Actual Waters Research Articles

Humic Acids Pyrolyzed onto Silica Microparticles for Solid-Phase Extraction of Benzotriazoles and Benzothiazoles from Environmental Waters

This work focuses on the extraction and determination of contaminants of environmental concern belonging to the classes of benzotriazoles and benzothiazoles from tap and raw river water samples. The sorbent, recently proposed by this research group, prepared by pyrolysis of humic acids (HAs) onto silica microparticles (HA-C@silica), was tested for fixed-bed SPE of benzotriazole and benzothiazole compounds by modulating its sorption affinity through the carbon loading. This was successfully increased from 10 to 20 wt% HAs and the obtained material, characterized by different techniques, provided quantitative adsorption at the sample native pH (7.5–8), for 50–250 mL samples spiked with each compound at the micrograms per litre levels. After extraction, the analytes were simultaneously desorbed by 4 mL methanol, even more reducible to small volume before HPLC–HESI-MS/MS analysis. Recovery was satisfactory for all compounds, ranging from 70 to 114%, with RSD values ≤ 16% (n = 3). The developed procedure allows quantitation of benzotriazoles at concentrations far below the environmental trigger limits. HA-C@silica turned out to be appealing in comparison with the commercial sorbents in terms of cost, recovery and pre-concentration for determination of such pollutants in actual surface waters. Good reproducibility was observed on independent HA-C@silica preparations.

Photochemical behavior of benzophenone sunscreens induced by nitrate in aquatic environments

Benzophenones (BPs), which are widely used UV filters, have aroused considerable public concern owing to their potential endocrine-disrupting activities. Herein, we systematically investigated their photochemical behavior and fate, which is mediated by nitrate in aquatic environments. The results showed that 10 μM of 3 BPs can be completely degraded within 4 h of simulated sunlight irradiation in a 10 mM nitrate solution at pH 8.0, and 2,4-dihydroxybenzophenone (BP-1) has a 31.6% mineralization rate after 12 h irradiation. Their photolytic rates (kobs) presented a significant linear correlation with the logarithmic values of the nitrate concentration for 0.1–10 mM (R2 > 0.98), and in three actual waters, the rates of BP-1 were also positively related to the intrinsic nitrate concentration. Furthermore, higher transformation rates under alkaline condition were observed, especially for BP-1, with its kobs at pH 10 being 8.3-fold higher than that at pH 6.0. Moreover, dissolved oxygen (DO) also has an impact on the reaction kinetics to some degree. According to the quenching experiments, we found that three reactive oxygen species (ROS), namely, •OH, •NO, and •NO2, participated in this photolysis of BPs, and the contribution of •OH accounted for 32.1%. Furthermore, we selected BP-1 as the model molecule to study the transformation pathways and toxicity changes in this system. Four main transformation pathways including hydroxylation, nitrosylation, nitration, and dimerization were proposed, based on liquid chromatography quadrupole time-of-flight mass spectrometry (LC-Q-TOF-MS) analysis and density functional theory (DFT). According to the toxicity test, the formed intermediates were more toxic to Photobacterium phosphoreum than the parent BP-1. Therefore, these results can help reveal primary phototransformation mechanisms and evaluate the potential ecological risks of BPs in aquatic environments.

Impact of the unsaturated zone in the hydrochemical and hydrodynamical functioning of karst aquifer: example of the Tlemcen Mountains, Northwest Algeria

The aim of this work is to understand the role of unsaturated zone on the functioning of karst aquifers. The easy infiltration of water into the system explains the expansion of karstification through the saturated zone. The unsaturated zone is largely involved in the flow on the overall karstic system. For this purpose, we use the environmental tracing, namely the calco-carbonic equilibrium elements (CO2, CO32−, HCO3−, Ca2+, Mg2+), TOC, and isotopic elements (14C, 13C, and 3H) interesting tracers of residence time. Result obtained from TOC and Mg2+ enabled us to classify the behavior of systems to fissured type with a low average and restricted fluctuation of TOC concentrations and relatively high Mg2+ (inertial system). The second functioning type is characterized by a very high average and important variation of TOC with low contents of Mg2+ (perched system with fast infiltration). The values of 3H and 14C allow to distinguish three categories of water (old, mixture actual-old, and actual) with the predominance of actual waters. The comparison of the measured δ13C with those calculated shows that the majority of the karstic aquifers of Tlemcen Mountains are open systems with respect to the soil biogenic CO2. The piston flow in the unsaturated zone puts in charge the drains and stops drainage in the lower part of the system. The direct participation of infiltration is relatively low for all systems.

