Equilibrium and thermodynamic investigation of biosorption of nickel from water by activated carbon made from palm kernel chaff

Novel biosorbents were derived from a waste product of palm kernel oil extraction known as palm kernel chaff (PKC). One portion of the PKC was carbonized in a furnace and then activated chemically, while the other half was activated without carbonization. Both were designated as CPKC and UPKC, respectively. The two biosorbents so produced were then used to conduct batch equilibrium and kinetic sorption studies at 30 degrees C, 35 degrees C and 40 degrees C and pH 3.0 and 9.0 for an agitation period of 5, 10, 20, 40, 60, 90, and 120 min. The Koble-Corrigan, Dubinin-Radushkevich, and the Freundlich isotherms fitted the experimental data very well with R-2 values of 0.97 to 1.0, 0.95 to 1.0, and 0.96 to 1.0, respectively. The linear type II Langmuir isotherm performed much better (0.96 <= R-2 <= 1.0) than the nonlinear isotherm. The maximum sorption capacity was obtained as 120.6 mg/g using CPKC at pH 9.0 and 35 degrees C. The Langmuir separation coefficient values (0.022 <= R-L <= 0.926) show that the sorption of nickel to PKC is favorable. The most favorable sorption condition was found for CPKC at pH 9 and temperature of 40 degrees C. The values of sorption energy (8.21 <= E <= 14.27) and the isosteric heat of sorption (-133.09 <= H-x <=-17.92) indicate that the mode of sorption is mostly ion exchange. Thermodynamic parameters also show that the process is exothermic and entropy-driven. The pseudo-second-order kinetic model shows the best correlation compared to the other kinetic models. The coefficient of correlation for the pseudo-second-order model was mostly within the range of 0.999-1.000 for 90% of all kinetic studies carried out.

Automated summary

Novel biosorbents were derived from a waste product of palm kernel oil extraction known as palm kernel chaff (PKC). The sorption capacity of CPKC for nickel ions was found to be the highest at pH 9.0 and 35 degrees C. The process was determined to be exothermic and entropy-driven, with the pseudo-second-order kinetic model showing the best correlation to the experimental data.