Native Desmodesmus sp. and Chlorella sp. isolated from the Reconquista River display a different binding preference for Cu(II) and Zn(II).

The present work was developed to study the metal removal performance of unicellular algae isolated from the Reconquista River and to evaluate the effect of the presence of more than one metal in the removal process. Thus, native species of unicellular algae were isolated from the highly contaminated Reconquista River. All of the isolates were classified, at genus level, based on their morphological appearance. Nine isolates were screened for their Zn(II) removal capacities. Chlorella sp. RR5 and Desmodesmus sp. RR7 were selected based on their removal performance, and their potential in the remediation of multiple metals was analyzed. Therefore, zinc (Zn(II)), copper (Cu(II)), and chromium (Cr(VI)) removal was evaluated in mono- and multi-metallic solutions. Biosorption capacities were high (0.8-1.8 mmol g-1) for Zn(II) and Cu(II) in mono-metallic solutions. Removal capacities decreased up to 48% in multi-metallic solutions. Interestingly, when multi-metallic systems were considered, each strain showed a metal preference. Chlorella sp. removed better Cu(II) meanwhile Desmodesmus sp. showed a preference for Zn(II). Thus, a metal-binding selectivity in each strain was determined. Chromium (VI) remediation was almost null in the conditions analyzed in this work. Fourier transformation infrared spectroscopy (FT-IR) analysis showed that polysaccharides were the main functional group involved in metal adsorption and, in some cases, also the carboxylates played an important role. Overall, we were able to analyze a new source of algal diversity and perform a metal removal characterization of them, leading to the identification of a metal selectivity based on the characteristics of the tested algal strains.

Chlorination of lanthanum oxide.

The reactive system La(2)O(3)(s)-Cl(2)(g) was studied in the temperature range 260-950 °C. The reaction course was followed by thermogravimetry, and the solids involved were characterized by X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy. The results showed that the reaction leads to the formation of solid LaOCl, and for temperatures above 850 °C, the lanthanum oxychloride is chlorinated, producing LaCl(3)(l). The formation of the oxychloride progresses through a nucleation and growth mechanism, and the kinetic analysis showed that at temperatures below 325 °C the system is under chemical control. The influence of diffusive processes on the kinetics of production of LaOCl was evaluated by studying the effect of the reactive gas flow rate, the mass of the sample, and the chlorine diffusion through the boundary layer surrounding the solid sample. The conversion curves were analyzed and fitted according to the Johnson-Mehl-Avrami description, and the reaction order with respect to the chlorine partial pressure was obtained by varying this partial pressure between 10 and 70 kPa. The rate equation was obtained, which includes the influence of the temperature, chlorine partial pressure, and reaction degree.