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Journal of Chemical Technology and Metallurgy, 51, 2, 2016, 210-214

CARBON ADSORBENTS ON THE BASIS OF BROWN COAL OF ANGREN FOR CLEANING INDUSTRIAL WASTEWATER

Dilnoza Jumayeva1, Izzat Eshmatov1, Berdah Jumabaev2, Anvarkhodja Agzamkhodjayev1

1 Institute of General and Inorganic Chemistry Academy of Sciences of the Republic of Uzbekistan Tashkent, 77-a, Mirzo Ulugbek str. 100170 Uzbekistan E-mail: d.jumayeva@list.ru; anvar381@rambler.ru 2 Hukus State Pedagogical Institute Hukus, A. Dusnazarova 104 str. 230105 Uzbekistan

ABSTRACT Activated carbon adsorbents were prepared on the ground of the Angren Brown coal of the Republic of Uzbekistan

(2BPK, ash-content of 12.7 %). They were used for wastewater purification from petroleum products and mineral impuri-ties. It was found that the adsorbent produced by coal heat treatment at 550°C had hydrophobic properties and mixed with calcium hydroxide was suitable for purification of wastewater containing petroleum products and composites. Coal of sorption capacity higher by 70 - 80 % when compared to that of the original carbon adsorbent was found suitable for wastewater purification from mineral impurities ions and its severity reduction. It was shown that the oil products content and the hardness extent decreased to zero, while the content of inorganic impurities became consistent with the maximum permissible concentration (MPC). The adsorbents tested are recommended for cleaning and softening of industrial waste-water from oil-gas processing and mining-metallurgical industries.

Keywords: industrial sewage, purification, softening, Angren coal, carbon composite adsorbent, absorbent, stiffness.

Received 27 March 2015Accepted 20 January 2016

INTRODUCTION

Intensive growth of man-made chemical pollution of water bodies is noted over the last decade around the world. The main source of reservoirs chemical pollution refers to the chemical production, oil-gas processing and mining-metallurgical industries, the production of new synthetic materials, pesticides, detergents, solid and liquid fuels treatment plants, etc. The discharge there of untreated or poorly treated wastewater poses a significant threat to the water bodies flora and fauna [1 - 3]. The pollutants content exceeds the maximum allowable con-centration. Adsorption treatment of industrial wastewater is one of the most effective cleaning methods used [4]. It becomes increasingly important for both regenerative and destructive industrial wastewater treatment, and recently it has been successfully used in the complex

wastewater treatment scheme [5, 6].In accordance with the above stated, the synthesis

of new carbon adsorbents on the basis of Angren deposit of brown coal of the Republic of Uzbekistan and the investigation of their adsorption properties in view of their effective practical application to the technology of purification of industrial wastewater are very relevant. We prepared [7 - 12] a number of carbon adsorbents on the basis of brown and hard coal of Uzbekistan for cleaning industrial wastewater from metallurgical and chemical industries. In the continuation of these studies the aim of this work is to study the opportunities of us-ing activated carbon and composite adsorbents obtained from Angren brown coal for cleaning and softening of (i) “Mubarek GPP” industrial wastewater containing 1.2 % - 1.8 % (or 9.8 mg l-1 - 14.6 mg l-1) of different products of the oil-gas processing industry and related

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inorganic mineral impurities and a degree of hardness is ct 9.0 mg. mgeq l-1; (ii) “Koh-Bulak JSC” and “Almalyk MMC” wastewater of concentrations of Ca2+ of 230.42 mg l-1, of Na+ of 156.0 mg l-1, of anions of 153.17 mg l-1, of sulphate of 2249.80 mg l-1 and total water hardness of 16.4 mgeq l-1.

EXPERIMENTAL

Angren brown coal (2BPK with ash content of 12.7 %) having specific physical and chemical properties was used. Heat treated adsorbents were obtained by heat treatment of the coal for 30 min at a temperature of 550oC in absence of air [13 - 15], activated adsorbents were prepared by processing of the coal with water vapor for 60 minutes at 800oC, while the composite adsorbents were fabricated through addition of calcium hydroxide to the coal [8].

The ratio of the components of the composite carbon adsorbents was determined by the chemical composition of the wastewater that had to be softened. For instance, to reduce “Mubarek GPP” wastewater rigidity by 8.9 mgeq l-1 it was enough to use a composite coal adsorbent containing 91 % of Angren coal and 9 % of calcium hydroxide. Thus the wastewater hardness was brought to 0.5 mgeq l-1 which corresponded to MPC norms. Physico-chemical and colloid research methods were

applied. The activated and composite carbon adsorbents obtained were tested for purification of waste waters containing dissolved oil products and inorganic mineral impurities. The tests were conducted within three phases in a laboratory installation. The first phase was carried out under static conditions using a treated steel carbon adsorbent, while the second and third phase experiments proceeded under dynamic conditions with the participa-tion of activated and composite carbon adsorbents

RESULTS AND DISCUSSION

The results of the laboratory investigation concern-ing the purification of “Mubarek gas processing plant” wastewater are given in Table 1.

The data received show that the degree of purification of wastewater from oil and gas processing products, as well as from inorganic mineral pollutants reach those required by maximum permissible concentration (MPC), when a heat-treated and an activated compositional adsorbent are used.

