Removal of Fe³⁺ ions from aqueous solutions using poly(methyl methacrylate)

Bioremoval of some heavy metals from aqueous solutions by two different indigenous fungi Aspergillus sp. AHM69 and Penicillium sp. AHM96 isolated from petroleum refining wastewater

Rare earth element (REE) patterns in natural water and geological samples provide information on previous changes in environmental conditions, such as redox changes and material cycles; however, quantitative analysis of REEs in these samples is complicated by the relatively low contents of REEs in such samples as well as mass interference from 135Ba16O and 137Ba16O in inductively coupled plasma mass spectrometry (ICP-MS) analyses. In this study, onsite solid-phase extraction and preconcentration methods for REEs using an iminobisacetic acid–ethylenediaminetriacetic acid chelate resin (Nobias Chelate PA1, Hitachi High-Tech Fielding) were adopted for the analyses. Standard reference materials (SPS-SW1 artificial surface water) and natural ground water and spring water samples were used to evaluate the methods. Using the chelate resin, background levels of REEs were found to be less than 0.3 ng L−1 and recovery rates (REEs, 1 ng L−1) were 97.9–106.7% for the artificial surface water. Ba contents were lower than the detection limit after extraction. Additionally, duplicate analyses were performed to check the reproducibility of the onsite extraction. The REE patterns in the natural water samples were in good agreement with those obtained using a previous method (the interference calibration method without solid-phase extraction). Therefore, onsite solid-phase extraction using the chelate resin was demonstrated to be a rapid and simple preparation technique for REE analyses.

Arsenic (III,V) removal from aqueous solution by ultrafine α-Fe 2O 3 nanoparticles synthesized from solvent thermal method

A novel catalytic kinetic method is proposed for the determination of Se(IV), Se(VI), and total inorganic selenium in water based on the catalytic effect of Se(IV) on the reduction of Celestine blue by sodium sulfide at pH 7.0 phosphate buffer. The fixed-time method was adopted for the determination and speciation of inorganic selenium. Under the optimum conditions, the two calibration graphs are linear with a good correlation coefficient in the range 2-20 and 20-200 μg•L^(-1) of See(IV) for the fixed-time method at 30℃. The experimental and theoretical detection limits of the developed kinetic method were found to be 0.21 and 2.50 μg•L•^(-1) for the fixed-time method (3 min). All of the variables that affect the sensitivity at 645 nm were investigated, and the optimum conditions were established. The interference effect of various cations and anions on the Se(IV) determination was also studied. The selectivity of the selenium determination was greatly improved with the use of the strongly cation exchange resin such as Amberlite IR120 plus as long as chelating agents of thiourea and thiosulphate. The proposed kinetic method was validated statistically and through recovery studies in natural water samples. The relative standard deviations (RSDs) for ten replicate measurements of 2, 10, and 20 μg•L^(-1) of Se(IV) change between 0.35% and 5.58%, while the RSDs for ten replicate measurements of 3, 6, and 12 μg•L^(-1) of Se(VI) change between 0.49% and 1.61%. Analyses of a certified standard reference material (NIST SRM 1643e) for selenium using the fixed-time method showed that the proposed kinetic method has good accuracy. The Se(IV), Se(VI), and total inorganic selenium in lake and river water samples have been successfully determined by this method after selective reduction of Se(VI) to Se(IV).

An anion exchange pretreatment method for the determination of low-level uranium in the environmental water samples

A modified SBA-15 mesoporous silica was developed, as an adsorbent, for the removal of Cr(VI) ions from natural-water samples. The effects of experimental parameters, including pH of solution, sample and eluent flow rate, the eluent composition, the eluent volume, and the effect of coexisting ions on the separation and determination of Cr(VI), were investigated. It was shown that Cr(VI) was selectively adsorbed from aqueous solution at pH 3, but Cr(III) could be adsorbed from solution at alkaline pH range. The retained Cr(VI) was eluted with 0.5 mol L−1 KCl solution in 0.1 mol L−1 Na2CO3 subsequently. Under the optimum conditions, the modified mesoporous silica (py-SBA-15) with a high pore diameter exhibited an adsorption capacity of 136 mg g−1 and a lower limit of detection than 2.3 µg L−1 by using diphenylcarbazide as a chromophorous reagent for the determination of Cr(VI) ions. A preconcentration factor as high as 200 was calculated for Cr(VI). The loaded py-SBA-15 can be reactivated with recovery of more than 98.5% over at least eight cycles. The relative standard deviation (RSD) for Cr(VI) ion recovery was less than 1.8%. Validation of the outlined method was performed by analysing a certified reference material (BCR 544). The proposed method was applied to determine Cr(VI) value in natural and waste water samples successfully.

