Lead concentration increase in the hepatic and gill soluble fractions of European chub (Squalius cephalus)—an indicator of increased Pb exposure from the river water

Purpose

To examine if chronic exposure of feral fish to elevated Pb concentrations in the river water (up to 1???g?L^?1), which are still lower than European recommendations for dissolved Pb in surface waters (7.2???g?L^?1; EPCEU (Official J L 348:84, 2008)), would result in Pb accumulation in selected fish tissues.

Methods

Lead concentrations were determined by use of HR ICP-MS in the gill and hepatic soluble fractions of European chub (Squalius cephalus) caught in the Sutla River (Croatia?CSlovenia).

Results

At the site with increased dissolved Pb in the river water, soluble gill Pb levels (17.3???g?L^?1) were approximately 20 times higher compared to uncontaminated sites (0.85???g?L^?1), whereas the ratio between contaminated (18.1???g?L^?1) and uncontaminated sites (1.17???g?L^?1) was lower for liver (15.5). Physiological variability of basal Pb concentrations in soluble gill and hepatic fractions associated to fish size, condition, sex, or age was not observed, excluding the possibility that Pb increase in chub tissues at contaminated site could be the consequence of studied biotic parameters. However, in both tissues of Pb-exposed specimens, females accumulated somewhat more Pb than males, making female chubs potentially more susceptible to possible toxic effects.

Conclusions

The fact that Pb increase in gill and hepatic soluble fractions of the European chub was not caused by biotic factors and was spatially restricted to one site with increased dissolved Pb concentration in the river water points to the applicability of this parameter as early indicator of Pb exposure in monitoring of natural waters.     

Synthesis of α-Fe2O3 nanofibers for applications in removal and recovery of Cr(VI) from wastewater

Purpose

Nanomaterials such as iron oxides and ferrites have been intensively investigated for water treatment and environmental remediation applications. The purpose of this work is to synthesize α-Fe₂O₃ nanofibers for potential applications in removal and recovery of noxious Cr(VI) from wastewater.

Methods

α-Fe₂O₃ nanofibers were synthesized via a simple hydrothermal route followed by calcination. The crystallographic structure and the morphology of the as-prepared α-Fe₂O₃ nanofibers were characterized by X-ray diffraction, scanning electron microscope, and transmission electron microscope. Batch adsorption experiments were conducted, and Fourier transform infrared spectra were recorded before and after adsorption to investigate the Cr(VI) removal performance and adsorption mechanism. Langmuir and Freundlich modes were employed to analyze the adsorption behavior of Cr(VI) on the α-Fe₂O₃ nanofibers.

Results

Very thin and porous α-Fe₂O₃ nanofibers have been successfully synthesized for investigation of Cr(VI) removal capability from synthetic wastewater. Batch experiments revealed that the as-prepared α-Fe₂O₃ nanofibers exhibited excellent Cr(VI) removal performance with a maximum adsorption capacity of 16.17 mg g^?1. Furthermore, the adsorption capacity almost kept unchanged after recycling and reusing. The Cr(VI) adsorption process was found to follow the pseudo-second-order kinetics model, and the corresponding thermodynamic parameters ΔG°, ΔH°, and ΔS° at 298 K were calculated to be ?26.60 kJ?mol^?1, ?3.32 kJ?mol^?1, and 78.12 J?mol^?1 K^?1, respectively.

Conclusions

The as-prepared α-Fe₂O₃ nanofibers can be utilized as efficient low-cost nano-absorbents for removal and recovery of Cr(VI) from wastewater.     

Adsorption and photodegradation of microcystin-LR onto sediments collected from reservoirs and rivers in Taiwan: a laboratory study to investigate the fate, transfer, and degradation of microcystin-LR

Background, aim, and scope

This study demonstrated the adsorption capacity of microcystin-LR (MC-LR) onto sediment samples collected from different reservoirs (Emerald and Jade reservoirs) and rivers (Dongshan, Erhjen, and Wukai rivers) in Taiwan to investigate the fate, transport behavior, and photodegradation of MC-LR.

Main features

Langmuir adsorption and photodegradation studies were carried out in the laboratory and tested the capability of sediments for MC-LR adsorption. These data suggested that sediments play a crucial role in microcystins degradation in aquatic systems.

