REMOVAL OF CHROMIUM FROM SIMULATED WASTEWATER USING PERIWINKLE SHELL ACTIVATED CARBON
Abstract
Chromium adsorption from wastewater onto periwinkle shell activated carbon was studied using
batch experiments. Periwinkle shell samples were prepared, pyrolysed at 700°C, activated with
nitric acid and characterized to determine its physiochemical properties. Batch adsorption
experiments were conducted to investigate the effects of process parameters (contact time,
adsorbent dosage and initial metal ion concentration) on adsorption rate. Adsorption kinetics was
tested using pseudo first and second order models. Adsorption Isotherms were analyzed using the
Langmuir and Freundlich isotherm models. Results showed that adsorption rate increased with
increase in contact time, adsorbent dosage and initial metal ion concentration. Batch adsorption
Kinetics experiments gave a Correlation coefficient value (R2 ) of 0.9337 and 0.9931 for the pseudo
First and Second order kinetic models respectively. This revealed that the mechanism of adsorption
followed pseudo-second-order kinetic model; this indicated that the adsorption process of
chromium (III) ions onto periwinkle shell activated carbon was controlled by chemisorption
mechanism. Adsorption Isotherm data showed a Correlation coefficient value (R2 ) of 0.987 and
0.8295 for Langmuir and Freundlich Isotherms respectively. This showed that the Langmuir
isotherm accurately described the adsorption data indicating that the adsorption process was mainly
monolayer on a homogeneous adsorbent surface. A model was developed for the adsorption process
and validated by plotting the percentage removal obtained from experiments against the predicted
values of the model. Results showed that the Correlation coefficient value (R2 ) was found to be
0.9998 which indicated a good fit and a valid model representation of the adsorption model
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