RU2597381C1 - Carbon-containing sorbent made of vegetable raw material and method of purifying water from sulphides based thereon - Google Patents

Abstract

FIELD: treatment plants.

SUBSTANCE: invention relates to water purification from sulphides and carbon-containing sorbent based on vegetable raw materials. Carbon-containing sorbent for cleaning water from sulphides has microporous structure with average pore diameter of about 2 nm, X-ray amorphous state and is made in form of bundles of fibres with diameter of 50-100 mcm with diameter of separate fibres is about 1.5 mcm. Sorbent is obtained by alkali treatment of rice straws, which are ground, washed with water and dried at room temperature, with an alkaline solution at temperature 90°C for one hour while stirring and volume ratio s: l = 1:13. Obtained fibre product is filtered, washed with distilled water, dried in air and carbonised with insufficient air, washed and dried.

EFFECT: invention provides an efficient sorbent from cheap raw materials.

2 cl, 4 dwg, 1 tbl

Description

The invention relates to a carbon-containing sorbent from plant materials and a method for purifying water from sulfides based on the obtained sorbent.

Sulfides are one of the most common substances that pollute natural waters. Sources of sulfides in the hydrosphere are domestic wastewater, chemical, mining, metallurgical, pulp and paper, oil and gas, oil refining and heat power industries. The presence of sulfides in water, in particular hydrogen sulfide, gives an unpleasant odor to water, intensifies the corrosion process of pipelines and causes them to overgrow due to the development of sulfur bacteria, and also has a toxic effect on living organisms. Currently, various methods have been proposed for purifying water from sulfides and hydrogen sulfide; a fairly common method is the reagent method.

There is a method of purification of natural water (mainly underground) and wastewater of a number of industrial enterprises (pulp and paper, chemical, leather, etc.) from sulfides and hydrogen sulfide [1]. The method consists in filtering the purified water through a layer of granular load, pre-filled with iron the reagent is iron (II) hydroxide or iron (III) hydroxide. The iron sulfide formed in the charge during the filter cycle is oxidized to iron hydroxide with atmospheric oxygen, which is fed at the beginning of the air-water washing through the granular charge layer until the bulk of the iron sulfide is oxidized. To increase the duration of the filter cycle, the purified water is saturated with oxygen and / or another oxidizing agent is introduced into the granular charge before being fed. The method has several disadvantages: the need to use reagents — iron (II) hydroxide or iron (III) hydroxide, which are added as a suspension to the water to be purified, and the need to oxidize iron sulfide with atmospheric oxygen to regenerate iron hydroxide.

A known method of purification from sulfides and hydrogen sulfide by filtration through a layer of granular charge filled with iron hydroxide and finely divided carbon material [2]. The catalytic effect of the carbon material provides an increase in the oxidation rate of hydrogen sulfide and sulfides by the oxygen of the air dissolved in the water to be purified before it is fed into the granular loading layer. However, this method, like the previous one, requires the use of reagents and the subsequent oxidation of the formed iron sulfide with atmospheric oxygen.

There is a method of purification of natural and waste water from hydrogen sulfide, sulfide and hydrosulfide ions, which includes treating water with iron hydroxide to form insoluble iron sulfides, oxidizing the suspension with atmospheric oxygen and separating solid cleaning products from purified water [3]. Chemical precipitation of particles of iron hydroxide is carried out in the presence of dispersed cellulose fibers in water to obtain a suspension of a composite material from fibers with particles of iron hydroxide immobilized by them. Oxidation of sulfides is carried out at elevated air pressure, and the separation of solid water purification products using pressure flotation. The disadvantages of this method include the use of reagents - iron (II) hydroxide or iron (III) hydroxide, the need for oxidation of iron sulfide with oxygen by air to regenerate iron hydroxide and the use of additional equipment - water is saturated with air in a saturator at an increased pressure, which makes the cleaning process more expensive.

