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The sorption of some benzene derivatives: o-xylene, toluene, phenol, benzyl alcohol, resorcinol and hydroquinone onto a zeolitic tuff-humic acid adduct (PCT-ImHA) was analysed by batch technique at 25°C and neutral pH. PCT-ImHA was prepared by binding leonardite-extracted humic acids (HA) to a zeolitic tuff sample rich in phillipsite and chabazite and enriched with Ca2+by cation exchange (Ca-PCT). The HA calcium salts were gently mixed with wet Ca-PCT; then, the mixture was heated at 330°C for 1.5h. An adduct with almost 2% of HA was obtained. The experimental data were well fitted by the Langmuir adsorption isotherm and showed that saturation capacity (qMax) increased with the octanol-water repartition coefficient (KO-W). The comparison with previous data on sorption onto immobilised HA highlights that qMaxvalues for PCT-ImHA are far higher than the sum of the contributions of the two separate components.

In this paper, Triclosan (5-chloro-2-(2,4-dichlorophenoxy)phenol; TCS) photodegradation is studied by using a lab-scale experimental apparatus with a parametric variation study. Experiments were performed by using a lab view experimental set-up, consisting in a batch reactor (Petri dish) irradiated by UV-light at a wavelength of 254 nm and an UV dose of 400 mJ m−2. The effect of Triclosan initial concentration (TCS0), irradiated solution volume (V), solution initial pH (pH), nitrate anions (NO3−) and humic acids (HA) as a function of the irradiation time (0–60 min) is investigated, in order to study both direct photolysis and the combination of direct and indirect photolysis. Furthermore, TCS heterogeneous catalytic photolysis is studied when titanium dioxide (TiO2) is added to the experimental solution. The main obtained results have shown that TCS removal seems not to be significantly affected by TCS0 and V, while pH, NO3−, HA and TiO2 appear to be effective for TCS degradation; in particular, TCS photodegradation is enhanced by titanium dioxide. Finally, photo-oxidation by-product identification was performed, by determining 2,8-DCDD and 2,4-DCP as TCS photolysis reaction products, and a photoreaction pathway has been proposed, which allowed to assess TCS photolysis degradation rate constants, 2,8-DCDD and 2,4-DCP generation rate constants.

The removal by electrochemical treatment in batch of humic acids (HA) extracted from leonardite has been analyzed using aluminum electrodes at 25°C and neutral pH, under galvanostatic conditions. HA removal, inferred from UV-Vis spectra and total organic carbon determination, occurred within few minutes of treatment under the experimental conditions tested, and no electrode passivation was observed. The removal rate increased with NaCl concentration and electric current density. Our data indicate that energy consumption per unit weight of HA removed can be significantly reduced by operating at low current density under galvanostatic conditions and/or high salt concentration, thus confirming electrochemical treatment as a powerful technology for wastewater treatment.

The advanced treatment of polluted liquid streams containing traces of pharmaceutical compounds is a major issue, since more and more effluents from pharma labs and wastewaters containing the excretions of medically treated humans and animals are discharged in the conventional wastewater treatment plants without previous effective treatments. Ibuprofen is a widely used non-steroidal anti-inflammatory drug (NSAID), which explains why it is found in wastewaters so often. In this paper, the removal of IBP from simulated water streams was investigated by using a lab-scale experimental device, consisting of a batch reactor equipped with a lamp emitting monochromatic UV light at a fixed wavelength (254 nm) and various intensities. Three sets of experiments were carried out: the first to study IBP concentration as a function of time, at different volumes of treated solutions (V = 10–30 mL); the second to explore the effect of pH on IBP degradation as a function of time (pH = 2.25–8.25) and the third to evaluate the effect of different UV light intensities on IBP degradation (E = 100–400 mJ m−2). The IBP initial concentration (IBP 0) was varied in the range 30–60 mg L−1. The results obtained show that the concentration of IBP decreases along with treatment time, with a negative effect of the treated volume, i.e. smaller volumes, such as lower liquid heights, are more easily degraded. Moreover, the higher the pH, the better the IBP degradation; actually, when pH increases from 2.25 to 6.6 and 8.25, the IBP concentration, after an hour of treatment, decreases respectively to 45, 34 and 27 % of its initial value. In addition, as the intensity of light increases from 100 to 400 mJ m−2, the IBP concentration decreases to 34 % of its initial value. A reaction scheme is put forward in the paper, which well describes the effects of volume, pH and light intensity on the IBP degradation measured experimentally. Moreover, the IBP degradation by-products have been identified.