Results and discussion

The results of batch experiments revealed that the adsorption of MC-LR varied significantly with texture, pH, and organic matter content of sediments. Silty and clay textures of the samples were associated with larger content of organic matter, and they displayed the enhanced MC-LR adsorption. Low pH sediment showed increased adsorption of MC-LR. The effective photodegradation of MC-LR (1.6 ??g/mL) was achieved within 60 min under 254 nm light irradiation.

Conclusion

A comparative study of adsorption capacity of all sediment samples was carried out and discussed with respect to different aspects. Among all, sediments collected from Jade reservoir showed enhanced MC-LR adsorption (11.86 ??g/g) due to favored textural properties (BET surface area = 20.24 m2/g and pore volume = 80.70 nm).

Perspectives

These data provide important information that may be applied to management strategies for improvement of water quality in reservoirs and rivers and other water bodies in Taiwan.     

Copper chitosan nanocomposite: synthesis, characterization, and application in removal of organophosphorous pesticide from agricultural runoff

Purpose

Removal of malathion from agricultural runoff was studied using novel copper-coated chitosan nanocomposite (CuCH)??a biopolymeric waste obtained from marine industry.

Methods

Synthesis and characterization of the adsorbent using different spectral techniques like Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy, energy-dispersive X-ray spectroscopy, Brunauer, Emmett, and Teller surface analyzer have been carried out. Equilibrium studies have been carried out to optimize the dose rate, pH, and the reaction time. Parathion and methyl parathion removal were also evaluated by CuCH in the batch mode. Using gas chromatography?Cmass spectrometry (GC?CMS) and FTIR studies suitable mechanism for adsorption has been suggested.

Results

The particle size of the adsorbent ranged from 700 to 750?nm. The surface area was found to be 20?m²?g^-1 with a pore volume of 0.11?cc?g^-1. The maximum adsorption capacity of malathion by CuCH was found to be 322.6?±?3.5?mg?g^-1 at an optimum pH of 2.0. Presence of copper ions enhanced the adsorption capacity of the adsorbent. The reaction was found to follow pseudo second-order kinetics with a rate constant of 0.53?g?mg^-1?min^-1. Evidence from FTIR indicated that copper ions form a dithionate complex with malathion during the adsorption stage. The adsorbent was found to remove malathion completely from spiked concentration of 2?mg?l^-1 in the agricultural run-off samples. It was also found that CuCH removed other organophospurous pesticides like methyl parathion and parathion under prevailing conditions.

Conclusions

The results indicated that CuCH could be applied for the removal of organophosphorous pesticides.     

Blooming of Microcystis aeruginosa in the reservoir of the reclaimed land and discharge of microcystins to Isahaya Bay (Japan)

Purpose

In the reservoir created in the reclaimed land in Isahaya Bay, Japan, Microcystis aeruginosa, which produces microcystins (MCs), bloomed every year, and the water with high levels of MCs in the reservoir has been often drained to Isahaya Bay to adjust the water level. The principal aims of this study are to clarify the water conditions suitable for blooming of M. aeruginosa in the reservoir, to follow the amount of distribution of MCs inside and outside the reservoir, and to discuss how blooming of M. aeruginosa is controlled in the reservoir and how MCs produced by Microcystis spread or accumulate in the aquatic environment.

Method

We monitored the water quality (temperature, salinity, dissolved inorganic nitrogen (DIN), and dissolved inorganic phosphorus) in the reservoir with seasonal blooming of microalgae including phytoplankton and M. aeruginosa using the concentrations of chlorophyll ?? and MCs, respectively, and collected the surface sediment in the reservoir and the bay to determine the MC content using the ELISA method.

Result

M. aeruginosa bloomed in extremely low DIN conditions of the water in warm seasons (spring and late summer to autumn). The year-mean standing stock of MCs was approximately 34.5?kg in the water and 8.4?kg in the surface sediment in the reservoir. Approximately 64.5?kg of MCs was discharged with the effluent to the bay in a year.

