INTRODUCTION:

Serious threat of pollutants in water bodies on human health and aquatic ecosystem. There are several water pollutants that have been classified as organic pollutants, inorganic pollutants, pathogens, radioactive pollutants and thermal pollution, etc^1,2.

Textile industries use distinctive raw materials such as cotton, wool fibers, and chemicals, including synthetic dyes³, the annual world production of these dyes exceeds 700 000 tonnes. Almost the third of this amount is lost to the environment by the textile industries^4,5.

To treat dye wastewaters, various physical, chemical, and biological methods are used, different techniques have been used for the removal of certain soluble pollutants in industrial or domestic effluents⁶. They are different from each other and can be cited by way of illustration: adsorption³, electrolysis, flotation, precipitation, ion exchange, liquid-liquid extraction, membrane filtration^7,8.

Activated carbon, which has a highly developed pore structure, is a very good adsorbent, catalyst and catalyst support, which is widely used to capture many pollutants in gases or liquids such as organics, pesticides, biological entities, dyes and other mineral materials^9,10. Activated carbon adsorption is known to be one of the best methods for treating heavy metals in our water^11,12.

Different studies have been devoted to the production of activated carbons from waste as raw materials (lignocellulosic residues)¹³, or from agricultural residues like date palm pits¹⁴. A comparison of microstructure and adsorption characteristics of activated carbons by CO₂ and H₃PO₄ activation from date palm pits¹⁵, Waste tea activated carbon¹⁶, pomegranate peel activated carbon prepared by microwave-induced KOH activation¹⁷, cherry stones by zinc chloride¹⁸, pumpkin seed hull^19,20.

To prepare activated carbon two common methods are widely used which are physical activation and chemical activation, Activation by medium strength acid which is phosphoric acid, it is one of the chemical activation methods that has been widely used in recent years. This is due to the fact that phosphoric acid activation has environmental and several other advantages²¹, Phosphoric acid has dehydrating properties, which helps a lot to improve the depolymerization and redistribution of biopolymers constituting the material², we can quote some studies on the activation with phosphoric acid with related details about activated carbon from date palm pitas (S^BET 952m²/g and Yield%=41), Eucalyptus biochar (S^BET 1239m²/g and Yield%=26)²², Bamboo (S^BET 1239m²/g and Yield%=26)²¹.

In this study, three different activated carbons were prepared from agricultural wastes wich are Ziziphus mauritiana Lam seeds by chemical activation using phosphoric acid followed by pyrolysis at different temperatures, elemental analysis and chemical composition of these agricultural wastes. Same parameters affecting the adsorption process like contact time, adsorbent mass, initial dye concentration and pH have been studied.

MATERIALS AND METHODS:

Adsorbate:

Methylene blue (MB), this cationic dye has the molecular formula C₁₆H₁₈N₃SCl and the molecular weight of 319.85 g/mol, of very high purity²³, All chemicals and reagents were procured by Merck, Germany, it was used as adsorbate in this study.

Preparation of activated carbons:

Ziziphus mauritiana Lam seeds have been used as raw materials for the preparation of activated carbons. Ziziphus mauritiana Lam fruits were harvested from the Batna region in Algeria.

First, to remove impurities, Ziziphus mauritiana Lam seeds were washed with distilled water and dried in an oven at 110 °C. for 24 hours. They were then crushed, sieved to the desired particle size between 0.4 and 0.5 mm.

Activation was performed by impregnating the samples with phosphoric acid in a 1:1 (w/w) ratio for 3h, then washed several times with distilled water until the pH of the wash solution reached 7. The samples were then dried at 100°C and pyrolyzed in a muffle furnace at 400, 500 and 600°C for 1 hour. Activated carbon samples are abbreviated as AC 400, AC 500 and AC 600 according to the activation temperatures: 400, 500 and 600 respectively.

