Comparative adsorption of selected pesticides from aqueous solutions by activated carbon and biochar

Abstract

This work aimed to determine activated carbon (AC) and hard wood derived biochar (BC) adsorption capacity for the uptake of four pesticides atrazine, chlorothalanil, α-endosulfan and β-endosulfan from aqueous solution by conducting batch experiments under different experimental conditions. Structural properties of AC and BC were determined through ‘SEM (Scanning Electron Microscope), FTIR (Fourier Transform Infrared Spectrometer) and XRD (X-ray Powder Diffraction Spectroscopy)’. The optimized pH, particle size, contact time, agitation speed and initial pesticides concentration for the maximum adsorption rates were found to be 7, 250 μm, 60 min, 180 rpm and 12 μgL−¹ respectively. Pesticides adsorption were enhanced by increasing pH to 7 while slight decrease were noted when pH increases from 7 to 9. The adsorption equilibrium data were well described by the Langmuir isotherm model having a significant correlation coefficient value from 0.9999 to 1. Adsorption kinetic data were well fitted with the Lagergren's Pseudo-Second-Order kinetic model. The standard Gibb's free energy (ΔG) negative value at every temperature shows the practicability and spontaneity of the adsorption process. While the negative value for enthalpy change (ΔH) indicated the collective impact of exothermic adsorptions process with randomness intensifying due to positive entropy change.