Regeneration of activated carbon by fenton and photofenton oxidation for the treatment of phenol wastewater

Advanced Oxidation Processes have emerged as promising technologies for the recovery of carbons saturated with aromatic molecules, owing to their potency to degrade a wide range of organic pollutants by the generation of very reactive and non selective free hydroxyl radicals. The purpose of this work is to study the adsorption of phenol on activated carbons (ACs) and the consecutive in-situ regeneration of carbon by Fenton oxidation. Two different processes have been carried out: - the first one is based on a complete batch system in order to investigate the influence of Fe2+ and H2O2 concentrations; - the second one consists in a continuous fixed bed adsorption, followed by a batch circulation of the Fenton’s reagent through the saturated AC bed, to examine the efficiency of the real process. Two different activated carbons have been also studied: a both micro- and mesoporous AC (L27) and an only microporous one (S23). In the batch reactor containing a 1 g/L phenol solution, the optimal conditions found for pollutant mineralization in the homogeneous Fenton system (Fe2+ = 10 mmol/L, [H2O2] = 1000 mmol/L, corresponding to 6.5 times the stoechiometric amount for complete mineralization) are not the best for AC regeneration: a continuous reduction of adsorption capacity of L27 from 100% to 23% is observed after 3 oxidations, due to the decrease of both AC weight and surface area. Higher concentration of Fe2+ (20 mmol/L) and lower concentration of H2O2 (2 times the stoechiometry) lead to a 50% recovery of the initial adsorption capacity during at least 4 consecutive cycles for L27, while about 20% or less for S23. In the consecutive continuous adsorption/batch oxidation process, the regeneration efficiency reaches 30% to 40% for L27 after two cycles whatever the feed concentration (0.1 g/L or 1 g/L of phenol) and less than 10% for S23 (0.1 g/L of phenol). During oxidation step, Total Organic Carbon removal is found to reach a limit, probably due to the formation of Fe3+/organic acid complex, hindering Fe2+ regeneration. Such complexes are stable in usual Fenton conditions, but can be destroyed by UV radiation. A photo-Fenton test performed on L27 indeed shows almost complete mineralization and improved recovery of AC adsorption capacity although not complete (56% after two cycles)

Altruistic and Joy-of-Giving Motivations in Charitable Behavior

This study theoretically and empirically examines altruistic and joy-of-giving motivations underlying contributions to charitable activities. The theoretical analysis shows that in an economy with an infinitely large number of donors, impurely altruistic preferences lead to either asymptotically zero or complete crowd-out. The paper then establishes conditions on preferences that are sufficient to yield zero crowd-out in the limit. These conditions are fairly weak and quite plausible. An empirical representation of the model is estimated using a new 1986–92 panel of donations and government funding from the United States to 125 international relief and development organizations. Be-sides directly linking sources of public and private support, the econ-ometric analysis controls for unobserved institution-specific factors, institution-specific changes in leadership, year-to-year changes in need, and expenditures by related organizations. The estimates show little evidence of crowd-out from either direct public or related private sources. Thus, at the margin, donations to these organizations appear to be motivated solely by joy-of-giving preferences. In addition to ad-dressing the basic question of motives behind charitable giving, the results help explain the existing disparity between econometric and experimental crowd-out estimates

Multi-orbital Kondo physics of Co in Cu hosts

We investigate the electronic structure of cobalt atoms on a copper surface and in a copper host by combining density functional calculations with a numerically exact continuous-time quantum Monte Carlo treatment of the five-orbital impurity problem. In both cases we find low energy resonances in the density of states of all five Co $d$-orbitals. The corresponding self-energies indicate the formation of a Fermi liquid state at low temperatures. Our calculations yield the characteristic energy scale -- the Kondo temperature -- for both systems in good agreement with experiments. We quantify the charge fluctuations in both geometries and suggest that Co in Cu must be described by an Anderson impurity model rather than by a model assuming frozen impurity valency at low energies. We show that fluctuations of the orbital degrees of freedom are crucial for explaining the Kondo temperatures obtained in our calculations and measured in experiments.Comment: 10 pages, 10 figure

Crossover from weak to strong coupling regime in dispersive circuit QED

We study the decoherence of a superconducting qubit due to the dispersive coupling to a damped harmonic oscillator. We go beyond the weak qubit-oscillator coupling, which we associate with a phase Purcell effect, and enter into a strong coupling regime, with qualitatively different behavior of the dephasing rate. We identify and give a physicaly intuitive discussion of both decoherence mechanisms. Our results can be applied, with small adaptations, to a large variety of other physical systems, e. g. trapped ions and cavity QED, boosting theoretical and experimental decoherence studies.Comment: Published versio