As a prototype, the method of sorption treatment of sulphide-containing wastewater was selected, which is closest to the claimed according to the essential features and the achieved result [4]. Glauconite sand of the Ayutinsky deposit (Rostov region) and aminolignin with a fused structure are used as sorbents. Glauconite sand of the Ayutinsky deposit (Rostov region) is a natural sorbent, a representative of layered and complex tape silicates with a content of glauconite in the rock of 40-50%. Aminolignin is obtained from hydrolysis lignin, which is a waste of hydrolysis production, by its modification in several stages. Aminolignin incorporates -COOH and -OH cation-exchange groups and -NH ₂ , -Cl anion-exchange groups. The process of processing hydrogen sulfide water on sorption materials is carried out sequentially. When processing hydrogen sulfide water on glauconite sand, the initial hydrogen sulfide content decreases by an average of 50%, at the second stage, the water is treated on aminolignin, which allows deep wastewater treatment from hydrogen sulfide to the maximum permissible values.

The disadvantage of this method is multi-stage - the use of sequential purification, including the use of two sorbents - glauconite sand of the Ayutinsky deposit and aminolignin obtained from hydrolysis lignin by processing it in several stages. The use of two sorbents of different nature and different preparation complicates and increases the cost of treatment technology for contaminated water.

The objectives of the invention are to obtain a new carbon-containing sorbent from plant wastes of renewable natural raw materials using rice straw as an example and to develop a method for purifying water from sulfides using it.

The technical result of the proposed method is to expand the range of sorbents used for the purification of sulfide-containing wastewater, and the possibility of solving the problem of recycling large-tonnage waste in rice production.

The tasks are solved by an effective carbon-containing sorbent obtained from renewable plant waste generated in the production of rice, rice straw, as well as a one-step method for purification of sulfide-containing water using this sorbent.

The tasks are optimally solved by a carbon-containing sorbent, which is obtained by carbonization of fibrous semi-finished products obtained by alkaline treatment of rice straw in the process of separation of silicon-containing substances (according to the patent [5, 6]) 1 M alkali solution - NaOH or KOH at a temperature of 90 ° C in for one hour with stirring and a volume ratio of T: W = 1: 13; The tasks are optimally solved by sorption treatment of water from sulfides, which is carried out using the obtained sorbent at a pH of 9-10 at a sorbent: water ratio of 1: 100 for 1 hour, followed by separation of the carbon-containing sorbent from purified water.

The chemical composition of the inventive sorbent was determined by energy dispersive x-ray fluorescence spectroscopy (ED XRF) on a Shimadzu EDX 800 HS spectrometer (Japan). X-ray phase analysis was performed on a D8 ADVANCE diffractometer in CuKα radiation. The morphology of the surface of the sorbent was studied on a Hitachi S 5500 high-resolution scanning electron microscope (SEM) (Japan). In order to determine the structure of the samples, IR absorption spectra in the region of 400–4000 cm ^–1 in potassium bromide were recorded on a Bruker Vertex 70 Fourier spectrometer (Germany). Bulk and true density was determined according to GOST 8269.0-97 [7]. The value of the specific surface and the total pore volume were determined by adsorption of water vapor according to [8], the effective pore diameter was determined by [9]. The pH of the aqueous extract was set according to GOST 4453-74 [10]. The adsorption activity of the obtained product was determined by iodine according to GOST 6217-74 [11], by methylene blue and methylene orange - according to GOST 4453-74 [10]. the pH of the solutions was measured on a pH meter pH-150M (Gomel); the presence of the smell of purified water was established according to GOST 3351-74 [12].

A distinctive feature of the proposed method for purification of water from sulfides is the use of a new effective carbon-containing sorbent obtained from waste from rice-rice straw. A comparative analysis of the essential features of the proposed method with the essential features of analogues and prototype indicates its compliance with the criterion of "novelty."

The proposed carbon-containing sorbent and a method for purifying water from sulfides based on it are illustrated by pictures, graphs and images shown in FIG. 1-4.

