Abstract
This research focuses on valorising waste burnt tires (BTs) through a two-phase oxidation
process, leading to the production of onion-like carbon-based nanostructures. The initial carbonization
of BTs yielded activated carbon (AC), denoted as “BTSA”, followed by further oxidation using the
modified Hummer’s method to produce onion-like carbon designated as “BTHM”. Brunauer–
Emmett–Teller (BET) surface area measurements showed 5.49 m2/g, 19.88 m2/g, and 71.08 m2/g
for raw BT, BTSA, and BTHM, respectively. Additional surface functionalization oxidations were
observed through Fourier-Transform Infrared (FTIR), X-ray diffraction (XRD), Scanning Electron
Microscopy (SEM), and Transmission Electron Microscopy (TEM) analyses. Raman spectroscopy
indicated an increased graphitic nature during each oxidation stage. BTHM was assessed in batch
adsorption studies for cupric wastewater remediation, revealing a two-phase pseudo-first-order
behaviour dominated by mass transfer to BTHM. The maximum adsorption capacity for Cu2+ on
BTHM was determined as 136.1 mg/g at 25 ◦C. Langmuir adsorption isotherm best described BTHM
at a solution pH of 6, while kinetics studies suggested pseudo-second-order kinetics. Furthermore,
BTHM, laden with Cu2+, served as a catalyst in a model coupling reaction of para-idoanisole and
phenol, successfully yielding the desired product. This study highlights the promising potential of
BTHM for both environmental remediation and catalytic reuse applications to avoid the generation
of secondary environmental waste by the spent adsorbent.