Recent trends in electrochemical detection of phosphate in actual waters

This review considers recent advances, during the last 3 years, devoted to electrochemical sensors adapted for phosphate determination in actual water samples. The recognition elements are classified as follows: metal-based electrodes, modified electrodes with polymers, metal complexes, such as phthalocyanines or molybdates, and a biological element, namely the enzyme pyruvate oxidase. The classical potentiometric or amperometric methods and also more sophisticate methods, such as field effect transistors, capacitive Mott-Schottky systems or electrochemical impedimetric method, are used for the transduction of the recognition signal. Analytical performance of these recently developed phosphate sensors are compared in terms of applicability to monitoring of natural and discharge waters.

Biopolymer Beads for Aqueous Phosphate Removal: Possible Applications in Eutrophic Lakes

Novel iron (Fe) cross-linked alginate (FCA) beads were used for phosphate removal from synthetic water, lake water, and wastewater. Batch experiments were conducted with the beads (0.118 g dry weight) using three different initial concentrations of phosphate (C0=5, 50, and 100 mg PO43−-P/L) as well as environmentally relevant (eutrophic lakes) concentration of 100 μg PO43−-P/L. Approximately 97% of phosphate (C0=5 mg PO43−-P/L) was removed by the beads in 360 min from an aqueous solution. In 360 min, beads removed ∼76% of phosphate from water with C0=50 PO43−-P/L and ∼46% from water with C0=100 mg PO43−-P/L. For 100 μg PO43−-P/L, 80% removal was achieved within 20 min. The second-order reaction fit well for all the concentrations with reaction rate constants (k) of 0.076 and 0.2027 L/mg/min (C0=5 mg and 100 μg PO43−-P/L, respectively). The maximum phosphate sorption capacity was found to be ∼79 mg PO43−-P/g of dry beads. No change in phosphate removal was observed in the presence of Cl−, HCO3−, SO42−, NO3−, and natural organic matter (NOM). To investigate the feasibility of using the FCA beads in a real-life situation (e.g., in eutrophic lakes), actual lake waters (11–69 μg PO43−-P/L) were used and 81–100% phosphate removal was observed in 24 h. Results presented here demonstrate the potential for the use of the FCA beads for the reclamation of eutrophic lakes (removal of excess of phosphate).

Effects of magnesium and potassium sulfates on oil recovery by water flooding

Conventional water flooding has been applied successfully worldwide using sea water and/or formation brine. Two processes are proposed to improve oil recovery by water flooding such as; lowering water salinity as LoSal (300 to 5,000ppm) and changing concentration of cations and/or anions as designer water.This experimental study investigates combined effects of concentration of magnesium and potassium sulfates with consideration of sodium chloride salinity on oil recovery by water flooding. To achieve the objectives of the study, nine flood experiments were conducted using actual sea water and synthetic water injected through actual sandstone reservoir cores. Three experiments were achieved using actual Egyptian sea waters of Al-Obayied, Balteam and Abo Rudies to investigate the combined effect of magnesium and potassium sulfate concentration on oil recovery. Three experiments were conducted to study the combined effect of Magnesium sulfate and sodium chloride contents on oil recovery. In addition, three other experiments were carried out to investigate the effect of potassium chloride concentrations associated with sodium chloride salinity (higher than the 5000ppm stated for low salinity process) on oil recovery.The results revealed that sea water of higher content of magnesium sulfate and potassium sulfate increases the oil recovery by water flooding. In addition, the increase of concentration of magnesium sulfate with lower sodium chloride increases the oil recovery by designer water injected containing sodium chloride. It is also concluded that the increase of potassium sulfate increases the oil recovery. The increment in oil recovery by increase of magnesium, and/or potassium sulfate is attributed to wettability alteration to more water-wet, higher pH condition and also to the decrease in sodium chloride associated in the same water injected.The application of the attained results will have real importance in designing the concentration of magnesium and/or potassium concentration of the designer water injected with consideration of sodium chloride salinity of the reservoir.

