André Gadelha de Oliveira

Green coconut shells applied as adsorbent for removal of toxic metal ions using fixed-bed column technology

This study applies green coconut shells as adsorbent for the removal of toxic metal ions from aqueous effluents using column adsorption. The results show that a flow rate of 2 mL/min and a bed height of 10 cm are most feasible. Furthermore, larger amounts of effluent can be treated for removal of single ions. The breakthrough curves for multiple elements gave the order of adsorption capacity: Cu(+2) > Pb(+2) > Cd(+2) > Zn(+2) > Ni(+2). Real samples arising from the electroplating industry can be efficiently handled.

Evaluation of a low-cost adsorbent for removal of toxic metal ions from wastewater of an electroplating factory.

In this study, sugar cane residue or bagasse was used for removal of toxic metal ions from wastewater of an electroplating factory located in northeast Brazil. Prior acid treatment increased the adsorption efficacies in batch wise experiments. The microstructure of the material before and after the treatment was investigated by X-ray diffraction, infrared spectroscopy and scanning electron microscopy. Column operations showed that removals of Cu(2+), Ni(2+) and Zn(2+) from wastewater (in the absence of cyanide) were 95.5%, 96.3.0%, and 97.1%, respectively. Regeneration of the adsorbent obtained in acid indicated that the efficiencies decreased only after the fourth cycle of re-use. Acid-treated sugar cane bagasse can be considered a viable alternative to common methods to remove toxic metal ions from aqueous effluents of electroplating industries.

Uso da casca de coco verde como adsorbente na remoção de metais tóxicos

Green coconut shells were treated with acid, base and hydrogen peroxide solutions for 3, 6, 12 and 24 h for removing toxic metals from synthetic wastewater. The removal of ions by the adsorbent treated with 0.1 mol L-1 NaOH/ 3h was 99.5% for Pb2+ and 97.9% for Cu2+. The removal of Cd2+, Ni2+, Zn2+, using adsorbent treated with 1.0 mol L-1 NaOH/3 h, was 98.5, 90.3 and 95.4%, respectively. Particle size, adsorbent concentration and adsorption kinetics were also studied. An adsorbent size of 60-99 mesh and a concentration of 30-40 g/L for 5 min exposure were satisfactory for maximum uptake of Pb2+, Ni2+, Cd2+, Zn2+ and Cu2+ and can be considered as promising parameters for treatment the aqueous effluents contaminated with toxic metals.

REMOÇÃO DE METAIS DE SOLUÇÃO AQUOSA USANDO BAGAÇO DE CAJU

The metal ions removal on cashew bagasse, a low-cost material, has been studied by batch adsorption. The parameters chemical treatment, particle size, biosorbent concentration, and initial pH were studied. In this study the maximum ions removal was obtained on the cashew bagasse treated with 0.1 mol/L NaOH/3 h, at optimum particle size (20-59 mesh), biosorbent concentration (50 g/L) and initial solution pH 5. The kinetic study indicated that the adsorption metal follows pseudo-second order model for a multielementary system and equilibrium time was achieved in 60 min for all metal ions.

Polymeric and silica sorbents on endocrine disruptors determination

ABSTRACTEndocrine disrupting determination at low concentration levels comprises one of the most important targets in environmental analytical chemistry. In spite of inherent high sensitivities obtained for HPLC, these techniques have some limitations depending on the contaminants. As a result, interest in preconcentration using solid–phase extraction (SPE) still continues increasingly for endocrine disrupting determinations by HPLC due to the high accuracy of this method. In this work, we evaluated three different adsorbents in preconcentration of endocrine disruptors in three different categories: pharmaceuticals (sulphamethoxazole, trimethoprim and diclofenac), hormones (estrone, 17β-estradiolacetate and 17β-estradiol) and plastic materials (bisphenol A) in multicomponent aqueous solution using the combination SPE -HPLC. The adsorbents investigated were such as modified silica (octadecylsilane)—DSC-18 (Supelco) and two polymers, a divinylbenzene-N-vinilpirolidona—Oasis® HLB (Waters) and a styrene-divin...

Degradation of the Pesticide Chlorpyrifos in Aqueous Solutions with UV/H2O2: Optimization and Effect of Interfering Anions

Abstract This study investigates the use of an advanced oxidation process (AOP) for removal of the pesticide chlorpyrifos in a recirculated system, especially considering the effects of temperature, hydrogen peroxide dosage, pH, pesticide concentration and added inorganic anions. The results indicate that a temperature of 45 °C gave the best performance using only UV-radiation, while for the UV/H2O2-method, the temperature did not affect the process. Variations of the pH for the H2O2- and the UV/H2O2-methods were investigated, where it was observed that pH values did not influence the efficiency of the UV/H2O2-method, but enhanced removal of the pesticide occurred at a pH of 10 for the H2O2-method. The optimum dosage for the H2O2-method was 1.5 g.L-1. The effects of the addition of 10 mM of chloride, nitrate, sulfate and bicarbonate anions were found not to be significant.

Treatment of Sulfonated Azo Dye Reactive Red 198 by UV/H2O2

UV/H2O2 system was tested on the color removal of sulfonated azo dye Reactive Red 198 (RR), which is widely used in textile process. The effects of hydrogen peroxide concentration, temperature, pH, and the in-line addition of hydrogen peroxide on high color and chemical oxygen demand (COD) removals were investigated. The kinetic of dye decolorization was also determined. The results showed that 2% H2O2 decreased the process efficiency, while 1% H2O2 solution led to a better performance of the system. Despite the fact that the pH increase had small effect on color removal, it affects positively COD removals. The same behavior was found for temperature increase. A high temperature resulted in a slight decrease in color removal and a sharp decrease for COD removal. In addition the H2O2 in-line provided a small improvement in both color and COD removals. UV/1% H2O2 treatment was the most efficient, the good performance was linked to higher amount of hydroxyl radicals formed.