Single-component Aqueous Solutions Research Articles

Ultrasonic Degradation of Endocrine Disrupting Compounds in Seawater and Brackish Water

In this study, a series of experiments was conducted on the relative degradation of commonly known endocrine-disrupting com- pounds such as bisphenol A (BPA) and 17α-ethinyl estradiol (EE2) in a single-component aqueous solution using 28 and 580 kHz ultrasonic reactors. The experiments were conducted with three different types of model water: deionized water (DI), synthetic brack- ish water (SBW), and synthetic seawater (SSW) at pH 4, 7.5, and 11 in the presence of inert glass beads and humic acids. Significantly higher sonochemical degradation (93-97% for BPA) occurred at 580 kHz than at 28 kHz (43-61% for BPA), regardless of water type. A slightly higher degradation was observed for EE2 compared to that of BPA. The degradation rate of BPA and EE2 in DI water, SBW, and SSW after 30 min of ultrasound irradiation at 580 kHz increased slightly with the increase in pH from 4 (0.073-0.091 min-1 for BPA and 0.081-0.094 min -1 for EE2) to 7.5 (0.087-0.114 min -1 for BPA and 0.092-0.124 min -1 for EE2). In contrast, significant degradation was ob - served at pH 11 (0.149-0.221 min-1 for BPA and 0.147-0.228 min-1 for EE2). For the given frequencies of 28 and 580 kHz, the degradation rate increased in the presence of glass beads (0.1 mm and 25 g) for both BPA and EE2: 0.018-0.107 min -1 without beads and 0.052-0.142 min-1 with beads for BPA; 0.021-0.111 min-1 without beads and 0.054-0.136 min-1 with beads for EE2. A slight increase in degradation of both BPA and EE2 was found as the concentration of dissolved organic carbon (DOC, humic acids) increased in both SBW and SSW: 0.107-0.115 min-1 in SBW and 0.087-0.101 min-1 in SSW for BPA; 0.111-0.111 min-1 in SWB and 0.092-0.105 min-1 in SSW for EE2. After 30 min of sonicating the humic acid solution, DOC removal varied depending on the water type: 27% (3 mg L -1 ) and 7% (10 mg L -1 ) in SBW and 7% (3 mg L-1) and 4% (10 mg L-1) in SSW.

Adsorption properties of a nanostructured hybrid material containing aluminium towards some metal ions

Abstract In the present work the adsorption of some transition metal ions from aqueous solutions on a silica-based nanostructured hybrid material modified by aluminium was investigated. The novel organic-inorganic material was synthesized via a sol-gel method through hydrolysis and co-condensation reactions. Its structure was characterized by means of SEM, XRD and FTIR. Based on the data obtained the most probable cross-linking mechanism for the derived xerogel was proposed. The characterization of its texture parameters was carried out by low-temperature adsorption of nitrogen. The adsorption properties of this material with respect to Cu(II), Cr(III) and Pb(II) ions from single-component aqueous solutions and multi-component aqueous solutions containing also Cd(II) and Fe(III) were evaluated. The effect of contact time, acidity of initial solutions and metal ion concentrations was investigated using the batch method. Pseudo-first order, pseudo-second order and intraparticle diffusion models were used to analyze kinetic data. In all cases the adsorption was significantly affected by the pH value. Equilibrium modelling data were fitted to linear Langmuir, Freundlich and Dubinin-Radushkevich models. Best fit was observed for Langmuir model, which showed determination coefficients greater than 0.992 for all ions studied. The maximum adsorption capacities for single- and multi-component adsorption were calculated.

Ultrasonic degradation of bisphenol A, 17β-estradiol, and 17α-ethinyl

This study examined the relative degradation of commonly known endocrine-disrupting compounds (EDCs) such as bisphenol A (BPA), 17β-estradiol (E2), and 17α-ethinyl estradiol (EE2) in single-component aqueous solution using 28, 580, and 1,000 kHz ultrasonic reactors. The degradation of EDCs follows a pseudo-first order rate kinetics; the order of degradation is EE2 ≥ BPA > E2. At different frequencies, the degradation of these compounds follows the order 580 kHz (92–97%) > 1,000 kHz (90–94%) > 28 kHz (62–67%) at an initial concentration of 1 μM of each compound with a contact time of 30 min. Additional experiments were performed to determine the effects of carbon tetrachloride (CCl4, H• scavenger) and tert-butyl alcohol (t-BuOH, HO• scavenger) on BPA, E2, and EE2 degradation at 580 kHz with a reaction time of 30min. The addition of t-BuOH slightly decreased the rate of BPA degradation as follows: no addition (97%), 0.01 mM (96%), and 0.1 mM (95%). At high t-BuOH concentrations of 1, 10, and 100 mM, the deg...