Conclusion

Since a large amount of MCs always suspends in the water in the reservoir and it has been discharged to the bay, suspension-feeding animals are exposed most seriously to the high levels of MCs occurring in these areas. We need to pay attention to the danger of widespread dispersal of MCs and biological concentration of MCs by fish and clam inside and outside the reservoir.     

Microbial structure and chemical components of aerosols caused by rotating brushes in a wastewater treatment plant

Purpose

Bacterial community structure and the chemical components in aerosols caused by rotating brushes in an Orbal oxidation ditch were assessed in a Beijing municipal wastewater treatment plant.

Methods

Air samples were collected at different distances from the aerosol-generating rotating brushes. Molecular culture-independent methods were used to characterize the community structure of the airborne bacteria in each sample regardless of cell culturability. A clone library of 16S rDNA directly amplified from air DNA of each sample was constructed and sequenced to analyze the community composition and diversity. Insoluble particles and water-soluble ions emitted with microorganisms in aerosols were analysis by a scanning electron microscope together with energy dispersive X-ray spectroscopy and ion chromatogram analyzer.

Results

In total, most of the identified bacteria were Proteobacteria. The majority of sequences near the rotating brushes (the main source of the bioaerosols) were Proteobacteria (62.97 %) with ??-(18.52 %) and ??-(44.45?%) subgroups and Bacteroidetes (29.63 %). Complex patterns were observed for each sampling location, suggesting a highly diverse community structure, comparable to that found in water in the Orbal oxidation ditch. Accompany with microorganisms, 46.36???g/m³ of SO ₄ ^2? , 29.35???g/m³ of Cl^?, 21.51???g/m³ of NO ₃ ^? , 19.76???g/m³ of NH ₄ ⁺ , 11.42???g/m³ of PO ₄ ^3? , 6.18???g/m³ of NO ₂ ^? , and elements of Mg, Cl, K, Na, Fe, S, and P were detected from the air near the aerosols source.

Conclusions

Differences in the structure of the bacterial communities and chemical components in the aerosols observed between sampling sites indicated important site-related variability. The composition of microorganisms in water was one of the most important sources of bacterial communities in bioaerosols. Chemical components in bioaerosols may provide a media for airborne microorganism attachment, as well as a suitable microenvironment for their growth and survival in the air. This study will be benefit for the formulation of pollution standards, especially for aerosols, that take into account plant workers?? health.     

Equilibrium and kinetics of adsorption of phosphate onto iron-doped activated carbon

Purpose

Two series of activated carbons modified by Fe (II) and Fe (III) (denoted as AC/N-Fe^II and AC/N-Fe^III), respectively, were used as adsorbents for the removal of phosphate in aqueous solutions.

Method

The synthesized adsorbent materials were investigated by different experimental analysis means. The adsorption of phosphate on activated carbons has been studied in kinetic and equilibrium conditions taking into account the adsorbate concentration, temperature, and solution pH as major influential factors.

Results

Maximum removals of phosphate are obtained in the pH range of 3.78?C6.84 for both adsorbents. Langmuir isotherm adsorption equation well describes the experimental adsorption isotherms. Kinetic studies revealed that the adsorption process followed a pseudo-second order kinetic model. Results suggest that the main phase formed in AC/N-Fe^II and AC/N-Fe^III is goethite and akaganeite, respectively; the presence of iron oxides significantly affected the surface area and the pore structure of the activated carbon.

Conclusions

Studies revealed that iron-doped activated carbons were effective in removing phosphate. AC/N-Fe^II has a higher phosphate removal capacity than AC/N-Fe^III, which could be attributed to its better intra-particle diffusion and higher binding energy. The activation energy for adsorption was calculated to be 22.23 and 10.89 kJ mol^?1 for AC/N-Fe^II and AC/N-Fe^III, respectively. The adsorption process was complex; both surface adsorption and intra-particle diffusion were simultaneously occurring during the process and contribute to the adsorption mechanism.     

Evaluation of adsorption characteristics of an anionic azo dye Brilliant Yellow onto hen feathers in aqueous solutions

Purpose and aim

Removal of an anionic azo dye Brilliant Yellow has been carried out from its aqueous solutions by using hen feathers as potential adsorbent.

