Influence of digestion methods on the recovery of Iron, Zinc, Nickel, Chromium, Cadmium and Lead contents in 11 organic residues

Abstract

SUMMARYThere are currently many devices and techniques to quantify trace elements (TEs) in various matrices, but their efficacy is dependent on the digestion methods (DMs) employed in the opening of such matrices which, although "organic", present inorganic components which are difficult to solubilize. This study was carried out to evaluate the recovery of Fe, Zn, Cr, Ni, Cd and Pb contents in samples of composts and cattle, horse, chicken, quail, and swine manures, as well as in sewage sludges and peat. The DMs employed were acid digestion in microwaves with HNO 3 (EPA 3051A); nitric-perchloric digestion with HNO 3 + HClO 4 in a digestion block (NP); dry ashing in a muffle furnace and solubilization of residual ash in nitric acid (MDA); digestion by using aqua regia solution (HCl:HNO 3 ) in the digestion block (AR); and acid digestion with HCl and HNO 3 + H 2 O 2 (EPA 3050). The dry ashing method led to the greatest recovery of Cd in organic residues, but the EPA 3050 protocol can be an alternative method for the same purpose. The dry ashing should not be employed to determine the concentration of Cr, Fe, Ni, Pb and Zn in the residues. Higher Cr and Fe contents are recovered when NP and EPA 3050 are employed in the opening of organic matrices. For most of the residues analyzed, AR is the most effective method for recovering Ni. Microwave-assisted digestion methods (EPA3051 and 3050) led to the highest recovery of Pb. The choice of the DM that provides maximum recovery of Zn depends on the organic residue and trace element analyzed.Index terms: aqua regia, heavy metals, manure, sewage sludge, compost, degree of humification.( A eficiência de determinação de teores de elementos-traço (ET) é dependente dos métodos de digestão (MD) empregados na abertura de matrizes, que, embora "orgânicas", podem conter constituintes inorgânicos de difícil solubilização. Objetivou-se, em razão do emprego de cinco MD, avaliar a recuperação de teores de Fe, Zn, Cr, Cd, Pb e Ni em 11 amostras de composto comercial, composto de lixo, composto orgânico, esterco de bovino, esterco de codorna, esterco de equino, esterco de galinha, esterco de suíno, lodo de esgoto de duas origens e turfa. Os métodos de digestão estudados foram: digestão ácida por micro-ondas com HNO 3 (EPA 3051); digestão nítrico-perclórica com HNO 3 + HClO 4 em bloco digestor (NP); digestão seca em forno tipo mufla com solubilização da cinza residual com ácido nítrico (MUFLA); digestão em solução água régia (HCl:HNO 3 ) em bloco digestor (AR) e digestão ácida com HNO 3 + H 2 O 2 e HCl (EPA 3050). O método da digestão seca é o que proporciona maior recuperação de Cd nos resíduos orgânicos, mas o método EPA 3050 pode ser uma alternativa para o mesmo fim. A digestão seca não deve ser empregada para determinar os teores de Cr, Fe, Ni, Pb e Zn nos resíduos; entretanto, Cr e Fe são recuperados quando a digestão é feita pelos protocolos nítrico-perclórico e EPA 3050 nas matrizes orgânicas. A água régia é o método de digestão mais eficiente em recuperar o Ni, para a maioria dos...

Digestion Procedure and Determination of Heavy Metals in Sewage Sludge—An Analytical Problem

“…Heavy metals determinations in samples mineralized with HNO 3 /HCl mixture as applied in all three procedures are reported in Table 1. This mixture is recommended as one of the most effective for decomposition of the organic matrix [32,[35][36][37]. According to Polish regulations, the error of heavy metals determination in sludge should not be higher than 10% of the respective allowable values, i.e., 75 mg/kg of Pb, 50 mg/kg of Cr, 2 mg/kg of Cd, 30 mg/kg of Ni, 250 mg/kg of Zn and 100 mg/kg of Cu [22].…”

“…The sample preparation is a crucial step which ensures the quality of the whole analytical process. Several procedures as used for the decomposition of sewage sludge and other samples with substantial organic matrix contributions (thermal or microwave destruction with different types of reagents) are reported in the scientific literature [30][31][32][33][34][35][36][37]. The authors of those works addressed the issue of environmental samples complexity with a special attention paid to organic carbon and silica.…”

Soil Fertility and Electrical Conductivity Affected by Organic Waste Rates and Nutrient Inputs

“…CEC: cation exchange capacity at pH 7 as a sum of basic cations plus titratable acidity measured by the SMP pH method; V: base saturation; C: organic carbon determined by dry combustion in an automated analyzer. Higashikawa et al, 2010;Abbruzzini et al, 2014) were performed with the following modifications: pH was determined using an organic waste:water ratio of 1:5, and total C content in the waste was determined in the same way as described for soil samples, in a TOC analyzer using 3-5 mg of dried waste sample.…”

Rapid production of organic fertilizer from degradable waste by thermochemical processing

“…TOC and N were determined using a CHNS analyzer (vario El cube, elementar, Germany). After nitricperchloric (4:1) wet digestion (Abbruzzini et al 2014) of the samples, total P was analyzed by the vanadomolybdic yellow color method (Greenberg et al 1992). K, Ca, and Mg were analyzed by atomic absorption spectrophotometer (novAA 350 BU, AnalytkjenaAG, Germany), the heavy metals Pb, Cd, Ni, Cr, and As were analyzed by inductively coupled plasma optical emission spectrometer (ICP OES Optima 8000, Perkin Elmer Inc., USA), and B was analyzed by the Azomethine-H method (Roignavarro et al 1996).…”