Preparation And Characterization Of Novel Iron (III) Hydroxide/Paper Mill Sludge Composite Adsorbent For Chromium Removal

Abstract

This work deals with the removal of Cr (III) and Cr (VI) from synthetic solutions via a novel compositeadsorbent prepared by precipitating iron (III) hydroxide on paper mill sludge (PMS). To obtain Fe(OH)3loaded PMS, -8+16 mesh fraction of PMS was saponified with NaOH solution, then iron (III) chloridewas impregnated, hydrolyzed in NaOH solution and dried. The influences of pH, time, initialconcentration and temperature on removal of Cr (III) and Cr (VI) were examined and it was determinedthat 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 intemperature. 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 and55 °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) andCr (VI) are endothermic and exothermic.