The Ni(II) adsorption capacity of carbon
derived from
Citrus limettioides
peel (CLP), which is a
novel waste material (CLPC), was evaluated regarding
contact time, pH and adsorbent dose during batch adsorption
processes with raw CLP. The optimal contact time for
the adsorption of Ni(II) ions onto the peel and peel carbon
was 3 h, and the optimal pH ranged from 5.0 to 8.0 for CLP
and 4.0–8.0 for CLPC, respectively. The removal percentage
decreased from 85.0 to 70.0 % for CLP and remained
nearly constant (99 %) for CLPC when the initial
Ni(II) concentration was increased from 10 to 50 mg L
-1.
The equilibrium data fit the Langmuir isotherm with a high
R2 value, indicating that the Ni(II) ions formed a homogenous
monolayer on the adsorbent surface. Adsorption
capacity of Ni(II) ions on peel (CLP) and peel carbon
(CLPC) was found to be 25.64 and 38.46 mg g
-1, respectively.
The surface morphology and functionality of
the CLP and CLPC before and after adsorption were
characterized using SEM, EDX and FT-IR. Various thermodynamic
parameters, including the standard Gibbs free
energy (Δ
Gº), standard enthalpy (Δ
Hº) and standard entropy
(Δ
Sº), were evaluated. The CLP and CLPC were
tested with Ni(II) plating wastewater through a batch-mode
process over five cycles; CLPC showed better results than
CLP.