Abstract: This paper describes the use of by-products as
adsorbents for removing heavy metals from aqueous effluent
solutions. Products of almond skin, walnut shell, saw dust, rice bran
and egg shell were evaluated as metal ion adsorbents in aqueous
solutions. A comparative study was done with commercial adsorbents
like ion exchange resins and activated carbon too. Batch experiments
were investigated to determine the affinity of all of biomasses for,
Cd(ΙΙ), Cr(ΙΙΙ), Ni(ΙΙ), and Pb(ΙΙ) metal ions at pH 5. The rate of
metal ion removal in the synthetic wastewater by the biomass was
evaluated by measuring final concentration of synthetic wastewater.
At a concentration of metal ion (50 mg/L), egg shell adsorbed high
levels (98.6 – 99.7%) of Pb(ΙΙ) and Cr(ΙΙΙ) and walnut shell adsorbed
high levels (35.3 – 65.4%) of Ni(ΙΙ) and Cd(ΙΙ). In this study, it has
been shown that by-products were excellent adsorbents for removal
of toxic ions from wastewater with efficiency comparable to
commercially available adsorbents, but at a reduced cost. Also
statistical studies using Independent Sample t Test and ANOVA Oneway
for statistical comparison between various elements adsorption
showed that there isn’t a significant difference in some elements
adsorption percentage by by-products and commercial adsorbents.
Abstract: The equilibrium, thermodynamics and kinetics of the
biosorption of Cd (II) and Pb(II) by a Spore Forming Bacillus (MGL
75) were investigated at different experimental conditions. The
Langmuir and Freundlich, and Dubinin-Radushkevich (D-R)
equilibrium adsorption models were applied to describe the
biosorption of the metal ions by MGL 75 biomass. The Langmuir
model fitted the equilibrium data better than the other models.
Maximum adsorption capacities q max for lead (II) and cadmium (II)
were found equal to 158.73mg/g and 91.74 mg/g by Langmuir model.
The values of the mean free energy determined with the D-R equation
showed that adsorption process is a physiosorption process. The
thermodynamic parameters Gibbs free energy (ΔG°), enthalpy (ΔH°),
and entropy (ΔS°) changes were also calculated, and the values
indicated that the biosorption process was exothermic and
spontaneous. Experiment data were also used to study biosorption
kinetics using pseudo-first-order and pseudo-second-order kinetic
models. Kinetic parameters, rate constants, equilibrium sorption
capacities and related correlation coefficients were calculated and
discussed. The results showed that the biosorption processes of both
metal ions followed well pseudo-second-order kinetics.