Characterization of activated carbon:

a) Carbon Yield_%:

The activated carbon yield can be calculated from(Eq 1):

activated carbon weight

Carbon Yield_% = ––––––––––––––––––––– × 100 (1)

raw material weight

In order to reduce production costs, high yield values are required in activated carbon production.

b) Bulk density:

The apparent or bulk density is the sum of the solid and pore fractions. It is determined by the method of the graduated test tube under specified conditions, it is a measure of the weight of material that can be contained in a given volume (Eq 2):

weight of dry material (g)

Bulk density = ––––––––––––––––––––––––––––– (2)

volume of packed dry material (ml)

c) Humidity content:

In permanent contact with the air or by its storage, the solids are loaded with a certain moisture due to the diffusion of water molecules in the structure and on the surface of the solid.

To obtain the water content, 2 g of activated carbon were placed in a weighed crucible. The activated carbon and crucible were dried for 24 h at 110 °C and reweighed.

d) Burn-off:

The "Burn-off" represents the loss of mass of the cores impregnated with phosphoric acid (H₃PO₄) due to the heat treatment at the activation stage (Eq 3):

Initial mass – Final mass

Burn – off (%) = ––––––––––––––––––––– (3)

Initial mass

e) FT-IR:

In order to investigate the surface groups, the functional groups were analyzed using FT-IR-8400S Fourier transform infrared spectroscopy (Bruker Tensor, Germany). 0.02g of the samples were mixed and ground with 0.2 g KBr as an interference-free matrix, to obtain pellets, and the scan region extended from 500 to 4000 cm⁻¹.

Adsorption experiments:

For adsorption studies²⁴, batch adsorption experiments were performed at room temperature, a stock solution of MB 100 mg/L was prepared by dissolving an appropriate amount of the dye in distilled water, the stock solution was diluted accordingly to obtain fresh solutions of desired concentrations.

To study the adsorption process in 50 ml of MB samples, the effects of contact time, adsorbent mass, initial dye concentration and solution pH, were studied in the range of 0-60 min, 0.1-0.6 g, 5-60 mg/L and 1.5-8.5 respectively. The percentage of adsorbed pollutant was studied by varying one parameter and holding the other parameters constant. The pH was adjusted using either NaOH (0.1 M) or HCl (0.1 M)²⁵.

Then, the mixtures samples were quickly centrifuged in order to minimize the effects of suspended particles in solution, and the remaining concentration of methylene blue was determined by measuring the absorbance at 665 nm using a UV/Visible spectrophotometer (OPTIZEN 1412V), using a calibration curve, the percentage removal of dye was calculated using the following relationship (Eq 4):

C₀ – C_e

Dye Removal efficiency (%) = ––––––––– × 100 (4)

C₀

where, C₀ is the concentration of methylene blue in the solution before adsorption, and C_e is the concentration of methylene blue in the sample solution after adsorption.

RESULT:

Characterization of ACs:

The results of the effect of final pyrolysis temperature on activated carbon production are presented in (table 1).

IR spectroscopy:

The best way to follow the effect of chemical activation as well as the effect of carbonization on the studied product is to follow it by the characterization technique FT-IR. The spectra showing this effect are shown in (figure 1).

Figure 1: FTIR spectra of AC400, AC 500 and AC 600

Adsorption of MB:

Effect of contact time:

The effect of contact time between adsorbent and adsorbate is one of the most important parameters that signify the efficiency of dye adsorption in the liquid phase. The study of the effect of contact time (0,10,20, 30, 40, 50, 60 minutes) on the percentage removal of MB dye was carried out at a fixed initial dye concentration (20 mg/l) which was placed in contact with (0.5g) of ACs in 50 ml of aqueous solution, After shaking, the samples were centrifuged to measure the residual concentration of BM by UV-Visible spectrophotometry at 650 nm. The results of the kinetic study of BM adsorption on AC are presented in the curve in (figure 2).

