Real Groundwater Samples Research Articles

Zerovalent iron encapsulated chitosan nanospheres – A novel adsorbent for the removal of total inorganic Arsenic from aqueous systems

Evaluation of Chitosan zerovalent Iron Nanoparticle (CIN) towards arsenic removal is presented. Addition of chitosan enhances the stability of Fe(0) nano particle. Prepared adsorbent was characterized by FT-IR, SEM EDX, BET and XRD. It was found that, with an initial dose rate of 0.5 g L −1, concentrations of As (III) and As (V) were reduced from 2 mg L −1 to <5 μg L −1 in less than 180 min and the adsorbent was found to be applicable in wide range of pH. Langmuir monolayer adsorption capacity was found to be 94 ± 1.5 mg g −1 and 119 ± 2.6 mg g −1 at pH 7 for As (III) and As (V) respectively. Major anions including sulfate, phosphate and silicate did not cause significant interference in the adsorption behavior of both arsenite and arsenate. The adsorbent was successfully recycled five times and applied to the removal of total inorganic arsenic from real life groundwater samples.

Use of Orange Peel Waste for Arsenic Remediation of Drinking Water

Arsenic is a toxic element and is found in natural waters throughout the globe. The purpose of present study is to demonstrate the As (V) uptake by orange peel from real ground water samples through adsorption. Different parameters such as pH, shaking speed, contact time, adsorbent dosage, concentration, volume and temperature etc, were optimized. The maximum uptake capacity was observed at pH-7. The sorption was found to be time dependent and the kinetics followed well by the Morris-weber, Pseudo second order and Elovich equations. The Freundlich, Langmuir, Dubinin Redushkevich and Flory–Huggins isotherm were used to model the adsorption behavior of arsenic retention. Thermodynamic parameters calculated from these isotherms show that the adsorption was spontaneous and endothermic in nature. Orange peel was found to be effective (~85%) for arsenic removal from real water systems containing concomitant ions.

Determination of As(III) in Nonacidified Groundwater Samples for Inorganic Speciation Analysis Using Flow Injection Hydride Generation Atomic Absorption Spectrometry

ABSTRACT A flow injection system coupled to hydride generation atomic absorption spectrometry with heated quartz tube atomizer was employed for the selective determination of As(III) in real groundwater samples under nonacidic conditions. The use of low-acidity conditions was carefully evaluated in order to minimize the interconversion of redox arsenic species. The As(III) hydride was generated using 0.1 mol L−1 HCl as carrier solution and 0.2% (m/v) NaBH4 in 0.025% NaOH as the reductant. A coil reaction larger than the used one for higher acidity conditions (480 mm instead of 115 mm) was selected. The generated hydride was transported to the atomizer by a nitrogen flow of 75 ml min−1. The main parameters that influenced the signal intensity and shape were studied. Under the best found experimental conditions, a detection limit (3σ) of 1.0 µg L−1 As(III) was obtained for a 500 µl sample volume. The analytical recovery ranged between 90% and 98%. In addition, the total inorganic arsenic concentration in the samples was determined on sample aliquots acidified with concentrated HCl and prereduced with 5% (m/v) KI–5% (m/v) C6H8O6 solution. HCl 1.2 mol L−1 as carrier solution, NaBH4 0.2% (m/v) as reductant, and a nitrogen flow rate of 75 ml min−1 were used in this case. The concentration of As(V) was calculated by difference between the total inorganic arsenic and As(III) concentrations.

Ecological monitoring of the fresh waters in Stara Zagora Region, Bulgaria: I. Quality analyses of nitrogen compounds contents

The aim of the present study was the ecological monitoring of the natural waters in Stara Zagora Region, Bulgaria, establishing of a database and correlations regarding three basic parameters — nitrates, nitrites and ammonium, to provide a framework for sustainable management of the natural surface and groundwaters in the stated region. To accomplish this goal, the concentrations of nitrogen compounds in real surface and groundwater samples taken from 16 sampling points situated in four municipalities of Stara Zagora Region were spectrophotometrically determined and the statistical significance of the data was tested. The results obtained displayed that nitrite–nitrogen could be classified as a potential pollutant in the surface waters from Stara Zagora and Chirpan municipalities. NH 4 +–N concentrations were in the range of 0.118–0.462 mg L − 1 in 6 of the samples, thus pertaining to II category surface waters. The comparative analyses proved that nitrate–nitrogen could not be classified as a contaminant. The derived exponential correlation between NO 3 −–N and NO 2 −–N concentrations in Tundzha River allows mathematical modelling of the results. The present study ascertained that the pollution thresholds for groundwaters, regarding nitrite and nitrates, were exceeded in three sampling points from Stara Zagora and Chirpan municipalities.

