Equilibrium studies and dynamic behavior of cadmium adsorption by palm oil boiler mill fly ash (POFA) as a natural low-cost adsorbent

Abstract

The highlight of this study is the adsorption properties and characterization of palm oil boiler mill fly ash (POFA) as a natural low-cost adsorbent for the removal of Cd(II) from aqueous solution. An array of batch adsorption studies has been done with the effects demonstrated by relevant parameters such as contact times, solution pH, adsorbent dosage, and initial Cd(II) concentration to investigate POFA performance. Energy-dispersive X-ray (EDX) analysis has shown that the structural surface of POFA containing porous carbon and revealing ion exchange may serve as one of the major mechanisms accountable for Cd(II) adsorption onto POFA. Fundamental batch investigations have implied that 80% of Cd(II) was removed in the first 30 min reaching equilibration, after only going through the process of agitation for 210 min. The Cd(II) uptake mechanism is specifically pH and concentration dependant with pH 7 being the optimum reading. A decreased adsorption capacity with an increased Cd(II) removal efficiency was obtained as the adsorbent dose increased. The experimental data adhered to the pseudo-second-order kinetics, which further confirms chemisorptions. The adsorption behavior of Cd(II) fits appropriately and accurately with the Langmuir isotherm model with maximum monolayer adsorption capacity of 15.82 mg/g. Therefore, it is illustrated by this study that POFA could be used effectively as a natural low-cost adsorbent for Cd(II) removal from aqueous solutions.