Electrochemical degradation of β-blockers. Studies on single and multicomponent synthetic aqueous solutions

As far as we know, this is the first study reporting the electrochemical decontamination of solutions containing β-blockers, which are pharmaceutical pollutants with a high occurrence in natural waters. The oxidation ability of two pre-eminent, eco-friendly electrochemical advanced oxidation processes (EAOPs), namely anodic oxidation (AO) and electro-Fenton (EF), has been compared at lab-scale by carrying out bulk electrolyses at pH 3.0 at constant current using a carbon-felt cathode able to electrogenerate H 2O 2 in situ. The studies of single component aqueous solutions were focused on atenolol as a model β-blocker. The AO process was proven much more effective using a large surface area boron-doped diamond (BDD) anode than a Pt one, which was explained by the great amount of active hydroxyl radicals (BDD( OH)) and the minimization of their parasitic reactions. The EF process with a Pt anode and 0.2 mmol l −1 Fe 2+ showed even higher performance, with fast destruction of atenolol following pseudo-first order kinetics and fast mineralization because the oxidation process in the bulk allows overcoming the mass transport limitations. The time course of the concentration of the aromatic and short-chain carboxylic acid intermediates demonstrated the progressive detoxification of the solutions. Almost 100% of the initial N content was accumulated as NH 4 +. Multicomponent solutions containing atenolol, metoprolol, and propranolol, which usually occur together in the aquatic environment, were treated by EF using the Pt/carbon felt cell. A high mineralization rate was observed up to the overall total organic carbon (TOC) removal, which allowed reducing the energy consumption. The absolute rate constant for the reaction of each β-blocker with OH was determined and the reactivity was found to increase in the order: atenolol (1.42 × 10 9 l mol −1 s −1) < metoprolol (2.07 × 10 9 l mol −1 s −1) < propranolol (3.36 × 10 9 l mol −1 s −1).

Biosorption of chromium, copper and zinc by wine-processing waste sludge: Single and multi-component system study

Wine-processing waste sludge (WPWS) has been shown to have powerful potential for sorption of some heavy metals (i.e., chromium, lead and nickel) in single-component aqueous solutions. But although most industrial wastewater contains two or more toxic metals, there are few sorption studies on multicomponent metals by WPWS. This study has two goals: (i) conduct competitive adsorption using Cr, Cu and Zn as sorbates and examine their interaction in binary or ternary systems; and (ii) determine the effects of temperature on the kinetic sorption reaction. The sludge tested contained a high amount of organic matter (38%) and had a high cation exchange capacity (CEC, 255 cmol c kg −1). Infrared analysis reveals that carboxyl is the main functional group in this WPWS. The 13C NMR determination indicates alkyl-C and carboxyl-C are major organic functional groups. At steady state, there are about 40.4% (Cr), 35.0% (Cu) and 21.9% (Zn) sorbed in the initial 6.12 mM of single-component solutions. Only pseudo-second-order sorption kinetic model successfully describes the kinetics of sorption for all experimental metals. The rate constants, k 2, of Cr, Cu and Zn in single-component solutions are 0.016, 0.030 and 0.154 g mg −1 min −1, respectively. The sorption of metals by WPWS in this competitive system shows the trend: Cr > Cu > Zn. Ions of charge, hydrated radius and electronic configuration are main factors affecting sorption capacity. The least sorption for Zn in this competitive system can be attributed to its full orbital and largest hydrated radius. Though the effect of temperature on Zn sorption is insignificant, high temperature favors the other metallic sorptions, in particular for Cr. However, the Cr sorption is lower than Cu at 10 °C. The Cr sorption by WPWS can be higher than that of Cu at 30° and 50 °C.

