Outstanding adsorption capacity of iron oxide synthesized with extract of açaí berry residue: kinetic, isotherm, and thermodynamic study for dye removal.

Contamination of water by toxic dyes is a serious environmental problem. Adsorbents prepared by an environmentally safe route have stood out for application in pollutant removal. Herein, iron oxide-based nanomaterial composed of Fe(III)-OOH and Fe(II/III) bound to proanthocyanidins, with particles in the order of 20 nm, was prepared by green synthesis assisted by extract of açaí (Euterpe oleracea Mart.) berry seeds from an agro-industrial residue. The nanomaterial was applied in the adsorption of cationic dyes. Screening tests were carried out for methylene blue (MB), resulting in an outstanding maximum adsorption capacity of 531.8 mg g-1 at 343 K, pH 10, 180 min. The kinetics followed a pseudo-second-order model and the isotherm of Fritz-Schülnder provided the best fit. Thermodynamic data show an endothermic process with entropy increase, typical of chemisorption. The proposed mechanism is based on the multilayer formation over a heterogeneous adsorbent surface, with chemical and electrostatic interactions of MB with the iron oxide nanoparticles and with the proanthocyanidins. The high adsorption efficiency was attributed to the network formed by the polymeric proanthocyanidins that entangled and protected the iron oxide nanoparticles, which allowed the reuse of the nanomaterial for seven cycles without loss of adsorption efficiency.

Characterization of a Ternary System Based on Hybrid Nanoparticles.

Hybrid nanoparticles (NPs) are emerging as an important family of multifunctional nanoscale materials. Due to its unique properties cyclodextrins (CDs) present the possibility to be employed in nanostructured devices for multiple applications. Therefore the study of hybrids NPs containing CDs, metal nanoparticles and an organic molecular guest is promising for applications in separation science, sensing, optics, catalysis and medical therapy. To investigate the hybrid nanoparticles properties in light of technological and medical science interfaces we chose tramadol hydrochloride as the model molecular guest. Using 2D 1H NMR and FTIR spectroscopies and ESI-MS we studied the topology and host-guest stoichiometry of inclusion compound between 2-hydroxypropyl-α-cyclodextrin and tramadol. These techniques confirmed that the inclusion compounds present 1:1 stoichiometry with the tramadol aromatic moiety inserted in the CD cavity and the amine part interacting with the CD superficial OHs. Performing capillary electrophoresis experiments, the stability constants of inclusion compounds were obtained and showed that the increase of temperature during the synthesis of these NPs can decrease their stabilities. Precipitated palladium nanoparticles were determined to have 80-200 nm of size distribution and the incorporation of tramadol was evidenced by additional 1H NMR experiments.

A ternary catalytic system for the room temperature Suzuki-Miyaura reaction in water.

The formation of Pd(0) in the absence of any classical reducing agent in a medium containing Mg(2+)/Al(3+) layered double hydroxide (LDH) and N,N-dimethylformamide was evidenced. XRD analysis showed the presence of crystalline phases of palladium in the Pd/LDH composite. Suzuki-Miyaura reactions in aqueous medium were carried out at room temperature, and good yields were obtained with bromoarenes and iodoarenes using the ternary system LDH-Pd-CD (cyclodextrin) as catalyst.