Novel process to prepare magnetic metal-ceramic nanocomposites from zeolite precursor and their use as adsorbent of agrochemicals from water

Abstract

In this work the preparation of two samples of magnetic adsorbent from a zeolite precursor was described. This process implied NH4+ and Fe2+ exchange of zeolite A and its subsequent thermal treatment at temperature 600–800 °C, under a reducing atmosphere. These two magnetic adsorbents, composed of Fe/Fe3O4 nanoparticles embedded in an amorphous silica-alumina ceramic phase, were fully characterized by determining their chemical composition, quantitative phase analysis, surface area, SEM and TEM analysis, pH of zero potential and magnetic properties. In particular, their Fe content was 0.2 or 4.8%, Fe3O4content 5.4 or 7.1% and the average dimension of nanoparticles was 1.82 or 11.13 nm. Then, the removal of the agrochemical simazine from water was performed by using these two magnetic adsorbents. The investigated parameters were pH, time, solid/liquid ratio and initial simazine concentration. The pH of maximum simazine adsorption was 6.5 and 3.0 for the two adsorbents. At these pH values, simazine adsorption occurred rapidly and massively even from very dilute simazine solutions (simazine concentration of about 0.25 μmole/L).Finally, a process of simazine removal from waters based on repeated cycles of adsorbent addition to simazine bearing water, followed by its easy magnetic separation, is proposed. This process allows bringing the final agrochemical concentration well below 0.05 mg/L, the maximum agrochemical concentration allowed by Italian laws in wastewaters. Simazine bearing exhausted adsorbents are regenerated by a (no more than) 5 min thermal treatment at 300 °C, which results in the decomposition of simazine without damage of the adsorbent.