STUDY OF ADSORPTION ACTIVITY OF CARBON ADSORBENT OBTAINED BY THERMOCHEMICAL ACTIVATION BASED ON COTTON PLANT RAW MATERIALS

ABSTRACT

This article talks about environmental and water pollution caused by dyes, which is a current problem today, and about adsorbents, in particular, activated carbons, which can be a solution to this problem. Methods of obtaining activated adsorbents using thermochemical methods based on cotton shells, the effect of pyrolysis temperature on the yield of coal formation, chemical activation of the obtained coal samples with alkali, methods and results based on them are described. The results of the studies show that the increase in the pyrolysis temperature from 300℃ to 500℃ caused a decrease in the yield of the produced coal. Due to the low adsorption property of the formed coal, it was thermochemically activated by chemical activation using alkalis such as NaOH and KOH. A photocolorimetric analysis of the adsorption of methylene blue solution of carbon samples activated by thermochemical activation at different temperatures of 350 (sample 1), 400 (sample 2) and 450 (sample 3) ^oC was carried out.

АННОТАЦИЯ

В данной статье говорится о загрязнении окружающей среды и воды красителями, что является актуальной проблемой на сегодняшний день, и об адсорбентах, в частности, об активированных углях, которые могут стать решением этой проблемы. Описаны методы получения активированных адсорбентов термохимическими методами на основе хлопковой шелухи, влияние температуры пиролиза на выход углеобразования, химическая активация полученных образцов угля щелочью, методы и результаты на их основе. Результаты исследований показывают, что увеличение температуры пиролиза с 300 ℃ до 500 ℃ привело к снижению выхода получаемого угля. В связи с низкой адсорбционной способностью образующегося угля его термохимическую активацию проводили методом химической активации с использованием щелочей, таких как NaOH и KOH. Проведен фотоколориметрический анализ адсорбции раствора метиленового синего образцами угля, активированными методом термохимической активации при различных температурах 350 (образец 1), 400 (образец 2) и 450 (образец 3) ^oC.

Keywords: cotton shells, wastewater, adsorption, adsorbent, activated carbon, pyrolysis, chemical activation, regeneration, dyes, methylene blue.

Ключевые слова: хлопковая коробочка, сточные воды, адсорбция, адсорбент, активированный уголь, пиролиз, химическая активация, регенерация, красители, метиленовый синий.

INTRODUCTION

At the time when industrial sectors around the world are rapidly developing, the pollution of wastewater due to the influence of dyes is becoming a serious problem. As a result of textile products, paper and plastic production, synthesis of dyes, dyeing of leather and fabric products, polygraphy and many other production processes, various dyes are formed in wastewater [1].

As a result of the rapid expansion of industrial enterprises and the improvement of production technology, it is becoming more and more difficult to remove dyes from wastewater. Wastewater containing dyes has a complex composition and the ability to biodegrade is very poor.Methylene blue is usually found among organic compounds in higher concentrations than other dyes [2] As a result of this, environmental pollution, damage to flora and fauna, and a serious threat to public health are observed. Therefore, it is necessary to immediately clean the wastewater from ions and compounds that cause pollution. At present, methods such as adsorption, chemical treatment, ion exchange, and coagulation are widely used for the purpose of wastewater treatment [3]. Wastewater treatment using the adsorption method is recognized as the most effective method. This is because it has a number of advantages such as abundance of sources, variety of species, low cost from an economic point of view, regeneration properties, high cleaning efficiency and ease of use. It has been proven that the efficiency of the adsorption process can reach 99.9% [4]. At the same time, this method is simple and cost-effective compared to other methods, and has good properties for cleaning wastewater from many types of pollutants, including dyes.

The most commonly used traditional adsorbents for cleaning water and air from various pollutants and gases are bio-adsorbents, zeolites (silicon oxide, aluminum oxide), activated carbon, clay, metal oxide, etc. [5].

Activated carbon (AC) is the most effective adsorbent material for removing many types of pollutants from wastewater [6]. Activated carbon is a widely used adsorbent, which is prepared by carbonization and activation of raw materials containing carbon. As raw materials, secondary agricultural raw materials such as rice straw, reed stalks, walnut shells, peanut shells and grape seeds are used [7] [8]. These raw materials are generated as waste in large quantities every year.

