Abstract:
The focus of this research was to synthesize novel clay-biochar composites by incorporating montmorillonite
(MMT) and red earth (RE) clay materials in a municipal solid waste (MSW) biochar for the adsorptive removal of
tetracycline (TC) from aqueous media. X-ray Fluorescence Analysis (XRF), Fourier Transform Infrared
Spectroscopy (FTIR), Powder X-ray Diffraction (PXRD) and Scanning Electron Microscopy (SEM) were used for
the characterization of the synthesized raw biochar (MSW-BC) and clay-biochar composites (MSW-MMT and
MSW-RE). Results showed that minute clay particles were dispersed on biochar surfaces. The FTIR bands due to
Si-O functional group vibrations in the spectra of the clay-biochar composites provided further evidence for
successful composite formation. The kinetic TC adsorption data of MSW-MMT were well fitted to the Elovich
model expressing high surface activity of biochar and involvement of multiple mechanisms in the adsorption.
The kinetic TC adsorption data of MSW-BC and MSW-RE were fitted to the pseudo second order model indicating
dominant contribution of chemisorption mechanism during the adsorption. The adsorption differentiation obtained
in the kinetic studies was mainly due to the structure of the combined clay material. The adsorption
isotherm data of all the adsorbents were well fitted to the Freundlich model suggesting that the adsorption of TC
onto the materials occurred via both physisorption and chemisorption mechanisms. In comparison to the raw
biochar and MSW-RE, MSW-MMT exhibited higher TC adsorption capacity. Therefore, MSW-MMT clay-biochar
composite could be applied in the remediation of TC antibiotic residues in contaminated aqueous media.
