Environmental Engineering and Management Journal November 2013, Vol.12, No. S11, Supplement, 3-6 http://omicron.ch.tuiasi.ro/EEMJ/ “Gheorghe Asachi” Technical University of Iasi, Romania WATER PURIFICATION FROM HUMIC ACIDS BY CLINOPTILOLITE-RICH TUFF Extended abstract Vincenzo Leone, Pasquale Iovino  , Silvana Canzano, Stefano Salvestrini, Sante Capasso Second University of Naples, Department of Environmental, Biological and Pharmaceutical Sciences and Technologies, Via Vivaldi, 43, 81100, Caserta, Italy Background Humic substances (HS) are natural polymers produced by biological decomposition of plants and other organisms (Abate and Masini, 2003) and accounting for 50–80% of natural organic matter in water, soil and sediment. HS are generally subdivided into humin, humic acids (HA) and fulvic acids (FA) based on their solubility under acidic or alkaline conditions in aqueous solution. Among numerous methods developed for HA removal from water, adsorption is the most promising approach. Adsorption by low-cost materials, either natural or by-products of industrial activity, has become the focus of intensive investigation (Leone et al., 2012). Previous work (Capasso et al., 2007a; Capasso et al., 2007b) has shown that the Neapolitan yellow tuff (NYT), a volcanic rock rich in phillipsite/chabazite zeolites, binds HA through the action of surface extra-framework exchangeable cations, whereas HA molecules are too big to enter the system of channels and cages of zeolite crystals. The binding ability is markedly enhanced when the zeolitic material is enriched with divalent cations, especially Ca 2+ , that act as micro- bridges between negative charges on the zeolite surface framework and HA carboxylic groups. Moreover, it has been shown that HA adsorption by natural zeolites is a relatively long-lasting process with kinetic curves characteristic of a two-stage adsorption process (Ambrosone et al., 2013; Capasso et al., 2007b). Here we report a study on the HA adsorption onto a clinoptilolite-rich tuff. The influence of calcium ions and particle sizes were analyzed. Objectives Adsorption of humic acids in water solution onto a clinoptilolite-rich tuff from New Mexico (USA) was investigated with the batch technique, with attention to the effects of adsorbent-bound Ca2+ and adsorbent particle size. Kinetic analysis showed that the adsorption process takes several days and follows a two-step pattern. In this study, two of the most established isotherm models were used for fitting the experimental data: the Langmuir and the Freundlich equation. Interestingly, the statistical parameters show that the Langmuir equation describes the experimental data more accurately for two of the three samples analyzed. The q m parameter did not change significantly with particle sizes and calcium concentration; the K parameter, which reflects energy interactions between the adsorbate and adsorbing sites, increased with calcium amount and decreased with particle size. The results point to the tuff investigated, a low-cost natural material, as a potentially useful adsorbent for water purification from humic acids. Methods 1. Clinoptilolite rich tuff (CCT) The clinoptilolite-rich tuff (CCT) used in the present investigation was extracted from a quarry in New Mexico (USA) and supplied by Coyote Cliff LLC Company. The mineralogical composition was determined by the company: clinoptilolite 89%, quartz 5% smectite <1%, feldspar <5%. The raw material was provided in two particle  Author to whom all correspondence should be addressed: e-mail: pasquale.iovino@unina2.it