Summary: | The ability of clay from Besito, Gebog, Kudus to adsorb congo red from aqueous
solution was investigated. Prior to the investigation, the Besito-Kudus natural
clay was physically and chemically activated. The activated clay was then
analyzed by X-ray diffractometry (XRD) and Fourier transform infrared (FTIR)
spectroscopy methods. Various parameters such as contact time, initial dye
concentration, grain size of clay, and temperature of adsorption were studied.
The adsorption data were then fitted with the Langmuir and Freundlich isotherm
equations. The thermodynamic parameters �Ho, �So and �Go were also
determined.
The result showed that the chemical activation using H2SO4 1.2 M gave a
better result than physical activation. The XRD analysis showed that Besito-Kudus
clay may contain feldspar, cristobalite, dickite, muscovite, anatase, aegirineaugite,
illite, quartz, dan ferrosillite. The dye adsorption equilibrium was rapidly
reached after 10 minutes contact time. Equilibrium adsorption isotherm data of
chemical activated Besito-Kudus clay exhibited better fitting to the Langmuir
isotherm model than to Freundlich isotherm model. The maximum adsorption
capacity of chemical activated Besito-Kudus clay obtained from Langmuir model
was 250.00 mg/g. Kinetic studies showed that adsorption of congo red on
chemical activated Besito-Kudus clay followed pseudo-second-order kinetics. The
adsorption rate constant was found to be 0.025 g.mg-1.min-1 at 100 mg/L dye
concentration. The initial dye concentration, grain size of clay, and temperature
of adsorption had significant effect to adsorption of congo red. The experiment
result of �Ho was +3.127 kJ.mol-1, �So was +64.717 J.mol-1.K-1, and �Go at 30, 35,
40 and 50 oC were -16.483
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