Development of Chitosan Microspheres through a Green Dual Crosslinking Strategy Based on Tripolyphosphate and Vanillin.

Microencapsulation procedures have recently focused attention on designing novel microspheres via green synthesis strategies. The use of chitosan (CS) as an encapsulating material has increased interest due to its unique bioactive properties and the various crosslinking possibilities offered by their functional groups. The consolidation of the microspheres by physical crosslinking using sodium tripolyphosphate (TPP) combined with chemical crosslinking using vanillin (VA) open new opportunities in the framework of green dual crosslinking strategies. The developed strategy, a straightforward technique based on an aqueous medium avoiding complex separation/washing steps, offers advantages over the processes based on VA, mostly using water-in-oil emulsion approaches. Thus, in this work, the combination of TPP crosslinking (3, 5, and 10 wt.%) via spray-coagulation technique with two VA crosslinking methods (in situ and post-treatment using 1 wt.% VA) were employed in the preparation of microspheres. The microspheres were characterized concerning morphology, particle size, physicochemical properties, thermal stability, and swelling behavior. Results revealed that the combination of 5 wt.% TPP with in situ VA crosslinking led to microspheres with promising properties, being an attractive alternative for natural bioactives encapsulation due to the green connotations associated with the process.

Adsorption study of heavy metals in aqueous solutions aiming at the treatment of contaminated groundwater.

This study evaluates the application of the vegetal activated carbon (AC), vegetable AC impregnated with Ag and Cu (0.08% m/m) and cationic SupergelTM SGC650H resin for adsorption of Fe3+ and Pb2+ ions in closed and batch system. The best adsorption capacities were obtained by using the cationic resin SGC650H, pH 3, temperature of 30 °C and stirring speed of 100 rpm. Thus, the kinetic and equilibrium experiments, in mono- and bicomponent, were performed using SGC650H resin, wherein the kinetic models of pseudo-first and pseudo-second order presented a good fit to the kinetic data, for mono- and bicomponent, respectively. The Langmuir isotherm adequately represented the monocomponent equilibrium data, showing maximum adsorption capacities values of 7.18 and 4.00 meq g-1 for Fe3+ and Pb2+, respectively. An inhibitory effect between the metal species was verified by fitting the modified extended Langmuir isotherm model to the binary equilibrium data, which allowed to predict changes in the surface affinity to the adsorbent by the metal ions. Based on the observed results, the use of SGC650H resin presents great potential for water treatment systems contaminated with heavy metals.

Groundwater quality monitoring of the Serra Geral aquifer in Toledo, Brazil.

In this work, a physical-chemical, elemental and microbiological groundwater monitoring was performed on wells of the Serra Geral aquifer, located in the western region of the Brazilian state of Paraná, along with an evaluation of the elemental composition of soil sediments in the region of groundwater monitoring. The monitoring was carried out in 10 wells distributed throughout the rural area of the municipality of Toledo-PR. Elemental analyses were performed using the analytical technique of total reflection X-ray fluorescence spectrometry. From the results obtained, it was observed that in some wells, iron and lead concentrations were above the maximum limits allowed by the Brazilian legislation in some months, demonstrating that the evaluated groundwater is susceptible to contamination. By the analysis of the soil sediments, the presence of iron and lead in the region soil/rock was verified, which may be associated to rainwater percolation making it necessary to periodically monitor the groundwater consumed by the population of the municipality of Toledo-PR.