It is worth noting that the application of heat-activat-ed adsorbent results in 90.0 % decrease of the content of oil- and gas processing products, i.e. their initial content of 14.6 mg l-1 t is decreased to 2.4 mg l-1 by adsorption treatment. Furthermore, the pollutants present on the wastewater surface are almost completely adsorbed by

Ingredients

Composition of UDP "Mubarek GPP" industrial

wastewater, mg l-1

Composition after cleaning

with heat-treated carbon

adsorbents (I-phase) mg l-1

Composition after purification with an

activated carbon adsorbent (II phase)

mg l-1

Composition after cleaning with a

composite carbon adsorbent (III phase)

mg l-1 1 Oil products 14,6 0,58 0,06 0,03 2 Potassium 3,2 2,8 2,6 1,0 3 Sodium 30,0 28,6 24,5 16,3 4 Calcium 80,8 75,8 70,2 23,4 5 Magnesium 22,7 21,6 18,2 8,1 6 Chlorides 53,2 52,0 38,7 8,4 7 Sulfates 129,8 127,0 108,0 32,0 8 рН 7,9 8,0 8,1 8,0 9 The dry residue 512,0 470,6 418,8 178,6 10 Total rigidity,

mg.ekv. l-1 8,9 8,4 8,0 0,5

Table 1. Experimental results referring to purification of wastewater from UDP “Mubarek GPP”, Republic of Uzbekistan.

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the thermally activated carbon adsorbent. The activated carbon adsorbs the remaining amount of oil and of gas processing products dissolved in wastewater (about 2.0 - 3.0 %, which is 0.58 mg l-1). Compositional carbon adsorbent mainly adsorbs inorganic mineral impurities that leads to reduction of calcium, magnesium, chlorides, sulfates, nitrates and dry residue content by 5-6 times. Hardness values are also reduced from 8.9 mgeq l-1 to 0.5 mgeq l-1.

The laboratory study showed that during the first step of treatment when thermally activated carbon was used, the extent of purification reached 96,0 - 97,0 %, while during the second and third purification steps, carried out using activated and compositional carbon adsorbent, correspondingly, the extent of purification of the wastewater reached MPC.

Initial coal of brand 2BPK and a composite carbon adsorbent obtained have been applied for wastewater purification of Koch-bulak mine “Almalyksky of MMC” (Table 2). The values of Ca2+, Na+, SO4

2-, Cl- concentra-tions and of water hardness, vary widely, sometimes considerably exceeding the required MPC.

It can be seen from the data in the Table 2, that the usage of initial Angren coal and a composite adsorbent, obtained on the basis of it, allowed to decrease the Ca2+ content from 230.42 to 24.25 mg l-1, Na+ - from 156.0 to 6.2 mg l-1, chlorides - from 153.17 to 20.10 mg l-1, sulfates - from 2249.80 to 214.5 mg l-1. The total hard-

ness of the water decreased from 16.4 to 8.1 mgeq l-1. Thus, there is a two-fold reduction of hardness and the calcium, magnesium, sodium, chlorides and sulfates concentrations meet the MPC.

Based on the results obtained, it was developed a 3-step procedure for industrial wastewater purification. The flow diagram is shown on Fig. 1. The polluted water is fed into a precipitation tank with a mixer (1) through a flow meter (2). After filling the wastewater is fed with the same portions. The estimated amount of thermally treated carbon is weighed on scales (3). Carbon adsorbent is precipitated together with oil prod-ucts at the bottom of the tank. The treated water flows for post-treatment in adsorption columns filled with an activated carbon (4) and a composite adsorbent (5). The treated water is flowing by gravitation into a reservoir.

CONCLUSIONS

For the first time a method for thermal activation of Angren Brown coal and activation with water vapor have been developed. A hydrophobic, highly porous carbon adsorbent (pore volume of 30 %) with capacity of 25 % to gasoline, during the heat treatment of coal (30 minutes at 550°C without air access), was obtained. It is suitable for selective industrial wastewater purifi-cation from petroleum products. It was established the possibility to obtain composite adsorbents from Angren

Table 2. Experimental results referring to purification of wastewater from “Koch-Bulak” mine of JSC “Almalyk MMC”.

№ Ingredients, mg l-1 Composition of

mine waters from "Koch-Bulak"

Composition after treatment with an initial coal of sort

BSSH

Composition after treatment with a

composite carbon adsorbent

1 Potassium 9.30 6.8 3.0 2 Sodium 156.00 6.4 6.2 3 Calcium 230.42 105.45 24.25 4 Chlorides 153.17 29.58 20.10 5 Sulfates 2249.80 349.37 214.58 6 pH 8.0 8.0 7.8 7 CO2 2.46 2.82 Not detected 8 Dry residue 3931.0 846.0 766.0

9 Total hardness, mgeq l-1 16.4 8.4 8.1

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Brown coal, with addition of calcium hydroxide, and to use them for decreasing the hardness of water and purifying it from dissolved inorganic mineral impurities to meet the requirements of MPC.

Three stage adsorptive procedure has been applied for purification of wastewater from UDP “Mubarek GPP”. It was found that the treated water reaches the standards of MPC. It was also shown that the original Angren coal and obtained on its basis composite ad-sorbent, are suitable for treatment of wastewater from “Koch-Bulak” AO “Almalyk MMC”.

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Fig. 1. The technological flow diagram for wastewater purification: 1 - precipitation tank with a mixer; 2 - flow meter for waste-water; 3 - scales; 4 - adsorption column with an activated coal as adsorbent; 5 - adsorption column with a composite adsorbent.

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