Highly efficient in situ oxidization of metal ions in porous media with high power laser

Metal ions in ground are hard to remove and constitute a serious environmental challenge. This paper reports a new laser-based method for in situ soil decontamination at high efficiency, in which a focused CO2 laser is used to oxidize metal contaminants from soil and fuse them with silica (base materials of soil), thus preventing undesired transport of metal ions within soil. Three types of metal ions (copper, nickel, and cadmium) adsorbed on porous silica plates are exposed to continuous laser irradiation. The lithographic mode of operation allows the accurate quantitation of laser effects. The effects of power, speed, frequency, and energy consumption on the efficiency of oxidation have been examined with high accuracy. The affected area increases with increases in laser power and decreases in scan speed and frequency. This method is promising for large scale in situ soil recovery due to high efficient oxidation of metal ions by high power laser.