Abstract This study describes the application of ZnO commercial oxide and ZnO/ZnFe2O4 mixed oxides to reduce the mercury ion (Hg2+) in the aqueous phase. The catalysts synthesized were characterized by thermogravimetric analysis, adsorption and desorption of N2, scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, photoacoustic spectroscopy and Mössbauer spectroscopy. The heterogeneous photocatalysis process was studied in synthetic effluent treatment containing mercury chloride (HgCl2) in a batch and solar reactor. The results indicated that commercial ZnO catalyst totally reduced the Hg (II), in all conditions and reaction systems studied. On the other hand, for the mixed oxides (ZnO/ZnFe2O4), there was a decrease in the reduction efficiency in the batch reactor, indicating no ability to reduce Hg(II) in the presence of sunlight.

This study describes the application of new and low cost biosorbent, shells of urucum (Bixa Orellana), for removal of lead ions (Pb(II)) from water solution. The urucum shells were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy techniques. Batch adsorption experiments were performed in order to evaluate the effect of pH, agitation speed, adsorbent dosage, contact time, temperature, presence of interfering ions and matrix effect on the adsorption of process. The kinetics of biosorption followed pseudo-second-order model. Langmuir and Freundlich isotherm models were applied to describe the biosorption of Pb(II) by urucum shells. The Langmuir model showed better fit and the estimated biosorption capacity was 43.6 mg g-1. The negative Gibbs free energy, ΔG°, confirms the spontaneous nature and positive value of enthalpy, ΔH°, the endothermic character of the process. Furthermore, we also performed an evaluation of matrix and others ions effect on the biosorption process.