Immobilisation of TiO2-nanoparticles on sewage sludge and their adsorption for cadmium removal from aqueous solutions

In this study, pure TiO2-nanoparticles and TiO2/sewage sludge (TS) as biomass material were synthesised via a sol-gel method. The adsorption potential of nanosized TiO2 and TS for removal of Cd(II) was investigated in a batch system. The prepared adsorbents were characterised using X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). The XRD analysis showed that pure TiO2 is in amorphous phase before calcination and in anatase phase at annealing temperature of 400 degrees C. TiO2/sewage sludge that calcined at 400 degrees C (TS400) was found to be the best adsorbent for cadmium removal from aqueous solution. Kinetic and isotherm studies were carried out by considering the parameters, pH, initial concentration and contact time. The optimum pH value for Cd(II) adsorption onto TS400 was found to be 6. Langmuir isotherm showed better fit than Freundlich isotherm and the maximum adsorption capacity was found to be 29.28 mg/g which is higher than that of many other adsorbents reported in literature. The sorption kinetic data were well fitted with a pseudo-second-order model. These results demonstrated that TS400 was readily prepared and is the promising and effective solid material for the removal of Cd(II) from aqueous solutions.