Simultaneous removal of methylene blue and Cd(II) by pecan shell–based activated carbon: adsorption kinetics, isotherms, and physicochemical characterization

Abstract

The coexistence of organic dyes and heavy metals in wastewater requires efficient and sustainable adsorbents capable of simultaneous contaminant removal. In this study, pecan shell–based activated carbons (PSC-0–PSC-3) were prepared by KOH activation using different impregnation ratios; their physicochemical properties and adsorption performance toward methylene blue (MB) and Cd(II) were systematically investigated under single- and binary-component systems. Among the prepared adsorbents, PSC-3 exhibited the highest BET specific surface area (2857 m² g⁻¹) and total pore volume (1.61 cm³ g⁻¹). MB adsorption was best described by the Freundlich isotherm model (R² = 0.998), indicating heterogeneous adsorption behavior. The Langmuir model estimated a maximum adsorption capacity of 529.5 mg g⁻¹. Under binary-component conditions, PSC-3 achieved nearly complete MB removal (≈ 100%), whereas Cd(II) removal was strongly dependent on solution pH and adsorbent dosage. The adsorption of Cd(II) was primarily governed by electrostatic attraction and surface complexation with oxygen-containing functional groups. Adsorption–desorption experiments demonstrated that PSC-3 retained approximately 85% and 80% of its initial adsorption efficiency for MB and Cd(II), respectively, after five regeneration cycles, indicating good reusability. These findings demonstrate that PSC-3 is a low-cost, sustainable, and highly efficient adsorbent with strong potential for the simultaneous removal of organic dyes and heavy metal ions from mixed wastewater.

Graphical abstract

Keywords

Pecan shell–based activated carbon / Simultaneous removal / Methylene blue / Cd(II) / Binary adsorption system

References

[1] Abdolali A, et al. . A breakthrough biosorbent in removing heavy metals: equilibrium, kinetic, thermodynamic and mechanism analyses in a lab-scale study. Sci Total Environ, 2016, 542(A): 603-611

[2] Alharby NF, Almutairi RS, Mohamed NA. Adsorption behavior of methylene blue dye by novel crosslinked O-CM-chitosan hydrogel in aqueous solution: kinetics, isotherm and thermodynamics. Polymers (Basel), 2021, 13(21): 3659

[3] Ali R, et al. . BET, FTIR, and RAMAN characterizations of activated carbon from waste oil fly ash. Turk J Chem, 2020, 442279-295

[4] Alkan M, et al. . Sorption of acid red 57 from aqueous solution onto sepiolite. J Hazard Mater, 2004, 116(1–2): 135-145

[5] Alsafran M, et al. . Principles and applicability of integrated remediation strategies for heavy metal removal/recovery from contaminated environments. J Plant Growth Regul, 2023, 42(6): 3419-3440

[6] Angaru GKR, et al. . Portable SA/CMC entrapped bimetallic magnetic fly ash zeolite spheres for heavy metals contaminated industrial effluents treatment via batch and column studies. Sci Rep, 2022, 12(1): 3430

[7] Azmi NH, et al. . Preparation of activated carbon using sea mango (Cerbera odollam) with microwave-assisted technique for the removal of methyl orange from textile wastewater. Desalin Water Treat, 2016, 576029143-29152

[8] Bahrudin NN, Nawi MA, Lelifajri. Kinetics and isotherm modeling of phenol adsorption by immobilizable activated carbon. React Kinet Mech Catal, 2019, 126(1): 61-82

[9] Baysal M, et al. . Preparation of high surface area activated carbon from waste-biomass of sunflower piths: kinetics and equilibrium studies on the dye removal. J Environ Chem Eng, 2018, 6(2): 1702-1713

[10] Belcaid A, et al. . Insight into adsorptive removal of methylene blue, malachite green, and rhodamine b dyes by cassava peel biochar (Manihot esculenta Crantz) in single, binary, and ternary systems: competitive adsorption study and theoretical calculations. Biomass Convers Biorefin, 2024, 14(6): 7783-7806

[11] Bello MO, et al. . Adsorption of Congo red dye from aqueous solution using ZnO and Al₂O₃/ZnO composite: isotherm, kinetic and thermodynamic data. J Appl Sci Environ Manag, 2022, 26(3): 439-447

[12] Danish M, Ahmad T. A review on utilization of wood biomass as a sustainable precursor for activated carbon production and application. Renew Sustain Energy Rev, 2018, 87: 1-21

[13] Dastgheib SA, Rockstraw DA. Pecan shell activated carbon: synthesis, characterization, and application for the removal of copper from aqueous solution. Carbon N Y, 2001, 39(12): 1849-1855

