Effect of water-soluble polymers, polyethylene glycol and poly(vinylpyrrolidone),on the gelation of aqueous micellar solutions of Pluronic copolymer F127

The micellization of F127 (E98P67E98) in dilute aqueous solutions of polyethylene glycol (PEG6000 and PEG35000) and poly(vinylpyrrolidone) (PVP K30 and PVP K90) is studied. The average hydrodynamic radius (rh,app) obtained from the dynamic light scattering technique increased with increase in PEG concentration but decreased on addition of PVP, results which are consistent with interaction of the micelles with PEG and the formation of micelles clusters, but no such interaction occurs with PVP. Tube inversion was used to determine the onset of gelation. The critical concentration of F127 for gelation increased on addition of PEG and of PVP K30 but decreased on addition of PVP K90. Small-angle X-ray scattering (SAXS) was used to show that the 30 wt% F127 gel structure (fcc) was independent of polymer type and concentration, as was the d-spacing and so the micelle hard-sphere radius. The maximum elastic modulus (G0 max) of 30 wt% F127 decreased from its value for water alone as PEG was added, but was little changed by adding PVP. These results are consistent with the packed-micelles in the 30 wt% F127 gel being effectively isolated from the polymer solution on the microscale while, especially for the PEG, being mixed on the macroscale

Chitosan/mangiferin particles for Cr(VI) reduction and removal

AbstractIn this work, chitosan/mangiferin particles (CMP) were prepared by spray-drying technique and characterized by SEM, DLS, FTIR, HPLC–UV and adsorption studies to investigate a possible application as a preventive material in cases of human and animal contamination with Cr(VI). CMP presented sizes ranging from nano to micrometers. Chitosan and mangiferin (MA) presence in the powder was confirmed by FTIR and MA quantification (136μg/mg) was performed using a calibration curve prepared by HPLC–UV. Adsorption capacity of Cr(VI) onto CMP was compared with chitosan and investigated in a batch system by considering the effects of various parameters like contact time, initial concentration of adsorbent and pH. Cr(VI) removal is pH dependent and it was found to be maximum at pH 5.0. The results showed that CMP has a potential application as a preventive material in cases of human or animal contamination with Cr(VI)

Sulfonated MCM-41 as potential catalyst to obtain biolubricants from vegetable oil

Biolubricants may be obtained from vegetable oils using appropriate chemical modifications, to improve their physicochemical properties for lubrication applications. In this study, the esterification of a free fatty acid (FFA) with long chain alcohols was performed using sulfonated mesoporous silica as catalyst. Fresh and functionalized MCM-41 samples were prepared to evaluate the effect of the sulfonic surface group on the esterification reaction. MCM-41 was functionalized via post-synthesis modification using 3-mercaptopropyltrimethoxysilane (MPTS) as silylating agent. The synthesized catalysts were characterized using several techniques. After the functionalization, a decrease in the apparent surface area and pore diameter were observed. The MCM-41/SO3H sample was applied in the esterification reaction of oleic acid (as a FFA model) using two different long-chain alcohols (octanol and 2-ethylhexanol). The catalytic results reveal that sulfonated catalyst showed excellent conversions (~ 100% mol when using octanol and > 93% mol using 2-ethylhexanol) and selectivities to esters (ca. 90%).The authors wish to acknowledge the financial support provided by FUNCAP (Fundação Cearense de Apoio ao Desenvolvimento Científico e Tecnológico) and CNPq (Conselho Nacional de Desenvolvimento Científico e Tecnológico). This study was financed in part by the CAPES (Coordenação de Aperfeiçoamento de Pessoal de Nível Superior)—Brazil, Finance Code 001. Also, financial support from GV (PROMETEOII/2014/004), MINECO (MAT2016-80285-p) and H2020 (MSCA-RISE-2016/NanoMed Project) is gratefully acknowledged

Sulfonated activated carbons as potential catalysts for biolubricant synthesis

In this study, sulfonated activated carbons have been prepared, under different conditions, with the purpose of evaluating the effect of the nature and amount of sulfonic surface groups on the esterification reaction of free fatty acids (FFA) with different long-chain alcohols. The synthesized catalysts were characterized using different techniques and 1H NMR was used for monitoring the reaction products. The modifications of the surface functionalities were assessed by X-ray Photoelectron Spectroscopy (XPS) and Thermogravimetric analysis (TGA), while changes in the porous network and morphology of the samples were evaluated before and after the treatment of the original activated carbon sample. XPS results showed the presence of two types of sulfur, one from thiophenic sulfur (present on all materials, including the unmodified sample), and the other from sulfonic groups (SO3H), at 168 eV (present only in the modified samples). These catalysts were applied in the esterification reaction and presented excellent catalytic performances, while the original activated carbon exhibited conversions similar to reactions without any catalyst. On the other hand, the conversion of fatty acids when using the modified carbons improves significantly with values up to ∼100 % to mono alcohols and 70 % to trimethylolpropane.The authors wish to acknowledge the financial support provided by CNPq (Conselho Nacional de Desenvolvimento Científico e Tecnológico). This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) – Brazil – Finance Code 001. FMTL and JSA acknowledge financial support from the University of Alicante (INV19-18). Also, financial support from MINECO (MAT2016-80285-p), GV (PROMETEOII/2014/004), and H2020 (MSCA-RISE-2016/NanoMed Project) is gratefully acknowledged