New environmental friendly sorption materials were synthesized and studied to remove organic contaminants in wastewater purification. Humic acids extracted from green-waste compost (HA(comp)) and from leonardite (HA(leo)) were chemically characterized by infrared spectroscopy, carbon nitrogen and hydrogen analysis, ash content, hydrophobicity tests, and molecular weight distribution. Humic acids were thermally immobilized at 330 A degrees C for 1.5 h and their sorbent properties towards of some benzene derivatives (toluene, o-xylene, phenol, and benzyl alcohol) with the batch equilibrium method were studied. HA(comp) was found to be less rich in aromatic rings and more hydrophobic than HA(leo). The maximum amount of sorbate bound at the equilibrium was consistently higher for the immobilized HA from compost than from leonardite and increased with the n-octanol/water partition coefficient of the adsorbate. The data point to hydrophobic interactions as the main force involved in the sorption of the compounds tested. The results showed that these materials can have potential applications in wastewater purification.

It has been recently shown that acid activation enhances the ability of zeolitic tuffs to bind weak organic bases. More specifically, tuff containing acid-resistant zeolites (i.e. clinoptilolite) exhibits higher sorption capacity than chabazite/phillipsite-rich tuff. Based on the above considerations, we investigated in depth the adsorption behaviour of two pesticides onto acid-activated clinoptilolitic tuff under different experimental conditions. The pesticides simazine and boscalid were chosen based on their different physico-chemical properties, simazine being a very weak organic base (pKa=1.6) of low hydrophobicity (KOW = 126) whereas boscalid is uncharged in the pH range 2-10 (pKa=12.1) and has a moderate hydrophobic character (KOW = 912). The acid-activated clinoptilolitic tuff adsorbent was obtained by treating a fixed amount of raw tuff with 0.1M HCl solution for two days. The results of the experiments indicate that sorption is fast for both pesticides, reaching the equilibrium within hours. The acid treatment significantly improved the sorption capacity of the clinoptilolitic tuff for simazine, increasing the saturation level by over 70 times. In contrast, the sorption of boscalid was barely affected by the treatment. pH, cation exchange type and ionic strength appeared to play a relevant role in the sorption process, whereas the temperature and the specific surface area had no significant influence. Fast kinetics and good sorption capacity suggest that clinoptilolitic tuff, conveniently treated with acids, could be a suitable adsorbent for simazine and similar compounds.

A major environmental concern has recently developed due to emerging pollutants (EC) that are nowadays being detected in the effluents of municipal and industrial wastewater treatment plants (WWTP) at very low concentrations, thanks to improved analytical techniques. Pharmaceutical compounds (PhACs) are some of the most hazardous EC. These compounds can be retained into the water cycle (from users to WWTP, and then to water sources by discharge) virtually endlessly. Thus innovative solutions are required, such as the advanced oxidation processes (AOP). Among them, combined treatments based on UV light appear to be eco-friendly, giving very interesting removal efficiencies if opportunely devised. In this paper, the removal of diclofenac, a widely used non-steroidal anti-inflammatory drug (NSAID), from synthetic water streams was explored by using a lab-scale experimental device, consisting of a batch reactor equipped with a lamp emitting monochromatic UV light at fixed wavelength and intensity (254 nm; 400 mJ m–2). The experimental tests have been carried out to evaluate the effect of treatment time and to verify the possibility of further degrading the obtained compound. The preliminary results confirm what has been recently and unexpectedly found in literature, that is the formation of a dimer during the first minutes of photolysis, carbazole, a very stable coloured intermediate. A major environmental concern has recently developed due to emerging pollutants (EC) that are nowadays being detected in the effluents of municipal and industrial wastewater treatment plants (WWTP) at very low concentrations, thanks to improved analytical techniques. Pharmaceutical compounds (PhACs) are some of the most hazardous EC. These compounds can be retained into the water cycle (from users to WWTP, and then to water sources by discharge) virtually endlessly. Thus innovative solutions are required, such as the advanced oxidation processes (AOP). Among them, combined treatments based on UV light appear to be eco-friendly, giving very interesting removal efficiencies if opportunely devised. In this paper, the removal of diclofenac, a widely used non-steroidal anti-inflammatory drug (NSAID), from synthetic water streams was explored by using a lab-scale experimental device, consisting of a batch reactor equipped with a lamp emitting monochromatic UV light at fixed wavelength and intensity (254 nm; 400 mJ m(-2)). The experimental tests have been carried out to evaluate the effect of treatment time and to verify the possibility of further degrading the obtained compound. The preliminary results confirm what has been recently and unexpectedly found in literature, that is the formation of a dimer during the first minutes of photolysis, carbazole, a very stable coloured intermediate.

