Estudo das Propriedades do Pseudofruto do Cajueiro na Adsorção de Cr (VI)

Abstract

In this study, the Cr (VI) adsorption properties by cashew (Anacardium occidentale L.) were studied in a batch system. The effects of pH (5.0 and 7.0), drying process – S (oven-dried and lyophilized), particle size – P (0.10 – 0.25 and 0.25 – 0.84 mm), mass of adsorbent – m (1.0 and 1.5 g) initial chromium concentration – C (500 and 1000 mg L-1) contact time – t (1 and 3 h) and stirring rate – v (0 and 150 rpm), on the adsorption process were studied using a fractional factorial design (27-4). Under ideal conditions the efficiency of adsorption of 87.24% for total chromium and 100.00% for Cr (VI) were achieved. The maximum adsorption capacity achieved was 11.43 mg/g. The adsorbent was characterized by infrared and X-ray fluorescence spectroscopy. Test reactions performed with Cr (VI) in conjunction with the aqueous extract of the adsorbent and pH monitoring during adsorption were carried out to better understand the mechanisms of adsorption. The proposed mechanism consists of two steps: reduction of Cr (VI) in solution or at the surface of the adsorbent, and subsequent adsorption of Cr (III) by ion exchange or complexation.

Keywords

• adsorption
• chromium
• cashew
• factorial design