Thermodynamic parameters for the complexation of Tc(IV) with bromide under aqueous conditions

Technetium-99 is a long-lived fission product present in nuclear wastes, found mainly as Tc(VII) and Tc(IV) in the environment. The quantification of the equilibrium constants for the formation of Tc(IV) aqueous complexes has been limited to carboxylate ligands and interactions with the halides is mostly unknown. This work reports equilibrium constants of the formation of the TcO(OH)+ complexes with Br−, in a 3 M NaClO4 solution of pcH 2 and varied temperature, using a liquid-liquid extraction system. Neutron activation confirmed the suitability of the extraction technique for this work. Under the working conditions, Br− forms a weak exothermic TcO(OH)Br complex, with a Gibbs free energy (ΔGr) of 3 ± 3 kJ · mol−1 at a temperature of 273.15 K. The values for ΔHr (−32 ± 3 kJ · mol−1) and ΔSr (106 ± 9 J · mol−1 · K−1) of the complexation reaction were quantified using a van’t Hoff analysis. This work also showed that bromide addition does not displace the hydroxide from TcO(OH)+, as the equilibrium constant of bromide addition is much weaker than the first hydrolysis constant of the metal.

Spectrophotometric Determination of the First Hydrolysis Constant of Praseodymium (III)

The behavior of the trivalent ion praseodymium in 2M of NaCl at 303 K and in CO2 free conditions, was studied. Spectrophotometric titrations of the soluble species were used, in order to obtain the value of the first hydrolysis constant of Pr(III). The data obtained were treated with both the program SQUAD and by a graphic method, respectively. The result obtained using SQUAD was log*ß1 = –8.94 ± 0.03, while it was log*ß1 = –8.77 ± 0.03, when calculated graphically. These results are similar to the value obtained previously with the potentiometric method.

Modelling the fill rate of pit latrines in Ifakara, Tanzania

A model of the rate at which pit latrines fill was developed and compared with actual fill rates measured in latrines in Ifakara, Tanzania. Model parameters were derived primarily from data collected during the field study in Tanzania, with one fitted parameter. Although the model did not accurately simulate the fill rate of individual pits, it provided a good simulation of the average fill rate of the pits and aided the identification of pits that were performing poorly. Laboratory experiments conducted on samples of sludge from the pits were used to identify the average hydrolysis constant for biodegradation of the organic material. The average hydrolysis constant (0.046 day−1) was higher than that identified in another modelling study (0.0015 day−1), conducted in South Africa. The higher hydrolysis constant provided a simulation of the profile of volatile solids with lower root mean square error in 17/24 of the pits, however, for the other pits a lower hydrolysis constant was more appropriate. A sensitivity study of the model indicated that the pit fill rates were particularly sensitive to the parameter that quantified water accumulation in the pit, as such quantifying water flow through the pit is a priority for future research.

Kinetic Constants of Decomposition of the Municipal Solid Waste Prior to and after Mechanical-Biological Processing. Field Scale / Stałe Kinetyczne Rozkładu Zmieszanych Odpadów Komunalnych Przed I Po Mechaniczno-Biologicznym Przetworzeniu. Skala Polowa

One of the major tasks of municipal waste management in European Union countries is the systematic reduction of waste that is removed and transported to landfills. This refers particularly to biodegradable waste. One of the methods employed to decrease waste amount is Mechanical-Biological Treatment (MBT) of the waste, before it is stored. The article presents characteristics of MSW and biologically pre-treated municipal solid waste, organic carbon loads emitted in biogas and leachate during waste deposition in a landfill. Its decomposition rate constants were determined on the basis of modified Zacharof and Butler’s stochastic model. The values of decomposition rate constants determined for MSW had similar change trends to those presented in the literature: the hydrolysis constant had the lowest value (2.6 × 10-5 d-1), the highest acid phase constant (4.1 × 10-4 d-1), while the methane phase constant - 2.2 × 10-4 d-1. The PMSW decomposition rate constants in each anaerobic waste degradation phase had similar change trends, though their values were higher, by 21, 11 and 19%, respectively.