Diclofenac (hereafter DCF) is an extensively used anti-inflammatory drug; therefore, it is found in many sewage treatment plant effluents and it is one of the most usually reported environmental pharmaceutical contaminants. In this work, the degradation of diclofenac in pure water under UV light was studied, and the influence of some variables, such as humic acids (HA), nitrate anions (NO3 −) and titanium dioxide (TiO2) on DCF photodegradation was investigated. The experimental activity was carried out in a batch reactor of 100 mL equipped with fixed UV light of 254 nm and an irradiation intensity of 400 mJ/m2. Diclofenac initial concentration was equal to 10 mg/L in pure water, and its removal was evaluated by varying HA concentration in the range 10–20 mg/L and NO3 − concentration in the range 25–50 mg/L. Furthermore, the heterogeneous catalysis with TiO2 (1–50 mg/L) was studied. Temperature in all experiments was kept constant at 20 °C. Experimental results show that while HA have a significant influence on DCF photodegradation, nitrate and titanium dioxide seem to be ineffective, at least in the tested conditions. Finally, DCF photolysis modelling was carried out and a pseudo-first-order kinetic model was used.

The sorption equilibrium of humic acids (HA) onto kaolinite and montmorillonite clays and, for comparison, onto a zeolite-rich tuff has been analyzed by the batch technique. The sorbents were both in the native and calcium enriched forms. The data fit well with the Henry model for sorption onto clay, and with the Freundlich model for sorption onto tuff. The Gibbs energy of sorption (Delta(s)G degrees) in the standard state, i.e., low-concentration HA solution and completely free sorbent, was markedly lower for sorption onto either type of clay than for the zeolitic tuff. Delta(s)G degrees was higher for the Ca2+-enriched form than for the native form.

This paper deals with a preliminary study aimed at investigating the adsorption capacity of an innovative natural environmental friendly adsorbing material, consisting in an organo-zeolite, made by irreversibly binding humic acids onto natural zeolite. The removal of ibuprofen sodium salt, a non-steroidal anti- inflammatory drug among the most detected emerging contaminants into aquatic environments, was investigated by batch tests. Experiments were carried out under neutral pH and at a temperature of 25 degrees C. The kinetic and the equilibrium adsorption capacity were also investigated. Data show that a pseudo-second order rate equation can be used to describe the kinetics of Ibuprofen adsorption, while the equilibrium adsorption is adequately described by the Langmuir isotherm model. A comparison between the organo-zeolite and the raw zeolite shows that the adsorption capacity of the organo-zeolite was about 3 times higher than that of the raw material with a maximum amount can be adsorbed (q(max)), extracted by Langmuir equation, of 0.205 mg g(-1) and 0.078 mg g(-1), respectively.