MATERIALS AND METHODS 

The purpose of the method is to obtain activated carbon from cotton shells by thermochemical activation. Cotton shells layers are separated from each other and crushed (figure1). The raw material was weighed in the amount of 200 g (accuracy 0.1 g) using analytical balances.

Figure 1. Cotton shell

In order to obtain carbon adsorbents based on raw materials containing carbon, they are first subjected to thermal treatment (carbonization). For this, they are pyrolyzed at high temperatures.

It was dried in a drying cabinet at 105℃ for 24 hours to remove moisture. The dried raw material was sent to the pyrolysis unit for pyrolysis. The part of the pyrolysis device where raw materials are placed is made of stainless steel.

It was found that the selected raw materials for obtaining activated carbon adsorbents turn into coal at a temperature of 300 ℃. The pyrolysis process was carried out in the temperature range from 300 ℃ to 500 ℃ (in the process, the temperature change every 50 0C was studied). Duration of pyrolysis time was chosen as 1.5 hours (table1).

Table 1.

 Effect of temperature on the yield of carbon adsorbent based on cotton shell

From Table 1, it can be seen that increasing the pyrolysis temperature from 300 ℃ to 500 ℃ leads to a decrease in the yield of the product. The sorption properties of thermally activated adsorbents are low. The obtained adsorbents are chemically activated in order to improve their adsorption properties.

The obtained coal product was crushed using a porcelain mortar. Then it was transferred to the chemical activation process. A chemical method was chosen for activation. KOH and NaOH solutions with different concentrations were used as chemical activators.

*100                                                     [1]

The alkali was mixed in a magnetic stirrer until it was completely dissolved in water. After activation, the coal was boiled with distilled water for 30 minutes to remove excess alkali from the coal, then filtered. The washing process was carried out 3 times (500 ml of water was used for each washing). Then it was treated with 0.n HCl (GOST 857-95, 30-32%) in order to remove ash. It was washed again with distilled water. The change in pH was monitored on an indicator piece of paper. It was dried at 105℃ for 24 hours (to absolute dry mass). The mesh was passed through a 0.1 mm sieve. The mass was measured.

Preparation of a solution of methylene blue. For this, 1.5 g of methylene blue indicator is taken on an analytical balance with an accuracy of 1000/1 and placed in a 1000 ml measuring flask. The indicator is dissolved in 200 ml of hot water with a temperature of 70-80 °C and cooled. After the solution has cooled to room temperature, it is filled with distilled water up to the mark of the flask. The concentration of the prepared solution is 1500 mg/ml.

The progress of the experiment. 0.10 g (accuracy of 0.001 g) is extracted from pre-dried cotton husk charcoal. Put it in a 100 ml measuring flask, pour 25 ml of methylene blue solution over it, close the mouth of the container with a stopper and shake it for 20 minutes in a multishaker device. Then the resulting charcoal suspension is placed in a centrifuge tube and centrifuged for 15 minutes. Carefully take 1 ml of the centrifuged solution with a pipette and put this sample into a 100 ml volumetric flask. Distilled water is poured over the added solution and the volume is brought up to the measuring line. The optical density of the resulting solution after dilution is 0.317, and the dilution factor is 100.

Based on the optical density value obtained, the residual mass concentration of methylene blue in the diluted solution is found using a graduation graph.

RESULTS AND DISCUSSION

Adsorption activity X (mg/ 1 g of coal) of charcoal obtained from cotton husks against methylene blue was calculated according to the following equation:

                                                      [2]

Here is C₁ the concentration of methylene blue primary solution, mg/l;

C₂ – concentration of the solution after clarification  with activated carbon, mg/l;

K - is the dilution coefficient of the solution;

0.025 – the volume of methylene blue solution taken for clarification, liter;

m - is the mass of activated carbon measured for analysis, in grams.

Making a graduation schedule. Solutions were prepared for comparison when plotting the graduation graph. For this, take 5 measuring flasks with a volume of 50 ml, pour 0.5, 1.0, 1.5, 2.0, 2.5 ml of methylene blue solution into them, and then fill them with distilled water up to the measuring line. The optical density of each solution is measured in a photoelectrocolorimeter at a wavelength of 400 nm (cuvette thickness 10 mm) on a blue light filter. Distilled water is used as a control solution. According to the obtained results, a graduation graph is drawn up. The optical density of solutions is given in the following table: (see table 2)..

