EQUILIBRIUM OF LEAD (II) BIOSORPTION AND CHARACTERIZATION THROUGH FT-IR AND SEM-EDAX ON Ascophyllum nodosum SEAWEED

Abstract

Lead (II) biosorption on Ascophyllum nodosum seaweed at 20°C and initial pH 4-5 was
studied, by using models of Langmuir and Freundlich isotherms. In order to establish
seaweed, CaCl2 was used. The granulometry used in the biosorbent was 0-75 μm. In Fourier

transform infrared spectroscopy, FT-IR, a shift in the signal of carbonyl group of crosslinked
sample before metal biosorption and after (1600.92 cm-1 to 1573.91 cm-1) and 1400 cm-1 (that
was from 1415.75 cm-1 to 1409.96 cm-1) was observed, suggesting a chelating (bidentate)
character of the metal biosorption onto carboxylic groups that belongs to the units of alginate
monomeric. The bands at 3305.99 cm-1 allowed the recognition of hydroxyl groups in the
biosorbent. The scanning electronic microscopy, SEM, verified heterogeneity of biosorbent
particles. In the energy-dispersive X-ray spectroscopy, EDAX, a very strong signal in the
carbon and another less strong for the oxygen characteristic of the biopolymer were observed.
The signal of calcium could be recognized in EDAX spectra of the sample after pre-treated.
The two peaks that correspond to lead element were observed in the sample after biosorption
process. Experimental data of biosorption equilibrium had greater correlation coefficient to
Langmuir isotherm model, reaching the maximum sorption capacity, qmax, of 228 mg/g. Lead
(II) residual concentration, Ceq, in the solutions after getting equilibrium, was determined
after 72h starting the process by atomic absorption spectroscopy. For data processing and
statistic treatment, Origin 6.0 informatics program was used.