The adsorption of some benzene derivatives-o-xylene, toluene, phenol, and benzyl alcohol onto dissolved humic acids (HA) was analyzed by equilibrium dialyses experiments. HA were extracted from compost and from leonardite. The humification index (E-4/E-6 ratio) and the distribution coefficient between ammonium sulfate/polyethylene glycol solutions show that HA from compost have a higher hydrophobicity. Assuming that the binding sites onto HA molecules are energetically equivalent, the binding curves were analyzed, and the amount of ligands bound per unit weight of HA and the association constants were derived. The binding capacity was higher for the HA from compost and for more hydrophobic ligands.

In this work, an experimental analysis of toluene adsorption from water solution on an organo-zeolite-adduct and onto zeolitic tuff from water solutions was carried out. This material is an organo-zeolite made by irreversibly binding the humic acids onto natural zeolite. Isotherms for sorption of toluene from water solutions have been determined by batch experiments at 4, 14, 24 and 34 degrees C. For both materials, the sorbitivity was good, particularly so for organo-zeolite adduct. The parameters of the Freundlich equation and isosteric and standard sorption enthalpies are analyzed.

In this work the ability of modified and unmodified montmorillonite to adsorb simazine and boscalid was evaluated. It was found that the adsorption behavior of the two compounds was greatly influenced by their different physicochemical properties. Acid-activated montmorillonite exhibited excellent adsorption capacity for simazine whereas montmorillonite treated with benzyltriethylammonium was suitable for removal of boscalid.

Sorption isotherms from water solution onto immobilized humic acid have been determined at 4, 14, 24, and 34°C for toluene, cyclohexane, o-xylene, benzyl alcohol, phenol, and cyclohexanol. The experimental data were well described by the Freundlich sorption equation. The higher values of K constant were obtained for the two aromatic hydrocarbon compounds, toluene (924 mmoln−1 Ln kg−1) and o-xylene (1,350 mmoln−1 Ln kg−1). The isosteric sorption enthalpy (ΔistH) and the standard enthalpy were negative for all compounds analyzed, and the absolute values of ΔistH decreased with increasing sorbate loading. Comparisons with data for a humic acid-zeolitic tuff adduct supports the conclusion that the sorption properties of combined materials may not be the sum of the components, thus strengthening the rationale for research of novel adducts.

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.

This is a comparative analysis of popular methods currently in use to derive sorption thermodynamic parameters from temperature dependence of sorption isotherms. It is emphasized that the standard and isosteric thermodynamic parameters have sharply different meanings. Moreover, it is shown with examples how the sorption model adopted conditions the standard state and consequently the value of ΔG and ΔS. These trivial but often neglected aspects should carefully be considered when comparing thermodynamic parameters from different literature sources. An effort by the scientific community is needed to define criteria for the choice of the standard state in sorption processes. © 2013 Elsevier Ltd. All rights reserved.

Sorption isotherms from water solutions for toluene, cyclohexane, o-xylene, benzyl alcohol, phenol and cyclohexanol onto a humic acid-zeolite adduct were determined at 4, 14, 24 and 34 °C and utilized to calculate the isosteric enthalpy (δ adsHi) and isosteric entropy (δ adsSi) of the process. For hydrocarbon compounds, toluene, cyclohexane and o-xylene, both δ adsHi and δ adsSi were negative, the process was exothermic. In contrast, for hydroxyl compounds, benzyl alcohol, phenol and cyclohexanol, δ adsHi and δ adsSi were positive, the increase in entropy possibly reflecting the release of water molecules during sorption. The results suggest that sorption/desorption of either class of compounds could be controlled by operating on the temperature. © 2013.

