{"content":[{"text":"the reduction of chromium (VI) to chromium (III) by the bacterium A. viscosus with adsorption of the \n dye and chromium in a zeolite.","bbox":{"left":0.142955,"top":0.116012,"width":0.7377940000000001,"height":0.030080999999999997}},{"text":"MATERIALS AND METHODS","bbox":{"left":0.142955,"top":0.170661,"width":0.22751899999999997,"height":0.01629}},{"text":"Dye \n Dye solutions were prepared with Azure B purchased from Aldrich (CAS Number 531-55-5). \n Aqueous solutions were prepared according to the experiments in concentrations between 1.5- \n 2500 mg/L.","bbox":{"left":0.142955,"top":0.198027,"width":0.737854,"height":0.05738700000000002}},{"text":"Metal \n Chromium solutions were prepared by diluting K2Cr2O7 (Riedel-de Haen) in distillated water.","bbox":{"left":0.142955,"top":0.266299,"width":0.682002,"height":0.030638999999999972}},{"text":"Zeolite \n NaY zeolite (relationship Si/Al 2.83, BET area 700 m2/g) was used as support. Prior to use, the \n faujasite zeolite NaY (Zeolyst International) was pre-treated by calcination at 500 ºC during 8 h \n under a dry air stream.","bbox":{"left":0.142955,"top":0.307348,"width":0.737687,"height":0.057281000000000026}},{"text":"Microorganism \n A. viscosus was obtained from the Spanish Type Culture Collection of the University of Valencia. A \n medium with 10 g/L of glucose, 5 g/L of peptone, 3 g/L of malt extract and 3 g/L of yeast extract \n was used for growth and maintenance of the microorganism.","bbox":{"left":0.142955,"top":0.375657,"width":0.738156,"height":0.05724400000000002}},{"text":"Dye batch adsorption \n Erlenmeyer flasks (250 mL) containing 1 g of zeolite in 150 mL of different Azure B solutions were \n employed. Isotherm studies were made with concentration solutions of Azure B between 1.5-2500 \n mg/L. Kinetic studies were made at a concentration of 10 mg/L for 15 minutes. \n To study the effect of pH on dye removal, pH values range from 2 to 7.5. The solution pH was \n regularly maintained at the desired value using H2SO4 or NaOH (0.1 M) solutions. \n All the experiments were performed in a rotary shaker at 150 rpm and 28ºC.","bbox":{"left":0.142955,"top":0.443929,"width":0.7379170000000002,"height":0.09829399999999999}},{"text":"Batch biosorption \n A. viscosus biofilm formation was prepared according to Quintelas and Tavares [3]. Bacterium was \n harvested during the exponential phase of the growth curve. The experiments were performed with \n 250 mL Erlenmeyer flasks containing 1 g of zeolite covered with biofilm (bacterium concentration 5 \n g/L) and 150 mL of the different solutions mixture of dye and chromium at concentrations: 100 \n mg/L chromium with 100, 150, 300, 450, 600 mg/L of dye. All biosorption experiments were \n performed in a rotary shaker at 150 rpm, temperature 28ºC. \n Samples of 1 mL were taken, centrifuged and analysed for dye and chromium determination. \n These experiments were performed twice, being the experimental error margin below 3%.","bbox":{"left":0.142955,"top":0.553132,"width":0.7381610000000001,"height":0.1256600000000001}},{"text":"Azure B determination \n The dye content was measured spectrophotometrically (T60 UV Visible, PG Instruments) in the \n supernatant based on the constructed calibration curves at maximum absorption wavelength (648 \n nm). The sample was diluted with distilled water if the absorbance exceeded the range of \n calibration curve.","bbox":{"left":0.142955,"top":0.689819,"width":0.737763,"height":0.0709280000000001}},{"text":"Chromium determination \n Hexavalent chromium was quantified by measuring absorbance at 540 nm of the purple complex of \n chromium (VI) with 1,5-diphenylcarbazide in acidic solution (T60 UV Visible, PG Instruments). For \n total chromium determination, the chromium (III) was first oxidized to chromium (VI) at high \n temperature by the addition of an excess of potassium permanganate previous to the reaction with \n 1,5-diphenylcarbazide. The chromium (III) concentration was calculated by the difference between \n the total chromium and chromium (VI) concentration.","bbox":{"left":0.142955,"top":0.771811,"width":0.737563,"height":0.09829299999999996}},{"text":"Azure B and chromium adsorption uptake and removal percentages","bbox":{"left":0.142955,"top":0.880985,"width":0.540796,"height":0.016290000000000027}}],"images_bbox":[],"images_bbox_not_text_overlap":[]}