André Leonardo P. Silva

Bio: André Leonardo P. Silva is an academic researcher from Federal University of Paraíba. The author has contributed to research in topics: Silica gel & Substrate (chemistry). The author has an hindex of 5, co-authored 7 publications receiving 107 citations.

Organofunctionalized silica gel as a support for lipase

Abstract: This work described the preparation of silica gel modified with cyanuric chloride. The modified silica gel was tested for the ability to immobilize Burkholderia cepacia lipase. Contact times ranging from 4 to 24 h were investigated to determine the optimal lipase immobilization time. Following immobilization, the enzyme activity was assessed by the hydrolysis of p-nitrophenylpalmitate (pNPP). Elemental analysis data revealed that 0.4 mmol of cyanuric chloride were anchored per gram of support, demonstrating the successful incorporation of the triazine molecule onto the silica surface. The tests of reusability and storage indicated that the enzyme-modified silica-gel (immobilization at 24 h) was more stable under reaction conditions than the other systems. The activity assays indicated high rates of enzymatic formation of p-nitrophenol (p-NP), demonstrating a maximum activity retention of 87%.

Synthesis and characterization of hybrids derived from vermiculite chloropropyl and aliphatic diamines

Abstract: Silylation of vermiculite surface with organosilane (H3CO)3SiR, being R is the corresponding organic moieties –CH2CH2CH2Cl, were carried out to yield organofunctionalized nanomaterial, named as VCl. The product reacted subsequently with three aliphatic diamines H2 N( CH 2)nNH2 (n=2, 4 and 6). The new hybrids were characterized by elemental analysis, infrared spectroscopy, X-ray diffraction and thermogravimetry. The grafting chloro derivates onto surface amounted to 2.1 mmol g –1 . The incorporation of alkyl amines was more effective for butyl>ethylene>hexyldiamines. The sequence is in agreement with thermogravimetry and elemental analysis data.

Rapid conversion of cyclohexenone, cyclohexanone and cyclohexanol to ε-caprolactone by whole cells of Geotrichum candidum CCT 1205

Abstract: ɛ-Caprolactone (ɛ-CL) was obtained with excellent conversion and short reaction times from the substrates cyclohexenone, cyclohexanone and cyclohexanol using whole cells of Brazilian Geotrichum candidum (CCT 1205). The reactions were monitored over time by gas chromatography, and the intermediates of the one-pot cascade biotransformation involving reductions of C=C and C=O bonds as well as the Baeyer–Villiger oxidation were identified and quantified. The Baeyer–Villiger monooxygenase (BVMO) enzyme was predominant, and all three substrates were completely converted into ɛ-CL. Furthermore, the whole cells of Geotrichum candidum were recycled and reutilized in the biotransformation of cyclohexanone, producing ɛ-CL at least six consecutive times without a significant loss of activity, reaction yields or product purity.

A mercapto functionalized magnetic Zr-MOF by solvent-assisted ligand exchange for Hg2+ removal from water

Abstract: A facile preparation of magnetic MOF composites with flexible mercapto group pendants in their pores is realized through solvent-assisted ligand exchange (SALE) under mild conditions in water, and terephthalate in UIO-66 is replaced with mercaptoacetic acid (MAA). After the SALE processing, the crystallinity, porosity, and superparamagnetism of the mercapto functionalized magnetic Zr-MOF (MFC-S) are well maintained, and the obtained MFC-S exhibits a higher adsorption capacity (282 mg g−1) for Hg2+ than that of the magnetic Zr-MOF (MFC-O). Furthermore, the prepared MFC-S can be regenerated easily by liquid desorption after adsorption of metal ions and be reused more than 5 times without obvious decrease in removal performance. The proposed SALE method for the preparation of mercapto functionalized magnetic MOF composites (MFCs) is easy-to-operate and low cost, providing not only a reliable porous MFC platform for the removal of metal ions, but also a simple and efficient synthesis route for the preparation of functionalized MFCs which cannot be achieved through conventional approaches.