In this work, an experimental and modeling analysis of the adsorption of four aromatic compounds (i.e., toluene, naphthalene, o-xylene and ethylbenzene) onto a commercial activated carbon is carried out. The aim is to assess the suitability of the adsorption process for the treatment of polluted groundwater, also when a multiple contamination is detected. Batch adsorption tests from simulated polluted groundwater are performed in single-compound systems and in two binary systems (i.e., toluene + naphthalene and o-xylene + ethylbenzene), at constant temperature (20°C) and pH (7). Experimental results in single-compound systems reveal that all of the analytes are significantly adsorbed on the tested activated carbon. In particular, toluene and naphthalene adsorption capacities are the highest and of similar value, while for o-xylene and ethylbenzene, the performances are lower. The adsorption of these compounds seems to be influenced by a combined effect of several parameters, such as hydrophobicity, molecule size, structure of the molecule, etc. Experimental results in binary systems show a different behavior of the two systems, which confirms their complexity and explains the interest in these complex adsorption systems. In particular, toluene and naphthalene are mutually competitive, while in the case of o-xylene + ethylbenzene, only the former undergoes competitive effects. The analysis of the entire experimental data set is integrated with a dedicated modeling analysis using the extended Langmuir model. For both single-compound and binary systems, this model provides acceptable results, in particular for low equilibrium concentrations, like those more commonly found in groundwater, and for the compounds involved in adsorptive competitive effects. © 2014 by the authors.

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 (t m ) in the exponential and slower characteristic lifetime.

The presence of surfactants in groundwater and in drinking and superficial waters is a major public health concern. Recently, various treatment technologies have been studied to remove these pollutants; among them, the treatments based on the sorption onto natural adsorbing materials appear more eco-friendly and with very interesting removal efficiencies. The sorption of the cationic surfactant benzyldimethyldodecyl ammonium chloride (BDC-12) onto zeolitic tuff (Si/Al ratio = 2.4) was well described by a pseudo-second-order equation with a kinetic constant not depending on the exchangeable cationic form of the zeolite. The isosteric enthalpies and entropies (∆istH and ∆istS) obtained from sorption isotherms were negative, and their absolute values increased with decreasing amounts of BDC-12 bound at the equilibrium (qe). Zeolite sorbitivity (qe/unit dry mass sorbent) for BDC-12 increased with NaCl concentration in the batch solution, suggesting that the sorption process does not involve cation exchange.

The presence of trace of pharmaceutical compounds (PhACs) in groundwater and in drinking and superficial waters is a major public health concern. Recently, various advanced treatment technologies have been studied to remove these kinds of pollutants; among them, combined treatments based on UV light appear to be more eco-friendly and with very interesting removal efficiencies if properly modified. In this paper, the removal of Ibuprofen (IBP) from synthetic water streams was investigated by using a lab-scale experimental device consisting of a batch reactor equipped with a lamp emitting monochromatic UV light (254 nm; 400 mJ m−2). The IBP initial concentration (C IBP 0 ) was 45.9 mg L−1. Two sets of experiments were carried out; the first one was aimed at studying the IBP concentration as a function of time, at different volumes of treated solution; the second one was aimed at exploring the effect of pH on IBP degradation as a function of time. The results obtained show that the concentration of IBP decreases along with treatment time, with a negative effect of the treated volume, i.e., smaller volumes, that is lower liquid heights, are more easily degraded. Moreover, the higher the pH, the better the IBP degradation; actually when pH increases from 2.25 to 5.51 and finally to 8.25, the IBP concentration, after an hour of treatment, decreases respectively to 45, 34, and 27 % from its initial value. A reaction mechanism is suggested, which well describes the effects of volume and pH on the experimentally measured IBP degradation.

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. 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 (E-EO) of 10.77 kWh m(-3) at an initial concentration of 200 mu g L-1 and a relative inlet pressure p(in) = 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 k(OH) and the maximum calculated (OH)-O-center dot 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. (C) 2015 Elsevier B.V. All rights reserved.

The sorption of humic acids (HA) on zeolitefeldspar- 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. © Springer Science+Business Media, LLC 2011.

