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Abstract
The 2-mercaptobenzimidazole loaded natural clay was prepared for the removal of Hg(II)
from aqueous media. Adsorption of the metal ions from aqueous solution as a function
of solution concentration, agitation time, pH, temperature, ionic strength, particle
size of the adsorbent and adsorbent dose was studied. The adsorption process follows
a pseudo-second-order kinetics. The rate constants as a function of initial concentration
and temperature were given. The adsorption of Hg(II) increased with increasing pH
and reached a plateau value in the pH range 4.0-8.0. The removal of Hg(II) was found
to be >99% at an initial concentration of 50 mg/l. Mercury(II) uptake was found to
increase with ionic strength and temperature. Further, the adsorption of Hg(II) increased
with increasing adsorbent dose and decrease with adsorbent particle size. Sorption
data analysis was carried out using Langmuir and modified Langmuir isotherms for the
uptake of metal ion in an initial concentration range of 50-1,000 mg/l. The significance
of the two linear relationships obtained by plotting the data according to the conventional
Langmuir equation is discussed in terms of the binding energies of the two population
sites involved which have a widely differing affinity for Hg(II) ions. Thermodynamic
parameters such as changes of free energy, enthalpy, and entropy were calculated to
predict the nature of adsorption. It was found that the values of isosteric heat of
adsorption were varied with surface loading. The chlor-alkali industry wastewater
samples were treated by MBI-clay to demonstrate its efficiency in removing Hg(II)
from wastewater.