Assessment comparison of commercial TiO2 and TiO2 sol-gel on the degradation of caffeine using artificial radiation.

The presence of endocrine disrupting compounds in water receptor bodies, such as drugs, currently has in scientific field a great focus of studies focused on advanced water treatment techniques that enable the decontamination of water sources and public supply. In this context, this study focused on the characterization and evaluation of photocatalytic activity of catalysts calcined and uncalcined synthesized TiO2 and the commercial sol-gel route from caffeine degradation. The photocatalysts were characterized by N2 physisorption, X-ray diffraction, scanning electron microscopy (SEM/EDS), photoacoustic spectroscopy, and infrared spectroscopy (FTIR). They seek to evaluate the main textural, structural, chemical, and morphological differences that the method of synthesis can promote in obtaining a titanium oxide-based catalyst. Thus, the results of this study demonstrate that the synthesis method significantly influences the activity of the materials and that calcined TiO2 catalyst prepared using the sol-gel method has promising photocatalytic capabilities for the elimination of drugs such as caffeine when present in wastewater.

Adsorption of Diuron from aqueous solution onto commercial organophilic clay: kinetic, equilibrium and thermodynamic study.

Due to their abundance in nature, clays have been frequently studied in the adsorption of different emergent contaminants, since they have good efficiency and low cost. Therefore, the present study aimed to evaluate the performance of commercial organoclays as an adsorbent in the environmental remediation of wastewater containing the herbicide Diuron. The clay was characterized by the techniques of N2 physisorption, X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and point of zero charge. In the batch adsorption experiments it was verified that the adsorption kinetics is ruled by the pseudo-second-order model (R2 > 0.97), and the adsorption equilibrium study at different temperatures (298, 302 and 308 K) showed that the non-linear models of Langmuir (R2 > 0.99) and Freundlich (R2 > 0.98) were those that present better adjustments to the experimental data. In addition, the adsorption capacity in monolayer (qmax) was 44.24 mg g-1, being higher or comparable to several works reported in the literature. As for the thermodynamic adsorption study, it was possible to infer that the process is spontaneous (ΔG°ads < 0) and endothermic (ΔH°ads = 71.58 kJ mol-1) in the temperature range studied. As far as the regeneration study was concerned, the maximum desorption capacity, 26.59 mg g-1, was obtained from the use of ethanol as eluent at 298 K.

Adsorption of herbicide 2,4-D from aqueous solution using organo-modified bentonite clay.

This study analyzed the performance of organophilic clays obtained from the chemical modification of sodium bentonite clay when applied to the adsorption of herbicide 2,4-dichlorophenoxyacetic acid (2,4-D). Kinetic curves and equilibrium isotherms were obtained in order to determine time and adsorption capacity of the material, as well as understand the mechanisms involved in this phenomenon. The results showed that the most predictive kinetic model for experimental data was of pseudo-second order (R2 > 0.98), and that external mass transfer is the dominant factor in the time of operation. Isotherms were obtained at temperatures of 298, 308, and 318 K, under which the Dubinin-Radushkevich model was shown to have a good fit to data (R2 > 0.96), according to mathematical adjustments. The maximum adsorption capacity obtained experimentally was 50.36 mg g-1, found at a temperature of 298 K, being higher or compatible with other materials reported in the literature. With help of the thermodynamic studies on the process, it was observed that the adsorption of 2,4-D in organophilic clays refers to a spontaneous (ΔG°ads < 0), exothermal (ΔH°ads = - 9.99 kJ mol-1) process of physical nature. Lastly, it was observed that the adsorbent can be easily regenerated when subjected to eluents such as mixtures containing fractions of ethanol/water (desorption = 95%).

Protic ionic liquid as additive on lipase immobilization using silica sol-gel.

Ionic liquids (ILs) have evolved as a new type of non-aqueous solvents for biocatalysis, mainly due to their unique and tunable physical properties. A number of recent review papers have described a variety of enzymatic reactions conducted in IL solutions, on the other hand, to improve the enzyme's activity and stability in ILs; major methods being explored include the enzyme immobilization (on solid support, sol-gel, etc.), protic ionic liquids used as an additive process. The immobilization of the lipase from Burkholderia cepacia by the sol-gel technique using protic ionic liquids (PIL) as additives to protect against inactivation of the lipase due to release of alcohol and shrinkage of the gel during the sol-gel process was investigated in this study. The influence of various factors such as the length of the alkyl chain of protic ionic liquids (monoethanolamine-based) and a concentration range between 0.5 and 3.0% (w/v) were evaluated. The resulting hydrophobic matrices and immobilized lipases were characterised with regard to specific surface area, adsorption-desorption isotherms, pore volume (V(p)) and size (d(p)) according to nitrogen adsorption and scanning electron microscopy (SEM), physico-chemical properties (thermogravimetric - TG, differential scanning calorimetry - DSC and Fourier transform infrared spectroscopy - FTIR) and the potential for ethyl ester and emulsifier production. The total activity yields (Y(a)) for matrices of immobilized lipase employing protic ionic liquids as additives always resulted in higher values compared with the sample absent the protic ionic liquids, which represents 35-fold increase in recovery of enzymatic activity using the more hydrophobic protic ionic liquids. Compared with arrays of the immobilized biocatalyst without additive, in general, the immobilized biocatalyst in the presence of protic ionic liquids showed increased values of surface area (143-245 m(2) g(-1)) and pore size (19-38 Å). Immobilization with protic ionic liquids also favoured reduced mass loss according to TG curves (always less than 42.9%) when compared to the immobilized matrix without protic ionic liquids (45.1%), except for the sample containing 3.0% protic ionic liquids (46.5%), verified by thermogravimetric analysis. Ionic liquids containing a more hydrophobic alkyl group in the cationic moiety were beneficial for recovery of the activity of the immobilized lipase. The physico-chemical characterization confirmed the presence of the enzyme and its immobilized derivatives obtained in this study by identifying the presence of amino groups, and profiling enthalpy changes of mass loss.