Materials and methods

Hen feathers procured from local poultry were cut, washed, and activated. Detailed chemical and physical analysis of hen feathers and its characterization through scanning electron microscopy, X-ray diffraction, and infrared measurements have been made. Procured dye has been adsorbed over under batch measurements and adsorption process is monitored using UV spectrophotometer.

Results

Optimum parameters for the adsorption of Brilliant Yellow over hen feathers have been determined by studying the effect of pH, temperature, concentration of dye, and amount of adsorbent. On the basis of Langmuir adsorption, isotherms feasibility of the ongoing adsorption has been ascertained and thermodynamic parameters have been calculated. Attempts have also been made to verify Freundlich, Tempkin, and Dubinin?CRadushkevich adsorption isotherm models. It is found that during adsorption, uniform distribution of binding energy takes place due to interaction of the dye molecules and the ongoing adsorption process is chemisorptions. The kinetic measurements indicate dominance of pseudo-second-order process during the adsorption. The mathematical treatment on the kinetic data reveals the rate-determining step to be governed through particle diffusion at 8?×?10^?5?M and involvement of film diffusion mechanism at higher concentration at temperatures at all the temperatures.

Conclusions

The developed process is highly efficient and it can be firmly concluded that hen feather exhibits excellent adsorption capacity towards hazardous azo dye Brilliant Yellow.     

Adsorptive removal of Pb2+ form aqueous solution by macrocyclic calix[4]naphthalene: kinetic, thermodynamic, and isotherm analysis

Background

The adsorption characteristics of Pb²⁺ ions from aqueous solutions onto calix[4]naphthalene have been investigated.

Method

Calix[4]naphthalene was prepared by the condensation of 1-naphthol and formaldehyde (1:2) in presence of hydrochloric acid at 80°C. The effect of various operation parameters, such as solution pH, initial metal ion concentration, contact time, and temperature, on the adsorption capacity of calix[4]naphthalene for Pb²⁺ have been investigated.

Result

Experimental results showed that the adsorption of Pb²⁺ ions increased with the increase in solution pH and temperature. Langmuir and Freundlich isotherms models were used to describe the adsorption behavior of Pb²⁺ by calix[4]naphthalene. Equilibrium data fitted well with the Langmuir isotherm model and the maximum adsorption capacity of calix[4]naphthalene for Pb²⁺ at 30°C was found to be 29.15 mg g^?1. Kinetic studies indicated that the adsorption followed pseudo-second order model and the thermodynamic studies revealed that the adsorption process was spontaneous and endothermic in nature. The obtained results demonstrated that calix[4]naphthalene can be used as an effective adsorbent for Pb²⁺ ions removal from water.     

Characteristics of an aerobic denitrifier that utilizes ammonium and nitrate simultaneously under the oligotrophic niche

Introduction

An aerobic denitrifier was isolated from the Hua-Jia-Chi pond in China and identified as Pseudomonas mendocina 3-7 (Genbank No. HQ285879). This isolated strain could express periplasmic nitrate reductase which is essential for aerobic denitrification occurred when the dissolved oxygen (DO) level maintains at 3?C10?mg?L^?1.

Methods

To determine whether the ability of isolated strain is exhibited in the bioremediation of polluted drinking source water, the heterotrophic nitrification and aerobic denitrification characteristics of P. mendocina 3-7 under different cultural conditions such as oxygen level, nitrate and organic concentrations were studied from the nitrogenous balance in the paper.

Results and conclusions

By measuring the nitrogen balance in all experiments under different culture conditions, the removal of total organic carbon and ammonium was positively correlated with total nitrogen removal, especially under high substrate level. With substrate concentration decreasing, ammonium and nitrate removal occurred separately, and ammonium was completely utilized first under low substrate concentration. Compared to that under high substrate level, the specific growth rate of P. mendocina 3-7 was not low under the low substrate level and the pollutant removal efficiencies remained high, which implies the stronger nitrogen removal and acclimatization capacities of the strain in oligotrophic niches.     

Isolation and characterization of 3-nitrophenol-degrading bacteria associated with rhizosphere of Spirodela polyrrhiza

Introduction

The accelerated biodegradation of 3-nitrophenol (3-NP) in the rhizosphere of giant duckweed (Spirodela polyrrhiza) was investigated.

