Comparing a modified low-value clay with commercial samples to remove pesticides from water

Clays, as natural materials or after diverse chemical modifications, have been widely studied in the last decades as possible adsorbents to remove pesticides or other organic contaminants from water1,2. The contamination of water, besides its scarcity, is encouraging research in water purification technologies. Rural environments suffer especially from water contamination because intensive crop management has increased the pesticide use, which then contaminate the surface and ground waters. Also, the after-crop processing industries produce waste water containing pesticides. This is a very serious concern in a region where a monoculture is established, as in Andalusia and many regions of the Mediterranean countries where hundreds of thousands of olives orchard are set up, causing contamination in their water bodies. These rural environments need the development of low-cost water purification technologies for small villages, scattered farmer houses or even small agro-industrial installations. This is the final target of our research, to look for low cost adsorbents to be used in filter systems for medium and small scale enterprises to remove pesticides from water. Several commercial clays (Cloisites and Bentonites SD, >95% smectite content) were assayed together with a local clay sample of low value because of its low 30%) smectitecontent (CTI from Bailen, Jaen, Spain), which was increased up to 60% after carbonate removing (CTIwc). The CTIwc sample was saturated in Fe3+, hexadecyltrimethylammonium (CTI-Fe3+ and CTI-HDTMA) and the polymer chitosan (CTI-CH4 and CTICH6). The clays assayed and their organic elemental analyses are summarized in TB1. The modified CTI clay was subjected to a granulation process with a natural polymer (carboxymehyl cellulose and wax) in order to get water resistance. The pesticides were selected as having a representative diverse chemical character as shown in TB2. The water was artificially contaminated with 1ppm of each compound and the adsorption measured using 20mg of clay in 8ml of water. The pesticides were analyzed by HPLC with diode-array detection.Grants P11-07400 and AGR-264 by Junta de Andalucía, Contract RECUPERA2020 MINECO CSIC and Grant AGL2011- 23779 by MINECO, all of them cofinanced with EU FEDER-FSE funds.Peer Reviewe