Potential of TiO₂ loaded almond shell derived activated carbon for leachate treatment: isotherms, kinetics, and Response Surface Methodology

ABSTRACT

In the present study, an agro-waste, almond shell was derived as activated carbon. Based on chemical oxygen demand (COD) removal of leachate, the optimised conditions of activated carbon were obtained and loaded with TiO₂ nanoparticles. Brunauer Emmett Teller analysis technique is used to probe the textural properties through the specific surface area. The specific surface area of the TiO₂ nanoparticle loaded activated carbon (TiO₂@ASAc-7) and efficiently activated carbon (ASAc-7) were 153.3 m²/g and 54.7 m²/g. A band at 536 cm⁻¹ in FTIR of TiO₂@ASAc-7 composite demonstrates the spreading of vibrational modes of TiO₂ in 4AS material. SEM-EDX shows the elemental peaks of carbon, oxygen and Ti nanoparticles along with atomic percentages of C 70.1, O 22.61, and Ti 7.29. The optimum values of pH 5.5, dose 1.75 g/50 mL, time 160 minutes and temperature 30°C were observed at maximum COD removal of 78.6%. The adsorption isotherm records were appropriately fitted to Freundlich, Hill, Khan, Redlich–Peterson, Toth, and Koble–Corrigan. The correlation coefficient (R² = 0.9707) and a comparatively low value of the root mean square error (RMSE = 3.97) demonstrates that the adsorption technique adapted a pseudo-second-order model. Negative values of ΔG⁰ signify that COD removal by TiO₂@ASAc-7 was spontaneous and positive values of the enthalpy change (∆H° = 37.816 kJmol⁻¹) indicate that the process was endothermic in nature. To optimise the COD removal efficiency from the leachate sample, a central composite design for a subset of the RSM was also performed.

KEYWORDS:

• Almond shell
• TiO2 nanoparticle
• adsorption
• leachate
• central composite design
• kinetic models

Nomenclature

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Acknowledgments

The authors acknowledge the TEQIP-III GJUS&T, Hisar for providing financial assistance with letter number TEQIP-III/2018/1841-1142 to conduct this research.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Ethical approval

This article does not include any studies with human participants or animals performed by any of the authors.

Supplementary material

Supplemental data for this article can be accessed here.

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Funding

This work was supported by the World Bank [TEQIP-III/2018/1841-1142].