The use of pine bark as a natural adsorbent for persistent organic pollutants - study of lindane and heptachlor adsorption

Pine bark obtained as a sawmill by-product in the north of Portugal was used for the adsorption of lindane and heptachlor, two organochlorine pesticides classified as POPs (Persistent Organic Pollutants), from aqueous solutions. It is intended that this natural adsorbent be used as an alternative to activated carbon in an innovative approach for the removal of these classes of compounds, reducing significantly the regeneration costs of the process, thus providing for its intensification. The analytical methodology validated for pesticides' quantification consisted of solid-phase microextraction (SPME) prior to gas chromatography with electron capture detection (GC-ECD), which presented limits of detection for lindane and heptachlor of 0.067 mug dm(-3) and 0.062 mug dm(-3), respectively. Repeatability, reproducibility and recovery were the parameters tested for validation, yielding better results for lindane. For the bark particle size used (125-300 mum), the average efficiency of removal attained for lindane was 80.6%, and 93.6% for heptachlor with the equilibrium time set at 24 h. Both Langmuir and Freundlich models were tested for the adsorption isotherm, but only the second approach produced reliable results for the adsorption parameters. Values obtained for log K-ow were 3.17 for lindane (R-2 = 0.9927) and 4.85 for heptachlor (R-2 = 0.9401). (C) 2003 Society of Chemical Industry.