Sakarya Üniversitesi Fen Bilimleri Enstitüsü Dergisi, cilt.23, sa.6, ss.1019-1026, 2019 (Hakemli Dergi)
This work deals with the removal of Cr (III) and Cr (VI) from synthetic solutions via a novel composite
adsorbent prepared by precipitating iron (III) hydroxide on paper mill sludge (PMS). To obtain Fe(OH)3
loaded PMS, -8+16 mesh fraction of PMS was saponified with NaOH solution, then iron (III) chloride
was impregnated, hydrolyzed in NaOH solution and dried. The influences of pH, time, initial
concentration and temperature on removal of Cr (III) and Cr (VI) were examined and it was determined
that Cr (VI) removal occurs simultaneously with a reduction reaction. Maximum removal yields for Cr
(III) and Cr (VI) occurred at approximately pH = 5 and the adsorption achieved equilibrium in 90 min.
Cr (VI) adsorption ratio decreases while Cr (III) removal percentage increases with raising in
temperature. Experimental results are consistent with Langmuir isotherm. Adsorption capacities of Cr
(III) and Cr (VI) were calculated as 8.49, 10.14, 12.62 mg/g and 7.64, 5.39 and 4.17 mg/g for 25, 40 and
55 °C, respectively. Enthalpy changes for Cr (III) and Cr (VI) were calculated as 24.67 kJ/mol and -
12.46 kJ/mol, respectively. These results demonstrated that the adsorption phenomenon of Cr (III) and
Cr (VI) are endothermic and exothermic.