Julio C.P. Vaghetti

Applications of Brazilian pine-fruit shell in natural and carbonized forms as adsorbents to removal of methylene blue from aqueous solutions-Kinetic and equilibrium study

The Brazilian pine-fruit shell (Araucaria angustifolia) is a food residue, which was used in natural and carbonized forms, as low-cost adsorbents for the removal of methylene blue (MB) from aqueous solutions. Chemical treatment of Brazilian pine-fruit shell (PW), with sulfuric acid produced a non-activated carbonaceous material (C-PW). Both PW and C-PW were tested as low-cost adsorbents for the removal of MB from aqueous effluents. It was observed that C-PW leaded to a remarkable increase in the specific surface area, average porous volume, and average porous diameter of the adsorbent when compared to PW. The effects of shaking time, adsorbent dosage and pH on adsorption capacity were studied. In basic pH region (pH 8.5) the adsorption of MB was favorable. The contact time required to obtain the equilibrium was 6 and 4h at 25 degrees C, using PW and C-PW as adsorbents, respectively. Based on error function values (F(error)) the kinetic data were better fitted to fractionary-order kinetic model when compared to pseudo-first order, pseudo-second order, and chemisorption kinetic models. The equilibrium data were fitted to Langmuir, Freundlich, Sips and Redlich-Peterson isotherm models. For MB dye the equilibrium data were better fitted to the Sips isotherm model using PW and C-PW as adsorbents.

Pecan nutshell as biosorbent to remove Cu(II), Mn(II) and Pb(II) from aqueous solutions.

In the present study we reported for the first time the feasibility of pecan nutshell (PNS, Carya illinoensis) as an alternative biosorbent to remove Cu(II), Mn(II) and Pb(II) metallic ions from aqueous solutions. The ability of PNS to remove the metallic ions was investigated by using batch biosorption procedure. The effects such as, pH, biosorbent dosage on the adsorption capacities of PNS were studied. Four kinetic models were tested, being the adsorption kinetics better fitted to fractionary-order kinetic model. Besides that, the kinetic data were also fitted to intra-particle diffusion model, presenting three linear regions, indicating that the kinetics of adsorption should follow multiple sorption rates. The equilibrium data were fitted to Langmuir, Freundlich, Sips and Redlich-Peterson isotherm models. Taking into account a statistical error function, the data were best fitted to Sips isotherm model. The maximum biosorption capacities of PNS were 1.35, 1.78 and 0.946mmolg(-1) for Cu(II), Mn(II) and Pb(II), respectively.

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.

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.

Pecan Nutshell as Biosorbent to Remove Toxic Metals from Aqueous Solution

Abstract In the present study we reported for the first time, the feasibility of pecan nutshell (PNS-Carya illinoensis) as an alternative biosorbent to remove Cr(III), Fe(III) and Zn(II) metallic ions from aqueous solutions. The ability of PNS to remove these metallic ions was investigated by using batch biosorption procedure. The effects, such as pH and the biosorbent dosage on the adsorption capacities of PNS were studied. Five kinetic models were tested, the adsorption kinetics being the better fitted one to the fractionary-order kinetic model. The equilibrium data were fitted to Langmuir, Freundlich, Sips, and Redlich-Peterson isotherm models. Taking into account a statistical error function, the data were best fitted to Sips isotherm models. The maximum biosorption capacity of PNS were 93.01, 76.59, and 107.9 mg g−1 for Cr(III), Fe(III), and Zn(II), respectively.

4-Phenylenediaminepropylsilica xerogel as a sorbent for copper determination in waters by slurry-sampling ETAAS

The synthesis of a new, hybrid mesoporous sorbent, 4-phenylenediaminepropylsilica (4-PhAP/silica xerogel) obtained by the sol–gel process is described. This material was characterized by infrared spectroscopy (IR), elemental analysis (CHN), and nitrogen adsorption–desorption isotherms. Subsequently, this material was employed for the successful pre-concentration of copper in natural water reference materials. The copper characteristic mass was 15.0 ± 0.2 pg. The detection limit for copper determination in natural waters employing the pre-concentration procedure was 0.2 µg l−1. The average tube lifetime was 750 analytical firings when 20 µl of 1.5% m/v copper sorbed on 4-PhAP/silica xerogel slurry was delivered to a previously treated W–Rh treated platform of a transversely heated graphite atomizer (TGA). The pre-concentration factor obtained with 4-PhAP/silica xerogel as adsorbent for copper determination was 3.75 and the retention capacity of the sorbent was 0.52 mmol copper per gram of sorbent.

Adsorption of Procion Blue MX-R dye from aqueous solutions by lignin chemically modified with aluminium and manganese

A macromolecule, CML, was obtained by purifying and carboxy-methylating the lignin generated from acid hydrolysis of sugarcane bagasse during bioethanol production from biomass. The CMLs complexed with Al(3+) (CML-Al) and Mn(2+) (CML-Mn) were utilised for the removal of a textile dye, Procion Blue MX-R (PB), from aqueous solutions. CML-Al and CML-Mn were characterised using Fourier transform infrared spectroscopy (FTIR), scanning differential calorimetry (SDC), scanning electron microscopy (SEM) and pHPZC. The established optimum pH and contact time were 2.0 and 5h, respectively. The kinetic and equilibrium data fit into the general order kinetic model and Liu isotherm model, respectively. The CML-Al and CML-Mn have respective values of maximum adsorption capacities of 73.52 and 55.16mgg(-1) at 298K. Four cycles of adsorption/desorption experiments were performed attaining regenerations of up to 98.33% (CML-Al) and 98.08% (CML-Mn) from dye-loaded adsorbents, using 50% acetone+50% of 0.05molL(-1) NaOH. The CML-Al removed ca. 93.97% while CML-Mn removed ca. 75.91% of simulated dye house effluents.

Evaluation of different permanent modifiers for the determination of arsenic in environmental samples by electrothermal atomic absorption spectrometry

Single noble metal permanent modifiers such as, Rh, Ir, and Ru, as well as mixed tungsten plus noble metal (W-Rh, W-Ru, W-Ir) permanent modifiers thermally deposited on the integrated platform of transversally heated graphite atomizer were employed for the determination of arsenic in sludges, soils, sediments, coals, ashes and waters by electrothermal atomic absorption spectrometry. Microwave digests of solid samples and water samples were employed for obtaining the analytical characteristics of the methods with different permanent modifiers. The performance of the modifiers for arsenic determination in the real samples depended strongly on the type of permanent modifier chosen. The single noble metal (Rh, Ir and Ru) permanent modifiers were suitable for the analyte determinations in simpler matrices such as waters (recoveries of certified values 95-105%), but the analyte recoveries of certified values in sludges, soils, sediments, coals, and ashes were always lower than 90%. On the other hand, for the determination of arsenic, using W-Rh, W-Ru, and W-Ir permanent modifiers presented recoveries of certified values within 95-105% for all the samples. Long-term stability curves obtained for the determination of arsenic in environmental samples with different permanent modifiers (Rh, Ir, Ru, W-Rh, W-Ir, W-Ru) showed that the improvement in the tube lifetime depends on the tungsten deposit onto the platform. The tungsten plus noble metal permanent modifier presents a tube lifetime of at least 35% longer when compared with single permanent modifier. The results for the determination of As employing different permanent modifiers in the samples were in agreement with the certified reference materials, since no statistical differences were found after applying the paired t-test at the 95% confidence level.

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.