A adsorção dos corantes aniônicos alaranjado IV, alaranjado G e alaranjado de xilenol pela quitina foi estudada empregando a isoterma de Langmuir. Os parâmetros de adsorção foram determinados utilizando várias regressões lineares da isoterma. Os resultados revelaram que a capacidade de adsorção é dependente do pH. Em pH ácido, os grupos aminos do polímero estão protonados e a cadeia polimérica está carregada positivamente, predominando a adsorção por troca iônica. Deve ocorrer também em pequena extensão adsorção de van der Walls e por ligações de hidrogênio. Para o alaranjado de xilenol uma relação linear com coeficiente angular de 0,726 L mg -1 foi encontrada. O aumento da temperatura diminui a capacidade de adsorção pela quitina, devido ao aumento da etapa de desorção no mecanismo. Os valores de ∆H de -10,9 kJ mol -1 para o alaranjado G e -28,9 kJ mol -1 para o alaranjado IV comprovam uma adsorção de natureza física para estes corantes sobre a superfície da quitina.The adsorption of the anionic dyes orange IV, orange G and xylenol orange on chitin was studied, employing the Langmuir isotherm. The adsorption parameters were determined utilizing various linear regressions of the isotherm. The results showed that the adsorption capacity is dependent on pH. In acid pH, the polymer amino groups are protonated and the polymer chain is positively charged, with a predominance of adsorption through ion exchange. Van der Waals adsorption, as well as adsorption through hydrogen bonding, is also likely to occur to some extent. For xylenol orange, a linear regression was found, with an angular coefficient of 0.726 L mg -1 . The temperature increase reduces adsorption capacity by chitin, due to the enhancement of the desorption step in the mechanism. ∆H values of -10.9 kJ mol -1 for orange G and -28.9 kJ mol -1 for orange IV prove the physical nature of the adsorption by these dyes on the chitin surface.

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Recebido em 27/1/09; aceito em 13/3/09; publicado na web em 2/4/09 CHITOSAN: FUNCTIONAL BYOPOLYMER WITH BIOMEDICAL INDUSTRIAL POTENTIAL. The importance of chitosan has grown significantly over the last two decades due to its renewable and biodegradable source, and also because of the recent increase in the knowledge of its functionality in the technological and biomedical applications. The present article reviews the biopolymer chitosan and its derivatives as versatile biomaterials for potential drug delivery systems, as well as tissue engineering applications, analgesia and treatment of arthritis.

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Recebido em 18/2/99; aceito em 27/1/00Calcium phosphate compounds such as Hydroxyapatite (HAp) were prepared by hydrothermal synthesis with phycogenic CaCO 3 as starting material. Material obtained was characterised by usual methods (XRD, FTIR, TG, N 2 -adsorption, SEM and EDX) in order to study its physical-chemical characteristics. The prepared HAp showed that it may be suitable for use as a biomaterial.

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