Surface interaction of humic acids with natural and synthetic phillipsite A. Colella • B. de Gennaro • S. Salvestrini • C. Colella Published online: 24 February 2015 Ó Springer Science+Business Media New York 2015 Abstract Starting from previous encouraging results, pointing out the ability of natural zeolites to remove large, hydrophilic, organic molecules from water, this paper deals with the surface interactions between humic acids, a fre- quent contaminant of natural waters, and the zeolite phillipsite, with the aim to obtain valuable insights on the possible use of low-cost, natural phillipsite-rich materials in decontamination technology. Accordingly, an enriched sample of Neapolitan yellow tuff, containing ca. 70 % phillipsite, was compared with a synthetic phillipsite in both kinetic and equilibrium sorption experiments of humic acids from model waters. Tests, carried out at 25 °C, were performed on Ca 2? -pre-exchanged samples, which proved to be more effective in the sorption process. The results highlighted the marked affinity of phillipsite for the humic acids, better than any other zeolite tested previously, pointing out, moreover, that natural phillipsite behaves as a slightly diluted phillipsite, with no adverse effects from the mineral impurities present in the sample. Moreover, natural phillipsite performance, in both kinetic tests and in sorption capacity, was comparatively better than the synthetic counterpart, which was attributed to the presence of structural defects in the latter, due to the stressing condi- tions under which it had been obtained. Keywords Sorption  Humic acids  Zeolite  Natural phillipsite  Synthetic phillipsite 1 Introduction Most recent research on natural zeolites is being devoted to their possible application in the control of environmental pollution and in the remediation of polluted environments (air, water, soil) [1–3]. Actually, natural zeolites can op- erate as cation exchangers for water and soil decon- tamination and as adsorbents for air purification. In the latest years, however, research opened novel spaces to natural zeolites application in environmental fields. These minerals proved, in fact, to be able to remove from aqueous bodies large organic contaminant molecules and retain them on their extended, electrically charged, external surfaces. This capability can be used, for instance, to remove humic acids (HA) from water. Humic substances, originating from the decomposition of plants and animals, are the major organic constituents of soil. They have a very complex chemistry and structure, an undefined stoichio- metry and therefore a variable molecular weight. The dark brown fraction of humic substances having a lower mole- cular weight, from about 10 to 100 kDa, and a fair solu- bility in alkaline media, is usually referred to as HA [4]. Humic acids can be carriers for metals and organic contaminants in natural waters [5, 6]. Their presence in drinking water is therefore undesirable, not only for the unpleasant colour and taste that these substances impart, A. Colella (&) Dipartimento di Scienze della Terra, dell’Ambiente e delle Risorse, Universita ` Federico II, Via Mezzocannone 8, 80134 Naples, Italy e-mail: abner.colella@unina.it B. de Gennaro  C. Colella Dipartimento di Ingegneria Chimica, dei Materiali e della Produzione Industriale, Universita ` Federico II, Piazzale V. Tecchio 80, 80125 Naples, Italy S. Salvestrini Dipartimento di Scienze e Tecnologie Ambientali, Biologiche e Farmaceutiche, Seconda Universita ` di Napoli, Via Vivaldi 43, 81100 Caserta, Italy 123 J Porous Mater (2015) 22:501–509 DOI 10.1007/s10934-015-9920-1