摘要：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.