Materials and methods

Biodegradation of 3-nitrophenol in the rhizosphere of a floating aquatic plant, S. polyrrhiza, was investigated by using three river water samples supplemented with 10?mg?l^?1 of 3-NP. Isolation and enrichment culture of 3-NP-degrading bacteria were performed in basal salts medium containing 3-NP (50?mg?l^?1). The isolated strains were physiologically and phylogenetically characterized by using an API20NE kit and 16S rRNA gene sequencing.

Results and discussion

Accelerated removal of 3-NP (100%) was observed in river water samples with S. polyrrhiza compared with their removal in plant-free river water. Also, 3-NP persisted in an autoclaved solution with aseptic plants, suggesting that the accelerated 3-NP removal resulted largely from degradation by bacteria inhabiting the plant rather than from adsorption and uptake by the plant. We successfully isolated six and four strains of 3-NP-degrading bacteria from the roots of S. polyrrhiza and plant-free river water, respectively. Phylogenetic analysis based on 16S rRNA gene divided the 3-NP-degrading bacteria into two taxonomic groups: the genera Pseudomonas and Cupriavidus. The strains belonging to the genus Cupriavidus were only isolated from the roots of duckweed. All strains isolated from the roots utilized 3-NP (0.5?mM) as a sole carbon and energy source, indicating that they could have contributed to the accelerated degradation of 3-NP in the rhizosphere of S. polyrrhiza.

Conclusions

The rhizoremediation using S. polyrrhiza and its rhizosphere bacteria can be an effective strategy for cleaning up the 3-NP-contaminated surface waters.     

Modelling the adsorption of mercury onto natural and aluminium pillared clays

Introduction

The removal of heavy metals by natural adsorbent has become one of the most attractive solutions for environmental remediation. Natural clay collected from the Late Cretaceous Aleg formation, Tunisia was used as a natural adsorbent for the removal of Hg(II) in aqueous system.

Methods

Physicochemical characterization of the adsorbent was carried out with the aid of various techniques, including chemical analysis, X-ray diffraction, Fourier transform infrared and scanning electron micrograph. Batch sorption technique was selected as an appropriate technique in the current study. Method parameters, including pH, temperature, initial metal concentration and contact time, were varied in order to quantitatively evaluate their effects on Hg(II) adsorption onto the original and pillared clay samples. Adsorption kinetic was studied by fitting the experimental results to the pseudo-first-order and pseudo-second-order kinetic models. The adsorption data were also simulated with Langmuir, Freundlich and Temkin isotherms.

Results

Results showed that the natural clay samples are mainly composed of silica, alumina, iron, calcium and magnesium oxides. The sorbents are mainly mesoporous materials with specific surface area of <250 m² g^?1. From the adsorption of Hg(II) studies, experimental data demonstrated a high degree of fitness to the pseudo-second-order kinetics with an equilibration time of 240 min. The equilibrium data showed the best model fit to Langmuir model with the maximum adsorption capacities of 9.70 and 49.75 mg g^?1 for the original and aluminium pillared clays, respectively. The maximum adsorption of Hg(II) on the aluminium pillared clay was observed to occur at pH 3.2. The calculated thermodynamic parameters (?G°, ?H° and ?S°) showed an exothermic adsorption process. The entropy values varied between 60.77 and 117.59 J?mol^?1 K^?1, and those of enthalpy ranged from 16.31 to 30.77 kJ mol^?1. The equilibrium parameter (R _L) indicated that the adsorption of Hg(II) on Tunisian smectitic clays was favourable under the experimental conditions of this study.

Conclusion

The clay of the Aleg formation, Tunisia was found to be an efficient adsorbent for Hg(II) removal in aqueous systems.     

Removal of arsenate from groundwater by electrocoagulation method

Purpose

Arsenic, a toxic metalloid in drinking water, has become a major threat for human beings and other organisms. In the present work, attempts have been made to remove arsenate from the synthetic as well as natural water of Ballia district, India by electrocoagulation method. Efforts have also been made to optimize the various parameters such as initial arsenate concentration, pH, applied voltage, processing time, and working temperature.