Two different acid-activated zeolite-rich tuffs were evaluated as potential adsorbents for atrazine removal from water. The materials investigated were: Neapolitan yellow tuff (NYT, containing 37% phillipsite and 17% chabazite) and a clinoptilolitic tuff from Eskişehir (Turkey) (T-CPL, 79% clinoptilolite). The T-CPL tuff exhibited the highest adsorption capacity. Atrazine adsorption, estimated by batch method, was likely to involve electrostatic interactions obeying a pseudo-second-order kinetic model, whereas hydrogen bonds did not appear to play a significant role. Pre-treatment of tuffs with increasing concentrations of HCl resulted in a sharp increase of atrazine adsorption capacity, followed by a progressive reduction for both types of tuff. The effects of acidification on zeolites were investigated by spectrophotometric measurement of dealumination and by FT-IR and XRD analysis.The results suggested that acid activation of zeolites enhanced their ability to bind atrazine, which accounts for the initial increase of the adsorption. Acid activation, however, attacked the zeolite structure, particularly of zeolites rich in aluminium or poor in silicon, e.g., phillipsite and chabazite. The alteration of the zeolite structure by acid could account for the decrease of atrazine adsorption observed with both tuff types and for the absolute low adsorption of NYT relative to T-CPL.The results of this exploratory investigation thus, indicate that acid-activated clinoptilolitic tuff could be considered a suitable material for removing atrazine and similar chemical compounds from water. Two different acid-activated zeolite-rich tuffs were evaluated as potential adsorbents for atrazine removal from water. The materials investigated were: Neapolitan yellow tuff (NYT, containing 37% phillipsite and 17% chabazite) and a clinoptilolitic tuff from Eskişehir (Turkey) (T-CPL, 79% clinoptilolite). The T-CPL tuff exhibited the highest adsorption capacity. Atrazine adsorption, estimated by batch method, was likely to involve electrostatic interactions obeying a pseudo-second-order kinetic model, whereas hydrogen bonds did not appear to play a significant role. Pre-treatment of tuffs with increasing concentrations of HCl resulted in a sharp increase of atrazine adsorption capacity, followed by a progressive reduction for both types of tuff. The effects of acidification on zeolites were investigated by spectrophotometric measurement of dealumination and by FT-IR and XRD analysis.The results suggested that acid activation of zeolites enhanced their ability to bind atrazine, which accounts for the initial increase of the adsorption. Acid activation, however, attacked the zeolite structure, particularly of zeolites rich in aluminium or poor in silicon, e.g., phillipsite and chabazite. The alteration of the zeolite structure by acid could account for the decrease of atrazine adsorption observed with both tuff types and for the absolute low adsorption of NYT relative to T-CPL.The results of this exploratory investigation thus, indicate that acid-activated clinoptilolitic tuff could be considered a suitable material for removing atrazine and similar chemical compounds from water. © 2010 Elsevier B.V.

BACKGROUND: Although biodegradation seems to be the main cause of herbicide degradation, abiotic degradation can also be important for chemicals such as phenylureas, which are subject to catalysed soil reactions. The aim of this work is to investigate the effect of dissolved humic acids (HAs), normally present in natural waters, on the hydrolysis of phenylurea herbicides, and it presents a kinetic model that takes into account the role of adsorption. RESULTS: The linearity of the adsorption isotherms indicates that phenylurea–humic acid interaction can be considered in terms of a repartition-like equilibrium of phenylurea between water and HAs. Kinetic experiments show that the degradation rates of phenylureas increase with HA concentration. CONCLUSION: The kinetic equation adopted adequately describes the experimental data trend, allowing the evaluation of the catalytic effect of HAs on the chemical degradation of phenylureas. Carboxyl groups of HAs seem to play a leading role in the catalysis. The kinetic equation derived in this work could be helpful in predicting the persistence of phenylureas and of related compounds in natural water. Copyright © 2008 Society of Chemical Industry

Background atmospheric levels of aldehydes, BTEX and PM10 pollutants were measured in the suburb of Caserta (Italy), 75 thousands inhabitants, 41degrees 04' N, on rainless weekdays and weekends during 2005. On weekdays the average daily concentrations (microg m(-3)) were 41.6 PM10, 8.6 benzene, 25.2 toluene, 6.3 ethylbenzene, 14.0 (m+p)-xylene, 11.7 o-xylene, 6.5 formaldehyde, 3.3 acetaldehyde. All the pollutant concentrations were strictly correlated (mean correlation coefficients = 0.90). At weekends the concentrations were lower by about 1.6 times. Both on weekdays and at weekends the PM10 and benzene levels exceeded the limits set by the EU Directive 30/1999 and 69/2000, respectively.

