Effect of critical batch variables on the efficiency and kinetics of adsorption of Ni (II) onto carbonized and uncarbonized palm kernel chaff

Abstract

A series of batch experiments were conducted for refined CPKC (carbonized sample) and UCPKC (uncarbonized sample) using 10, 30, 50, 70, 100 and 120 mg/L of Ni (II) solution at 30ᵒC, 35ᵒC and 40ᵒC at pH 3 and pH 9. Adsorption kinetics were investigated by determining the concentration of Ni (II) removed by the adsorbent at precise moments of time of 5, 10, 20, 30, 40, 60, 90 and 120 minutes. Standard kinetic equations were used to model data obtained from the experiments. For the range of conditions studied, the best improvement in the rate of adsorption and the adsorption capacity was observed for the carbonized sample at a temperature of 35oC. The rate constants of PKC were notably higher in an alkaline solution when the initial pH at the start of mixing was measured at 9, compared to the acidic solution with an initial pH of 3, across all studied temperatures. The rate constants of PSO₁, PSO₂, PSO₃, PSO4, PSO₅ and PSO₆ for CPKC ranged from 0.06 – 0.16, 0.14 – 0.44, 0.13 – 0.42, 0.13 – 0.30 and 0.09 – 0.59 g/mg.min^-1. In nearly all cases, PSO₁ model showed better correlation than other kinetic models with R² values ranging from 0.8 to 1.0. The average increase in adsorption rate constant for CPKC (pH 3), CPKC (pH 9), UCPKC (pH 3) and UCPKC (9) for 1oC increase in temperature was 0.31, 0.98, 0.51 and 0.43 mg/g.min respectively. The kinetic models were ranked as follows: /PSO₁/>/PFO/>/PSO_{2 - 5}/>/PSO₆/.