Fast adsorption of nickel ions by porous graphene oxide/sawdust composite and reuse for phenol degradation from aqueous solutions.

This work describes the preparation of an effective and low-cost porous graphene oxide/sawdust composite by a freeze-drying method. The composite exhibits a strong ability to adsorb nickel ions. The nickel ions adsorbed on graphene oxide/sawdust composite was reduced by sodium borohydride to generate a catalyst which was used in the degradation of phenol in water. The composite and the catalyst were characterized by XPS, FTIR, XRD and SEM. The adsorption of nickel ions by graphene oxide/sawdust composite was initially very fast and then slowly reached equilibrium in around 30 min. The adsorption of nickel ions by the composite could be well-described by the Freundlich isotherm model and the pseudo-second order kinetic model. The performance of the catalyst in phenol degradation was studied as a function of reaction time, dosage, temperature and initial pH. It was found that the catalyst optimally improved the degradation rate at pH 10 with a dose of 2 g/L in about 30 min. The results show that the degradation of phenol was an endothermic reaction and was a good fit to the Langmuir isotherm model.