Patrícia Benedini Martelli

Adsorção de fenol sobre carvão ativado em meio alcalino

The present study describes phenol adsorption on commercial active carbon (CAF) under alkaline conditions in the concentration range of 0.01 to 2.08xa0mmol L-1. Surface characterization has been performed by means of surface area measurements, IR spectroscopy and Boehm titration. The effect of temperature on the adsorption equilibrium isotherm was investigated at 23, 30, 40, 50 and 60 °C. The results showed that adsorption capacity decreased with increasing temperature. The adsorption kinetics and the role of surface characteristics on the adsorption of phenol also discussed.

Characterization of copper adsorption on oxidized activated carbon

This paper discusses Cu(II) ion adsorption onto oxidized activated carbon with HNO3. The modifications introduced on the activated carbon (AC) surface were characterized by surface area measurement, FT-IR spectroscopy, titration by the traditional Boehm procedure, and potentiometric titration. A nonlinear method for fitting acid-base potentiometric titration data was applied to determine the concentration and pKa distributions of the ionizable acidic sites on AC, before and after HNO3 oxidation. Adsorption studies were conducted in batch mode for the concentration range 0.08 to 1.75 mmol L-1 and pH = 4.0. Results showed that the acid treatment of AC leads to a decrease in apparent surface areas and produces slight modifications in pore structure. However, oxidation strongly influenced the AC surface chemical structures by increasing the concentration of acidic groups with pKa < 6.0, which significantly improved Cu(II) ion adsorption. The uptake enhanced for oxidized carbon was related to the presence of acidic groups with pKa lower than 4, revealing the important role of acidic groups in adsorption by ion-exchange mechanisms.

Utilization of rice husk to remove Cu2+, Al3+, Ni2+ and Zn2+ from wastewater

The potential use of rice husk as biosorbent to remove Cu2+, Al3+, Ni2+ and Zn2+ ions from aqueous solutions was investigated under both noncompetitive and competitive conditions. The biosorbent was used in the form of particles with size smaller than 0.5 μm and in the concentration of 500 mg L-1 (dry weight). The experiments were performed using batch adsorption technique for concentrations of 10, 30 and 70xa0mgxa0L-1 of metal ions at pH 4.0 and 5.0. The chemical speciation of metals in the experimental conditions used in this work was predicted by the software Visual MINTEQ 2.6.

Determination of cadmium and lead in beverages after leaching from pewter cups using graphite furnace atomic absorption spectrometry.

Two simple methods have been developed to determine cadmium and lead in different kinds of beverages and vinegar leached from pewter cups produced in Brazil. Leaching experiments have been carried out with different solutions: beer, sugar cane spirit, red and white wine, vinegar and a 3% acetic acid solution. The solutions were kept in cups with and without solder for 24h. Lead and cadmium have been determined using graphite furnace atomic absorption spectrometry with deuterium background correction. The limits of detection were 0.05 and 1.4 μg L(-1), and the characteristic mass was 1.0 pg and 19 pg for Cd and Pb, respectively. With the developed methods it was possible to determine accurately cadmium and lead by direct analysis in these liquids and to evaluate the leaching of these metals from pewter cups. The results presented in this work show that pewter cups are not cadmium- and lead-free; this point goes against the manufacturers declaration that their products are lead-free.

A Multicommuted Flow Procedure for the Determination of Cholesterol in Animal Blood Serum by Chemiluminescence

Abstract An automatic flow procedure for cholesterol determination in animal blood serum using enzymatic reaction and detection by chemiluminescence is described. Cholesterol esterase and cholesterol oxidase were immobilized on glass beads packed into two mini-columns (15 mm × 5 mm), which were coupled to flow system. Produced H2O2 reacted with luminol produced chemiluminescence that was detected using a solid-state detector. The flow system comprised a set of three-way solenoid valves assembled to implement multicommutation. A microcomputer with an electronic interface controlled the solenoid valves and performed data acquisition. Profitable features such as a sampling throughput of 40 determinations per hour, linear response ranging from 25 to 125 mg L−1 cholesterol (r = 0.998), detection limit of 3.7 mg L−1 cholesterol, relative standard deviation of 2.3% (n = 20), and low reagents consumption 0.22 mg luminol and 2.7 mg hexacyanoferrate(III) per determination were achieved. Comparing the results with those obtained using the conventional spectrophotometric method no significant difference at the 95% confidence level was observed.

Development of non-enzymatic glucose sensor using recycled cobalt from cell phone Li-ion batteries.

This article aims to present an alternative to recycling of spent Li-ion batteries applied to electrochemical sensor manufacturing. The cobalt, from cathode of Li-ion batteries, was recovered by electrodeposition onto AISI 430 stainless steel substrate and applied as glucose sensor. The composition of cathode utilized was obtained by AAS measures and corresponds to LiNi0,40Co0,60O2. Despite this composition, in the cobalt electrodeposition onto AISI 430 stainless steel the Ni is less of 1.7% (w/w) due the anomalous electrodeposition. The sensitivity of cobalt electrode for glucose detection is 70.2 μA/mmol cm(2) and the linear range is 1-10 mmol/L. This result shows that the Co electrodeposited onto AISI 430 stainless steel is a promissory and low-cost non-enzymatic glucose sensor.

Efficiency of sugarcane bagasse-based sorbents for oil removal from engine washing wastewater.

This work evaluates the efficiency of sugarcane bagasse-based sorbents in the sorption of oil from engine washing wastewater. The sorbents were obtained from sugarcane bagasse in the natural form (SB-N) and modified with either acetic anhydride (SB-Acet) or 3-aminopropyltriethoxysilane (SB-APTS). The results showed that the sorption capacity of these materials decreased in the following order: SB-APTS > SB-N > SB-Acet. The superior oil sorption capacity observed for SB-APTS was attributed to the polar amino end groups in the silane structure, which acted to increase the hydrophilic character of the fibers. However, all the sorbents obtained in this study were able to clean a real sample of wastewater from engine washing, leading to significant reductions in suspended matter, sediment, anionic surfactants, and turbidity.