Properties of non-regenerable bio-adsorbent (NRBA) for waste water treatment associated with energy recovery

One-step pyrolysis process in a "retort" reactor, using agricultural byproducts or fallow land growing permitted elaboration of Non-Regenerable Bio-Adsorbent (NRBA).Correlation between specific area and adsorption capacity on various samples of raw materials (Eucalyptus, triticale straws, Miscanthus, poplar, ...) are studied. First we observed that Eucalyptus-based NRBA have a greater specific area and better adsorption capacity than the others. Then, the competitive adsorption of several carboxylic acids has been studied. Two linear acids and two ramified acids were used for this study. Linear acids presented a better adsorption than the ramified acids. We also noted that the number of carbon in the acid molecules is a significant parameter for adsorption performance. So we tried to define three ratios: the linear hydrophobicity ratio (LHR), the ram ified hydrophobicity ratio (RHR) and the selectivity ratio (SR). Competitive adsorption of four linear carboxylic acids have been also measured, and the importance of the molecular chain length on the adsorptive capacity was observed. It is established that adsorption capacity is a function of the acid length and consequently of the pollutant solubility. We observe the importance of the molecule length and aspect (linear or ramified) for the adsorption selectivity. (Résumé d'auteur