In FIG. 1 shows a probe photograph of the surface of the sorbent, indicating that its surface layer contains ~ 68.69% C and ~ 18.66% O. The X-ray amorphous state of the sorbent is confirmed by FIG. 2, which shows the x-ray of the sorbent, characteristic of amorphous products. In FIG. 3 shows microphotographs of the surface of the sorbent (3a - with an increase of 20 microns, 3b - with an increase of 500 microns), indicating its fibrous structure. The IR spectrum of the carbon-containing sorbent is given in FIG. 4 in the region of 400-4000 cm ^-1 . His analysis indicates the presence in the sorbent of decomposition products of a fibrous semi-finished product, the basis of which is cellulose: an intense wide absorption band with a maximum in the region of 3433 cm ^-1 corresponds to stretching vibrations of OH groups of various nature; the absorption band in the region of 2920 cm ^-1 corresponds to stretching vibrations of aliphatic groups. The presence in the spectrum of an intense band in the region of 1595 cm ^-1 indicates the presence of conjugated bonds —C = C— of condensed aromatic structures; In the same range of ~ 1600 cm ^–1 , deformation vibrations of OH groups also appear.

In addition, absorption bands are observed in the spectrum of the carbon-containing sorbent at 1695 cm ^-1 (corresponds to stretching vibrations of carbonyl groups C = O), at 1238 cm ^-1 (corresponding to stretching vibrations of С-O bonds of secondary alcohols) and at 1375 cm ^-1 (corresponding to deformation vibrations of CH ₂ and CH ₃ groups).

The bulk density of the product is 91 kg / m ³ and the true density is 1440 kg / m. The value of the specific surface, established by water vapor, is ~ 45 m ² / g; the total pore volume in water is 0.15 cm ³ / g; The pH of the aqueous extract is in the range of the neutral medium. The iodine adsorption activity of the inventive carbon-containing sorbent is 43%, for methylene blue - 130 mg / g, for methylene orange - 63 mg / g.

The proposed method for purifying water from sulfides differs from the methods known from the prior art in that for its use a carbon-containing sorbent is first obtained from renewable plant waste - rice straw. The resulting product is a solid powder product, which is in an x-ray amorphous state, which is confirmed by x-ray phase analysis; consists of bundles of fibers with a diameter of 50-100 microns; the diameter of an individual fiber is about 1.5 microns; characterized by a microporous structure with an average pore diameter of ~ 2 nm.

The inventive method of purification of water from sulfides is implemented in two stages.

At the first stage of the implementation of the proposed method receive carbon-containing sorbent according to the method described in example 1, and at the second conduct water purification from sulfides. The experiments were carried out with distilled water, artificially contaminated with sodium sulfide with a concentration of 700 μg / l at pH 9-10. The cleaning method is as follows: a weighed sample of a sorbent weighing 0.5 g is placed in a flask, 50 ml of artificially contaminated water are poured and the mixture is shaken on a LAB-PU-01 mixing device for 1 hour to establish equilibrium, after which the suspension is filtered through a blue filter tape". The residual sulfide ion content in the solution is determined spectrophotometrically on a Hach DR2700-01B1 spectrophotometer with N, N-dimethyl-p-phenylenediamine sulfate. The efficiency of extraction of sulfide ions from aqueous solutions (a,%) is calculated by the formula:

where C _ref . and C _equal . - initial and equilibrium concentration of sulfide ions, μg / ml.

The experimental data indicating the sorption activity of the inventive sorbent relative to sulfide ions in comparison with a commercial sample - activated carbon brand P-709, are presented in the table.

As the data in the table indicate, the sorption capacity of a commercial product is two times lower than the claimed sorbent, and the absence of a characteristic odor (along with data obtained by the efficiency of sorption of sulfide ions) indicates a sufficient degree of purification from sulfide ions.

The amount of sorbed sulfide ions (G, μg / g) was calculated by the formula:

where m is the mass of the sorbent, g;

With _ref. and C _equal. - initial and equilibrium concentrations, μg / ml;

V - sample volume, ml.

Thus, the proposed method allows you to remove sulfides from water with high efficiency (≥91%), as well as expand the range of sorbents obtained from environmentally friendly renewable natural raw materials, which is a large-tonnage waste from rice production.

The method can be applied for the purification and post-treatment of wastewater and natural waters; the method is simple to implement and does not require the use of special equipment; its application solves the problem of recycling rice production waste.

