1. Technology Center, Federal Univ. of Alagoas, Avenida Lourival Melo Mota, s/n, Cidade Universitária, CEP 57072, Maceió, Alagoas, Brazil (corresponding author).
2. Dept. of Chemical Engineering, Federal Univ. of São Carlos, Rodovia Washington Luís, Km 235, CEP 13565, São Carlos, São Paulo, Brazil.