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Les résidus de transformation du bois tels les écorces et la sciure de bois ont été largement étudiés depuis quelques années pour leur propriété d'adsorption et d'enlèvement des métaux toxiques contenus dans les effluents contaminés. En ce qui concerne la sciure de bois, les recherches répertoriées ont porté principalement sur l'utilisation du sapin rouge, du manga, du tilleul, de l'épinette, du pin, du cèdre, du teck, de l'akamatsu et du buna. Pour ce qui est des écorces de bois, plusieurs espèces ont été étudiées, notamment les écorces de pin, de chêne et d'épinette. La présente revue fait le point sur les performances de ces différents adsorbants peu coûteux pour l'adsorption des principaux métaux contaminants (Cd, Cr, Cu, Hg, Ni, Pb et Zn). Les points discutés portent sur les méthodes de préparation (lavage, séchage et tamisage) et de traitement chimique de l'adsorbant (traitement acide ou basique, traitement à la formaldéhyde, phosphatation, carboxylation, sulfoéthylation, carboxyméthylation, etc.), les conditions opératoires utilisées lors de l'adsorption, les modèles thermodynamiques, cinétiques et autres applicables au couple adsorbant-adsorbat, l'effet des principaux paramètres opératoires (temps de contact, pH de traitement, température, concentration d'adsorbant, taille des particules, etc.), les principes et les mécanismes impliqués dans l'élimination des contaminants métalliques par les adsorbants présentés.Wood industry by-products such as barks and sawdusts have been widely studied in recent years for their property of metal adsorption and metal removal from contaminated effluents. Concerning the utilization of sawdusts, many researchers have studied metal adsorption on material from species such as red fir, mango, lime, pine, cedar, teak, Japanese red pine and Japanese beech. As regards wood barks, several species were studied, in particular pine, oak and spruce. The present review gives a progress report on the efficiency of these various inexpensive materials for the adsorption of different metals (Cd, Cr, Cu, Hg, Ni, Pb and Zn). The points discussed relate to the preparation methods (washing, drying, screening) and the chemical treatments of the adsorbents (acid or base treatment, formaldehyde treatment, phosphatation, carboxylation, sulfoethylation, carboxymethylation, etc.). We also consider the operating conditions used during adsorption, the thermodynamic, kinetic and other models applicable to the adsorbent-adsorbate couple, the effect of the operational parameters (time of contact, pH, temperature, adsorbent concentration, particle size, etc.), as well as the principles and mechanisms involved in metal removal by the adsorbents.The accumulation of organic or inorganic matter at the solid-liquid interface is the basis of almost all surface reactions. Adsorption is often a process described in terms of isotherms, which represent the relationship between the concentration of a solute in solution and the quantity adsorbed at the surface at constant temperature. The isotherms are often used to...

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AbstractBiosorbents, especially those derived from seaweed (macroscopic algae) and alginate derivatives, exhibit high affinity for many metal ions. Because biosorbents are widely abundant (usually biodegradable) and less expensive than industrial synthetic adsorbents, they hold great potential for the removal of toxic metals from industrial effluents. Various studies have demonstrated the efficiency of living and non-living micro-organisms, such as bacteria, yeasts, moulds, micro-algae, cyanobacteria and biomass from water treatment sewage to remove metals from solution. Several types of organic and inorganic biomass have also been used as sorbent materials. In addition, by-products from the forestry industry, as well as agriculture waste and natural sorbents, have also been studied. This paper reviews and summarizes some key recent developments in these areas and it describes and discusses some specific applications of selected natural sorbents.

The Canadian Nuclear Laboratories (CNL) is developing a long-term management strategy for its existing inventory of solid radioactive cemented wastes, which contain uranium, mercury, fission products, and a number of minor elements. The composition of the cemented radioactive waste poses significant impediments to the extraction and recovery of uranium using conventional technology. The goal of this research was to develop an innovative method for uranium, mercury and cesium recovery from surrogate radioactive cemented waste (SRCW). Leaching using sulfuric acid and saline media significantly improves the solubilization of the key elements from the SRCW. Increasing the NaCl concentration from 0.5 to 4 M increases the mercury solubilization from 82% to 96%. The sodium chloride forms a soluble mercury complex when mercury is present as HgO or metallic mercury but not with HgS that is found in 60 °C cured SRCW. Several leaching experiments were done using a sulfuric acid solution with KI to leach SRCW cured at 60 °C and/or aged for 30 months. Solubilization yields are above 97% for Cs and 98% for U and Hg. Leaching using sulfuric acid and KI improves the solubilization of Hg by oxidation of Hg0, as well as HgS, and form a mercury tetraiodide complex. Hg and Cs were selectively removed from the leachate prior to uranium recovery. It was found that U recovery from sulfuric leachate in iodide media using the resin Lewatit TP260 is very efficient. Considering these results, a process including effluent recirculation was applied. Improvements of solubilization due to the recycling of chemical reagents were observed during effluent recirculation.