of the synthesized carbons was determined using the methodology described
by Libbrecht et al.(67 (link)) First,
a 500 mg/L HA solution was prepared by dispersing 500 mg of HA in
1 L of deionized water. HA was dissolved by adding 0.1 M sodium hydroxide
solution until it reached pH 12, and ultrasonic treatment was carried
out for 30 min. After dissolution, the solution was neutralized to
pH 7 with 0.1 M hydrochloric acid solution. Next, 10 mg of the adsorbent
was added to 50 mL of the 500 mg/L HA solution. These mixtures were
incubated in a thermostatic shaker (Infors HT Multitron Standard)
at 25 °C and 200 rpm for 7 days to ensure equilibrium. After
incubation, the solution was filtered through a 0.45 μm PET
syringe filter, and its HA concentration was measured by UV–vis
at 254 nm using a Thermo Scientific Evolution 60 UV–vis spectrometer
with VISIONlight 4 software. The HA concentration of the 500 mg/L
solution was determined by the same procedure (filtration and UV–vis
analysis). All adsorption experiments were performed in triplicate.
The adsorption capacity was calculated using the equation where qe (mg/g)
is the HA adsorption capacity at equilibrium, C0 and Ce (mg/L) are the initial
and equilibrium concentration of HA, m (mg) is the
mass of the adsorbent, and V (L) is the solution
volume.