Method

Electrocoagulation is a fast, inexpensive, selective, accurate, reproducible, and eco-friendly method for arsenate removal from groundwater. The present paper describes an electrocoagulation method for arsenate removal from groundwater using iron and zinc as anode and cathode, respectively.

Results

The maximum removal of arsenate was 98.8% at 2.0?mg?L^?1, 7.0, 3.0?V, 10.0?min, and 30°C as arsenate concentration, pH, applied voltage, processing time, and working temperature, respectively. Relative standard deviation, coefficient of determination (r ²), and confidence limits were varied from 1.50% to 1.59%, 0.9996% to 0.9998%, and 96.0% to 99.0%, respectively. The treated water was clear, colorless, and odorless without any secondary contamination. The developed and validated method was applied for arsenate removal of two samples of groundwater of Ballia district, U.P., India, having 0.563 to 0.805?mg?L^?1, arsenate concentrations.

Conclusions

The reported method is capable for the removal of arsenate completely (100% removal) from groundwater of Ballia district. There was no change in the groundwater quality after the removal of arsenate. The treated water was safe for drinking, bathing, and recreation purposes. Therefore, this method may be the choice of arsenate removal from natural groundwater.     

Genotoxic effect of ciprofloxacin during photolytic decomposition monitored by the in vitro micronucleus test (MNvit) in HepG2 cells

Purpose

Ciprofloxacin (CIP), a broad-spectrum, second-generation fluoroquinolone, has frequently been found in hospital wastewaters and effluents of sewage treatment plants. CIP is scarcely biodegradable, has toxic effects on microorganisms and is photosensitive. The aim of this study was to assess the genotoxic potential of CIP in human HepG2 liver cells during photolysis.

Methods

Photolysis of CIP was performed in aqueous solution by irradiation with an Hg lamp, and transformation products were monitored by HPLC-MS/MS and by the determination of dissolved organic carbon (DOC). The cytotoxicity and genotoxicity of CIP and of the irradiated samples were determined after 24?h of exposure using the WST-1 assay and the in vitro micronucleus (MN) test in HepG2 cells.

Results

The concentration of CIP decreased during photolysis, whereas the content of DOC remained unchanged. CIP and its transformation products were not cytotoxic towards HepG2 cells. A concentration-dependent increase of MN frequencies was observed for the parent compound CIP (lowest observed effect level, 1.2???mol?L^?1). Furthermore, CIP and the irradiated samples were found to be genotoxic with a significant increase relative to the parent compound after 32?min (P?P?Conclusions Photolytic decomposition of aqueous CIP leads to genotoxic transformation products. This proves that irradiated samples of CIP are able to exert heritable genotoxic effects on human liver cells in vitro. Therefore, photolysis as a technique for wastewater treatment needs to be evaluated in detail in further studies, not only for CIP but in general.     

Aquatic photochemistry of paracetamol in the presence of dissolved organic chromophoric material and nitrate

Purpose

This study contains some new findings connected to the photolysis of the drug paracetamol (hereinafter APAP) especially in light of estimating natural conditions, and it will offer information to better evaluate environmental problems connected with this widely used analgesic agent. Only a few studies, so far, have focussed on the photodegradation process of APAP in the natural environment, and the question about the role of the colored/chromophoric dissolved organic matter (CDOM) and nitrate (NO ₃ ^? ) as photoinductors is almost open.

Methods

APAP dissolved in freshwater and pure laboratory water in the presence and absence of CDOM and NO ₃ ^? ions was irradiated using weak-energy photon energies simulating natural conditions.

Results

CDOM and NO ₃ ^? as photoinductors produced only the slow phototransformation of APAP under weak energy radiation, and APAP seemed to be practically resistant to direct photolysis under weak radiant energies available in natural conditions. The estimated reaction efficiencies, in addition to half-lives, speak for that NO ₃ ^? and CDOM do not act as quite independent photoinductors but their effect in conjunction (CDOM?CNO ₃ ^? ?Cwater) is stronger than the separate ones. The principal phototransformation intermediates of APAP were mono-hydroxy derivatives, depending on available photon energies formed via ortho- or meta-hydroxylation, possessing substantial power of resistance to further specific transformation reactions.

Conclusions

The estimated half-life of the phototransformation of APAP in the natural aqueous environment and in the presence of suitable photoinductors will be about 30?days or more.     

