Isotherm and mechanism investigation of low-cost activated carbon from colocynth (Citrullus colocynthis) rind for Congo Red removal from textile effluent
DOI:
https://doi.org/10.64354/89ygnf55Keywords:
Activated carbon; Colocynth rind; Congo Red; Adsorption isotherm; Adsorption mechanism; Textile effluent.Abstract
Textile wastewater carrying synthetic azo dyes is still one of the more stubborn environmental burdens in arid regions, and Congo Red (CR) in particular is awkward to treat because of its bulky aromatic backbone and high solubility. In the present work an inexpensive activated carbon, here denoted CRAC, was produced from colocynth (Citrullus colocynthis) rind, a desert agricultural residue that is plentiful and normally thrown away. The precursor was impregnated with phosphoric acid and carbonised at 500 °C, then characterised by FTIR, XRD and FESEM together with N₂ adsorption–desorption analysis. A BET surface area of 712 m² g⁻¹ was obtained, with a largely amorphous and microporous texture. Batch experiments were used to study the influence of pH, adsorbent dose, contact time, initial dye concentration and temperature. The largest uptake was found at pH 3, where the protonated carbon surface favours electrostatic attraction toward the sulfonate groups of the dye, and equilibrium was reached in roughly 90 min. The equilibrium data were best fitted by the Langmuir isotherm (R² = 0.998), yielding a monolayer capacity of 185.2 mg g⁻¹, while the kinetics followed a pseudo-second-order rate law. Thermodynamic parameters indicated that adsorption was spontaneous and endothermic. Spectroscopic shifts and modelling outcomes together pointed to a mixed mechanism in which electrostatic interaction, π–π stacking, hydrogen bonding and pore filling all play a part. Overall the results suggest that colocynth-rind carbon is a promising and economical adsorbent for treating CR-bearing textile effluent.
References
1 [1] Yagub, M.T., Sen, T.K., Afroze, S., Ang, H.M. Dye and its removal from aqueous solution by adsorption: A review. Advances in Colloid and Interface Science, 209, 172–184 (2014).
2 [2] Lellis, B., Favaro-Polonio, C.Z., Pamphile, J.A., Polonio, J.C. Effects of textile dyes on health and the environment and bioremediation potential of living organisms. Biotechnology Research and Innovation, 3(2), 275–290 (2019).
3 [3] Mittal, A., Mittal, J., Malviya, A., Gupta, V.K. Adsorptive removal of hazardous anionic dye Congo Red from wastewater using waste materials. Journal of Colloid and Interface Science, 340(1), 16–26 (2009).
4 [4] Katheresan, V., Kansedo, J., Lau, S.Y. Efficiency of various recent wastewater dye removal methods: A review. Journal of Environmental Chemical Engineering, 6(4), 4676–4697 (2018).
5 [5] Gupta, V.K., Suhas. Application of low-cost adsorbents for dye removal – A review. Journal of Environmental Management, 90(8), 2313–2342 (2009).
6 [6] Rafatullah, M., Sulaiman, O., Hashim, R., Ahmad, A. Adsorption of methylene blue on low-cost adsorbents: A review. Journal of Hazardous Materials, 177(1–3), 70–80 (2010).
7 [7] Ahmad, T., Danish, M. Prospects of banana waste utilization in wastewater treatment: A review. Journal of Environmental Management, 206, 330–348 (2018).
8 [8] Bhatnagar, A., Sillanpää, M. Utilization of agro-industrial and municipal waste materials as potential adsorbents for water treatment – A review. Chemical Engineering Journal, 157(2–3), 277–296 (2010).
9 [9] Hussain, A.I., Rathore, H.A., Sattar, M.Z.A., Chatha, S.A.S., Sarker, S.D., Gilani, A.H. Citrullus colocynthis (L.) Schrad (colocynth): Biological and phytochemical properties review. Journal of Ethnopharmacology, 155(1), 54–66 (2014).
10 [10] Foo, K.Y., Hameed, B.H. Coconut husk derived activated carbon via microwave induced activation. Chemical Engineering Journal, 184, 57–65 (2012).
11 [11] Prahas, D., Kartika, Y., Indraswati, N., Ismadji, S. Activated carbon from jackfruit peel waste by H₃PO₄ chemical activation. Chemical Engineering Journal, 140(1–3), 32–42 (2008).
12 [12] Hesas, R.H., Daud, W.M.A.W., Sahu, J.N., Arami-Niya, A. The effects of a microwave heating method on the production of activated carbon: A review. Journal of Analytical and Applied Pyrolysis, 100, 1–11 (2013).
