Modification and characterization of solid waste: an effective adsorbent for heavy metal removal

摘要

In this study, hydrothermal modification of fly ash (FA) using titanium dioxide (TiO2) and its application as an adsorbent for the removal of Ni(II) and Zn(II) ions from aqueous solution was explored. The FA and modified FA were characterized using scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray diffraction. Experiments were carried out in a batch mode to study the effect of various parameters on adsorption. The adsorption equilibrium was attained at 180 min with an optimum pH 6 for both metal ions. The kinetic study reveals that the adsorption follows pseudo-second-order model. Experimental data of adsorption have been fitted with the Langmuir, Freundlich, Dubinin-Radushkevich and Temkin equations. In order to determine the best fit isotherm, five error analysis methods were used, namely the sum-of-squared errors, the hybrid fractional error function, the Marquardt's percent standard deviation, the average relative error and the sum of absolute error. The error values demonstrated that the Freundlich isotherm model provided the best fit to the experimental data. The adsorption capacities are 4.397 and 6.226 mg g(-1) for Zn(II) and Ni(II) ions, respectively. The thermodynamic parameters evaluated showed that the adsorption process is spontaneous and exothermic.