Silvana Canzano

Degradation of ibuprofen by hydrodynamic cavitation: Reaction pathways and effect of operational parameters

Ibuprofen (IBP) is an anti-inflammatory drug whose residues can be found worldwide in natural water bodies resulting in harmful effects to aquatic species even at low concentrations. This paper deals with the degradation of IBP in water by hydrodynamic cavitation in a convergent-divergent nozzle. Over 60% of ibuprofen was degraded in 60 min with an electrical energy per order (EEO) of 10.77 kWh m(-3) at an initial concentration of 200 μg L(-1) and a relative inlet pressure pin=0.35 MPa. Five intermediates generated from different hydroxylation reactions were identified; the potential mechanisms of degradation were sketched and discussed. The reaction pathways recognized are in line with the relevant literature, both experimental and theoretical. By varying the pressure upstream the constriction, different degradation rates were observed. This effect was discussed according to a numerical simulation of the hydroxyl radical production identifying a clear correspondence between the maximum kinetic constant kOH and the maximum calculated OH production. Furthermore, in the investigated experimental conditions, the pH parameter was found not to affect the extent of degradation; this peculiar feature agrees with a recently published kinetic insight and has been explained in the light of the intermediates of the different reaction pathways.

A novel organo-zeolite adduct for environmental applications: Sorption of phenol

A novel organo-zeolite adduct has been synthesized by sorbing humic acids (HA) onto zeolitic tuff and then heating the resulting complex at 330°C for 1.5h. Desorption tests showed that this procedure effectively immobilized HA on the tuff. The crystal structure of the zeolitic tuff and the chemical structure of HA were not altered during the preparation. Phenol sorption analysis demonstrated that the HA-zeolite adduct had good sorbing properties; moreover, the sorbed amount markedly decreased with increased ionic strength. These results point to prospective application of the HA-zeolite adduct as a low-cost and environmentally friendly sorbent for water purification from phenol and possibly other neutral organic pollutants.

Comment on “Removal of anionic dye Congo red from aqueous solution by raw pine and acid-treated pine cone powder as adsorbent: Equilibrium, thermodynamic, kinetics, mechanism and process design”

* Corresponding author. Tel.: þ39 0 823 2746 E-mail address: sante.capasso@unina2.it 0043-1354/

Sorption of humic acids by a zeolite-feldspar-bearing tuff in batch and fixed-bed column

e see front matter a 2012 Publi doi:10.1016/j.watres.2012.05.040 Recently, Dawood and Sen (2012) published a paper reporting a kinetic analysis of Congo red adsorption by natural material. In section 2.4.4. Thermodynamic study, they describe the determination of the thermodynamic parameters DH e DS by means of the van’t Hoff equation as follows:

Modelling the biphasic sorption of simazine, imidacloprid, and boscalid in water/soil systems

The sorption of humic acids (HA) on zeolite-feldspar-bearing Phlegraean Yellow Tuff enriched with calcium ions has been investigated at neutral pH both on fixed-bed columns and in batch. A two-step sorption kinetics and a relatively long time to reach the equilibrium were observed in batch. In line with this behaviour, the breakthrough curves and shipping curves from exhaust columns showed distinctive properties that cannot be easily modelled by the common mass balance equations; noteworthy, the breakthrough curves were dependent on the space velocity also for very slow processes and the bed sorption capacity decreased linearly with the space velocity. Moreover, after an initial high-rate burst, HA desorption from exhausted columns proceeded at a very slow rate, particularly so for columns loaded with higher amounts of HA.

Use and Misuse of Sorption Kinetic Data: A Common Mistake that Should be Avoided

The sorption kinetics of simazine (6-chloro-N,N′-diethyl-1,3,5-triazine-2,4-diamine), imidacloprid (1-(6-chloro-3-pyridylmethyl)-N-nitroimidazolidin-2-ylideneamine), and boscalid (2-chloro-N-(4′-chlorobiphenyl-2-yl)nicotinamide), three pesticides of wide use in agriculture, was determined in five different water/soil systems over a time interval from the initial few seconds to about 1 month. In all the experiments, sorption kinetics showed a biphasic pattern characterized by an initial, relatively short phase with a high sorption rate and a later phase with much a lower sorption rate. Initial sorption capacity increased with soil organic carbon content and with sorbate hydrophobicity. We postulate that the first phase of the process involves a fast second-order sorption reaction on superficial sites of soil particles, whereas the second phase depends on diffusion-controlled migration to internal binding sites. A kinetic equation based on this hybrid model accurately fitted all data sets. Less satisfactory results were obtained employing the pseudo-first order, pseudo-second order, Elovich, two site non-equilibrium, or Weber-Morris equation. The superior performance of the hybrid model for describing boscalid sorption probably reflects the high hydrophobic character and consequent low diffusion rates of this compound. The accuracy of modelling was in any case strongly dependent on the time interval considered.

