L. S. Lima

Bio: L. S. Lima is an academic researcher from Sao Paulo State University. The author has contributed to research in topics: Thermal decomposition & Thermogravimetry. The author has an hindex of 10, co-authored 22 publications receiving 246 citations.

Thermal behaviour of fumaric acid, sodium fumarate and its compounds with light trivalent lanthanides in air atmosphere

Abstract: Characterization, thermal stability and thermal decomposition of light trivalent lanthanide fumarates, as well as, the thermal behaviour of fumaric acid and its sodium salt were investigated employing simultaneous thermogravimetry and differential thermal analysis, differential scanning calorimetry, Fourier transform infrared spectroscopy (FTIR), TG–FTIR techniques, elemental analysis and complexometry. On heating, sublimation of fumaric acid is observed, while the thermal decomposition of the sodium fumarate occurs with the formation of a mixture of sodium carbonate and carbonaceous residue. The thermal decomposition of light trivalent lanthanide fumarates occurs in consecutive and/or overlapping steps with the formation of the respective oxides: CeO2, Pr6O11, and Ln2O3 (Ln = La, Nd, Sm, Eu, Gd).

Thermal behaviour of succinic acid, sodium succinate and its compounds with some bivalent transitions metal ions in dynamic N2 and CO2 atmospheres

Abstract: Thermal stability and thermal decomposition of succinic acid, sodium succinate and its compounds with Mn(II), Fe(II), Co(II), Ni(II), Cu(II) and Zn(II) were investigated employing simultaneous thermogravimetry and differential thermal analysis (TG-DTA) in nitrogen and carbon dioxide atmospheres and TG-FTIR in nitrogen atmosphere. On heating, in both atmospheres the succinic acid melt and evaporate, while for the sodium succinate the thermal decomposition occurs with the formation of sodium carbonate. For the transition metal succinates the final residue up to 1180 oC in N2 atmosphere was a mixture of metal and metal oxide in no simple stoichiometric relation, except for Zn compound, where the residue was a small quantity of carbonaceous residue. For the CO2 atmosphere the final residue up to 980 oC was: MnO, Fe3O4, CoO, ZnO and mixtures of Ni, NiO and Cu, Cu2O.

Power of Infrared and Raman Spectroscopies to Characterize Metal-Organic Frameworks and Investigate Their Interaction with Guest Molecules

Abstract: The variety of functionalities and porous structures inherent to metal-organic frameworks (MOFs) together with the facile tunability of their properties makes these materials suitable for a wide range of existing and emerging applications. Many of these applications are based on processes involving interaction of MOFs with guest molecules. To optimize a certain process or successfully design a new one, a thorough knowledge is required about the physicochemical characteristics of materials and the mechanisms of their interaction with guest molecules. To obtain such important information, various complementary analytical techniques are applied, among which vibrational spectroscopy (IR and Raman) plays an important role and is indispensable in many cases. In this review, we critically examine the reported applications of IR and Raman spectroscopies as powerful tools for initial characterization of MOF materials and for studying processes of their interaction with various gases. Both the advantages and the limitations of the technique are considered, and the cases where IR or Raman spectroscopy is preferable are highlighted. Peculiarities of MOFs interaction with specific gases and some inconsistent band assignments are also emphasized. Summarizing the broad analytical possibilities of the IR and Raman spectroscopies, we conclude that it can be applied in combinations with other techniques to explicitly establish the structure, properties, and reactivity of MOFs.

Iron-based metal organic framework, MIL-88A, as a heterogeneous persulfate catalyst for decolorization of Rhodamine B in water

Abstract: While Metal Organic Frameworks (MOFs) have been extensively investigated as photocatalysts to eliminate toxic pollutants in water, studies using MOFs as chemical oxidative catalysts to degrade contaminants are still limited. MOFs used as catalysts for chemical oxidation reactions were prepared in N,N-dimethylformamide (DMF), a potential carcinogenic solvent. If such MOFs are not well activated and have not properly undergone solvent exchange, DMF can still be encapsulated inside MOFs, leading to secondary pollution. Considering the essence of wastewater treatment and pollutant reduction, DMF-free MOFs which still exhibit the catalytic activity to activate oxidants should be developed. Thus, we selected an iron-based MOF, MIL-88A, which can be prepared using Fe3+ with fumaric acid just in water. The as-synthesized MIL-88A is evaluated as the heterogeneous catalyst to activate persulfate for the decolorization of Rhodamine B (RB) dye. Iron oxide clusters (i.e., Fe2O3) form within MIL-88A through the coordination of Fe3+ and fumaric acid. Fe3+ of Fe2O3 is expected to induce the generation of persulfate radicals which in turn lead to the formation of sulfate radicals to decolorize RB dye. Factors influencing the activation of persulfate and RB decolorization were examined including persulfate dosage, MIL-88A loading, temperature, pH, UV and US irradiation as well as inhibitors. MIL-88A was assessed for the multiple-cycle activation of persulfate without additional regeneration of spent MIL-88A. These features make MIL-88A an effective and recyclable heterogeneous catalyst for the activation of persulfate.