Removal mechanisms and kinetics of trace tetracycline by two types of activated sludge treating freshwater sewage and saline sewage

Understanding the removal mechanisms and kinetics of trace tetracycline by activated sludge is critical to both evaluation of tetracycline elimination in sewage treatment plants and risk assessment/management of tetracycline released to soil environment due to the application of biosolids as fertilizer. Adsorption is found to be the primary removal mechanism while biodegradation, volatilization, and hydrolysis can be ignored in this study. Adsorption kinetics was well described by pseudo-second-order model. Faster adsorption rate (k ₂?=?2.04?×?10^?2?g?min^?1?μg^?1) and greater adsorption capacity (q _e?=?38.8 μg?g^?1) were found in activated sludge treating freshwater sewage. Different adsorption rate and adsorption capacity resulted from chemical properties of sewage matrix rather than activated sludge surface characteristics. The decrease of tetracycline adsorption in saline sewage was mainly due to Mg²⁺ which significantly reduced adsorption distribution coefficient (K _d) from 12,990?±?260 to 4,690?±?180 L?kg^?1. Species-specific adsorption distribution coefficients followed the order of $ K_{\mathrm{d}}^{{ + 00}} \gg K_{\mathrm{d}}^{{ + - 0}} > K_{\mathrm{d}}^{{ + - - }} $ . Contribution of zwitterionic tetracycline to the overall adsorption was >90 % in the actual pH range in aeration tank. Adsorption of tetracycline in a wide range of temperature (10 to 35 °C) followed the Freundlich adsorption isotherm well.     

Adsorption of Remazol Red 198 onto magnetic N-lauryl chitosan particles: equilibrium, kinetics, reuse and factorial design

Purpose

The discharge of colored effluents from industries is an important environmental issue and it is indispensable to remove the dyes before the water gets back to the rivers. The magnetic adsorbents present the advantage of being easily separated from the aqueous system after adsorption by positioning an external magnetic field.

Methods

Magnetic N-lauryl chitosan (L-Cht/??-Fe₂O₃) particles were prepared and characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, transmission electron microscopy, and vibrating sample magnetometry. Remazol Red 198 (RR198) was used as a reactive dye model for adsorption on L-Cht/??-Fe₂O₃. The adsorption isotherms were performed at 25°C, 35°C, 45°C, and 55°C and the process was optimized using a 2³ factorial design (analyzed factors: pH, ionic strength, and temperature). The desorption and regeneration studies were performed in a three times cycle.

Results

The characterization of the material indicated that the magnetic particles were introduced into the polymeric matrix. The pseudo-second order was the best model for explaining the kinetics and the Langmuir?CFreundlich was the best-fitted isotherm model. At room temperature, the maximum adsorption capacity was 267?mg?g^?1. The material can be reused, but with a decrease in the amount of adsorbed dye.

Conclusions

L-Cht/??-Fe₂O₃ is a promising material to remove RR198 and probably other similar reactive dyes from aqueous effluents.     

Efficient biosorption of chromium(VI) ion by dry Araucaria leaves

Background

In this paper, batch removal of hexavalent chromium from aqueous solutions by Araucaria heterophylla leaves was investigated. The batch experiments were conducted to study the adsorption of metal species and effect of different pH, contact time, metal concentration, biosorbent concentration, and adsorption capacity.

Method

Freundlich and Langmuir??s isotherm model were used to describe the adsorption behavior, and the experimental results fitted Freundlich model well.

Results

The adsorption efficiency observed for all chromium concentrations, i.e., 1, 3, 5, and 10?mg/L was 100% and the equilibrium was achieved in 30?min for 1 and 3?mg/L, whereas for 5 and 10?mg/L, it was less than 60?min. FTIR spectra was taken to identify functional groups involved in the biosorption.

Conclusion

Thus, Araucaria leaves can be considered as one of the cheap and efficient biosorbent for toxic hexavalent chromium removal from natural or wastewaters.     

