Analysis of Metal Cations and Inorganic Anions in Olive Oil Mill Waste Waters by Atomic Absorption Spectroscopy and Ion Chromatography. Detection of Metals Bound Mainly to the Organic Polymeric Fraction

Abstract

Metal cations were quantitatively detected by atomic absorption spectrometry in samples of olive oil mill waste waters obtained by a pressure process (omww(1)) (K, 17.1; Mg, 2.72; Ca, 2.24; Na, 0.40; Fe, 0.123; Zn, 0.0630; Mn, 0.0147; Cu, 0.00860 g L(-)(1)) and a centrifugation process (omww(2)) (K, 9.80; Mg, 1.65; Ca, 1.35; Na, 0. 162; Fe, 0.0330; Zn, 0.0301; Mn, 0.00910; Cu, 0.00980 g L(-)(1)). The inorganic anions, determined in the same samples by ion chromatography, proved to be Cl(-), H(2)PO(4)(-), F(-), SO(4)(2)(-), and NO(3)(-) (1.61, 1.05, 0.66, 0.52, and 0.023 g L(-)(1), respectively, in omww(1) and 0.61, 0.40, 0.25, 0.20, and 0.0090 g L(-)(1), respectively, in omww(2)). Most of the metal cations were revealed to be bound to the omww organic polymeric fraction (opf), composed of polysaccharides, phenol polymers, and proteins. Opf relative molecular weight was substantially estimated in the range between 1000 and 30000 Da for approximately 75% and in the range from 30000 to 100000 Da for approximately 25%. The free residual cations pool proved to be neutralized by the inorganic counteranions. Finally, the possible exploitation of this material in agriculture and in environmental biotechnology processes is also discussed in the light of its chemical and biochemical oxygen demand parameters.