sulfuric acids) negatively influence the organoleptic quality of the water, have corrosive, toxic properties and harm human health, imposing the need to eliminate or reduce their content to the extent allowed.

Elimination of sulfur compounds by aeration in the presence of adsorbents and / or catalysts, for example activated carbon, higher oxides! of manganese, iron complexes have the disadvantage that they require special equipment and materials, the processes being expensive.

The process of purifying hydrogen sulphide water is known to consist of the use of BAU-A activated carbon, where when the air is bubbled through water, hydrogen sulphide and sulphides oxidize [1].

The disadvantage of the process is that in the process of water treatment, on the surface of the coal colloidal sulfur is formed that blocks the pores, thus removing it quickly from use.

Also known is the process of purifying hydrogen sulphide and / or sulfur waters by aerating the water in the presence of activated carbon, where as active carbon is used oxidized activated carbon, and aerating the water is performed for 30 ... 90 min, with an air flow rate of 10 ... 15 L / hour per 1 g of oxidized activated carbon, at a mass ratio of oxidized activated carbon: water of 1: (350 ... 450) and water pH of 7, 5 ... 8.5 [2].

The disadvantage of this process is that the carbon adsorbents are relatively expensive, compared to the mineral ones, which is why the use of the mineral adsorbents is often given priority.

As the closest solution, the process of oxidation of water sulphides is presented in the presence of the "green sand" (greensand) adsorbent, natural or specially processed with manganese salts, then with potassium permanganate solution. The form obtained by Mn-glauconite and manganese oxides serve as catalyst and oxidants in the water treatment process [3]. '

The disadvantage of this process is that the required material, ie the adsorbent (green sand) is very expensive being an imported material.

In the composition of the diatomite, significant resources are located along the Dniester river, recommended for use in sorbent processes, from flocculation-sedimentation to wastewater treatment, along with the siliceous material from the diatoms, there are minerals such as mon tmorilonite, ilite , kaolinite, as well as amorphous alumosilicaf components, oxides of aluminum and iron. The generalized chemical composition of the diatomite is presented as follows (%): SiO₂ - 85, A1₂A₃ - 3, Faith₂A₃ - 2, MgO - 0.5, CaO - 2, calcination losses - 7.

The problem solved by the invention is the elaboration of a simple and cheap process for purifying hydrogen sulphide and sulfur water.

Compared to alfalfa adsorbents, the diatomite is cheaper, and their polymineral composition, as well as the chemical modification, allow to exhibit increased catalytic properties of adsorption.

The process according to the invention consists in the use of the modified diatomite, obtained by the preventive treatment of the diatomite with a solution of 24% NaOH, taken in a ratio of 1: (10 ... 15), for 12 hours, after which the suspension obtained heat on water bath at boiling temperature for 2 hours, add in excess о 30% solution of MnCl₂ and is kept for 24 hours at room temperature, the solid phase is filtered, immersed and kept in 24% NaOH solution for 24 hours at room temperature, the supernatant is decanted and the solid phase is exposed to air, after which wash with distilled water until the negative reaction to the ions of СГ, is granulated and dried at the temperature of 105 ... 200 ° C, at the same time the ratio of the adsorbent to the purified water is 1: 800.

The result of the invention consists in the elaboration of a simple and inexpensive process of purifying hydrogen sulphide and sulfur water by increasing the efficiency of the use of the diatomite.

According to the invention, the process has the following advantages:

MD 4142 Cl 2012.07.31

- In the processes of purification of hydrogen sulphide and sulphide water, native diatomite, cationic modified in the form of Mn (IV) -diatomite is used.

- Due to the pronounced porosity (about 30 times greater than that of glauconite), larger quantities of manganese compounds per unit mass can be fixed in the diatomite particles, ensuring a longer service life.

- Low density (about 0.3 g / cm³) of the diatomite, compared to the "green sand", allows the use of other types of water treatment devices, with adsorbent / catalyst in suspension, which makes the proposed water purification process cheaper, more advantageous and special the one taken as the closest solution.