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.

This work is an experimental analysis of the adsorption of ibuprofen (IBP) onto a granular activated carbon. Ibuprofen is a NSAID (non-steroidal anti-inflammatory drug) and is now an emerging contaminant of the aquatic environment. The effect of IBP concentration, pH and temperature on the equilibrium adsorption capacity is investigated through batch tests. The experimental results show that the highest adsorption capacity is observed under acidic pH and high temperature conditions. The combined effect of pH and temperature on IBP dissociation in water seems to play a major role in determining the IBP adsorption capacity of the activated carbon. Low pH and high temperature, in fact, reduce the IBP dissociation grade and increase the concentration of the non-ionized IBP species, which is likely to have a higher adsorption capacity with respect to the ionized one. The study puts forward a model to describe the IBP adsorption mechanism considering the variability of the dissociation grade. The model is based on the multicomponent Langmuir adsorption theory applied to the ionic species in solution. It shows that the adsorption capacity is strictly dependent on the IBP speciation in solution, allowing for a correct interpretation of the effects pH and temperature on IBP adsorption capacity. Finally, one of the main goals of this model is to preserve the exothermicity of the adsorption phenomena despite the trend observed in the experimental results: the increase in adsorption capacity with temperature appears to be related to a lower level of IBP dissociation.

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 1.5 h. 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.

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/q t 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(q t /q e )/Δt versus 1 – q t /q e and versus (1 – q t /q e ) 2 plots is suggested. Some recent papers reporting incorrect sorption kinetic analyses are discussed.

With the objective of developing new agents for the removal of humic substances from water, the sorption properties of Ca-enriched Neapolitan Yellow Tuff (NYT), obtained by cation exchange at room temperature or by treatment with CaCl2 at high temperature, were tested. Sorption of humic acids onto NYT samples was evaluated at neutral pH and room temperature by batch sorption tests and dynamic experiments on small columns. The salt-thermal treatment gives rise to samples with higher calcium content and superior sorption ability. For all the samples tested the sorption capacity increased with the contact time between the solid phase and the humic acids solution. The Langmuir parameters of the sorption isotherms and the breakthrough curves recorded by dynamic experiments indicate that high-temperature Ca-enriched NYT exhibits sorption properties higher than that recorded for commercial activated carbon and at least comparable to those of other materials recently investigated. With the objective of developing new agents for the removal of humic substances from water, the sorption properties of Ca-enriched Neapolitan Yellow Tuff (NYT), obtained by cation exchange at room temperature or by treatment with CaCl2 at high temperature, were tested. Sorption of humic acids onto NYT samples was evaluated at neutral pH and room temperature by batch sorption tests and dynamic experiments on small columns. The salt-thermal treatment gives rise to samples with higher calcium content and superior sorption ability. For all the samples tested the sorption capacity increased with the contact time between the solid phase and the humic acids solution. The Langmuir parameters of the sorption isotherms and the breakthrough curves recorded by dynamic experiments indicate that high-temperature Ca-enriched NYT exhibits sorption properties higher than that recorded for commercial activated carbon and at least comparable to those of other materials recently investigated.

Atmospheric BTEX [benzene, toluene, ethylbenzene, o-xylene and (m + p)-xylene] concentrations have been determined in the Naples metropolitan area (NMA) and in two suburban areas located on the north within about 25 km, during 2006. The pollutants were collected by passive samplers (24-h samplings), and analysed by GC-MS. In all the areas analysed the average atmospheric benzene concentrations were higher than the limit value fixed by the European Union for 2010 and in NMA the average concentration (9.8 μg m-3) also exceeded the limit fixed for 2006. High linear correlation coefficients between the average daily concentrations of the different BTEX are indicative of a single major source, most likely the vehicular traffic. The temporal and spatial distribution of BTEX relative concentrations suggest that massive emissions in NMA negatively affect the quality of the air in northern suburban areas, prevalently during the hottest months of the year, probably due to transport by local seasonal winds. The ratios between BTEX daily concentrations showed a clear dependence on the intensity of solar actinic flow, indicating a major role of photochemical processes in the air cleaning from these volatile organic pollutants. © Springer Science+Business Media B.V. 2008.

