Desenvolvimento de metodologia analítica para extração e pré-concentração de Ag(I) utilizando a moringa oleifera Lam

Abstract

Industrial process have been historically an important factor of environmental degradation. The disposal of industrial wastes, mainly containing toxic metals, in water sources represents a problem of great concern not only in relation to biota in receiving environment but also to humans. In this work, the adsorptive capacity of the crushed seeds of Moringa oleifera Lam. was evaluated in order to quest alternative materials for removal and preconcentration of silver ions. The first chapter describes the results of removal of Ag(I) ions in contaminated aqueous systems utilizing moringa seeds. Preliminary tests were carried out using the seeds of moringa as: non-shelled, shelled seeds and husks were tested for their adsorption potential for ions Ag(I). The results showed greater efficiency for non-shelled seeds. The parameters evaluated were: particle size, pH and agitation time, concentration and volume of solution, adsorbent mass. Silver was quantified before and after treatment, by Flame Atomic Absorption Spectrometry. The optimum conditions were: particle size ≤ 500 μm, pH = 6.5, agitation time = 20 minutes, adsorbente mass = 2.0 g, concentration of Ag(I) = 25 mg L-1 and volume = 100 mL. In these conditions, the removal of ions Ag(I) was 98%. The proposed methodology was applied to the treatment of the following samples: residue of experimental classes of Analytical Chemistry and analysis of chemical oxygen demand, generated at the university, and waste photographic material from local industries. The values obtained for the removal of Ag(I) were 92%, 82% and 91% respectively, using the non-shelled seeds of moringa as adsorbent. Also, it was studied the possible interference of other metals in proposed method, namely Cd(II), Co(II), Cu(II) e Pb(II). The value of the maximum adsorptive capacity for ions Ag(I) was 25.56 mg g-1 obtained through of the adsorption isotherm. Characterization techniques, including infrared spectrometry, X-ray diffraction, thermogravimetric analysis and scanning electron microscopy were used to assess physical and chemical proprieties of nonshelled seeds of moringa. The second chapter was presented a method for preconcentration of v ions using flow system and non-shelled seeds of Moringa oleifera Lam. as adsorbent material. The preconcentration system was coupled to FAAS. The following experimental conditions carried out: for 4 minutes leachate solution of Ag(I) 0.01 mg L-1, about of ground seeds of moringa packaged in a mini-column flow of. The elution was performed with of HNO3 0.5 mol L-1. The concentration factor was 35, resulting in detection limit of 0.22 μgL-1 e quantification limit of 0.73 μgL-1. Accuracy of the method was cheked by using certified reference material for water APS-1071 (Alpha Resources 3090 Johnson RD, Stevensville, USA). The proposed method has advantages such as low cost of sorbent, high efficiency and minimization of chemical sludge. The moringa is an alternative material for chemical remediation and is economically and environmentally friendly.