Sorption-desorption studies on alumina pretreated with acids: I. The anionic dye orange II

• Published in: Surface technology 1985, Vol.26 (4), p.295-314
• Main Authors: Jain, V.K., Mundhara, G.L., K. Mishra, Ramesh, Tiwari, J.S.
• Format: Article
• Language: English
• Subjects: Chemistry; Exact sciences and technology; General and physical chemistry; Solid-liquid interface; Surface physical chemistry
• ISSN: 0376-4583
• DOI: 10.1016/0376-4583(85)90094-9

Brockmann alumina was subjected to chemical pretreatment with HNO 3, H 2 SO 4 and H 3 PO 4 of various concentrations, and samples of surface phase pH 3.5 − 8.5 ( HNO 3 Al 2 O 3( n), H 2 SO 4-treated Al 2 O 3( s)) and pH 4.0 − 8.0 ( H 3 PO 4-treated Al 2 O 3( p)) were prepared. Sorption-desorption behaviour of the anionic dye Orange II (C.I.15510) with change in pH on these substrates was studied. Quantitative sorption is shown at pH ⩽ 4.0 ( Al 2 O 3( n)), and a maximum is observed at pH 5.0 ( Al 2 O 3( s)) and pH 3.0 ( Al 2 O 3( p)). Variation in the amount of sorption with time (10 min – 72 h), temperature (30 – 60 °C) and regeneration of the substrates with aqueous inorganic electrolytes is also reported. Desorption efficacy of the anions is in the order PO 4 3− > SO 4 2− > NO 3 −. The acid treatment, and hence the specifically adsorbed anions ( NO 3 −, SO 4 2−, PO 4 3−), appears to lower the isoelectric pH of alumina (pH 8.0). The results show the involvement of anion-exchange properties of the alumina.