Figure 2: Effect of contact time on the removal of MB dye

Effect of adsorbent mass:

The evolution of the removal efficiency of BM for varying mass of the adsorbent (0.1, 0.2, 0.3, 0.4, 0.5 and 0.6 g) of the same sample of activated carbon is followed. The tests were carried out by fixing the initial BM concentration of 20 mg/l.

The removal efficiency of the methylene blue dye by the mass change effect is shown graphically in (figure 3).

Figure 3: Effect of adsorbent mass on methylene blue removal.

Effect of initial dye concentration:

The purpose of this test is to study the influence of the initial BM concentration on the percentage removal dye. The initial concentrations are between 5 and 60 mg/l, the adsorbent mass is kept at 0.5g for these experiments, the removal efficiency is highly dependent on the initial concentration of the adsorbate solution (figure 4).

Figure 4: Effect of initial concentration on adsorption of MB with ACs.

Effect of pH:

The effect of pH on the removal of methylene blue in the presence of activated carbon is studied in the range of pH 1.5- 8.5, as can be seen in (figure 5).

Figure 5: Effect of pH on MB adsorption.

DISCUSSION:

Ziziphus mauritiana Lam seeds, these raw materials seem to be very suitable raw materials for activated carbon production²⁶. Because of its good yield value especially for AC 500. A low yield value is not desirable because it reduces the mechanical strength and adsorption capacity of the and the adsorption capacity of the produced activated carbon²⁷. The carbon yield did not change substantially. The highest yield was obtained when the activated particles were pyrolysis at 500°C. It can be seen that increasing the temperature decreases the carbon yield. Activated carbons prepared at 500°C from jujube had the highest surface area²⁸.

The spectra of the three prepared activated carbon samples AC 400, AC 500 and AC 600 (figure 2) revealed the presence of several peaks of different functional groups located on the surface of the carbon. These peaks indicate the presence of alkyl halides, carboxylic acids, alkanes, aliphatic amines, alkynes, nitro compounds, alcohols, esters and phenols. The most abundant type of bonding on carbons is O-H stretching in alcohols. During the chemical activation process, the O-H groups were attacked by a very strong agent, phosphoric acid, leading to the alteration of the adsorption bands attributed to O-H vibrations, which have decreased, which explains why almost all the oxygen has been used in the activation process, resulting in a porous structure on the carbon. The carbons contain an asymmetric N-O stretch which is a very strong covalent bond between the wave numbers of 1550 to 1475 cm^-1. Because of the hydrogen bonding with other hydroxyl bonds, the effect of the hydroxyl group is more experienced because they do not exist in isolation to form a stable structure²⁹.

The MB removal rate increases rapidly for AC 500 during the first 10 minutes of contact between activated carbon and dye in aqueous solution, and then more slowly until equilibrium is reached. This can be explained by a strong attraction force between the anionic sites of the activated carbons and the positive sites of the cationic dye³⁰. On the other hand, the percentage of MB dye removal is lower at the beginning for AC 400 and AC 600, but it gradually increases with time. About 45 minutes is the time needed to reach equilibrium for AC 500. On the other hand, the removal rate is lower at the beginning for AC 400 and AC 600, but it gradually increases with time until equilibrium is reached. The removal time is estimated about 120 minutes for AC 400 and AC 600 for the concentration used.

The effect of mass of adsorbent on the percentage removal of dye shown in (Figure 4). The percentage removal of the dye increased sharply with an increased in the adsorbent mass. This may be due to the increase in availability of more adsorbent sites as well as greater availability of specific surfaces of the adsorbents^31,32. However, no significant changes in removal efficiency were observed beyond 0.5 g adsorbent mass. At equilibrium time Maximum dye removal percent are 97,28 %, 100% and 89,2 % for AC 400, AC 500 and AC 600, respectively.

With the increase in initial methylene blue concentration from 5 to 60 mg/l, The percentage removal of the dye was found to decrease (Figure 5). It was probably attributed that the active sites on adsorbent for dye removal decreases whith increasing of dye concentration^33,34.