Oxidation of odor compound indole in aqueous solution with ferrate (VI): Kinetics, pathway, and the variation of assimilable organic carbon

Indole is a typical fecal odor compound and has negative impact on water quality at low concentrations. Here, the oxidation of indole by ferrate [Fe(VI)] was investigated, in terms of the reaction kinetics, the oxidation products, and the variation of assimilable organic carbon (AOC). The oxidation of indole was pH-dependent (6.0–9.5), and the pH-dependent profile could be well explained by the acid-base equilibrium of Fe(VI). The apparent second-order rate constants (kapp) for indole oxidation with Fe(VI) ranged from 692±26M−1s−1 at pH 6.0 to 3.08±0.15M−1s−1 at pH 9.5. The results of experiments conducted under real source water background showed that indole could be effectively removed by Fe(VI) from actual polluted waters. After analyzing the reaction pathway, it was found that the initial steps in the oxidation of indole were the hydroxylation of indole to 2,3-dihydroxyindole, followed by the cleavage of N-heterocyclic ring. Formanilide was a major oxidation product in this process, and it is less reactive with Fe(VI) than that of indole. High concentrations of Fe(VI) could effectively oxidize indole in the water and has little impact on the microbiological stability of the treated water. Based on the results, Fe(VI) can be an effective agent for the control of indole in water treatment.

Evaluation of Rice Husk for SPE of Fluoroquinolones from Environmental Waters Followed by UHPLC-HESI-MS/MS

Untreated rice husk (RH) was evaluated as solid-phase extraction (SPE) sorbent for Fluoroquinolone antibiotics (FQs). This natural material, made of cellulose, hemicellulose, lignin and silica, and containing various functional groups, i.e., carboxyl, hydroxyl, and amidogen residues, is a potential sorbent material for polar aromatics like FQs. First, the RH capability to adsorb FQ species from water was studied by batch sorption experiments in tap and river waters, and the experimental data, fitted by the Langmuir model, gave adsorption capacities up to 32 mg g−1. Then, RH was tested as column-packed sorbent for pre-concentration of tap and not tampered river waters spiked with six widely employed FQs, i.e., Ciprofloxacin, Danofloxacin, Enrofloxacin, Levofloxacin, Marbofloxacin, and Norfloxacin. The analytes were quantitatively adsorbed on the RH cartridge at the native pH, simultaneously eluted by NH3–MeOH mixture, separated in an 8 min ultrahigh-performance liquid chromatography run and quantified/confirmed by electrospray ionization tandem mass spectrometric detection in single reaction monitoring mode. Recoveries in the range 71–120% were observed (RSD < 15%, n = 3) for 75–1000 ng L−1 spikes. Method detection limits were in the range 25–33 ng L−1. The batch-to-batch reproducibility was assessed, and the analytical procedure was applied to the determination of FQs in actual environmental waters.

