Cold finger with semi closed reflux system for sample preparation aiming at Al, Ca, Cr, Cu, Fe, K, Mg, Mn, Ni, V and Zn determination in Drinking Water Treatment Sludge by MIP OES.

This study presents method development and optimization, based on statistical approaches, of an alternative sample preparation methodology for Drinking Water Treatment Sludge, through decomposition in semi closed system with cold finger, aiming at the determination of Al, Ca, Cr, Cu, Fe, K, Mg, Mn, Ni, V and Zn by microwave induced plasma optical emission spectrometry. This system was employed to decompose three different Drinking Water Treatment Sludge samples, from three different treatment plants. The compromise conditions were 250 mg of dried sample, 5 mL of HNO3, 1 mL of H2SO4 and heating at 225 °C for 150 min. After the digestion, 1% of cesium and lanthanum chloride buffer solution was added to all samples and standard solutions. The accuracy of the proposed sample preparation method was evaluated by analyzing a sediment certified reference material (CRM NIST 1646a) as well as the spike recovery technique. The recoveries ranged from 83% to 119% for all elements, and the found concentrations for the CRM agreed with the respective certified values, at 95% confidence level. The correlation coefficients for all investigated elements were higher than 0.999. The method LOQ values were adequate and complied with the Drinking Water Treatment Sludge regulation avaliable, ranging from 0.3 (V) and 32 (Zn) µg L-1, or 0.1 (V) to 13 (Zn) mg kg-1. The digestion procedure in acidic medium showed suitable to measure the analytes in the investigated matrix by microwave induced plasma optical emission spectrometry.

Environmentally friendly system for the degradation of multipesticide residues in aqueous media by the Fenton's reaction.

A Fenton oxidation system employing zero-valent iron (whose source was swarf, a residue of metallurgical industries, in powder form) and hydrogen peroxide for the treatment of an aqueous solution with six pesticides was developed, and the effect of the iron metal content, pH, and hydrogen peroxide concentration was evaluated. The characterization of the aqueous solution resulted in: pH 5.6, 105 mg L(-1) of dissolved organic carbon, and 44.6 NTU turbidity. In addition, the characterization of the swarf by FAAS and ICP-MS showed 98.43 ± 7.40 % of zero-valent iron. The removal was strongly affected by the content of iron metal, pH, and hydrogen peroxide concentration. The best degradation conditions were 2.0 g swarf, pH 2.0, and 5 mmol L(-1) H2O2. At the end of the treatment, the pesticide degradation ranged from 60 to 100%, leading to 55% mineralization. Besides, all hydrogen peroxide was consumed and the determination of total dissolved iron resulted in 2 mg L(-1). Thus, the advantages of this system are rapid degradation (up to 20 min), high-degradation rates, simple handling, and low cost.