Ibuprofen degradation in aqueous solution by using UV light

Numerical simulation of sorption dynamics showed that the use of data recorded at (or very close to) equilibrium in the search for the kinetic equation that best describes the process frequently leads to incorrect conclusions. Notably, it has been demonstrated that the fit of the adsorption data at equilibrium (t/qt versus t) is a straight line irrespective of the sorption kinetics. In order to distinguish pseudo-first-order from pseudo-second-order sorption kinetics, the data near the equilibrium should be omitted from the least-squares fit and the result confirmed by a different method. A straightforward method based on Δ(qt/qe)/Δt versus 1 – qt/qe and versus (1 – qt/qe)2 plots is suggested. Some recent papers reporting incorrect sorption kinetic analyses are discussed.

A Phenomenological Interpretation of Two-Step Adsorption Kinetics of Humic Acids on Zeolitic Tuff

AbstractRecent regulation policies are focusing on the presence of priority and emerging pollutants in water, among them, pharmaceutical residues are of particular public concern since trace of these molecules is commonly found in drinking and superficial waters. Progresses in innovative technologies for wastewater treatment are mandatory in order to improve their abatement efficiencies for water source prevention and reclamation. The OH-based technologies, a group of different techniques usually called advanced oxidation processes (AOPs), can be used to mineralize organic pollutants. In particular, combined treatments based on UV light appear to be more eco-friendly, also giving very interesting removal efficiencies if opportunely devised. Moreover, many of the commonly detected pharmaceutical compounds are susceptible to degradation by UV at disinfection doses. In this paper, the removal of ibuprofen (IBP)—a widely used non-steroidal anti-inflammatory drug (NSAID)—from synthetic water streams was explor...

Experimental analysis of benzene derivative adsorption in single and binary systems using activated carbon

In this study, the kinetics of adsorption of humic acid (HA) from aqueous solution onto a zeolitic tuff were investigated. X-ray diffraction, scanning electron microscopy, porosity and pore-size distribution measurements indicate that macromolecules can diffuse into the material. The kinetic curves show a two-stage adsorption. The adsorbed amount increases up to 2 days, remains constant and then increases again to attain equilibrium. There is a remarkable similarity between this adsorption behaviour of HA on zeolitic tuff and the behaviour observed when ultrathin multi-layers of polymeric materials are fabricated by self-assembly technique. Experiments reveal two distinct stages: the first corresponds to the macromolecules being driven towards the substrate, while the second is the result of arrangement of macromolecules. The first stage is a first-order kinetics with characteristic lifetime of 1–2 days, whereas the second stage is a Johnson–Mehl–Avrami function with (tm) in the exponential and slower characteristic lifetime.

Considerations about the correct evaluation of sorption thermodynamic parameters from equilibrium isotherms

This work is an experimental analysis of o-xylene and ethylbenzene adsorption onto a commercial activated carbon in both single-compound and binary systems. The effect of temperature and salinity was assessed for single-compound systems, confirming that the adsorption of these analytes is an exothermic phenomenon occurring in active sites other than those where ionic substances are adsorbed. The estimate of the isosteric heat of adsorption allowed demonstrating that there are no lateral interactions between o-xylene and ethylbenzene molecules and that the Langmuir model can be used for data interpretation. Adsorption tests in binary systems showed that o-xylene adsorption is affected by the presence of ethylbenzene, while the adsorption capacity of ethylbenzene remains unchanged in both single-compound and binary systems. Finally, based on a modelling analysis of the binary systems, the Langmuir multicomponent model appears to be a statistically reliable tool for o-xylene binary data prediction, while the Langmuir single-compound model is suitable for the prediction of ethylbenzene binary data, in line with the experimental evidence showing the absence of any competition phenomena.