The ability of activated carbon which was produced by
chemical
activation using zinc chloride from tea industry wastes (TIWAC) to
adsorb phenol molecules from aqueous solution was tested by equilibrium,
kinetic, and thermodynamic parameters. Phenol adsorption on TIWAC
took place with a high yield at pH values in the range 4 to 8. The
optimum contact period was observed as 4.0 h and from the adsorption
graphs plotted as a function of time; it was established that phenol
adsorption on TIWAC conformed more to a pseudosecond-order kinetic
model. Additionally, it was determined that the adsorption rate is
controlled by intraparticle diffusion as well as film diffusion. It
was established that phenol adsorption on TIWAC can be better defined
by the Langmuir adsorption model and its adsorption capacity was 142.9
mg·g–1 from the linear Langmuir equation. Temperature
had an adverse effect on adsorption yield, and hence, the adsorption
process was exothermic in our case. Moreover, increasing electrolyte
concentration in the medium has a positive effect on adsorption yield.
From the data obtained, it was concluded that the removal of phenol
from aqueous solution by TIWAC produced from tea industry wastes with
a very low cost took place with an extremely high performance.
The removal of copper (II) and cadmium (II) ions from aqueous solutions, by adsorption on activated carbon prepared from rice hulls (ACRH), was investigated depending on pH, activated carbon dosage, contact time, initial metal concentration and solution temperature. The optimum values of pH, ACRH dosage and contact time were determined to be 5-8, 0.5 g ACRH/25 mL solution an 60 minutes respctively for the adsorption of Cu (II) ions and 5-8, 1.5 g ACRH/25 mL solution and 60 minutes for the adsorption of Cd (II) ions. From the initial concentrations, the constants for the Freundlich and Langmuir isotherm were calculated at 293 K and 313 K. The adsorption of Cu (II) and Cd (II) ions from aqueous solutions was found to be exothermic [ ∆ H • =-13.474 KJ/mol for Cu (II) and ∆ H • =-2.302 KJ/mol for Cd (II)]. Furthermore, the other thermodynamic data for ∆ G • and ∆ S • , were also calculated at 293 K and 313 K.
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