Detection of free microcystins in the liver and muscle of freshwater fish by liquid chromatography-tandem mass spectrometry

MC analysis of biological tissue is considered to be very difficult due to the lack of validated methods. This is the primary limiting factor for monitoring potential risks in both the flesh of aquatic organisms and the aquatic ecosystem. In this study, an effective method to determine free MCs (MC-LR and MC-RR) in the muscle and liver tissues of freshwater cultured fish was developed using solid-phase extraction (SPE) and liquid chromatography-tandem mass spectrometry (LC/MS-MS). The extraction solvent, time of extraction, eluent and purification of the extract were optimized. Various SPE cartridges were also investigated. In this optimized analytical procedure, an 85% methanol/water solution (v/v) was selected as the extraction solvent, after which the extracts were purified by removing fats and proteins; a HLB cartridge was chosen for MCs enrichment; and 90% methanol containing 0.02% formic acid/water solution (v/v) was used as the eluent. Under the optimized pretreatment conditions and instrument parameters, good recoveries of MC-LR and MC-RR were obtained at three concentrations (0.5, 1.0 and 2.0 µg g^?1 dry weight (DW)), with values ranging from 92.5 to 98.3% and 92.1 to 98.6%, respectively. The method detection limit (MDL) for muscle samples was 0.5 µg kg^?1 and 0.4 µg kg^?1 (DW) for MC-LR and MC-RR, respectively. The MDL for the liver samples was 0.8 µg kg^?1 (DW) for both MC-LR and MC-RR. The developed procedure was successfully applied to analyze MCs in the muscle and liver of fish samples collected from a Chinese freshwater aquaculture pond during bloom seasons. The MC-LR concentrations ranged from below the MDL to 4.17 µg kg^?1 and the MC-RR concentrations ranged from below the MDL to 2.64 µg kg^?1.     

Occurrence of cyclophosphamide and epirubicin in wastewaters by direct injection analysis–liquid chromatography–high-resolution mass spectrometry

Background, aim, and scope

According to the high incidence of cancer worldwide, the amount of cytostatic drugs administered to patients has increased. These compounds are excreted to wastewaters, and therefore become potential water contaminants. At this stage, very little is known on the presence and elimination of cytostatic compounds in wastewater treatment plants (WWTP). The aim of this study was to develop a liquid chromatography?Chigh-resolution mass spectrometry (LC?COrbitrap?CMS) method for the determination of cyclophosphamide and epirubicin in wastewaters. These compounds represent two outmost used cytostatic agents.

Materials and methods

Extraction and analytical conditions were optimized for cyclophosphamide and epirubicin in wastewater. Both solid-phase extraction using Oasis 200?mg hydrophilic?Clipophilic balanced (HLB) cartridges and direct injection analysis were evaluated. Mass spectral characterization and fragmentation conditions were optimized at 50,000 resolving power (full width at half maximum, m/z 200) to obtain maximum sensitivity and identification performance. Quality parameters (recoveries, limits of detection, and repetitivity) of the methods developed were determined, and best performance was obtained with direct water analysis of the centrifuged wastewater. Finally, this method was applied to determine the presence of cyclophosphamide and epirubicin in wastewaters from a hospital effluent, an urban effluent, and influents and effluents from three WWTP.

Results and discussion

Cyclophosphamide and epirubicin were recovered after 50?mL preconcentration on solid-phase extraction 200?mg Oasis HLB cartridges (87% and 37%, respectively), and no breakthrough was observed by extracting 500?mL of water. Limits of detection were of 0.35 and 2.77?ng/L for cyclophosphamide and epirubicin, respectively. On the other hand, direct injection of water spiked at 1???g/L provided recoveries of 107% for cyclophosphamide and 44% for epirubicin and limits of detection from 3.1 to 85?ng?L^?1, respectively. The analysis of wastewaters using direct injection analysis revealed the presence of cyclophosphamide and epirubicin in WWTP influents and hospital and urban effluents at levels ranging from 5.73 to 24.8???g?L^?1.

Conclusions

The results obtained in this study demonstrate the capability of LC?COrbitrap?CMS for accurate trace analysis of these very polar contaminants. This method permitted to identify cyclophosphamide and epirubicin in wastewaters and influents of WWTP, but no traces were detected in WWTP effluents. The methodology herein developed is sensitive and robust and applicable for screening of a large number of samples since no preconcentration is needed.