Assessing the photocatalytic transformation of norfloxacin by BiOBr/iron oxides hybrid photocatalyst: Kinetics, intermediates, and influencing factors

Norfloxacin (NOR) is a widely used fluoroquinolone antibacterial that has drawn much concern due to its adverse effect on aquatic ecology and human health. In this study, a novel magnetically recoverable BiOBr/iron oxides (BiOBr/Fe3O4) heterojunction photocatalyst with high photocatalytic activity on NOR was successfully synthesized using a facile in-situ coprecipitation method. The samples were characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, UV–vis diffuse reflectance spectra, N2 adsorption-desorption analysis, and vibrating sample magnetometer. Several factors affecting the catalytic performance of BiOBr/Fe3O4 were investigated. Results showed that the catalytic degradation efficiency of NOR increased with the increasing bicarbonate doses, but decreased with the increasing natural organic matter concentrations. The presence of nitrate stimulated NOR degradation by BiOBr/Fe3O4 at low concentrations but inhibited the degradation at high concentrations. The photogenerated reactive species were determined based on free radicals trapping experiments, revealing that the photodegradation of NOR over BiOBr/Fe3O4 under visible light was dominated by superoxide radicals and hydroxyl radicals rather than oxidation by direct holes. On the basis of the degradation products identified by HPLC–MS, the NOR degradation pathway was proposed. NOR possibly underwent the piperazine ring transformation, decarboxylation and defluorination to generate eleven intermediates. Toxicity assays by Vibrio fischeri proved that the NOR photocatalytic transformation products retained negligible antibacterial activity relative to the parent compound. The catalytic degradation of NOR by BiOBr/Fe3O4 was also effective in the actual natural waters.

A physical basis for designing integrated acoustic network systems for underwater observations

A concept for designing network systems for underwater observations based on the joint development of hydroacoustic radiating and receiving elements integrated with different channels of communication is discussed. The main requirements for such systems, principles, and algorithms of their operation under nonstationary conditions of actual marine waters are formulated. The results from several numerical and field experiments demonstrating the performance of certain elements of such systems in typical shallow water basins are presented.

Formation of assimilable organic carbon during the oxidation of water containing Microcystis aeruginosa by ozone and an advanced oxidation process using ozone/hydrogen peroxide

Cyanobacteria may cause an increase in the amount of assimilable organic carbon (AOC) that can lead to extensive microbial growth in the water. The present study systematically examined AOC formation from the oxidation of a pure culture of Microcystis aeruginosa by ozone and the advanced oxidation process of ozone/hydrogen peroxide (O3/H2O2) and also explored the major mechanisms by monitoring the change of the algal integrity and structural change of algal organic matter.The results show that AOC formation followed a rapid-slow pattern during the ozonation of the algal suspensions. The rapid formation of AOC was attributed to the release of highly bioavailable intracellular organic matter, and the slow increase in AOC was due to the reaction of the algal organic matter with molecular ozone and/or OH. Compared to ozone alone, a remarkable increase in AOC at the same ozone exposure was observed during O3/H2O2, in which the increase in AOC was mainly attributed to the reaction of OH with algal organic matter, resulting in its molecular weight change. A significant increase in the AOC concentration after oxidation of algae in actual waters was also seen, and a slightly higher amount of AOC was formed during O3/H2O2 compared to ozone alone.

Chemical modeling for precipitation from hypersaline hydrofracturing brines

Hypersaline hydrofracturing brines host very high salt concentrations, as high as 120,000–330,000 mg/L total dissolved solids (TDS), corresponding to ionic strengths of 2.1–5.7 mol/kg. This is 4–10 times higher than for ocean water. At such high ionic strengths, the conventional equations for computing activity coefficients no longer apply; and the complex ion-interactive Pitzer model must be invoked. The authors herein have used the Pitzer-based PHREEQC computer program to compute the appropriate activity coefficients when forming such precipitates as BaSO4, CaSO4, MgSO4, SrSO4, CaCO3, SrCO3, and BaCO3 in hydrofracturing waters. The divalent cation activity coefficients (γM) were computed in the 0.1 to 0.2 range at 2.1 mol/kg ionic strength, then by 5.7 mol/kg ionic strength, they rose to 0.2 for Ba2+, 0.6 for Sr2+, 0.8 for Ca2+, and 2.1 for Mg2+. Concurrently, the γSO42− was 0.02–0.03; and γCO32− was 0.01–0.02. While employing these Pitzer-derived activity coefficients, the authors then used the PHREEQC model to characterize precipitation of several of these sulfates and carbonates from actual hydrofracturing waters. Modeled precipitation matched quite well with actual laboratory experiments and full-scale operations. Also, the authors found that SrSO4 effectively co-precipitated radium from hydrofracturing brines, as discerned when monitoring 228Ra and other beta-emitting species via liquid scintillation; and also when monitoring gamma emissions from 226Ra.

