Metal extractants of 2-hydroxyphenyldiazole compounds according to Formula :and tautomers and salts thereof, are disclosed, wherein substituents R5, R7, R9, and R10 are as defined herein. The method may include implanting carbon below the screen layer and forming a thin layer of in-situ epitaxial carbon doped silicon above the screen layer. The temperature of the aromatic saturation process can be controlled to make a distillate product having a desired aromatic content, such as less the 0.