A column solid-phase extraction procedure for separation and preconcentration of bismuth in natural water samples using sodium diethyldithiocarbamate (NaDTTC) or piperidene dithiocarbamate (pipDTC)-coated Amberlite XAD-7 resin prior to their determination by inductively coupled plasma atomic emission spectrometry (ICP-AES) is reported. The results showed that solution pH and flow rate would affect the sorption of bismuth. The sorbed bismuth was eluted with 4 M/L of HNO3. The extractor system has good sorption capacity values of 9.82 mg/g of Bi on NaDTTC-coated resin and 9.56 mg/g of Bi on pipDTC-coated resin. The preconcentration factor was 150 and 170 for pipDTC-coated resin and NaDTTC-coated resin, respectively. The detection limits are 0.9 and 1.2 µg/L for resin-coated with NaDTTC and pipDTC, respectively. The results showed that resin coated with NaDTTC performs slightly better in the recovery of bismuth than resin coated with pipDTC. The accuracy of the proposed method was investigated by determining the bismuth in spiked water samples. The relative standard deviations of the determination of bismuth were below 5%. The proposed procedure was applied for the determination of bismuth in natural water and seawater samples.

The concentration levels of mercury (Hg) species in natural water samples are usually low. Consequently, accurate analysis with low detection limits is still a major problem. In this work, a method was applied for the simultaneous direct determination of dissolved mercury species in water samples by on-line hydride generation (HG), cryogenic trapping (CT), gas chromatography (GC) and detection by atomic fluorescence spectrometry (AFS). The suitability of the method for real samples with different organic matter and chloride contents was evaluated by recovery experiments in synthetic and natural spiked water samples. The HG method was compared with other current available methods for mercury analysis with respect to the different fraction of mercury analysed, i.e. 'reactive', 'reducible' or total. HG derivatization and SnCl2 reduction (with and without previous oxidation with BrCl) were applied to synthetic and natural (spiked and non-spiked) water samples. The influence of chloride and dissolved organic matter concentrations was studied. The results suggest that the HG procedure is suitable for the simultaneous determination of Hg2+ and MeHg+ in surface water samples. Inorganic mercury analysed by HG (i.e. reducible) is close to the total inorganic mercury.

Direct determination of rare earth elements in natural water samples by inductively coupled plasma tandem quadrupole mass spectrometry with oxygen as the reaction gas for separating spectral interferences

The applicability of ozone as a digesting agent in the trace analysis of arsenic in natural water samples has been investigated. Differential pulse polarographic (DPP) and spectrophotometric (SP) methods were applied for the determination of arsenic in ozone and, as reference, in persulphate treated samples. Additionally, inductively coupled plasma mass spectrometry (ICP-MS) was used for the total arsenic determinations. No significant differences were found between the results of the measurements using different techniques in the investigated natural ground water samples. Similar detection limits of 5 µg/L, lower quantification limits of approximately 10 µg/L and linearity limit up to 300 µg/L were estimated for the both DPP and SP measurements. Thus, ozone treatment may, in many cases, be successfully used for the pretreatment of samples prior to both DPP and SP determination of arsenic in natural water samples.

This work describes the application of gold electrodes constructed from recordable compact discs for the analytical determination of the herbicide paraquat in natural water samples using square wave voltammetry. The detection limit for pure water (laboratory samples) was 21 µg L−1, lower than the EPA limit for drinking water (100 µg L−1). The experimental quantification limit was determined as 73 µg L−1. In polluted creek water samples the detection limit rose to 76.4 µg L−1 and is shown to be dependent on BOD and COD values. Recovery measurements in tea and natural water samples were approximately 95%, which indicates that the methodology can be employed to analyze paraquat in such matrices. The authors acknowledge the financial support of FAPESP and CNPq.