Iron Kinetics and Evolution of Microbial Populations in Low-pH, Ferrous Iron-Oxidizing Bioreactors

Iron-rich, acidic wastewaters are commonplace pollutants associated with metal and coal mining. Continuous-flow bioreactors were commissioned and tested for their capacities to oxidize ferrous iron in synthetic and actual acid mine drainage waters using (initially) pure cultures of the recently described acidophilic, iron-oxidizing heterotrophic bacterium Acidithrix ferrooxidans grown in the presence of glucose and yeast extract. The bioreactors became rapidly colonized by this bacterium, which formed macroscopic streamer growths in the flowing waters. Over 97% of ferrous iron in pH 2.0-2.2 synthetic mine water was oxidized (at up to 225 mg L(-1) h(-1)) at dilution rates (D) of 0.6 h(-1). Rates of iron oxidation decreased with pH but were still significant, with influent liquors as low as pH 1.37. When fed with actual mine water, >90% of ferrous iron was oxidized at D values of 0.4 h(-1), and microbial communities within the bioreactors changed over time, with Atx. ferrooxidans becoming increasingly displaced by the autotrophic iron-oxidizing acidophiles Ferrovum myxofaciens, Acidithiobacillus ferrivorans, and Leptospirillum ferrooxidans (which were all indigenous to the mine water), although this did not have a negative impact on net ferrous-iron oxidation. The results confirmed the potential of using a heterotrophic acidophile to facilitate the rapid commissioning of iron-oxidizing bioreactors and illustrated how microbial communities within them can evolve without compromising the performances of the bioreactors.

Application of integrated forward and reverse osmosis for coal mine wastewater desalination

Abstract Water management is an integral part of coal mining operations. Due to the constraints on releasing saline water, coal mines require additional water storage facilities and therefore seek to minimise their inventory of saline water. Adopting efficient treatment technologies on-site would minimise the risk of wet season run-offs, freshwater contamination and allow segregation of different qualities of water to enable greater water recycling. This study aims to evaluate the application of an integrated forward osmosis (FO) and reverse osmosis (RO) system with three different actual coal mine waters, containing various concentrations of sulphates and silica that are generally associated with scaling and fouling of membrane systems. Three different FO draw solutions, di-sodium hydrogen phosphate (DHSP), sodium hexametaphosphate (SHMP) and sodium lignosulphonate (SLS) were evaluated. Two different modes of integrating the FO and RO systems were identified. The integrated system was able to concentrate the brackish mine waters, recovering more than 80% of the volume of mine water and obtaining dischargeable quality treated water. Simple physical cleaning with clean water circulation was found to be effective in restoring the FO water flux. The osmotic gradient between two mine waters was also utilised to adopt mine water as a draw solution. The effect of solution temperature on stand-alone and integrated FO and RO systems was also evaluated. The combination of FO with RO provided a better performance than individual FO or RO in treating coal mine wastewater. The FO unit served as an effective pre-treatment system prior to RO and the integrated FO–RO systems has a strong potential to successfully eliminate conventional pre-treatment processes for RO.

Bioremediation potential of Pseudomonas sp. isolated from a 2, 4, 6-trinitrotoluene contaminated site

Pseudomonas mosselii and Pseudomonas stutzeri isolated from TNT contaminated site were evaluated for their TNT degrading potential in aqueous phase. Free and immobilised cell cultures of P. mosselii and P. stutzeri were evaluated individually and in combination, by shake flask studies for degrading TNT in synthetic solutions and in actual waste waters respectively. All the flasks were incubated at temperature 37°C at 120 rpm for 48 hours in continuous mode. Biodegradation of TNT was monitored by carrying out qualitative and quantitative studies. Spectro-photometric measurements of the density of free suspended cells in the culture broth indicate the positive growth of the bacteria under toxic conditions of TNT contamination. The immobilised cells showed over all better performance as compared to free cells. The qualitative and quantitative analysis by HPLC revealed the 100% biodegradation of TNT to secondary metabolites of bacterial metabolism within 24 hours and 28 hours of incubation, by immobilised cells of P. mosselii in synthetic and in actual waste waters respectively.

