ORIGINAL PAPER Synthesis, characterization, and sorption properties of water-insoluble poly(2-acrylamido-2-methyl-1-propane sulfonic acid)–montmorillonite composite Bruno F. Urbano • Bernabe ´ L. Rivas Received: 25 October 2012 / Revised: 10 November 2012 / Accepted: 4 December 2012 / Published online: 18 December 2012 Ó Springer-Verlag Berlin Heidelberg 2012 Abstract The sorption properties of composites based on 2-acrylamido-2-methyl-1- propane sulfonic acid and montmorillonite are presented. Gel-type composites were obtained via in situ polymerization. Resin particles presented exfoliated morphologies, as suggested by X-ray diffraction. The addition of montmorillonite resulted in enhanced mechanical properties, as evaluated by Vickers microhardness tests. The swelling performances of the resins exhibited a fast initial water uptake, reaching the maximum absorption capacity after less of 1 h of contact. A batch procedure was used to evaluate the sorption characteristics of the composites, and the effects of pH, montmorillonite content, and time were studied. The composites showed high adsorption capacities at pH values of 3.0 and 5.0, and the addition of montmorillonite did not result in a significant enhancement of their adsorption capacity. The equilibrium adsorption performance can be described by the Langmuir isotherm, while kinetic experiments revealed an excellent agreement with the pseudo-second-order model. Keywords Composite  Montmorillonite  Adsorption  Mechanical properties  Kinetic Introduction Hydrophilic crosslinked polymeric matrices consist of water-insoluble polymers that, due to the hydrophilic nature of their functional groups, have the ability to swell. In addition, hydrophilic functional groups such as carboxylic acids, amides, amines, and others can interact with metal ions via coordinative or ionic interactions, allowing the use of these materials for water treatment. In the field of metal ion B. F. Urbano  B. L. Rivas (&) Department of Polymer, Faculty of Chemical Science, University of Concepcio ´n, Casilla 160-C, Concepcio ´n, Chile e-mail: brivas@udec.cl 123 Polym. Bull. (2013) 70:1143–1162 DOI 10.1007/s00289-012-0894-8