Flávio André Pavan

Application of Brazilian pine-fruit shell as a biosorbent to removal of reactive red 194 textile dye from aqueous solution kinetics and equilibrium study.

The Brazilian pine-fruit shell (Araucaria angustifolia) is a food residue, that was used as biosorbent for the removal of non-hydrolyzed reactive red 194 (NRR) and hydrolyzed reactive red 194 (HRR) forms from aqueous solutions. Chemical treatment of Brazilian pine-fruit shell (PW), with chromium (Cr-PW), with acid (A-PW), and with acid followed by chromium (Cr-A-PW) were also tested as alternative biosorbents for the removal of NRR and HRR from aqueous effluents. It was observed that the treatment of the Brazilian pine-fruit shell with chromium (Cr-PW and Cr-A-PW) leaded to a remarkable increase in the specific surface area and average porous volume of these biosorbents when compared to unmodified Brazilian pine-fruit shell (PW). The effects of shaking time, biosorbent dosage and pH on biosorption capacity were studied. In acidic pH region (pH 2.0) the biosorption of NRR and HRR were favorable. The contact time required to obtain the equilibrium was 24h at 25 degrees C. The equilibrium data were fitted to Langmuir, Freundlich, Sips and Redlich-Peterson isotherm models. For NRR reactive dye the equilibrium data were best fitted to the Sips isotherm model using PW and A-PW as biosorbents, and Redlich-Peterson isotherm model using Cr-PW and Cr-A-PW as biosorbents. For HRR reactive dye the equilibrium data were best fitted to the Sips isotherm model using PW, A-PW and Cr-A-PW and the Redlich-Peterson isotherm model for Cr-PW as biosorbent.

Microwave-assisted activated carbon from cocoa shell as adsorbent for removal of sodium diclofenac and nimesulide from aqueous effluents

Microwave-induced chemical activation process was used to prepare an activated carbon from cocoa shell for efficient removal of two anti-inflammatories, sodium diclofenac (DFC) and nimesulide (NM), from aqueous solutions. A paste was obtained from a mixture of cocoa shell and inorganic components; with a ratio of inorganic: organic of 1 (CSC-1.0). The mixture was pyrolyzed in a microwave oven in less than 10 min. The CSC-1.0 was acidified with a 6 mol L(-1) HCl under reflux to produce MWCS-1.0. The CSC-1.0 and MWCS-1.0 were characterized using FTIR, SEM, N2 adsorption/desorption curves, X-ray diffraction, and point of zero charge (pHpzc). Experimental variables such as initial pH of the adsorbate solutions and contact time were optimized for adsorptive characteristics of MWCS-1.0. The optimum pH for removal of anti-inflammatories ranged between 7.0 and 8.0. The kinetic of adsorption was investigated using general order, pseudo first-order and pseu do-second order kinetic models. The maximum amounts of DCF and NM adsorbed onto MWCS-1.0 at 25 °C are 63.47 and 74.81 mg g(-1), respectively. The adsorbent was tested on two simulated hospital effluents. MWCS-1.0 is capable of efficient removal of DCF and NM from a medium that contains high sugar and salt concentrations.

Adsorption of Methylene Blue by ultrasonic surface modified chitin.

HYPOTHESIS Chitin is a biopolymer which can be used as a low-cost and eco-friendly material for dyes adsorption. The use of chitin for dyes removal is little investigated, due its low surface area, porosity and high crystallinity. So, an ultrasonic surface modified chitin (USM-chitin) was prepared and used for Methylene Blue (MB) adsorption. EXPERIMENTS Chitin was obtained from shrimp wastes and its surface was modified by an ultrasound-assisted treatment. USM-chitin was characterized by N2 adsorption/desorption isotherms (BET surface area, total pore volume), infrared spectroscopy, X-ray diffraction and scanning electron microscopy. The adsorption of MB on USM-chitin was studied by kinetic, equilibrium, thermodynamic, interactions analysis, desorption and mass transfer aspects. FINDINGS USM-chitin presented surface area 25 times higher than raw chitin. The porosity was increased and the crystallinity was decreased. The general order model was suitable to represent the adsorption kinetics and the Langmuir model was adequate for the equilibrium. The maximum adsorption capacity was 26.69 mg g(-1). The adsorption was spontaneous, favorable and exothermic. USM-chitin can be used seven times maintaining the same adsorption capacity.

Application of carbon adsorbents prepared from Brazilian-pine fruit shell for the removal of reactive orange 16 from aqueous solution: Kinetic, equilibrium, and thermodynamic studies.

Activated (AC-PW) and non-activated (C-PW) carbonaceous materials were prepared from the Brazilian-pine fruit shell (Araucaria angustifolia) and tested as adsorbents for the removal of reactive orange 16 dye (RO-16) from aqueous effluents. The effects of shaking time, adsorbent dosage and pH on the adsorption capacity were studied. RO-16 uptake was favorable at pH values ranging from 2.0 to 3.0 and from 2.0 to 7.0 for C-PW and AC-PW, respectively. The contact time required to obtain the equilibrium using C-PW and AC-PW as adsorbents was 5 and 4h at 298 K, respectively. The fractionary-order kinetic model provided the best fit to experimental data compared with other models. Equilibrium data were better fit to the Sips isotherm model using C-PW and AC-PW as adsorbents. The enthalpy and entropy of adsorption of RO-16 were obtained from adsorption experiments ranging from 298 to 323 K.