Graphene-derivatized silica as an efficient solid-phase extraction sorbent for pre-concentration of fluoroquinolones from water followed by liquid-chromatography fluorescence detection

This work presents a novel analytical method based on graphene for the determination of five widely used fluoroquinolones (FQs) in aqueous matrices. The procedure entails solid-phase extraction (SPE) on graphene-derivatized silica (200mg), followed by liquid chromatography with fluorescence detection. Monolayer graphene oxide (GO) flakes were covalently bonded onto aminopropyl silica microparticles, and then treated with aqueous hydrazine to obtain the reduced GO (RGO). The final material (RGO–silica) was characterized by thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and BET analysis, and for the first time evaluated as mixed-mode sorbent for the SPE of FQs from natural waters. Accuracy was studied on tap/raw river water in the concentration range 5–10,000ngL−1, obtaining mean absolute recoveries from 72 to 118%. The inter-day precision was good, showing relative standard deviations (RSDs) in the range 5–15%. Sample volumes up to 1L provided enrichment factors up to 1000, achieving accurate quantification of concentrations as low as 5ngL−1. The analytes were simultaneously and quantitatively eluted from the RGO–silica cartridge in a single fraction by using acetonitrile combined with aqueous tetrabutyl ammonium hydroxide. The batch-to-batch reproducibility was verified on three independently prepared RGO–silica samples. RGO–silica was advantageous in terms of adsorption capacity and reusability with respect to commercial sorbents; the cartridge proved to be reusable for at least 10 consecutive extractions, with no significant loss of efficiency (recovery >70%). The analytical procedure was applied to the determination of FQs in actual environmental waters.

Effect of pH on Four Defluoridation Adsorbents under Natural High Fluoride Groundwater

Appropriate drinking water defluoridation technology is urgently needed in china, which has a wide fluoride-rich area. The adsorption defluoridation method in the industrial high fluoride wastewater treatment is generally considered to be efficient and economic. However, the practical application of the method is not ideal in obtaining drinking water defluoridation. Four representative adsorbents activated alumina, activated zeolite, hydroxyapatite and hydrous zirconium oxide have been tested in terms of defluoridation efficiency under natural high fluoride groundwater and compared to clarify existing problems of adsorption methods. Results show that pH significantly affected adsorption efficiency. The adsorbents have low adsorption capacity under natural high fluoride groundwater and can achieve good adsorption effect under acidic conditions. However, in adjusting the water to the appropriate pH range, the adsorption method loses its advantages of convenience and affordability. Therefore, any adsorbent should be tested with actual field waters before designing filed application systems. Further research is also warranted in evaluating the field performance and the economic acceptance of the proposed method.

A novel capillary electrophoresis method with pressure assisted field amplified sample injection in determination of thiol collectors in flotation process waters