The removal rate of methylene blue by different types of activated carbons increased in all three activated carbons by changing the pH from 1.5 to 8.5. The trend of increasing dye removal with increasing pH depends on the nature of this adsorbent. The graphs indicate that the removal of the dye using activated carbon with different surface characteristics that depend on the acidic or basic medium that will have an influence on the pH^35,36.

CONCLUSION:

In this work, Activated carbons produced from agricultural waste (Ziziphus mauritiana Lam seeds) have been used for the removal of methylene blue dye from aqueous solutions. The activation was performed using phosphoric acid in different operating temperatures.

The chemical and physical properties of activated carbon (such as Burn-off, surface area, bulk density...) vary with the activation temperature. These properties are not directly related to the efficiency of their application, but they are important for commercial use. The results showed that the change in final activation temperature, was important to determine the quality of the of the activated carbon.

The adsorption was influenced by different parameters such as contact time, adsorbent mass, initial dye concentration and pH.

The removal efficiency increases with decreasing dye concentration and increasing adsorbent mass. Maximum adsorption of MB dye by activated carbons took place in alkaline solutions.

Therefore, the use of Ziziphus mauritiana Lam seeds for the production of activated carbons is very important from an economic point of view activated carbons is very important from the economic point of view because they are widely available.

REFERENCES:

1. Pooja D, Kumar P, Singh P, Patil S, eds. Sensors in Water Pollutants Monitoring: Role of Material. Springer Singapore; 2020. doi:10.1007/978-981-15-0671-0

2. De Gisi S, Lofrano G, Grassi M, Notarnicola M. Characteristics and adsorption capacities of low-cost sorbents for wastewater treatment: A review. Sustainable Materials and Technologies. 2016; 9: 10-40. doi:10.1016/j.susmat.2016.06.002

3. Goudjil MB, Sid N, Ayachi AO, et al. Textile Dye removal by Adsorption on Olive Grain as Solid Waste from the Olive Oil Extraction. Asian Journal of Research in Chemistry. 2020; 13(6): 424-432. doi:10.5958/0974-4150.2020.00077.2

4. Holkar CR, Jadhav AJ, Pinjari DV, Mahamuni NM, Pandit AB. A critical review on textile wastewater treatments: Possible approaches. Journal of Environmental Management. 2016; 182: 351-366. doi:10.1016/j.jenvman.2016.07.090

5. Li W, Mu B, Yang Y. Feasibility of industrial-scale treatment of dye wastewater via bio-adsorption technology. Bioresource Technology. 2019; 277: 157-170. doi:10.1016/ j.biortech.2019.01.002

6. Qadir I, Chhipa RC. Studies on the Removal of Acid Violet 49 Dye by Activated Carbon obtained from Neem Leaves (Azadirachta indica). Asian Journal of Research in Chemistry. 2017; 10(3): 345-348. doi:10.5958/0974-4150.2017.00058.X

7. Wang J, Wang S. Removal of pharmaceuticals and personal care products (PPCPs) from wastewater: A review. Journal of Environmental Management. 2016; 182: 620-640. doi:10.1016/ j.jenvman.2016.07.049

8. Al-Mamun MR, Kader S, Islam MS, Khan MZH. Photocatalytic activity improvement and application of UV-TiO2 photocatalysis in textile wastewater treatment: A review. Journal of Environmental Chemical Engineering. 2019; 7(5): 103248. doi:10.1016/ j.jece.2019.103248

9. Jia Q, Lua AC. Effects of pyrolysis conditions on the physical characteristics of oil-palm-shell activated carbons used in aqueous phase phenol adsorption. Journal of Analytical and Applied Pyrolysis. 2008; 83(2): 175-179. doi:10.1016/j.jaap.2008.08.001

10. Nakagawa K, Namba A, Mukai SR, Tamon H, Ariyadejwanich P, Tanthapanichakoon W. Adsorption of phenol and reactive dye from aqueous solution on activated carbons derived from solid wastes. Water Research. 2004; 38(7): 1791-1798. doi:10.1016/ j.watres.2004.01.002