- The native diatomite, as a raw material for obtaining adsorbents / catalysts, is cheaper and presents real prospects for requests from a wider spectrum of users.

Concrete example of realization

For example, the diatom from Ghidirim locality was used. The diatomite sample (fraction <0.14 mm) was modified by preventive treatment of the diatomite with 24% NaOH solution, taken in a ratio of 1: (10 ... 15), for 12 hours, after which the suspension obtained heat on water bath at boiling temperature for 2 hours, add in excess о 30% solution of MnCl₂ and is kept for 24 hours at room temperature, the solid phase is filtered, immersed and kept in 24% NaOH solution for 24 hours at room temperature, the supernatant is decanted and the solid phase is exposed to air, after which wash with distilled water until the negative reaction to the CT ions, granulate and dry at 105 ... 200 ° C, while the ratio of the adsorbent to the purified water is 1: 800.

The oxygen reaction of Mn (II) to Mn (IV) presents an autocatalytic process, schematically including the steps:

slow

Mn (II) + O₂------> MnO₂(s) (a) quick

Mn (II) + MnO₂(s) -------> Mn (II) -MnO₂(s) (b) slow.

Mn (II) -MnO₂(s) + O₂------> 2MnO₂(S) (c)

Testing the adsorption / oxidation capacity of sulphide ions in the presence of mineral adsorbents was performed using Na model solution₂S (pH 8.86, adjusted with sodium tetraborate buffer solution), with a recalculated content of S ions²about 250 mg S²per liter. The contact of the model solution with the exemplary adsorbents was performed in static conditions, at the solid ratio: liquid equal to 1: 800, for 24 hours at room temperature, after which the equilibrium concentration of the sulfide ions in the supernatant was determined, using the colorimetric method with lead salts.

For comparison, the natural natural diatomite (fraction <0.14 mm) and the adsorbent obtained after treatment with manganese salt under the conditions described above were tested, the results being presented in the table.

Table

Removal capacity of hydrogen sulphide from the model solution Solids ratio 1: 800. Initial concentration C₀= 268 mg / L, pH = 8.86

<td rowspan="2">adsorbent</td><td rowspan="2">Balance concentration C_is, mg / L</td><td colspan="2">The adsorption / oxidation capacity</td><td rowspan="2">Organoleptic characteristics of the treated water</td>

<td>mg / g</td><td> %</td>

<td>Natural diatomite. Dry sample at 105 ° C</td><td> 80</td><td> 150</td><td> 70</td><td>The balance solution is opaque, it has the smell of H₂S</td>

<td>Diatomite treated with manganese salt. Dry sample at 105 ° C</td><td> 0</td><td> 214</td><td> 100</td><td>The balance solution is slightly opalescent, colored in pale pink, smelling of H₂S does not feel</td>

<td>Diatomite treated with manganese salt. Dry sample at 200 ° C</td><td> 0</td><td> 214</td><td> 100</td><td>The balance solution is not colored, smells of H₂S does not feel</td>

MD 4142 Cl 2012.07.31

The adsorbent synthesized by impregnating the diatomite with Mn (IV) oxide hydrographs has a capacity of about 1.5 times higher removal of sulphuretted hydrogen from the solutes, in comparison with the initial diatomite. The adsorbent can be granulated (briquetted in different sizes) and the granules after calcining at 200 ° C have! о mechanical hardness! enough, it does not disperse! m medium aqueous and does not color! treated water !, what I present! real prospects of use in practice! for water purification.

(56) Bibliographic references cited in the description:

1. Nikoladze G.I. Improving the quality of groundwater. Moscow. Stroyizdat,

1987, p. 240

2. MD 2480 G2 2005. 02. 28

3. Kogel JE, Trivedi NC, Barker JM, Krukowski ST Industrial Minerals and Rocks: commodities, markets, and uses. shock. for Mining. Metallurgy and exploration, Colorado, 2006, pp. 495-505