Table 2.

Optical density values of methylene blue solutions

 The obtained spectrophotometric results are presented in Figure 2 below:.

Figure 2. Optical density graph of methylene blue solutions

 According to the obtained results, the following graduation graph was created based on the results of the relationship between the concentrations and optical densities of methylene blue solutions after quenching with activated carbon.

Figure 3.  Graduation graph based on the results of the relationship between the concentration and optical density of methylene blue solutions after quenching with activated carbon

CONCLUSION

 Activated carbon samples with thermochemical activation at different temperatures of 350 (Sample 1), 400 (Sample 2) and 450 (Sample 3) ^oC were taken from the cotton shell. Photocolorimetric analysis of the adsorption of methylene blue solution of these samples was carried out. According to the results of the research, a graduation graph of the solution was created.

References:

1.  Chaojun Fang. Effective adsorption of methylene blue from aqueous solution by coal gangue-based zeolite granules in a fluidized bed: Fluidization characteristics and continuous adsorption// Powder Technology. Volume 408, August 2022, https://doi.org/10.1016/j.powtec.2022.117764]
2. Bo Huang, Rong Zhao, Hongxiang Xu, Jiushuai Deng, Weichao Li, Jingzheng Wang, Han Yang, Li Zhang. Adsorption of Methylene Blue on Bituminous Coal: Adsorption Mechanism and Molecular Simulation // ACS OmegaVolume 4/Issue August 16, 2019 14032-14039 p.
3. V. K. Gupta, I. Ali, T.A. Saleh, A. Nayak, Sh. Agarwal. Chemical treatment technologies for waste-water recycling—an overview// RSC Advances Issue 16, 2012 6380-6388pPrichko, T.G., Smelik, T.L., Khrapov, V.O., & Majar, D.A. (2013). Fruit growing and viticulture in the south of Russia. Fruit Growing and Viticulture, 20(2).
4. R. Rashid, I. Shafiq, P. Akhter, M. J. Iqbal, M. Hussain. A state-of-the-art review on wastewater treatment techniques: the effectiveness of adsorption method//Environmental Science and Polluti [Bo Lv, Bobing Dong, Chuanxiang Zhang, Zeng qiang Chen, Zeya Zhao, Xiaowei Deng, on Research. 2021. Volume 28, pages 9050–9066]..
5. Sh. Wadhawan, A. Jain, J. Nayyar, S. K. Mehta Role of nanomaterials as adsorbents in heavy metal ion removal from waste water: A review// Journal of Water Process Engineering. Volume 33. 2020, 101038
6. K. Azam, N. Shezad, I. Shafiq, P. Akhter, F. Akhtar, F. Jamil, S. Shafique, Y. K. Park, M. Hussain. A review on activated carbon modifications for the treatment of wastewater containing anionic dyes// Chemosphere, Volume 306, 2022, 1-19 b
7. Урунова Х.Ш., Темироов Ў.Ш., Умиров Ф.Э. Mахаллий минерал хом ашёлар ва шоли қипиғи асосида адсорбентлар олиш// International Journal of Advanced Technology and Natural Sciences Vol.3(4), 2023. 61-65b
8. L. Wu, Z. Shang, H. Wang, W. Wan, X. Gao, Z. Li, N Kobayashi. Production of activated carbon from walnut shell by CO2 activation in a fluidized bed reactor and its adsorption performance of copper ion// Production of activated carbon from walnut shell by CO2 activation in a fluidized bed reactor and its adsorption performance of copper ion// Journal of Material Cycles and Waste Management, 20 (3) (2018), pp. 1-13.
9. Bektemirov, A., & Soliev, M. (2023). The study of the biological effectiveness of the "AKARAGOLD 72% em.k." drug for solving problems of environmental protection. In III International Conference on Geotechnology, Mining and Rational Use of Natural Resources (GEOTECH-2023), 417. Navoi, Uzbekistan
10. Dospehov, B.A. (1985). Methodology of field experience (with the basics of statistical processing of research results). Moscow: Agropromizdat.