A new capillary electrophoresis method was developed for the quantification of diisobutyldithiophosphate (DTP), diisobutyldithiophosphinate (DTPI) and ethyl and isobutyl xanthates (EX, IBX) all of which are used as thiol collectors in froth flotation. This method uses pressure assisted field amplified sample injection (PA-FASI) to concentrate the analytes at the capillary inlet. The background electrolyte in electrophoretic separation was 60millimolar (mM) from 3-(cyclohexylamino)propane-1-sulfonic acid (CAPS) in 40mM NaOH solution. The similar CAPS electrolyte solution has earlier been used for screening for diuretics that contained sulphonamide and/or carboxylic groups. In this study, the functional groups are xanthate, phosphate and phosphinate. The method was developed using actual flotation process waters. The results showed that the water delivered from the plant did not contain significant amount of collectors; therefore, method development was accomplished by spiking analytes in these waters. Separation of analytes was achieved in 15min. The range of quantification was 0.27–66.6mg/L (R2 0.9991–0.9999) for all analytes other than ethyl xanthate, for which the range was 0.09–66.6mg/L (R2 0.9999). LOD (S/N=3) and LOQ (S/N=10) values for DTP, DTPI, IBX and EX were 0.05, 0.07, 0.06 and 0.01mg/L and 0.16, 0.25, 0.21 and 0.04mg/L, respectively. No interference from the matrices was observed, when the method was tested at a gold concentrator plant.

Major, trace element and stable isotope composition of water and muds precipitated from the hot springs of Bolivia: Are the waters of the spring's potential ore forming fluids?

The deposition of metal-rich black or reddish muds by many thermal springs in the Cordilleras and the Altiplano of Bolivia suggest that these geothermal waters may be related to those that once formed the world-class Bolivian tin, silver and gold mineralisation. The discharge temperatures of these springs are as high as 70°C. According to δ18O, δD, tritium data and Ar/N2 ratios these waters are predominantly of meteoric origin. Less than 10% of the discharging thermal water represents deep-seated metal-rich thermal brines of at least 530°C according to carbon exchange between CO2 and CH4. These brines ascend along tectonic faults and mix with low-temperature meteoric water in surface-near aquifers. The meteoric component of the thermal water is recharged in the high Cordilleras with residence times exceeding 50 years. The chemical composition of the thermal water is dominated by the rather inefficient low-temperature leaching of the surface-near aquifer rocks by meteoric water. The small fraction of metal-rich hot deep-seated water is not able to increase the metal content of the water mix to a level sufficient to classify these thermal waters as ore-bearing. Surface-near leaching is supported, e.g., by the B/Li ratios of the spring water of the Western Cordillera and Caleras/Pulacayo in the Eastern Cordillera that correspond very closely to that of the easily leachable glassy inclusions of the outcropping andesitic lavas. The often remarkable metal content of the muds deposited by the springs originate from efficient scavenging of heavy metals by ferric oxyhydroxides. Under the given arid to semi-arid climate the muds are additionally enriched in metals by wind-transported dust. The present study does support a relation of the actual thermal waters with neither the classical subduction-related Upper Tertiary tin, silver and gold mineralisation nor the supposed younger Sb mineralisation of Bolivia.

Enhanced ozonation degradation of di-n-butyl phthalate by zero-valent zinc in aqueous solution: Performance and mechanism

Enhanced ozonation degradation of di-n-butyl phthalate (DBP) by zero-valent zinc (ZVZ) has been investigated using a semi-continuous reactor in aqueous solution. The results indicated that the combination of ozone (O3) and ZVZ showed an obvious synergetic effect, i.e. an improvement of 54.8% on DBP degradation was obtained by the O3/ZVZ process after 10min reaction compared to the cumulative effect of O3 alone and O2/ZVZ. The degradation efficiency of DBP increased gradually with the increase of ZVZ dosage, enhanced as solution pH increasing from 2.0 to 10.0, and more amount of DBP was degraded with the initial concentration of DBP arising from 0.5 to 2.0mgL−1. Recycling use of ZVZ resulted in the enhancement of DBP degradation, because the newly formed zinc oxide took part in the reaction. The mechanism investigation demonstrated that the enhancement effect was attributed to the introduction of ZVZ, which could promote the utilization of O3, enhance the formation of superoxide radical by reducing O2 via one-electron transfer, accelerate the production of hydrogen peroxide and the generation of hydroxyl radical. Additionally, the newly formed zinc oxide on ZVZ surface also contributed to the enhancement of DBP degradation in the recycling use of ZVZ. Most importantly, the O3/ZVZ process was also effective in enhanced ozonation degradation of DBP under the background of actual waters.