The possibility of carrying out the invention is confirmed by the following examples.

Example 1

Rice straw is crushed into pieces of about 2 cm in size, washed with distilled water and dried in air. A sample of prepared rice straw weighing 50 g is placed in a flask, filled with 650 ml of 1 M NaOH (ratio T: W = 1: 13), stirred at 95 ° C for one hour on a WiseStir (HS-50) vertical mixer with an anchor mixing device . The treated straw together with the solution is cooled to room temperature and the solution (hydrolyzate) is separated from the insoluble residue of the raw material (fibrous semi-finished product). The yield of washed to neutral wash water and air-dried fibrous semi-finished product is ~ 44% of the total mass. Further, the fibrous prefabricated product is carbonized in a glassy carbon tray with a lack of air at an optimum temperature of 350-400 ° C, until volatile components are removed within 0.5 hours. The resulting sample was again washed with distilled water and dried in an oven at t = 105 ° C to constant weight.

A weighed portion of a sorbent weighing 0.5 g is placed in a flask, pour 50 ml of water, artificially contaminated with sodium sulfide with a concentration of 700 μg / l at pH 9-10, shake the flasks on a mixing device LAB-PU-01 for 1 h to establish equilibrium, after which the suspension is filtered through a blue ribbon filter. The residual sulfide ion content in the solution is determined spectrophotometrically on a Hach DR2700-01B1 spectrophotometer with N, N-dimethyl-p-phenylenediamine sulfate. The arithmetic mean of the results of three parallel definitions is taken as the result of the analysis. The efficiency of extraction of sulfide ions from aqueous solutions (α,%) calculated by the formula (1) is 91%.

Example 2

Example 2 is carried out according to example 1; the difference lies in the fact that the hydrolysis of the crushed and prepared according to example 1 raw materials is carried out 1 M KOH. The efficiency of extraction of sulfide ions from aqueous solutions is also 91%.

Literature

1. RF patent №2285670, publ. 10/10/2005

2. RF patent No. 2361822, publ. July 20, 2009

3. RF patent No. 2482066, publ. 05/20/2013

4. RF patent No. 2090514, publ. 09/20/1997

5. RF patent No. 2394764, publ. 07/20/2010 r.

6. Application for the grant of a patent of the Russian Federation for invention No. 2014113045 of 04/03/2014.

7. GOST 8269.0-97. Crushed stone and gravel from dense rocks and industrial waste for construction work. Methods of physical and chemical tests.

8. Greg S., Sing K. Adsorption, specific surface area, porosity: trans. from English, 2nd edition. M .: Mir, 1984. 306 p.

9. Dubinin M.M. Adsorption of water vapor into microporous structures of carbon adsorbents // Bulletin of the USSR Academy of Sciences. Chemical series. 1981. No. 1. S. 9-23.

10. GOST 4453-74. Powdered active clarifying charcoal.

11. GOST 6217-74. Crushed active charcoal. Technical conditions

12. GOST 3351-74. Drinking water. Methods for determining taste, smell, color and turbidity.

Claims (2)

1. Carbon-containing sorbent for water purification from sulfides, having a microporous structure with an average pore diameter of about 2 nm, an X-ray amorphous state made in the form of fiber bundles with a diameter of 50-100 μm with a single fiber diameter of about 1.5 μm, obtained by alkaline treatment of crushed washed with water and dried at room temperature rice straw with 1 M alkali solution - NaOH or KOH at a temperature of 90 ° C for one hour with stirring and a volume ratio of T: W = 1: 13, after which the fibrous product is filtered washed with distilled water, dried in air and carbonized with a lack of air at an optimum temperature of 350-400 ° C, until volatile components are removed for 0.5 hours, and then the resulting product is washed with distilled water and dried in an oven at t = 105 ° C to constant weight. 2. A method of purifying water from sulfides, including mixing the purified water with the carbon-containing sorbent described in paragraph 1, with a sorbent: water ratio of 1: 100 and a pH of 9-10, followed by filtration of the purified water.

Images