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Adsorption of C.I. Acid Red 97 dye from aqueous solution onto walnut shell: kinetics, thermodynamics parameters, isotherms
Ghazi Mokri, H.S.; Modirshahla, N.; Behnajady, M.A. & Vahid, B.
Abstract
This study aims to investigate the adsorption of
C.I. Acid Red 97 (AR97) onto walnut shell (WS) in order
to find out the desired conditions. The effect of operational
parameters including adsorbent dosage, agitation speed,
contact time, pH and temperature was studied in a batch
mode. The results revealed that 73.33 % of AR97 (50 mg/
L) was decolorized at 60 min of contact time, agitation rate
of 140 rpm and 12 g/L of adsorbent at 291 K. The rate of
adsorption follows pseudo-second-order kinetics with the
high correlation coefficient, which was more than 0.99.
Specific surface area of WS was calculated as 1.28 m2/g by
BET method. It was observed from the values of thermodynamics
parameters such as Gibbs free energy (ΔG°),
enthalpy (ΔH°) and entropy (ΔS°) that the nature of
adsorption process is spontaneous, exothermic and mainly
physical. Langmuir, Fruendlich and Redlich–Peterson isotherms
were applied for mathematical description of
equilibrium data and findings indicated that it is in good
agreement with Fruendlich model.
Keywords
C.I. Acid Red 97; Adsorption; Walnut shell; Kinetics; Thermodynamics parameters; Isotherm
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