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A novel system for sample digestion was proposed based on microwave-induced combustion in disposable vessels (MIC-DV) for trace elements determination by inductively coupled plasma optical emission spectrometry (ICP-OES). As a proof of concept, botanical samples were digested by MIC-DV for further determination of Al, Cr, Cu, Fe, Mn, Sr, and Zn. The system consists of a quartz holder (a modified version of conventional MIC) placed inside disposable polypropylene (PP) vessels. The quartz holder was carefully designed to avoid excessive heating and damaging of the vessel walls. For the combustion, the PP vessels containing the quartz holder and sample were placed in a specially designed metallic rotor that prevents the heating of absorbing solution and allows the use of a domestic microwave oven for sample ignition. After combustion, the digestion vessel was shaken to ensure the analytes’ absorption. The single-vessel principle was fulfilled, since no further dilution or liquid transfer was required and the same PP vessel used for digestion allowed solution storage until element determination. The influences of absorbing solution (diluted HNO3 and water) and sample mass (10 to 30 mg) were evaluated. By using the proposed MIC-DV system, low volumes of diluted absorbing solutions (5 mL of 1 mol L–1 HNO3) were possible, allowing the use of low reagent amounts and low energy consumption, since microwave irradiation is used only for sample ignition. The agreement with certified values ranged from 92 to 108% for all analytes, whereas the precision was below 15%. All of these advantages, combined with the use of low-cost disposable vessels and instrumentation, make MIC-DV suitable to be used for research and routine analysis.

ABSTRACT. This study evaluated the adsorption capacity of the methylene blue dye in macadamia residues, in natura and chemically modified. The waste characterization was performed using SME and spectroscopy in the infrared region, indicating the presence of carboxyl, carbonyl and hydroxyl groups. The equilibrium time for both residues was 240 minutes, following a kinetic described by models of the pseudo second-order and intra-particle diffusion. The maximum adsorption capacity was 117 mg g -1 to the residue in natura and 184 mg g -1 for the modified one, and was described by the Freundlich isotherm model. The system demonstrated to be spontaneous and favorable for both studied materials. Thus, these residues are promising for the adsorption of methylene blue dye in effluents.Keywords: effluent, agro industrial waste, methylene blue, Macadamia biomass.Resíduo de macadâmia como biossorvente para adsorção de corante catiônico em solução aquosa RESUMO. O presente trabalho avaliou a capacidade de adsorção do corante azul de metileno em resíduos de noz-macadâmia in natura e quimicamente modificado. A caracterização dos resíduos foi realizada utilizando MEV e espectroscopia na região do infravermelho a qual indicou a presença de grupos carboxílicos, carbonila e hidroxila. O tempo de equilíbrio alcançado para ambos os resíduos foi de 240 min., seguindo a cinética descrita pelos modelos de pseudo segunda-ordem e difusão intrapartícula. A capacidade máxima de adsorção foi 117 mg g -1 para o resíduo in natura e 184 mg g -1 para o modificado, sendo descrita pelo modelo isotérmico de Freundlich. O sistema mostrou-se espontâneo e favorável para os dois materiais estudados. Desta forma, estes resíduos são promissores para a adsorção do corante azul de metileno em efluentes.Palavras-chave: efluente, resíduo agroindustrial, azul de metileno, biomassa de macadâmia.

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