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Arsenic(III) removal from aqueous solution by raw and zincloaded pine cone biochar: equilibrium, kinetics, and thermodynamics studies
Van Vinh, N.; Zafar, M.; Behera, S.K. & Park, H.S.
Abstract
The potential of raw pine cone (PC) biochar
and its modified form (Zn-loaded biochar) was evaluated
for the removal of trivalent arsenic [As(III)] from the
aqueous solution. The influence of treatment of PC biochar
with Zn(NO3)2 on the physico-chemical properties of biochar
was examined using elemental analyzer, surface area
analyzer, thermo-gravimetric analyzer, Fourier transform
infrared spectroscopy, and scanning electron microscopy.
Experimental results revealed that the removal of As(III)
was almost consistent (66.08 ± 3.94 and 87.62 ± 3.88 %
on raw and Zn-loaded biochar, respectively) over an acidic
pH range of 2–4 as a consequence of high affinity between
the positively charged biochar surface and the predominant
arsenic species (H3AsO3 and H2AsO4
-), followed by a
decrease with increase in pH in the range of 4–12. Langmuir
isotherm model was well fitted to the experimental
equilibrium data (R2 = 0.93) rendering the maximum
adsorption capacity of 5.7 and 7.0 μg g-1 on raw and Zn-loaded
PC biochar, respectively. The adsorption of As(III)
was well represented by pseudo-second order with reaction
rate constant (k2) of 0.040 and 0.282 mg g-1 min on raw
and zinc-loaded PC biochar, respectively, and was mainly
controlled by boundary layer diffusion followed by some
extent of intra-particle diffusion. The adsorption process
was spontaneous with Gibb’s free energy (ΔG°, -4.42 ±
0.72 and -11.86 ± 1.78 kJ mol-1) and exothermic in
nature with enthalpy (ΔH°, 13.25 and 31.10 kJ mol-1) and
entropy (ΔS°, 0.058 and 0.141 kJ mol-1 K-1) for raw and
zinc-loaded adsorbent, respectively.
Keywords
Pine cone; Biochar; Arsenic removal; Equilibrium; Kinetics; Thermodynamic
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