11. Youssef AM, El-Nabarawy Th, Samra SE. Sorption properties of chemically-activated carbons. Colloids and Surfaces A: Physicochemical and Engineering Aspects. 2004; 235(1-3): 153-163. doi:10.1016/j.colsurfa.2003.12.017

12. Abhilash DP, Rose SV, Indirani B. Removal of Cadmium (II) from aqueous solution using Coffee powder - A Kinetic study. Asian Journal of Research in Chemistry. 2018; 11(2): 360-364. doi:10.5958/0974-4150.2018.00065.2

13. Karagoz S, Tay T, Ucar S, Erdem M. Activated carbons from waste biomass by sulfuric acid activation and their use on methylene blue adsorption. Bioresource Technology. 2008; 99(14): 6214-6222. doi:10.1016/j.biortech.2007.12.019

14. Haimour NM, Emeish S. Utilization of date stones for production of activated carbon using phosphoric acid. Waste Management. 2006; 26(6): 651-660. doi:10.1016/j.wasman.2005.08.004

15. Mosafa L, Moghadam M, Shahedi M. Papain enzyme supported on magnetic nanoparticles: Preparation, characterization and application in the fruit juice clarification. Chinese Journal of Catalysis. 2013; 34(10): 1897-1904. doi:10.1016/S1872-2067(12)60663-9

16. Auta M, Hameed BH. Preparation of waste tea activated carbon using potassium acetate as an activating agent for adsorption of Acid Blue 25 dye. Chemical Engineering Journal. 2011; 171(2): 502-509. doi:10.1016/j.cej.2011.04.017

17. Ahmad MA, Ahmad Puad NA, Bello OS. Kinetic, equilibrium and thermodynamic studies of synthetic dye removal using pomegranate peel activated carbon prepared by microwave-induced KOH activation. Water Resources and Industry. 2014; 6: 18-35. doi:10.1016/j.wri.2014.06.002

18. Angin D. Production and characterization of activated carbon from sour cherry stones by zinc chloride. Fuel. 2014; 115: 804-811. doi:10.1016/j.fuel.2013.04.060

19. Njoku VO, Foo KY, Hameed BH. Microwave-assisted preparation of pumpkin seed hull activated carbon and its application for the adsorptive removal of 2,4-dichlorophenoxyacetic acid. Chemical Engineering Journal. 2013; 215-216: 383-388. doi:10.1016/ j.cej.2012.10.068

20. Pezoti O, Cazetta AL, Souza IPAF, et al. Adsorption studies of methylene blue onto ZnCl2-activated carbon produced from buriti shells (Mauritia flexuosa L.). Journal of Industrial and Engineering Chemistry. 2014; 20(6): 4401-4407. doi:10.1016/ j.jiec.2014.02.007

21. Liou T-H. Development of mesoporous structure and high adsorption capacity of biomass-based activated carbon by phosphoric acid and zinc chloride activation. Chemical Engineering Journal. 2010; 158(2): 129-142. doi:10.1016/ j.cej.2009.12.016

22. Zhang H, Sun Y, Li S, Li X, Zhou H, Tian Y. Preparation, characterization, and efficient chromium (VI) adsorption of phosphoric acid activated carbon from furfural residue: an industrial waste. Water Science and Technology. 2020; 82(12): 2864-2876. doi:10.2166/wst.2020.530

23. Arunadevi R, Kavitha B, Karthiga R, Krishnan M. Effect of Fe and Cu codoped NiMoO4 nanopartcles on the photocatalytic degradation of Methylene blue Under visible light irradiation. Asian Journal of Research in Chemistry. 2018; 11(3): 663-670. doi:10.5958/0974-4150.2018.00119.0

24. Kale AA. Kinetic and Thermodynamic Study of Adsorption Methylene Blue by Nitrated Biomass of Prunus Cerasus. Asian Journal of Research in Chemistry. 2021; 14(4): 242-246. doi:10.52711/0974-4150.2021.00041