The development of colour-encapsulated microspheres for novel colour cosmetics

In the present study, the preparation, characterization and colour retention properties of organic colour-loaded microspheres are described. The study aimed to produce shatter-resistant, low-bleeding polymeric microspheres with particle diameters of 20 µm containing 10–20% (w/w) of the Food, Drug, and Cosmetic grade colourants FD&C Blue No. 1 Al Lake, FD&C Yellow No. 5 Al Lake and D&C Red No. 36 by utilizing an aqueous-dispersed polymer water-in-oil (W/O) solvent evaporation process featuring styrene/acrylates-based copolymers. The influences of matrix polymeric components on the shape, integrity and dye retention of the microspheres were studied. Encapsulation matrices based on alkali soluble polymers yielded misshapen spheroids that were prone both to swelling and decreased dye retention in aqueous environments, as well as loss of shape at 70°C in cosmetic oils under shear. A resin supported emulsion (RSE)-based matrix, in comparison, yielded highly spherical microspheres resistant to shape deformation and swelling. Additions of up to 15% (w/w) of an alkali soluble polymer to the RSE system improved colour dispersion without detrimentally affecting the structural integrity of the microspheres while also slightly decreasing dye concentrations released into aqueous solutions. The in vitro dye release of the colour-loaded microspheres in a cosmetic-type water-in-silicone (W/Si) emulsion was evaluated and compared to the in vitro dye release studies in aqueous solutions. No direct correlations between the emulsion system and single-component aqueous solutions could be made. Dye-release levels evaluated from contacting the microspheres with a complex aqueous medium (CAM5), which incorporated ingredient classes typically encountered in the aqueous phase of an emulsion, were found to correlate to levels determined in the generic W/Si emulsion with a 93% linear regression between the data sets. This study demonstrates that the CAM5 protocol (or, alternatively, a CAM2.5 protocol) satisfactorily predicted that the commercial materials derived, in part, from this study (Ciba: ENCAPSULENCE™ Blue 1, ENCAPSULENCE™ Yellow 5 and ENCAPSULENCE™ Red 36) are well suited to retain their colour and shape in liquid cosmetic foundations.

Uptake of Fluoride by Al3+ Pretreated Low‐Silica Synthetic Zeolites: Adsorption Equilibrium and Rate Studies

The removal of fluoride from single component aqueous solution using Al3+‐ pretreated low‐silica synthetic zeolites (Al‐Na‐HUD, Al‐HUD, Al‐F9, and Al‐A4) was studied. The effects of adsorbent mass, initial solution pH, and initial concentration on fluoride removal in a batch system were evaluated. Equilibrium data were simulated using simple isotherms such as the Freundlich (F), Langmuir‐Freundlich (LF), Redlich‐Peterson (RP) and Dubinin‐Radushkevitch (DR) isotherms. From the DR model, initial pH effects and desorption studies, it was considered that the fluoride adsorption onto the zeolites proceeded by ion‐exchange or chemisorption mechanism. In interpreting the kinetic results, reaction kinetics (using Elovich equation) and mass transfer processes (both external mass transfer and intraparticle diffusion) were considered. Equilibrium and kinetic results of fluoride adsorption onto the adsorbents demonstrated the following order of performance: Al‐Na‐HUD>Al‐F9> Al‐HUD>Al‐A4.

Sorption of levulinic acid onto weakly basic anion exchangers: Equilibrium and kinetic studies

The equilibrium and dynamics of levulinic acid sorption on two weakly basic anion exchangers, in free base form, in single-component aqueous solutions were investigated. Adsorption isotherms such as Langmuir, Sips, Radke–Prausnitz, and Toth were applied to correlate the experimental data in the temperature range 285 – 315 K . Modeling results showed that the Toth model is the best one to correlate the sorption isotherms. The resulting Toth equations were used with the Clausius–Clapeyron equation to determine the isosteric heat of sorption. The sorption kinetics was experimentally measured via a completely stirred finite-bath batch experiment under different initial concentrations and at varying solution temperatures. The pseudo-second-order kinetic model and the Elovich equation were used to represent the kinetic data and the equation parameter values were also evaluated. The pseudo-second-order equation cannot simulate the experimental kinetic data, while the Elovich equation fitted the sorption dynamic data very well under all the operating conditions studied. Finally, the apparent activation energy of sorption was also determined.

