ORIGINAL RESEARCH
Using Acid-Activated Azad Kashmir Clays
to Remove Cadmium and Lead Ions
from Wastewater
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1
College of Earth and Environmental Sciences, University of the Punjab, Lahore, Pakistan
2
Pakistan Council of Scientific and Industrial Research Labs, Lahore, Pakistan
3
Department of Environmental Science and Policy, Lahore School of Economics, Pakistan
Submission date: 2019-08-06
Final revision date: 2019-10-25
Acceptance date: 2019-11-21
Online publication date: 2020-03-27
Publication date: 2020-05-12
Corresponding author
Nadia Ayub
College of Earth and Environmental Sciences, University of the Punjab, Lahore, Pakistan
Pol. J. Environ. Stud. 2020;29(5):3041-3047
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ABSTRACT
The adsorption of cadmium and lead ions on purified and acid-activated Azad Kashmir clays were
investigated in a batch system. Solutions of lead and cadmium having concentrations typically found in
industrial wastewater were used to develop a cheap and reliable adsorbent using local clay for removal
of heavy metals from wastewater. The raw clay sample was purified and activated by sulphuric acid
before being used for adsorption study. It was characterized by X-ray diffraction and chemical analysis
according to the International Standards of Testing (ASTM C 323-56, 2016). The effects of factors
like pH, adsorbent quantity, concentration of adsorbate and temperature were studied for both metals.
The Langmuir and Freundlich models were used for analysis of adsorption equilibrium. Thermodynamic
parameters were calculated. Azad Kashmir clay removed lead and cadmium with maximum adsorption
capacity of 3.93 mg metal/g and 7.81 mg metal/g of clay (30ºC; pH 7.3). These values were calculated by
applying Langmuir and Freundlich adsorption isotherms to the actual experimental results obtained in
this study. The thermodynamic data indicated that the adsorption reaction for cadmium is spontaneous
and exothermal while it is endothermic for lead. The Freundlich model provided best fit for sorption
isotherms for both cadmium and lead.