CC BY
0INCREASING THE EFFICIENCY OF WASTEWATER TREATMENT OF "MAXAM -
CfflRCHIK" JSC
Maksudova Aziza, aziza.maksudova2015@gmail.com, Adilova Klara, klaraadilova61@gmail.com,
Tashkent Institute of Chemical Technology, Department of Industrial Ecology,
Republic of Uzbekistan https://doi.org/10.5281/zenodo.10848462
In recent years, the problem of water resources necessary for the functioning of various systems of human life has become particularly relevant. The specificity of this problem for the countries of Central Asia lies not only in the shortage of water resources, but also in their qualitative condition. Along with the lack of drinking water, there is an urgent issue of pollution of surface and groundwater with wastewater from industrial enterprises.
Thus, according to numerous studies as a result of monitoring the condition of the Chirchik and Akhangaran rivers, which are sources of industrial and domestic drinking water supply for a large part of the population, it has been determined that the water quality indicators in them do not meet the established standards for the values of BOD, COD, and the content of nitrogen compounds and heavy metals, the concentrations of which exceed the MPCs established for them [1].
The main sources of river pollution are discharges of insufficiently treated industrial wastewater from enterprises producing mineral fertilizers - "Maksam-Chirchik" JSC and the Almalyk Mining and Metallurgical Plant.
In wastewater, heavy metal ions such as copper, zinc, nickel, and lead, which have toxic carcinogenic and mutagenic properties, are particularly dangerous. They can accumulate in the body, causing serious illnesses. In this regard, the problem of cleaning industrial and domestic wastewater and preparing water for technical, household and drinking purposes is becoming increasingly important every year.
The most common methods of treating wastewater from heavy metal ions are reagent methods, which involve converting them into insoluble metal hydroxides and settling them in the form of sludge . Due to the increase in the volume of wastewater generated and the tightening of sanitary requirements for the quality of treated water, these methods currently do not provide the required degree of water purification, which leads to their entry into natural reservoirs and further into the human body through the food chain.
Another important problem is the use of outdated treatment plants in many enterprises, which require reconstruction to improve their efficiency, which is expensive. It is very difficult to achieve sanitary and hygienic standards under such conditions.
Thus, it seems most appropriate to use methods for post-treatment of wastewater after reagent treatment. One of the effective post-treatment methods is the adsorption method.
Recently, bioadsorbents obtained from agricultural waste are increasingly used as adsorbents [2]. Various plant wastes can be used as bioadsorbents, among which rice husks occupy the most advantageous place for our region, since they are a cheap, annually renewable resource and do not pose a threat to the environment.
The composition of the husk includes organic compounds, the main of which are cellulose (fiber), hemicelluloses, containing mainly pentosans and lignin, which imparts rigidity to the structure, and silicon oxide predominates among inorganic compounds. Pre-treatment of rice husks contributes to the partial dissolution of organic substances and fats, which prevents an increase in the COD and BOD values of water during the purification process, and also helps to increase the porosity of the structure and increase its adsorption capacity [3].
The purpose of this work was to obtain an adsorbent by chemical modification of rice husk with an aqueous solution of amino alcohol (monoethanolamine) with a component ratio: rice husk
(1g):modifier solution (100ml) = 1:100. The treatment was carried out for 24 hours at room temperature. Next, the solution was filtered, the rice husks were washed with water and dried.
The resulting adsorbent was used to purify wastewater from Cu ( II ) and Ni ( II ) ions. To study the adsorption capacity, 100 ml of a wastewater solution of a given concentration was poured into 250 ml flasks and 1 g of adsorbent was added. The flasks were kept for 60 minutes with constant shaking. Next, the solutions were filtered and the content of metal ions in water was determined by the atomic absorption method.
The dependence of the adsorption value on the process time is shown in Fig. 1.
30
25
0
O 10 20 30 40 50 60 70
T, rnin
Figure 1. Adsorption versus time: ▲ - for Cu (II) ions, • - for Ni (II) ions
The adsorption rate is maximum at the initial moment of time in the presence of a large number of free binding sites on the surface of the adsorbent, as they are filled, equilibrium is achieved.
As can be seen from the figure, at the beginning of the process there was a rapid increase in adsorption, which amounted to 21 mgxg"1 for copper ions and 14,5 mgxg"1 for nickel ions, then the adsorption rate slowly decreased, and then adsorption changes slightly until 60 minutes, after which it remains constant, i.e. balance is achieved. This can be explained by the fact that at the beginning of the purification process, active centers filled with metal ions are present in fairly large quantities, and then over time, the internal pores of the adsorbent begin to fill.
The results of the study showed that adsorbents obtained by chemical treatment of rice husks with an aqueous solution of amino alcohol can be used as effective, inexpensive and environmentally friendly bioadsorbents for treating wastewater from copper and nickel ions.
References:
1. I. A. Usmanov, D. I. Makhmudova, G. A. Khodzhaeva, A. K. Musaeva. Environmental monitoring of the state of the Chirchik and Akhangaran rivers to develop measures for their protection. Ecology And aquatic economy, No. 1(01), 2019, pp. 30-45.
2. Kupchik L., Denisovich V., Salavor O., Nychyk O. E ffect of Rice Husk Mercerizing on Its Sorption Properties after Removal of Cd(II), Pb (II) and Sr (II) Ions from Solutions // Vestnik Vitebsk state technological university _ No. 2 (33). EE "VSTU".
3.Rodionov, A.I.; Klushin, V.N.; Torocheshnikov, N.S. Environmental protection technology. Publisher: M.: Khimiya, 512 pages; 1989.