Environmental pollution, mainly in the aquatic systems, due to developments in industry, is one of the most significant problems of this century. Many industrial wastewater streams contain heavy metals, which are of great environmental concern and must be removed prior to water discharge or water recycling. The present study aims to develop a simple and rapid procedure for lead (II) removal. Laboratory-scale adsorption experiments were conducted aiming to remove lead from water samples. They were based on using powdered activated carbon (PACI), which was prepared from olive stones generated, as plant wastes, and modified with aqueous oxidizing agent such as (NH 4 ) 2 S 2 O 8 . The main parameters (pH, sorbent, lead concentrations, stirring times and temperature) influencing the sorption process in addition to the effect of some foreign ions were investigated. The results obtained indicated that the sorption of Pb 2+ ions onto PACI is well described by the Langmuir, Freundlich and Dubinin- Radushkevich (D-R) adsorption models over the concentration range studied. Under the optimum experimental conditions employed, the removal of ca. 100% of Pb 2+ ions was attained. The procedure was successfully applied to the removal of lead from aqueous and different natural water samples.

Environmental pollution, mainly in the aquatic systems, due to developments in industry, is one of the most significant problems of this century. Many industrial wastewater streams contain heavy metals, which are of great environmental concern and must be removed prior to water discharge or water recycling. The present study aims to develop a simple and rapid procedure for lead (II) removal. Laboratory-scale adsorption experiments were conducted aiming to remove lead from water samples. They were based on using powdered activated carbon (PACI), which was prepared from olive stones generated, as plant wastes, and modified with aqueous oxidizing agent such as (NH4)2S2O8. The main parameters (pH, sorbent, lead concentrations, stirring times and temperature) influencing the sorption process in addition to the effect of some foreign ions were investigated. The results obtained indicated that the sorption of Pb2+ ions onto PACI is well described by the Langmuir, Freundlich and Dubinin-Radushkevich (D-R) adsorption models over the concentration range studied. Under the optimum experimental conditions employed, the removal of ca. 100% of Pb2+ ions was attained. The procedure was successfully applied to the removal of lead from aqueous and different natural water samples. Key words: Sorption, lead, activated carbon, kinetics and water.

In this study, we report the feasibility of using nano chamomile waste (NCW) as a selective solid phase extractor for heavy metal ions. The experimental parameters including pH (1.0–6.0), metal ion concentration (10–100 mole), adsorbent dose (10–1000 mg), and biosorption time (0.5–90 min) were altered by using the batch technique to optimize the maximum capacity of this new biosorbent. The experimental data by NCW agreed with both Freundlich and Langmuir models (R2 =0.999) with maximum uptake capacities of 621.6 mgg–1 (3 mmolg–1) for Pb (II), 163.9 mgg–1 (2.58 mmolg–1) for Cu (II), and 522.7 mgg–1 (9.36 mmolg–1) for Fe (III). In addition, the values of metal uptake as a function of time agreed with the kinetic pseudo-second-order model. The kinetic experiments confirmed the fast accessibility of metal ions to the biosorbent surface resulting in equilibrium within 30 s. NCW was also characterized using FT-IR spectra and the crystallinity of the biosorbent was characterized using X-ray diffraction (XRD). The morphological characterization and particle size of NCW were obtained using SEM and TEM, respectively. Our method was investigated to measure Pb (II), Cu (II), and Fe (III) with a certain spiked amounts in natural water samples such as groundwater (GW), drinking tap water (DTW), natural drinking water (NDW), Nile River water (NRW), seawater (SW), and wastewater (WW). A removal efficiency of ≥98% was obtained for all collected samples using batch experiments and without matrix interferences. Considering its cheap source, simple, economic and fast uptake process, NCW can be used as a low-cost nano biosorbent for the removal of metal ions from natural water samples.

Characteristics of four natural water samples from urban and rural areas and the efficiency of a new purifying agent, potassium ferrate K2FeO4, were studied by bacterial luminescence bioassay for 30 minutes. It was revealed that two samples of water from the urban areas are toxic, while the other two samples (one from urban and one from rural environment) are nontoxic. Numerous data obtained on the increase in toxicity index with time allow reasonable conclusions to be made about the chemical nature of substances present in the test water samples. Toxic natural water samples were likely to contain heavy metals and were well purified using potassium ferrate, including via their adsorption. In nontoxic natural water samples, toxic complexes with organic compounds present in water could form at the addition of potassium ferrate. The obtained data call for further studying the properties of potassium ferrate complexes with organic compounds. Bacterial luminescence bioassay is a promising method for the rapid assessment of properties of various water sources (their integral toxicity and presumable chemical composition) and new reagents for their purification (effective concentrations, bactericidal properties, and mechanisms of interacting with heavy metals and organic substances in water).