The concentrations of benzene, toluene, ethylbenzene and the isomeric xylenes (BTEX) were determined in the atmosphere of S. Maria Capua Vetere city, in sixteen sites, ten times per site, during 2006. This city is of medium size, with about 32,000 inhabitants and is located in Southern Italy. Passive adsorption samplers, followed by GC/MS analyses, were used for BTEX determinations. The 24-hour average BTEX concentrations showed a marked variability from site to site. In some streets the pollutant concentrations were above the limit values required by the European Union. These streets were characterised by relatively intense traffic, but are rather narrow and have high buildings on either side. In the entire city the main pollutant source was road traffic. Moreover, analyses of the correlation coefficients among the BTEX concentrations and GIS maps highlighted the contribution of stationary sources to toluene air concentration. Their contribution has been quantified. © 2007 WIT Press.

The sorption of humic acids (HA) by phillipsite- and chabazite-rich Neapolitan Yellow Tuff (NYT) and a clinoptilolite-rich tuff from Turkey (CLT), both in the native and in Ca-enriched forms, have been investigated. Experimental data showed that the sorption capacity of the Ca-enriched forms was higher than that of the native forms. NYT, in particular, was very effective in removing humic acids from water. Its sorption capacity was higher than that of CLT, although the latter material had a higher zeolite content (CLT: 79% clinoptilolite; NYT: 37% phillipsite + 17% chabazite). HA sorption by Ca-enriched NYT readily attained a pseudo steady-state, after which the tuff/HA-solution system evolved in a few months to a final equilibrium state characterized by a much higher sorption capability. Desorption experiments at high pH levels resulted in a HA recovery >80%. The UV-vis spectrum and the gel permeation chromatogram of the recovered HA solution were indistinguishable from those obtained for a freshly prepared HA solution. © 2007 Elsevier Inc. All rights reserved.

The ability of the natural zeolited Neapolitan Yellow Tuff (NYT) enriched with calcium ions to remove humic acids from water was evaluated by batch adsorption equilibrium tests and dynamic experiments carried out by percolating humic acid solutions through a small NYT column (breakthrough curves). Under the experimental condition explored, the sorption capacity increases with the ionic strength and has the highest value at pH 7.4. The partition coefficient for a low concentration of humic acid ([humic acid] --> 0), at pH 7.4 in 0.01 M sodium chloride, was approximately 1000 L/kg, versus the value of approximately 100 L/kg in the absence of the alkaline metal salt. Therefore, after humic acids have been adsorbed in a column filled with the calcium-ion-enriched tuff, a reduction of the salt concentration in the ongoing solution enhances the release of the adsorbed material. These findings show that NYT can be used for the removal of humic acids from water.

The capacity of an organo-zeolite aggregate, namely a humic acid (HA) bound to a sample of Ca2+-enrichedNeapolitan Yellow Tuff (NYT), to remove phenylurea herbicides from water has been analysed by the batch method. The experimental results showed that this aggregate is an effective sorbent for phenylureas and that sorption capacity is linearly related to the amount of HA in the aggregate and to the specific value of the octanol-water partition coefficient of the herbicide tested. NYT surface was proved to be irrelevant to the sorption process itself, its only role being to immobilize the active HA. The capacity of an organo-zeolite aggregate, namely a humic acid (HA) bound to a sample of Ca2+-enrichedNeapolitan Yellow Tuff (NYT), to remove phenylurea herbicides from water has been analysed by the batch method. The experimental results showed that this aggregate is an effective sorbent for phenylureas and that sorption capacity is linearly related to the amount of HA in the aggregate and to the specific value of the octanol-water partition coefficient of the herbicide tested. NYT surface was proved to be irrelevant to the sorption process itself, its only role being to immobilize the active HA. © 2007 Elsevier B.V. All rights reserved.