13 [13] Namasivayam, C., Kavitha, D. Removal of Congo Red from water by adsorption onto activated carbon prepared from coir pith. Dyes and Pigments, 54(1), 47–58 (2002).
14 [14] Theydan, S.K., Ahmed, M.J. Adsorption of methylene blue onto biomass-based activated carbon by FeCl₃ activation. Journal of Analytical and Applied Pyrolysis, 97, 116–122 (2012).
15 [15] Tan, I.A.W., Ahmad, A.L., Hameed, B.H. Adsorption of basic dye on high-surface-area activated carbon prepared from coconut husk. Journal of Hazardous Materials, 154(1–3), 337–346 (2008).
16 [16] Vimonses, V., Lei, S., Jin, B., Chow, C.W.K., Saint, C. Kinetic study and equilibrium isotherm analysis of Congo Red adsorption by clay materials. Chemical Engineering Journal, 148(2–3), 354–364 (2009).
17 [17] Ahmad, R. Studies on adsorption of crystal violet dye from aqueous solution onto coniferous pinus bark powder. Journal of Hazardous Materials, 171(1–3), 767–773 (2009).
18 [18] El Qada, E.N., Allen, S.J., Walker, G.M. Adsorption of basic dyes from aqueous solution onto activated carbons. Chemical Engineering Journal, 135(3), 174–184 (2008).
19 [19] Hameed, B.H., Ahmad, A.A. Batch adsorption of methylene blue from aqueous solution by garlic peel. Journal of Hazardous Materials, 164(2–3), 870–875 (2009).
20 [20] Önal, Y., Akmil-Başar, C., Sarıcı-Özdemir, Ç. Investigation of kinetics and isotherm of adsorption of malachite green onto activated carbon. Journal of Hazardous Materials, 146(1–2), 194–203 (2007).
21 [21] Hameed, B.H., Din, A.T.M., Ahmad, A.L. Adsorption of methylene blue onto bamboo-based activated carbon. Journal of Hazardous Materials, 141(3), 819–825 (2007).
22 [22] Auta, M., Hameed, B.H. Optimized waste tea activated carbon for adsorption of methylene blue and acid blue 29 dyes. Chemical Engineering Journal, 175, 233–243 (2011).
23 [23] Hall, K.R., Eagleton, L.C., Acrivos, A., Vermeulen, T. Pore- and solid-diffusion kinetics in fixed-bed adsorption. Industrial & Engineering Chemistry Fundamentals, 5(2), 212–223 (1966).
24 [24] Freundlich, H.M.F. Over the adsorption in solution. Journal of Physical Chemistry, 57, 385–471 (1906).
25 [25] Dubinin, M.M. The potential theory of adsorption of gases and vapors. Chemical Reviews, 60(2), 235–241 (1960).
26 [26] Ho, Y.S., McKay, G. Pseudo-second order model for sorption processes. Process Biochemistry, 34(5), 451–465 (1999).
27 [27] Weber, W.J., Morris, J.C. Kinetics of adsorption on carbon from solution. Journal of the Sanitary Engineering Division, 89(2), 31–60 (1963).
28 [28] Saha, P., Chowdhury, S. Insight into adsorption thermodynamics. In: Thermodynamics, InTech, Rijeka, 349–364 (2011).
29 [29] Mall, I.D., Srivastava, V.C., Agarwal, N.K., Mishra, I.M. Removal of Congo Red from aqueous solution by bagasse fly ash and activated carbon. Chemosphere, 61(4), 492–501 (2005).
30 [30] Tran, H.N., You, S.J., Hosseini-Bandegharaei, A., Chao, H.P. Mistakes and inconsistencies regarding adsorption of contaminants: A critical review. Water Research, 120, 88–116 (2017).
31 [31] Lafi, R., Hafiane, A. Removal of methyl orange dye from aqueous solution onto activated carbon prepared from coffee residue. Journal of the Taiwan Institute of Chemical Engineers, 58, 424–433 (2016).
32 [32] Hu, Z., Chen, H., Ji, F., Yuan, S. Removal of Congo Red from aqueous solution by cattail root and banana-peel derived carbons. Journal of Hazardous Materials, 173(1–3), 292–297 (2010).
33 [33] Han, R., Ding, D., Xu, Y., Zou, W., Wang, Y., Li, Y., Zou, L. Use of rice husk for the adsorption of Congo Red from aqueous solution in column mode. Bioresource Technology, 99(8), 2938–2946 (2008).
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