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

Abstract

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.