Arsenic oxidation by UV radiation combined with hydrogen peroxide

Arsenic is a widespread contaminant in the environment around the world. The most abundant species of arsenic in groundwater are arsenite [As(III)] and arsenate [As(V)]. Several arsenic removal processes can reach good removal yields only if arsenic is present as As(V). For this reason it is often necessary to proceed with a preliminary oxidation of As(III) to As(V) prior to the removal technology. Several studies have focused on arsenic oxidation with conventional reagents and advanced oxidation processes. In the present study the arsenic oxidation was evaluated using hydrogen peroxide, UV radiation and their combination in distilled and in real groundwater samples. Hydrogen peroxide and UV radiation alone are not effective at the arsenic oxidation. Good arsenic oxidation yields can be reached in presence of hydrogen peroxide combined with a high UV radiation dose (2,000 mJ/cm(2)). The quantum efficiencies for As(III) oxidation were calculated for both the UV photolysis and the UV/H(2)O(2) processes.

Method validation in solvent extraction for 210Po determination from groundwaters

The suitability of solvent extraction for 210Po analysis from groundwater samples was assessed using three extractive scintillation cocktails, POLEX, TOPO and TNOA. Validation of the extraction method was carried out using both distilled water samples with some radionuclides added and real groundwater samples. Extraction of polonium from spiked waters was successful and no co-extraction of 234U or 238U occurred. However, the extraction results from groundwaters differed greatly from the spiked water samples. The main interfering nuclides were 234U and 238U, which led to incorrect results in 210Po analysis. Due to the co-extraction of uranium from real groundwaters, validation of the method was unfeasible.

Advanced high-performance liquid chromatography method for highly polar nitroaromatic compounds in ground water samples from ammunition waste sites

An advanced HPLC-photodiode array detection method for the determination of 12 selected highly polar nitroaromatic compounds in ground water samples of ammunition waste sites has been developed and validated. After solid-phase extraction the limits of detection were in the range 0.1–0.5 μg/l. To prove the applicability of the method to other polar nitroaromatic compounds the retention time of another 32 polar compounds under the specified chromatographic conditions were determined and their UV spectra recorded. To review the method, interlaboratory comparisons were performed with a spiked and a real ground water sample.

Treatment of groundwater contaminated with gasoline components by an ozone/UV process

In this paper, the treatment of real groundwater samples contaminated with gasoline components, such as benzene, toluene, ethylbenzene, and xylene (BTEX), methyl tert-butyl ether (MTBE), tert-butyl alcohol (TBA), and other gasoline constituents in terms of total petroleum hydrocarbons as gasoline (TPHg) by an ozone/UV process was investigated. The treatment was conducted in a semi-batch reactor under different experimental conditions by varying ozone gas dosage and incident UV light intensity. The groundwater samples contained BTEX compounds, MTBE, TBA, and TPHg in the ranges of 5–10 000, 3000–5500, 80–1400, and 2400–20 000 μg l −1, respectively. The ozone/UV process was very effective compared to ozonation in the removal of the gasoline components from the groundwater samples. For the various gasoline constituents, more than 99% removal efficiency was achieved for the ozone/UV process and the removal efficiency for ozonation was as low as 27%. The net ozone consumed per mol of organic carbon (from BTEX, MTBE, and TBA) oxidized varied in the range of 5–60 for different types of groundwater samples treated by the ozone/UV process. In ozonation experiments, it was observed that the presence of sufficient amount of iron in groundwater samples improved the removal of BTEX, MTBE, TBA, and TPHg.

OXIDATION OF NONIONIC SURFACTANTS BY FENTON AND H2O2/UV PROCESSES

The oxidation of 10 nonionic surfactants (6 alcohol ethoxylates and 4 alkylphenol ethoxylates) by Fenton and H2O2/UV processes was investigated in synthetic (deionized water) and real aqueous matrices, i.e. secondary effluent from municipal wastewater treatment plant and groundwater. Batch tests were carried out to assess the optimal dosages of reagents leading to the total removal of surfactants. Regardless to the specific surfactant, both Fenton and H2O2/UV treatments of synthetic solutions containing one single surfactant (C0=14 mg l−1) always caused its rapid and quantitative removal (96–99%) with a corresponding very low (0–18%) TOC decrease. Only for the Fenton treatment, linear relationships were found between the amounts of H2O2 and Fe2+ necessary for surfactant removal and the ethoxy chain length of each surfactant. Conversely, in the case of H2O2/UV treatment the H2O2 dosage causing the quantitative oxidation of the treated surfactant depended on the length of both chains: the ethoxy and the hydrophobic one. Mixtures of the 10 surfactants (1.4 mg l−1 each) were treated in both synthetic and real matrices. These latter were different in the case of Fenton (i.e. municipal secondary effluent) or H2O2/UV (i.e. real groundwater) treatments. Fenton treatment of municipal secondary effluent containing the surfactants mixture led to its total removal when a molar ratio [Total surfactants]/[H2O2]/[Fe2+] equal to 1/17/12 was used. As for H2O2/UV treatment of real groundwater samples, quantitative removal of surfactants mixture was achieved with a molar ratio [Total surfactants]/ [H2O2] equal to 1/7.4. Surfactants mixture removals, if compared in deionized water and in real matrices, showed the same matrix effect during both treatments, i.e. less amounts of reagents were always required in synthetic solutions.