[14] Frescura LM, et al. . Physical and chemical characterization, adsorption kinetics, thermodynamic analysis, and the mechanism involved in the removal of methylene blue dye by a biosorbent from pecan nutshells. ACS Omega, 2026, 11(4): 6707-6717

[15] Guarín JR, Moreno-Pirajan JC, Giraldo L. Kinetic study of the bioadsorption of methylene blue on the surface of the biomass obtained from the algae D. antarctica. J Chem, 2018, 2018(1): 1-12

[16] Hasan MK, Shahriar A, Jim KU. Water pollution in Bangladesh and its impact on public health. Heliyon, 2019, 5(8): e02145

[17] Heschel W, Klose E. On the suitability of agricultural by-products for the manufacture of granular activated carbon. Fuel Lond, 1995, 74121786-1791

[18] Ho YS, McKay G. Pseudo-second order model for sorption processes. Process Biochem, 1999, 34(5): 451-465

[19] Jahan K, et al. . Development of activated carbon from KOH activation of pre-carbonized chickpea peel residue and its performance for removal of synthetic dye from drinking water. Biomass Convers Biorefin, 2023, 13(8): 6913-6923

[20] Jasri K, et al. . Mesoporous activated carbon produced from mixed wastes of oil palm frond and palm kernel shell using microwave radiation-assisted K₂CO₃ activation for methylene blue dye removal: optimization by response surface methodology. Diam Relat Mater, 2023, 131: 109581

[21] Jawad AH, et al. . Mesoporous high-surface-area activated carbon from biomass waste via microwave-assisted-H₃PO₄ activation for methylene blue dye adsorption: an optimized process. Diam Relat Mater, 2022, 128109288

[22] Jawad AH, et al. . Adsorptive removal of methylene blue by chemically treated cellulosic waste banana (Musa sapientum) peels. J Taibah Univ Sci, 2018, 12(6): 809-819

[23] Jawad AH, et al. . High surface area and mesoporous activated carbon from KOH-activated dragon fruit peels for methylene blue dye adsorption: optimization and mechanism study. Chin J Chem Eng, 2021, 32281-290

[24] Jawad AH, et al. . Mesoporous activated carbon from mangosteen (Garcinia mangostana) peels by H₃PO₄ assisted microwave: optimization, characterization, and adsorption mechanism for methylene blue dye removal. Diam Relat Mater, 2022, 129: 109389

[25] Jia Z, et al. . Adsorption behaviors of magnetic carbon derived from wood tar waste for removal of methylene blue dye. Diam Relat Mater, 2022, 130109408

[26] Johns MM, Marshall WE, Toles CA. Agricultural by-products as granular activated carbons for adsorbing dissolved metals and organics. J Chem Technol Biotechnol, 1998, 71(2): 131-140

[27] Kaveeshwar AR, et al. . Pecan shell based activated carbon for removal of iron (II) from fracking wastewater: adsorption kinetics, isotherm and thermodynamic studies. Process Saf Environ Prot, 2018, 114107-122

[28] Kaveeshwar AR, et al. . Adsorption properties and mechanism of barium (II) and strontium (II) removal from fracking wastewater using pecan shell based activated carbon. J Cleaner Prod, 2018, 193: 1-13

[29] Khurshid K, et al. . Optimization of heavy metals removal through pecan shell-based modified activated carbon from pharmaceutical wastewater and evaluation of the treated effluent for irrigating Pisum sativum. Int J Environ Res, 2025, 19(2): 60

[30] Kumar S, et al. . Graphene oxide–MnFe₂O₄ magnetic nanohybrids for efficient removal of lead and arsenic from water. ACS Appl Mater Interfaces, 2014, 62017426-17436

[31] Kumar U, Bandyopadhyay M. Sorption of cadmium from aqueous solution using pretreated rice husk. Bioresour Technol, 2006, 97(1): 104-109

[32] Lan D, et al. . Preparation and characterization of high value-added activated carbon derived from biowaste walnut shell by KOH activation for supercapacitor electrode. J Mater Sci Mater Electron, 2020, 31(21): 18541-18553

[33] Lellis B, et al. . Effects of textile dyes on health and the environment and bioremediation potential of living organisms. Biotechnol Res Innov, 2019, 3(2): 275-290

[34] Li X, et al. . Removal of toxic dyes from aqueous solution using new activated carbon materials developed from oil sludge waste. Colloids Surf A Physicochem Eng Aspects, 2019, 578: 123505

[35] Li X, et al. . Characterization and comparison of walnut shells-based activated carbons and their adsorptive properties. Adsorpt Sci Technol, 2020, 38(9–10): 450-463

