Juliene Tomé Oliveira

Treatment influence on green coconut shells for removal of metal ions: pilot-scale fixed-bed column

This work investigates copper, nickel and zinc ion biosorption in single- and multi-component systems in a fixed-bed column using green coconut shells (CS). Approximately 85% of biosorbents are in a particle size ranging from 0.25 to 2 mm. Operational parameters selected include a flow rate of 200 mL min−1 and a bed height of 100 cm, which were selected for a shorter execution time and good adsorption capacity. Empty-bed contact time and Thomas models were applied, showing a good fit with the experimental data. The column adsorption capacity increased after the green CS powder was treated in a column with NaOH at a concentration of 0.1 mol L−1. The highest values of adsorption capacities founded were 0.69, 0.45 and 0.39 mmol L−1 for Cu(II), Ni(II) and Zn(II), respectively, using green CS treated inside a column with NaOH of 0.1 M. The pH and chemical oxygen demand were monitored in the treatment solution and indicated that the adjustment of these parameters is necessary before disposal of these solutions. A study of desorption using an acid solution was carried out for recovery of metal ions.

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.