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Abstract: Calibration of kinetic models of wet air oxidation (WAO) is usually performed through minimisation algorithms with respect to total organic carbon (TOC) experimental data. However, the reliability of the estimated value of the kinetic parameters is frequently not reported. Moreover, the influence of data quantity/quality in the kinetic parameters identifiability is not properly assessed. The objective of this study is to compare the calibration goodness of a proposed kinetic model when using one set of data (total effluent TOC [TOCeff]) or two sets of independent experimental measurements (total effluent TOC [TOCeff] and residual TOC of target pollutant [TOC[A]]). The systematic comparison was made using identifiability analysis with contour plots of both objective functions and the confidence intervals were calculated through the Fisher information matrix (FIM). The experimental data used in this study comes from a previous one, where WAO was investigated as a suitable precursor for the biological treatment of industrial wastewater containing high concentrations of o-cresol or 2-chlorophenol [M.E. Suárez-Ojeda, J. Carrera, I.S. Metcalfe, J. Font, Wet air oxidation (WAO) as a precursor to biological treatment of substituted phenols: refractory nature of the WAO intermediates, Chem. Eng. J. 144 (2008) 205–212.]. The results show that the model correctly fitted the experimental [TOCeff] in all cases with less than 6% as averaged relative deviation, either using one set of data ([TOCeff]) or two sets of independent experimental measures ([TOCeff] and [TOC[A]]) in the objective function. However, when using only [TOCeff], the model was not capable of fitting the proportion between [TOC[A]] and intermediates TOC. The obtained E ACT for the calibration made with [TOCeff] and [TOC[A]] were 71±20kJmol−1 (R 2 =0.92) and 47±9kJmol−1 (R 2 =0.96) for o-cresol and 2-chlorophenol, respectively. However, when using just [TOCeff], the obtained E ACT values were not in the range of the values reported in the literature and had smaller regression coefficients. Moreover, the calibration with just [TOCeff] presented a high correlation between the obtained rate constants, whereas the calibration with [TOCeff] and [TOC[A]] was statistically more reliable. As example, the D-criterion values are three to six times larger for the calibration made with ([TOCeff] and [TOC[A]] than for the calibration made only with [TOCeff], in the framework of OED/PE criteria, this is related to minimisation of the geometric mean of the identification errors. [Copyright &y& Elsevier]

Abstract: Wet air oxidation (WAO) was investigated as a suitable precursor for the biological treatment of industrial wastewaters that contained high concentrations of phenol, o-cresol or 2-chlorophenol. Two hours WAO semi-batch experiments were conducted at 2 and 9bar of oxygen partial pressure () and at 215, 240 and 265°C with total organic carbon (TOC) abatement up to 86%. The influence of hydroxyl-, methyl- and chloride ring substitution on the oxidation mechanism of aromatic compounds was established. Also, the readily biodegradable COD fraction (%CODRB) of the WAO effluents was found by respirometric techniques. The maximum %CODRB was 24% for phenol WAO at 265°C and 9bar of , 10% for o-cresol WAO at 265°C and 9bar of and 19% for 2-chlorophenol WAO at 215°C and 2bar of . These results allow comparison of whether or not the WAO effluents were suitable for a conventional activated sludge plant with non-acclimated biomass. Also, the results were compared to those obtained from a previous study for the same model compounds but using catalytic WAO (CWAO) with activated carbon (AC) as a catalyst [1]. This comparison allows us to establish whether or not the WAO effluents were less biodegradable or had more refractory intermediates than CWAO effluents. [Copyright &y& Elsevier]

[Display omitted] • Chemical looping allows for H 2 production with inherent carbon separation. • It can achieve 95% conversion of H 2 O at 1073 K outperforming a WGS reactor. • A numerical model with no fitted parameters can simulate a working reactor. • This was confirmed using operando gas and solid oxygen capacity measurements. • This system is thermodynamically limited. H 2 is an important feedstock for many industrial processes and could be used as an energy carrier in a low carbon economy. This means that carbon neutral methods for H 2 production are of vital importance. Chemical looping allows for H 2 production with inherent carbon separation, making it an ideal system to produce low carbon H 2. This work generates insights into the production of high purity H 2 using a chemical looping packed bed reactor system containing an oxygen carrier of variable oxygen non-stoichiometry. Such a system has been shown to achieve 95% conversion of H 2 O to H 2 at 1073 K outperforming the maximum theoretical conversions of 50% achieved by a conventional water gas shift reactor at that temperature. A numerical model was developed from theoretical consideration, with no fitted parameters and used to simulate the working reactor. Operando measurement of gas conversions and changes in solid oxygen capacity, through synchrotron X-ray diffraction, were used to validate the numerical model and confirmed that the reaction was thermodynamically limited. The model the model was shown to reproduce the conversion of the oxygen carrier, the reactant conversion and the product evolution. Sensitivity analysis showed that the relationship between the oxygen carrier material oxygen content and the chemical potential of oxygen in the carrier was the key consideration for the design and operation of a packed bed chemical looping reactor using an oxygen carrier of variable non-stoichiometry. [ABSTRACT FROM AUTHOR]