Removal of Cu(II), Fe(III), and Cr(III) from Aqueous Solution by Aniline Grafted Silica Gel

Abstract The aniline moiety was covalently grafted onto silica gel surface. The modified silica gel with aniline groups (SiAn) was used for removal of Cu(II), Fe(III), and Cr(III) ions from aqueous solution and industrial effluents using a batch adsorption procedure. The maximum adsorption of the transition metal ions took place at pH 4.5. The adsorption kinetics for all the adsorbates fitted better the pseudo second‐order kinetic model, obtaining the following adsorption rate constants (k2): 1.233 · 10−2, 1.902 · 10−2, and 8.320 · 10−3 g · mg−1 min−1 for Cr(III), Cu(II), and Fe(III), respectively. The adsorption of these transition metal ions were fitted to Langmuir, Freundlich, Sips, and Redlich‐Peterson isotherm models; however, the best isotherm model fitting which presented a lower difference of the q (amount adsorbed per gram of adsorbent) calculated by the model from the experimentally measured, was achieved by using the Sips model for all adsorbates chosen. The SiAn adsorbent was also employed for the removal of the transition metal ions Cr(III) (95%), Cu(II) (95%), and Fe(III) (94%) from industrial effluents, using the batch adsorption procedure.

Metal Nanoparticle/Ionic Liquid/Cellulose: New Catalytically Active Membrane Materials for Hydrogenation Reactions

Transition metal-containing membrane films of 10, 20, and 40 μm thickness were obtained by the combination of irregularly shaped nanoparticles with monomodal size distributions of 4.8 ± 1.1 nm (Rh(0)) and 3.0 ± 0.4 nm (Pt(0)) dispersed in the ionic liquid (IL) 1-n-butyl-3-methylimidazolium bis(trifluoromethane sulfonyl)imide (BMI·(NTf)(2)) with a syrup of cellulose acetate (CA) in acetone. The Rh(0) and Pt(0) metal concentration increased proportionally with increases in film thickness up to 20 μm, and then the material became metal saturated. The presence of small and stable Rh(0) or Pt(0) nanoparticles induced an augmentation in the CA/IL film surface areas. The augmentation of the IL content resulted in an increase of elasticity and decrease in tenacity and toughness, whereas the stress at break was not influenced. The introduction of IL probably causes an increase in the separation between the cellulose macromolecules that results in a higher flexibility, lower viscosity, and better formability of the cellulose material. The nanoparticle/IL/CA combinations exhibit an excellent synergistic effect that enhances the activity and durability of the catalyst for the hydrogenation of cyclohexene. The nanoparticle/IL/cellulose acetate film membranes display higher catalytic activity (up to 7353 h(-1) for the 20 μm film of CA/IL/Pt(0)) and stability than the nanoparticles dispersed only in the IL.

FTIR thermal analysis on anilinepropylsilica xerogel

FTIR thermal analysis was used for a hybrid xerogel, anilinepropylsilica, obtained from three different organic precursor amounts, using HF and NaF as catalysts in the sol–gelprocess. The aniline ring vibrational mode at 1500 cm−1 of attached aniline groups was used to obtain the relative aniline content in the xerogel materials after being submitted to thermal treatment in the temperature range from 100 to 400°C. This technique allowed to evaluate the thermal stability of organic phase. The organic coverage on the surface and the fraction of trapped organic groups in closed pores can also be evaluated.

Methylene blue immobilized on cellulose acetate with titanium dioxide: an application as sensor for ascorbic acid

. The electrode response was very fast, with an elapsed time of about 1.0 s, showing the potentiality to be utilized as an electrochemical sensor for determination of ascorbic acid in commercial samples.

Effects of first-row transition metals and impregnation ratios on the physicochemical properties of microwave-assisted activated carbons from wood biomass

First-row transition metals (Co, Ni, Cu and Zn) were successfully used in the preparation of activated carbons from wood biomass via microwave-assisted irradiation. Physical-chemical properties of the produced materials (MWAC) were studied by nitrogen adsorption-desorption curves, SEM, FTIR, UV-vis DRS and synchronous fluorescence spectroscopy, CHN elemental analysis, TGA/DTG, pHzpc, hydrophobic properties, and total acidity and basicity groups. Results showed that the metals were bound successfully in different amounts with surface functional groups of the wood biomass through ion exchange and surface complexation interaction during the impregnation step. Zn2+ and Cu2+ formed the most complexes. MWAC impregnated with Zn2+ showed higher pore volumes and surface areas, followed by Cu2+, Co2+ and Ni2+, independently of the ratio used. As the metal : biomass ratio was increased from 0.5 to 2, the surface area of MWAC increased from 300 to 620m2g-1 for Co-MC, 260 to 381m2g-1 for Ni-MC, 449 to 765m2g-1 for Cu-MC and from 572 to 1780m2g-1 for Zn-MC. The samples showed high values of carbon contents and oxygen-containing groups. An adsorption experiment revealed that samples prepared using ZnCl2 showed the highest sorption capacities (qe) for the tested adsorbates, followed by CuCl2, CoCl2 and NiCl2. These results matched with the surface areas and pore volumes trends, which were found to follow atomic number and melting point trends-Ni(II)bisphenol A>hydroquinone>4-nitro phenol>2-naphtol>paracetamol>caffeine>resorcinol.

Supported ionic liquid phase rhodium nanoparticle hydrogenation catalysts

Rh(0) nanoparticles (ca. 4 nm) dispersed in an ionic liquid (1-n-butyl-3-methylimidazolium tetrafluoroborate) were immobilized within a silica network, prepared by the sol-gel method. The effect of the sol-gel catalyst (acid or base) on the encapsulated ionic liquid and Rh(0) content, on the silica morphology and texture, and on the catalyst alkene hydrogenation activity was investigated. The Rh(0) content in the resulting xerogels (ca. 0.1 wt% Rh/SiO(2)) was shown to be independent of the sol-gel process. However, acidic conditions afforded higher contents of encapsulated ionic liquid and xerogels with larger pore diameters, which in turn might be responsible for the higher catalyst activity in hydrogenation of the alkenes.