Equilibrium and kinetic adsorption studies of reactive orange onto resorcinol-formaldehyde carbon gel

Abstract

Adsorbents in granular form with small particle size are not suitable for continuous adsorption process. Resorcinol-formaldehyde carbon gel is a synthetic polymeric adsorbent that can be moulded to desired size and shape of high surface area and porosity, and controllable porous structures. This work aims to evaluate the feasibility of carbon gel as the adsorbent in dye wastewater treatment. The carbon gels were prepared by mixing resorcinol and formaldehyde in a presence of sodium carbonate catalyst at resorcinol/catalyst (R/C) ratios of 100, 200, 1,000 and 2,000. The carbonisation of carbon gels was fixed at 600 °C for 3 h, whereby part of the carbonised carbon gels was oxidised with nitric acid (HNO3). The performance of carbon gels was investigated by the adsorption of reactive orange 16 (RO16). Carbon gel with R/C ratio of 1,000 displays a specific surface area of 638.9 m2/g and RO16 maximum capacity of 6.8 mg/g. The oxidised carbon gels exhibit poorer adsorption performance when compared to the non-oxidised ones. The equilibrium data of RO16 by the non-oxidised carbon gels fitted well with Langmuir model, suggesting a monolayer adsorption process. The kinetics data indicates that physisorption plays a dominating role in the adsorption of RO16.