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Cerium dioxide was used for the first time as reactive sorbent for the degradation of the organophosphate pesticides parathion methyl, chlorpyrifos, dichlofenthion, fenchlorphos, and prothiofos, as well as of some chemical warfare agents-nerve gases soman and O -ethyl S -[2-(diisopropylamino) ethyl] methylphosphonothioate (VX). CeO 2 specimens were prepared by calcination of basic cerous carbonate obtained by precipitation from an aqueous solution. The CeO 2 samples containing certain amounts (1 wt.%-5 wt.%) of the neighboring lanthanides (La, Pr, Nd) were prepared in a similar way from pure lanthanide salts. It was shown that ceria accelerated markedly the decomposition of parathion methyl causing the cleavage of the P-O-aryl bond in the pesticide molecule. A similar reaction mechanism was proposed for the degradation of other organophosphate pesticides and nerve agents. The degradation times (reaction half-times) were in an order of minutes in the presence of CeO 2 , compared to hours or days under common environmental conditions. The reaction in suitable organic solvents allowed conversions of about 90% for parathion methyl loading of 20 mg pesticide/g CeO 2 within 2 h with a reactant half-life in the order of 0.1 min. The key parameter governing the degradation efficiency of CeO 2 was the temperature during calcination. At optimum calcination temperature (about 773.15 K), the produced ceria retained a sufficiently high surface area, and attained an optimum degree of crystallinity (related to a number of crystal defects, and thus potential reactive sites). The presence of other lanthanides somewhat decreased the reaction rate, but this effect was not detrimental and permitted the possible use of chemically impure ceria as a reactive sorbent. A fast organophosphate degradation was demonstrated not only in non-polar solvents (such as heptane), but also in polar aprotic solvents (acetonitrile, acetone) that are miscible with water. This opens new possibilities for designing more versatile decontamination strategies. The cleavage of phosphate ester bonds is of a great importance not only for the degradation of dangerous chemicals (chemical weapons, pesticides), but also for interactions of ceria (especially the nano-sized one) in biologically relevant systems.

Naturally occurring kind of weathered and oxidized young brown coal called oxihumolite was used for an adsorptive removal of heavy metal cations (Cd 2+ , Cu 2+ , Co 2+ , Ni 2+ , Pb 2+ , Zn 2+ ) from waters. A working range for the oxihumolite as a sorbent is in a slightly acidic medium (pH ca. 3.5–4.5), where it exhibits a sufficient stability and sorption capability. Typical sorption capacities estimated from equilibrium measurements (sorption isotherms) ranged from ca. 0.1 to 0.4 mmol g −1 . The kinetic dependencies for the metal sorption were measured in a batch arrangement and evaluated using both pseudo-first- and pseudo-second-order kinetic models. The metal sorption was a quite rapid process that may be characterized by half-times ranging from ca. 10 to 80 min. The intraparticle diffusion was identified as the main mechanism controlling the rate of the sorption. Various extraction tests, namely the standardized leaching test with water and the three-step sequential BCR test, were used to examine a leachability of the heavy metals from the loaded sorbents and to assess potential risks of their subsequent liberation into the environment. Certain differences in the sorption and extraction behaviours of the examined metal ions (e.g. a high sorption capacity and low leachability of Pb 2+ ) can be related to the well-known “selectivity sequences” (or stabilities of the metal–humate complexes) as published in literature.

Spruce wood shavings from Picea abies were used for an adsorptive removal of both basic as well as acid dyes from waters. The sorption properties of the sorbents were modified with HCl, Na(2)CO(3) and Na(2)HPO(4). The treatment of the wood sorbents with alkaline carbonate solution as well as with phosphate solution increased the sorption ability for the basic dye (Methylene Blue), whereas the treatment with mineral acid decreased the sorption ability for Methylene Blue to some extent. The opposite is true for the sorption of the acid dye--Egacid Orange. The maximum sorption capacities estimated from the Langmuir-Freundlich isotherms ranged from 0.060 to 0.165 mmol g(-1) for Methylene Blue, and from 0.045 to 0.513 mmol g(-1) for Egacid Orange. The basic dye sorption decreased at low pH values in accordance with a presupposed ion-exchange mechanism of the sorption. The sorption of acid dye, on the other hand, decreased with increasing pH. The presence of inorganic salts as well as surfactants exhibited only minor effects on the dye sorption.