25. Ma X, Ouyang F. Adsorption properties of biomass-based activated carbon prepared with spent coffee grounds and pomelo skin by phosphoric acid activation. Applied Surface Science. 2013; 268: 566-570. doi:10.1016/j.apsusc.2013.01.009

26. Sivarajan, A, Shanmugapriya, V. Determination of isotherm parameters for the adsorption of Rhodamine B dye onto activated carbon prepared from Ziziphus jujuba seeds. Asian Journal of Research in Chemistry. 2017; 10(3): 362-368. doi:10.5958/0974-4150.2017.00062.1

27. Soleimani M, Kaghazchi T. Agricultural Waste Conversion to Activated Carbon by Chemical Activation with Phosphoric Acid. Chem Eng Technol. 2007; 30(5): 649-654. doi:10.1002/ ceat.200600325

28. Han Q, Wang J, Goodman BA, Xie J, Liu Z. High adsorption of methylene blue by activated carbon prepared from phosphoric acid treated eucalyptus residue. Powder Technology. 2020; 366: 239-248. doi:10.1016/j.powtec.2020.02.013

29. Igwegbe CA, Onukwuli OD, Ighalo JO, Okoye PU. Adsorption of Cationic Dyes on Dacryodes edulis Seeds Activated Carbon Modified Using Phosphoric Acid and Sodium Chloride. Environ Process. 2020; 7(4): 1151-1171. doi:10.1007/s40710-020-00467-y

30. Ghaedi M, Tashkhourian J, Pebdani AA, Sadeghian B, Ana FN. Equilibrium, kinetic and thermodynamic study of removal of reactive orange 12 on platinum nanoparticle loaded on activated carbon as novel adsorbent. Korean J Chem Eng. 2011; 28(12): 2255-2261. doi:10.1007/s11814-011-0142-1

31. Zhang Y, Zhao J, Jiang Z, Shan D, Lu Y. Biosorption of Fe(II) and Mn(II) Ions from Aqueous Solution by Rice Husk Ash. BioMed Research International. 2014; 1-10. doi:10.1155/2014/973095

32. Garg VK, Gupta R, Bala Yadav A, Kumar R. Dye removal from aqueous solution by adsorption on treated sawdust. Bioresource Technology. 2003; 89(2): 121-124. doi:10.1016/S0960-8524(03)00058-0

33. Mahmoodi NM, Hayati B, Arami M, Lan C. Adsorption of textile dyes on Pine Cone from colored wastewater: Kinetic, equilibrium and thermodynamic studies. Desalination. 2011; 268(1-3): 117-125. doi:10.1016/j.desal.2010.10.007

34. Rahman MA, Amin SMR, Alam AMS. Removal of Methylene Blue from Waste Water Using Activated Carbon Prepared from Rice Husk. Dhaka Univ J Sci. 2012; 60(2): 185-189. doi:10.3329/ dujs.v60i2.11491

35. Kavitha D, Namasivayam C. Experimental and kinetic studies on methylene blue adsorption by coir pith carbon. Bioresource Technology. 2007; 98(1): 14-21. doi:10.1016/ j.biortech.2005.12.008

36. Faria PCC, Órfão JJM, Pereira MFR. Adsorption of anionic and cationic dyes on activated carbons with different surface chemistries. Water Research. 2004; 38(8): 2043-2052. doi:10.1016/j.watres.2004.01.034

Received on 16.09.2021 Modified on 20.10.2021

Asian J. Research Chem. 2021; 14(6):435-440.

DOI: 10.52711/0974-4150.2021.00075

Sample	Carbon Yield (%)	Bulk density (g/ml)	Humidity content (%)	Burn-off	S_BET (m²/g)
AC 400	30,9	0,475	0,01	69,1	891,08
AC 500	38,625	0,426	0,01	78,375	915,58
AC 600	27,25	0,419	0,01	85,75	636,40