Environ Chem Lett (2004) 2:1–4 DOI 10.1007/s10311-003-0057-0 ORIGINAL PAPER Michele Aresta · Angela Dibenedetto · Carlo Fragale · Tiziano Pastore High-energy milling to decontaminate soils polluted by polychlorobiphenyls and atrazine Received: 11 July 2003 / Accepted: 5 December 2003 / Published online: 31 March 2004 # Springer-Verlag 2004 Abstract Mechanical energy has been used so far for running chemical reactions and for preparing new mate- rials in absence of solvents. Very recently, the technology has been applied to solve environmental problems. In this paper, we describe the application of high-energy mill- ing (HEM) for the remediation of soils contaminated by chlorinated organic compounds such as polychloro- biphenyls (PCBs) and agrochemicals like atrazine. NaBH 4 and LiAlH 4 have been successfully used for the total dehydrohalogenation of both classes of compounds, leav- ing a residue lower than 2 ppmw of the starting compound in the treated soil. LiAlH 4 was found to be more active than NaBH 4 . Keywords High energy milling · Polychlorobiphenyls · Agrochemicals · Solid state dechlorination · Ternary hydrides Introduction The theoretical basis of high energy milling (HEM) was described by Heinicke in 1984. The mechanical energy transferred to particles during the collision with milling bodies such as spheres and rings causes their deformation, fracture, and welding. As a consequence, reactions be- tween solids occur at an average temperature close to room temperature. It is not well known whether the re- acting particles are in the solid or liquid state during the collision. Indeed, the increase of the temperature, the ac- tion of pressure, and also a particular ratio of the reagents, may generate a mixture that has a lower melting temper- ature than the starting individual species. Theoretical studies have been carried out in order to forecast the be- haviour of the reactive system. Nevertheless, several is- sues still need deeper investigation in order to throw light on the scientific basis of the technology and master its use. Mechanochemistry has been used for many practical applications for a long time (Benjamin 1970) and has also found an industrial utilisation more than thirty years ago (Benjamin and Volin 1974). The most recent application of high-energy milling has been found in the field of treatment of contaminated soils. Only few recent reports can be found in the literature (Cocco et al 1999) that show the usefulness of the technology for soil decontamination. We have developed a specific application of high-energy milling for the dehalogenation of chlorinated organics and especially polychlorobiphenyls, which are ubiquitous pollutants (Hutzinger 1974; Lang 1992) recalcitrant to most bacteria and difficult to convert into less noxious species by using simple chemical processes. We describe here the application of high-energy mill- ing for the dehalogenation of polychlorobiphenyls (PCBs) present in landfill soils and for the treatment of farm-soils contaminated with atrazine. We show that ternary hy- drides are able to depollute the soil by converting PCBs into biphenyl, which could be further biodegraded, or other halogenated compounds into their hydrogen-form. Solid hydrides like NaBH 4 or LiAlH 4 were singularly mixed with a sample of soil and different weight ratios were tested. The efficiency of abatement varied with the hydride used, reaching 99.99% under the best operative conditions. Experimental Reagents Here we report the results of a laboratory-scale experi- ment using a bench ring-mill to test NaBH 4 or LiAlH 4 as M. Aresta ( ) ) · A. Dibenedetto · C. Fragale METEA Research Centre, University of Bari, Via Celso Ulpiani 27, 70126 Bari, Italy e-mail: aresta@metea.uniba.it Tel.: +39 080 5442430 Fax: +39 080 544 2429 T. Pastore INCA, Unit of Bari, METEA Research Centre, University of Bari, Via Celso Ulpinai 27, 70126 Bari, Italy