A Study of the Adsorption of Acrylic Acid and Maleic Acid from Aqueous Solutions onto Alumina

✍ Scribed by Ying Mao; B.M. Fung

• Publisher: Elsevier Science
• Year: 1997
• Tongue: English
• Weight: 113 KB
• Volume: 191
• Category: Article
• ISSN: 0021-9797
• DOI: 10.1006/jcis.1997.4954

✦ Synopsis

where C i is the initial concentration of the adsorbate in solu-The adsorption of acrylic acid and maleic acid on alumina was tion before adsorption, V is the volume of the solution, and studied, and it has been found that the adsorption obeys the Lang-W is the weight of the adsorbent. Adsorption isotherms demuir isotherm. The adsorption of the acids is dependent on the pend on the specific surface area and the surface chemistry pH of the solutions. For acrylic acid, the optimal pH is 4.5; for of solid adsorbents, the nature of adsorbates, and the pH of maleic acid, the optimal pH is 1.1-1.6. These pH values are close the medium (1, 2).

to the pK a for acrylic acid and pK a 1 for maleic acid, respectively.

For amphoteric oxides such as alumina (3), the property

The maximum amount of each acid adsorbed at its optimal pH of the surface is very dependent on pH (3, 4). The pH value was obtained by fitting the adsorption data to the Langmuir isoat which the surface charge is zero is called the zero point therm, and the values are 727 mmol/g for acrylic acid and 525 mmol/g for maleic acid. These values are consistent with mono-of charge (ZPC). The ZPC of a-alumina is 9.1 { 0.1 (5), layer adsorption. Solid state 13 C NMR was used to investigate the and that of other forms of alumina varies between 7 and 9 nature of the adsorption. It is suggested that the adsorbed carbox-(4). Therefore, the surface is positively charged in an acid ylic acids are present in the undissociated form. ᭧ 1997 Academic Press medium (pH õ ZPC) and negatively charged in a basic