[36] Lima HHC, et al. . Synthesis and characterization of pecan nutshell-based adsorbent with high specific area and high methylene blue adsorption capacity. J Mol Liq, 2019, 276570-576

[37] Liu Z, et al. . Efficient removal of Congo red and methylene blue using biochar from Medulla Tetrapanacis modified by potassium carbonate. Bioresour Technol, 2023, 376: 128912

[38] Mabuza M, Premlall K, Daramola MO. Modelling and thermodynamic properties of pure CO2 and flue gas sorption data on South African coals using Langmuir, Freundlich, Temkin, and extended Langmuir isotherm models. Int J Coal Sci Technol, 2022, 9(1): 45

[39] Métivier-Pignon H, Faur-Brasquet C, Le Cloirec P. Adsorption of dyes onto activated carbon cloths: approach of adsorption mechanisms and coupling of ACC with ultrafiltration to treat coloured wastewaters. Sep Purif Technol, 2003, 3113-11

[40] Mojoudi N, et al. . Phenol adsorption on high microporous activated carbons prepared from oily sludge: equilibrium, kinetic and thermodynamic studies. Sci Rep, 2019, 9(1): 19352

[41] Murphy OP, et al. . A review on the adsorption isotherms and design calculations for the optimization of adsorbent mass and contact time. ACS Omega, 2023, 82017407-17430

[42] Negi R, et al. . Biosorption of heavy metals by utilising onion and garlic wastes. Int J Environ Pollut, 2012, 49(3/4): 179-196

[43] Owamah HI, Chukwujindu IS, Asiagwu AK. Biosorptive capacity of yam peels waste for the removal of dye from aqueous solutions. Civ Environ Res, 2013, 3(1): 3648

[44] Patel H. Batch and continuous fixed bed adsorption of heavy metals removal using activated charcoal from neem (Azadirachta indica) leaf powder. Sci Rep, 2020, 10116895

[45] Sharma P, et al. . Removal of cadmium from aqueous system by shelled Moringa oleifera Lam. seed powder. Bioresour Technol, 2006, 972299-305

[46] Shooto ND, et al. . Lead ions and methylene blue dye removal from aqueous solution by mucuna beans (velvet beans) adsorbents. J Environ Chem Eng, 2020, 8(2): 103557

[47] Singh KK, Singh AK, Hasan SH. Low cost bio-sorbent’wheat bran’for the removal of cadmium from wastewater: kinetic and equilibrium studies. Bioresour Technol, 2006, 978994-1001

[48] Surip SN, et al. . H₂SO₄-treated Malaysian low rank coal for methylene blue dye decolourization and cod reduction: optimization of adsorption and mechanism study. Surf Interfaces, 2020, 21100641

[49] Teğin İ, et al. . Investigation of the effectiveness of waste nut shell–based hydrochars in water treatment: a model study for the adsorption of methylene blue. Biomass Convers Biorefin, 2024, 14(9): 10399-10412

[50] Thabede PM, Shooto ND, Naidoo EB. Removal of methylene blue dye and lead ions from aqueous solution using activated carbon from black cumin seeds. S Afr J Chem Eng, 2020, 33(1): 39-50

[51] Toles CA, Marshall WE, Johns MM. Granular activated carbons from nutshells for the uptake of metals and organic compounds. Carbon, 1997, 35(9): 1407-1414

[52] Tu W, et al. . A novel activation-hydrochar via hydrothermal carbonization and KOH activation of sewage sludge and coconut shell for biomass wastes: preparation, characterization and adsorption properties. J Colloid Interface Sci, 2021, 593390-407

[53] Turhan K, Ozturkcan SA. Decolorization and degradation of reactive dye in aqueous solution by ozonation in a semi-batch bubble column reactor. Water Air Soil Pollut, 2013, 224(1): 1353

[54] Wang J, Guo X. Adsorption kinetics and isotherm models of heavy metals by various adsorbents: an overview. Crit Rev Environ Sci Technol, 2023, 53211837-1865

[55] Weber WJJr, Morris JC. Kinetics of adsorption on carbon from solution. J Sanit Eng Div, 1963, 89(2): 31-59

[56] Xiong Q, et al. . An efficient and simple approach to remove Cd(II) in aqueous solution by using rice straw biochar: performance and mechanisms. Environ Sci Pollut Res Int, 2024, 31(11): 16782-16794

[57] Zhu Y, et al. . Removal of aquatic cadmium ions using thiourea modified poplar biochar. Water, 2020, 1241117

Funding

National Research Foundation of Korea (NRF) grant funded by the Korean Government (MSIT)(2023R1A2C1007137)

Chosun University(K206953007)

RIGHTS & PERMISSIONS

The Author(s)