Enhanced fluoride removal from drinking water by magnesia-amended activated alumina granules

Abstract This paper describes the fluoride removal potential of a novel sorbent, magnesia-amended activated alumina (MAAA) from drinking water. MAAA, prepared by calcining magnesium hydroxide impregnated alumina at 450 °C has shown high fluoride sorption potential than activated alumina from drinking water. Batch sorption studies were performed as a function of contact time, pH, initial fluoride concentration, and adsorbent dose. Studies were also performed to understand the effect of various other co-existing ions present in real ground water samples. X-ray powder diffraction (XRD), scanning electron microscope (SEM), energy dispersive X-ray (EDAX) and a gas adsorption porosimetry analyses were used to characterize the physicochemical properties of MAAA. More than 95% removal of fluoride (10 mg l−1) was achieved within 3 h of contact time at neutral pH. Sorption of fluoride onto MAAA was found to be pH dependant and a decrease in sorption was observed at higher pHs. Among the kinetic models tested, pseudo-second-order model fitted the kinetic data well, suggesting the chemisorption mechanism. Among the various isotherm model tested, Sips model predicted the data well. The maximum sorption capacity of fluoride deduced from Sips equation was 10.12 mg g−1. Most of the co-existing ions studied have negligible effect on fluoride sorption by MAAA. However, higher concentrations of bicarbonate and sulfate have reduced the fluoride sorption capacity.

Arsenic removal from aqueous solutions by adsorption on laterite soil

Laterite soil was used as an adsorbent for arsenic removal from contaminated groundwater. Effects of pH, adsorbent dose, adsorbent size, contact time, initial arsenic concentration and presence of interfering species on arsenic removal were found out. Laterite soil was found to be very effective for arsenic adsorption. It was found that 4 h contact time was sufficient for ∼ 98% and ∼95% removal from the contaminated water samples at an adsorbent dose of 10 g/L and 20 g/L for As(III) and As(V) respectively at an initial concentration level of 0.5 mg/L at a pH of 5.7 ± 0.2. Although there was no significant interference from Cl−, NO3 −, SO4 − 2, Ca2 +and Fe2 +/3 + on arsenite removal but its removal was little affected due to the presence of HPO4 − 2 and SiO3 − 2. Arsenate removal efficiency, however, was decreased to a large extent in presence of HPO4 − 2 and SiO3 − 2. The other ions Cl−, NO3 −, SO4 − 2, Ca2 + and Fe2 +/3 + had no significant interference on arsenate removal. The common organic contaminants such as 2,4-dichlorophenoxyacetic acid (2,4- D), atrazine, endosulfan and humic acid had no effect on As(III) removal, but they (excepting 2,4-D) cause decrease in the removal efficiency for As(V). Both Langmuir and Freundlich adsorption isotherm models fitted well and the maximum adsorption capacity was estimated to be 1.384 mg/g and 0.04 mg/g for arsenite and arsenate respectively. The real arsenic contaminated groundwater was also tested and it was found that laterite soil is very effective for arsenic removal from real groundwater sample, and up to ∼ 99% removal could be achieved under normal condition. The advantage of the material is that the pH of the raw water did not change after arsenic removal, and iron was not leached.

Sorption Kinetics of As(V) with Iron-Oxide-Coated Cement–A New Adsorbent and its Application in the Removal of Arsenic from Real-Life Groundwater Samples

