Chars were generated by pyrolyzing pine wood at temperatures between 300 °C and 700 °C for 6 h and at 500 °C for 10–300 min. Their organic content and surface acidity decreased, and BET surface area increased, with increasing pyrolytic temperature and time. The uptake of benzene and nitrobenzene increased with increasing pyrolytic temperature and time with isotherms characterized by a transition from less to more concave-downward. The isotherms with low-temperature and short-time chars were fitted to the dual Langmuir-partition model, whereas those with high-temperature chars to the dual-Langmuir model. Calculations suggest that the organic phases of chars functioned as partition media and the uptake of benzene and nitrobenzene on carbonized chars occurred first in micropores via pore-filling and later in larger pores through capillary condensation and adsorption. It is concluded that chars may be considered to consist of the partition domain, the high-energy micropores domain and the low-energy large pores domain. Pine chars consist of the partition domain, the micropores domain and the large pores domain in terms of organic contaminant uptake.

Introduction The pyrolytic method was employed to recycle metals and brominated compounds blended into printed circuit boards (PCBs). Methods PCBs were crushed into pieces 4.0-4.8 mm in size, and the crushed pieces were pyrolyzed at temperatures ranging from 200 to 500°C. The compositions of pyrolytic residues, liquid products, and exhaust were analyzed by inductively coupled plasma atomic emission spectrometer, inductively coupled plasma mass spectrometry, and gas chromatography-mass spectrometry. Pyrolytic exhaust was collected by an impinger system in an ice bath cooler to analyze the composition fraction of the liquid product, and uncondensable exhaust was collected for gas constituent analysis. Results Phenol, methyl-phenol, and bromo-phenol were attributed mainly to the liquid product. Metal content was low in the liquid product. In addition, CO, CO₂, CH₄, and H₂ were the major components of pyrolytic exhaust. Conclusions Brominated and chlorinated compounds—i.e., dichloromethane, trans-1,2 dichloroethylene, cis-1,2 dichloroethylene, 1,1,1-trichloroethane, tetrachloromethane, bromophenol, and bromoform—could be high, up to the several parts per million (ppm) level. Low molecular weight volatile organic compounds (VOCs)—i.e., methanol, acetone, ethyl acetate, acrylonitrile, 1-butene, propene, propane, and n-butane—contributed a large fraction of VOCs. The concentrations of toluene, benzene, xylene, ethylbenzene, and styrene were in the ppm range.