Kinetic modeling of liquid-phase adsorption of reactive dyes on activated carbon

In this paper, adsorption equilibrium and kinetics of three reactive dyes from their single-component aqueous solutions onto activated carbon were studied in a batch reactor. Effects of the initial concentration and adsorbent particle size on adsorption rate were investigated Adsorption equilibrium data were then correlated with several well-known equilibrium isotherm models. The kinetic data were fitted using the pseudo-first-order equation, the pseudo-second-order equation, and the intraparticle diffusion model. The respective characteristic rate constants were presented. A new adsorption rate model based on the pseudo-first-order equation has been proposed to describe the experimental data over the whole adsorption process. The results show that the modified pseudo-first-order kinetic model generates the best agreement with the experimental data for the three single-component adsorption systems.

Mixing of the Organic Aerosol Fractions: Liquids as the Thermodynamically Stable Phases

An increasing number of single-particle measurements show that organic and inorganic constituents of the atmospheric aerosol are internally mixed within the particles. Therefore, the phases of the aerosol will be influenced by both mixing of the organic substances with each other and mixing between organic and inorganic constituents. In this work, the mixing properties of the organic aerosol fractions have been investigated theoretically and experimentally with respect to melting and deliquescence. We show that a liquid (or an amorphous solid) is the thermodynamically stable phaseeven in the absence of water as a solventprovided that a sufficiently high number of miscible components are present. Furthermore, we show experimentally that the deliquescence relative humidity of aqueous solutions of dicarboxylic acids decreases with an increasing number of components present in the solution. A five-component mixture consisting of malic, malonic, maleic, glutaric, and methylsuccinic acids deliquesces at a relative humidity (RH) as low as 45.4% RH, while the pure dicarboxylic acids exhibit deliquescence points between 72 and 96% RH. A further reduction of the deliquescence relative humidity is observed when an inorganic salt is added to the dicarboxylic acid five-component mixture. For NaCl, deliquescence of the eutonic composition occurred at 41.3%, for ammonium sulfate at 36.4%, and for ammonium nitrate even at 27.1% RH. Interactions between the solutes lead to either higher or lower solubilities in the multicomponent mixture as compared to the respective single-component aqueous solutions. In the mixed dicarboxylic acids/inorganic salt solutions, the solubilities of ammonium nitrate and sulfate are increased by ∼40%, the one of sodium chloride is decreased by a similar amount. In summary, these mixing properties suggest that small fractions of organic species prevent tropospheric aerosols from becoming fully solid, and the organic fraction may even stay fully liquid irrespective of tropospheric humidity.

Adsorption and desorption studies in the aqueous phase for the toluene/activated carbon system

AbstractThe activated carbon adsorption and desorption of toluene in single‐component aqueous solutions were investigated. Adsorption equilibrium and batch rate studies were conducted to measure the capacity of Filtasorb‐300 (F‐300) for toluene and to determine the effects of the initial toluene concentration, the F‐300 particle size, and the hydrodynamic conditions in the liquid phase on the rate of toluene adsorption on F‐300. The results of the adsorption rate experiments were successfully fitted with the homogeneous surface diffusion (HSD) model and a surface diffusion coefficient which varies exponentially with surface coverage. The model also accounted for the dependence of the external toluene mass transfer coefficient on the hydrodynamic conditions in the liquid phase. The reversibility of toluene adsorption on F‐300 was addressed in desorption equilibrium experiments which indicated that only about five percent of the toluene molecules adsorb irreversibly on the surface of F‐300. Batch desorption rate studies were conducted for different initial toluene surface concentrations, F‐300 particle sizes, and liquid/solid ratios. Use of the previously determined toluene transport parameters in the HSD model allowed for successful prediction of the experimental desorption rates.

Activated carbon adsorption and desorption of toluene in the aqueous phase

AbstractThe equilibrium and dynamics of toluene adsorption and desorption in singlecomponent aqueous solutions were investigated. Adsorption rates in a batch reactor under a variety of operating conditions were fitted successfully with the homogeneous surface diffusion model and a surface diffusion coefficient that increases exponentially with surface concentration. The dependence of the external mass‐transfer coefficient on the hydrodynamic conditions in the liquid phase was taken into account. Desorption studies in the aqueous phase and solvent regeneration of tolueneloaded activated carbon suggest that only a small fraction of toluene adsorbs irreversibly. Moreover, irreversible adsorption occurs only on virgin activated carbon, while adsorption on solvent‐regenerated activated carbon is fully reversible. After accounting for irreversible adsorption, the model successfully predicted toluene desorption rates in the aqueous phase under various operating conditions using toluene transport parameters determined from the adsorption studies.