In the search of alternative adsorbents for the removal of arsenic, a new adsorbent (iron-oxide coated cement) was examined under various conditions to evaluate its suitability in removing As(V). A removal of more than 99% was obtained within 2 h for an initial As(V) concentration of 1 mg/L. Kinetic studies showed a removal which became somewhat constant after 2 h. Thorough investigations to understand the mechanism of solute adsorption onto the new sorbent with the help of four kinetic models, viz. ∼ first-order reversible kinetics model, pseudo-first-order kinetic model, second-order kinetic model, and pseudo-second-order kinetic model showed that the sorption kinetics is consistent with the pseudo-second-order model from which it can be inferred that the mechanism of adsorption is chemical interaction or chemisorption. The equilibrium data followed the Langmuir isotherm at low concentrations of As(V) (≤4 mg/L), but followed the Freundlich isotherm over a wide range of concentrations (0.5–10 mg/L) which can be due to solid solution precipitation. Studies on the effect of pH on As(V) removal revealed somewhat constant (∼95%) As(V) removal over a wide pH range of 4–10. The efficiency of this adsorbent was also checked for the removal of arsenic from three real ground water samples containing both As(III) and As(V) with total arsenic in the range of 0.33–1.2 mg/L. The total arsenic removal was 71%, 87% and 75% for the samples containing 0.33, 0.88 and 1.2 mg/L total arsenic, respectively at the same adsorbent dose of 3 g/L. However, increasing the adsorbent dose will enhance removal capacity. Investigations of these real samples with the four kinetic models revealed most reliable fit with the pseudo-second order model. However, good fit was also obtained with the other three models. Values of the diffusion coefficients calculated from the first order kinetics data, indicated that, film diffusion is the rate limiting step for each of the three real life groundwater samples.

On the use of a small synthetic calibration set for the simultaneous spectrophotometric multivariate determination of Ca 2+ and Mg 2+ in groundwater: chemical and spectral considerations

A critical evaluation of chemical and spectral considerations for the simultaneous spectrophotometric determination of calcium and magnesium in groundwater samples with methylthymol blue (MTB) using a calibration set composed by synthetic standards is presented. The method is based upon the spectral changes observed in MTB spectra in the visible region (400–700 nm) when concentrations of calcium and magnesium are varied. First-order multivariate calibration models were built using net analyte pre-processing followed by classical least-squared regression (NAP/CLS) method. The concentration of MTB, the pH of the solution at which the reaction is carried out and the spectral range were optimised. Based on theoretical concentration distribution plots, discussion of experimental effect of each chemical variable is provided. Through a suitable chemical and spectral optimisation and based on a factorial central composite design, we succeeded in obtaining excellent prediction results using a calibration set composed only by eight synthetic solutions in the analytical concentration range of 0–200 and 0–100 mg L −1 for Ca 2+ and Mg 2+, respectively. The developed methodology was applied to real groundwater samples from Great Buenos Aires area, with no pre-treatment except filtration of turbid samples, showing a very good agreement with the well-known flame atomic absorption spectrometry technique, which was used as reference method. Critical performance comparison with previous work is provided.

Removal of arsenic from groundwater using low cost ferruginous manganese ore

A low cost ferruginous manganese ore (FMO) has been studied for the removal of arsenic from groundwater. The major mineral phases present in the FMO are pyrolusite and goethite. The studied FMO can adsorb both AS(III) and As(V) without any pre-treatment, adsorption of As(III) being stronger than that of As(V). Both As(III) and As(V) are adsorbed by the FMO in the pH range of 2–8. Once adsorbed, arsenic does not get desorbed even on varying the pH in the range of 2–8. Presence of bivalent cations, namely, Ni 2+, Co 2+, Mg 2+ enhances the adsorption capability of the FMO. The FMO has been successfully used for the removal of arsenic from six real groundwater samples containing arsenic in the range of 0.04–0.18 ppm. Arsenic removals are almost 100% in all the cases. The cost of the FMO is about 50–56 US$ per metric tonne.

Applications of solid-phase microextraction (SPME) in the determination of residues of certain herbicides at trace levels in environmental samples.

A new analytical procedure based on solid-phase microextraction (SPME) has been developed for the determination of residues of eight selected herbicides: trifluralin, butachlor, pretilachlor, metolachlor, atrazine, acetochlor, alachlor, and fluroxypyr-meptyl, in ground water samples. Carbowax divinylbenzene was used for SPME of the herbicides. Quantification was done at equilibrium. Various parameters, such as, effect of pH, ionic strength, humic acid content and exposure time of fiber, were investigated to find the extraction efficiency. The linearity was determined. The method was found suitable for the determination of residues of herbicides at concentration levels from 5 to 20 ng L-1. The relative standard deviation of the detection limits were calculated. The humic acid content was found to interfere more significantly in the determination of residues. An ionic chloride strength, in terms of sodium chloride, of up to 10% did not have any significant impact on the determination. Furthermore, there was an enhanced sensitivity of detection up to pH 3.0. The method was applied to the analysis of the residue contents of the pesticides under investigation in real ground water samples collected from susceptible places. The results when compared with the standard methods published in the literature showed no significant deviation in their quantification and the values were comparable.