Removal of trivalent chromium from tannery waste waters using bone charcoal

The ability of bone charcoal to remove Cr(III) from aqueous solutions by adsorption has been investigated. The adsorbent used was first characterised and then the adsorption was studied as a function of time and amount of charcoal. Tests were carried out with synthetic solutions whose Cr concentrations (500 mg L(-1)) were similar to those found in some effluents of Moroccan tannery industries. Cr removal efficiencies higher than 90% were obtained at pH 3.5 using 3 g of bone charcoal and a stirring time of about 30 min. Results of Cr removal by all sieved fractions of bone charcoal had shown the same interesting capabilities for Cr(III) retention. The cross interference with other elements was also investigated. Pre-treatment of bone charcoal by nitric acid led to an increase in its specific surface area but induced a drastic reduction in its Cr elimination abilities. Adsorption tests were also carried out using calcinated bone charcoal. The results obtained showed a similar percentage of Cr retention to those found with untreated bone charcoal. On the other hand, a double treatment of bone charcoal with HCl and NaOH provided an enhancement of Cr(III) retention. The role played by the mineral fraction of the solid phase of bone was thus evidenced.     

The use of amidoximated cellulose for the removalof metal ions and dyes from waste waters

The adsorption of metal ions such as Cu(II), Cr(III), Cd(II) and Ni(II)and dyes such as Acid Blue 25, Calmagite and Eriochrome Blue Black Bis performed onto amidoximated cellulose (Am-Cell). Different ways are possible for theadsorption of these pollutants onto Am-Cell : adsorption of each pollutantaloneon the support, or cumulative adsorption of both metal ions and dyes on the samesupport. In the last case, the pollutants may be adsorbed simultaneously from aunique solution, or successively from two different solutions, whatever theorder. Am-Cell loaded or not with metal ions shows a high capacity for dyeadsorption. Ternary complexes involving metal/dye/amidoxime are formed. Theobserved stoichiometries are 1/1/1 with Cu(II), Cr(III) and Cd(II) ions and1/1/2with Ni(II) ion. A quasi-total and specific desorption of either metal ions (bytreatment with ethylenediaminetetracetic salt) or of dyes (by heating inaqueoussolution) is possible from these ternary complexes. Concerning the dyes, manysuccessive adsorption/desorption cycles are possible without a noticeablechange in the adsorption capacity.     

The speciation of trace elements in waters

Speciation (determination of the different physico-chemical species formed by an element) in a water sample is necessary for an understanding of the toxicity, bioavailability, bioaccumulation and transport of a particular element. The importance of speciation measurements and the various factors leading to changes in speciation are discussed in this review. Speciation in natural waters is a difficult task, and the analytical methods available and the results obtained are critically assessed.     

Arsenic speciation in waste waters by extraction chromatography followed by atomic absorption spectrometry

Summary A method is described for the determination of arsenic(III) and arsenic(V) in water samples. The sample (adjusted to pH 2.5 to 3.5 with HCl or NaOH) is passed through a chromatographic column filled with inert support modified with the organotin reagent (C₈H₁₇)₂SnCl₂. Under these conditions arsenate is quantitatively retained, while arsenite is not. Arsenate is eluted from the column with 2 mol/l HCl (1–2 ml). Both effluate [As(III)] and eluate [As(V)] are analyzed by flame or graphite furnace AAS. The method was applied to the analysis of waste waters from a metallurgical plant and potable water from the same region. Recoveries are in the range of 85–115%.     

Arsenic speciation in freshwater organisms from the river Danube in Hungary

Total arsenic and arsenic species were determined in a range of freshwater samples (sediment, water, algae, plants, sponge, mussels, frog and fish species), collected in June 2004 from the river Danube in Hungary. Total arsenic concentrations were measured by ICPMS and arsenic species were measured in aqueous extracts of the samples by ion-exchange HPLC-ICPMS. In order to separately determine the efficiency of the extraction method and the column recovery, total arsenic concentrations in the extracts were obtained in three ways: (i) ICPMS determination after acid digestion; (ii) flow injection analysis performed directly on the extract; (iii) the sum of arsenic species eluting from the HPLC column. Extraction efficiencies were low (range 10-64%, mean 36%), but column recovery was acceptable (generally >80%) except for the fish samples, where substantial, currently unexplained, losses were observed. The dominating arsenic species in the extracts of freshwater algae were arsenosugars, whereas arsenate [As(V)] was present only as a minor constituent. On the other hand, plant extracts contained only inorganic arsenic, except for two samples which contained trace amounts of dimethylarsinate (DMA) and the tetramethylarsonium cation (TETRA). The oxo-arsenosugar-phosphate (ca. 35% of extractable arsenic) and the oxo-arsenosugar-glycerol (ca. 20%) as well as their thio-analogues (1-10%) were found in the mussel extracts, while arsenobetaine (AB) was present as a minor species only. In general, fish extracts contained only traces of arsenobetaine, and the oxo-arsenosugar-phosphate was the major arsenic compound. In addition, samples of white bream contained thio-arsenosugar-phosphate; this is the first report of a thio-arsenical in a fish sample. The frog presented an interesting arsenic speciation pattern because in addition to the major species, arsenite [As(III)] (30%) and the tetramethylarsonium cation (35%), all three intermediate methylation products, methylarsonate (MA), dimethylarsinate and trimethylarsine oxide (TMAO), and arsenate were also present. Collectively, the data indicate that arsenobetaine, the major arsenical in marine animals, is virtually absent in the freshwater animals investigated, and this represents the major difference in arsenic speciation between the two groups of organisms.     

Redox speciation of plutonium in natural waters

Data on the stability of Pu(V) as the dominant oxidation state of tracer concentrations of plutonium in natural waters is reviewed. Laboratory experiments for solutions of 0.1 and 1.0M (NaCl) ionic strength and pH 3–10 confirm the dominance of Pu(V) as the state in solution. Humics in the waters can cause reduction to Pu(IV).     

Chemical speciation of mercury in natural waters

Improved sensitivity of the cold-vapour atomic absorption method for mercury can be obtained by equilibrating the reduced sample with a small volume of air at 90°C. An automated system has been developed that has a detection limit of 1 ng Hg l^-1. By changing the reducing conditions three species of mercury can be differentiated and determined, inorganic mercury, arylmercury compounds such as phenylmercury(II) chloride, and alkylmercury compounds such as methylmercury(II) chloride. Speciation of mercury in natural waters is possible.     

Arsenic speciation in soil-pore waters from mineralized and unmineralized areas of south-west England

Arsenale, arsenite and monomethylarsonic acid (MMAA) have been characterized in soil-pore waters extracted from soils in mineralized and unmineralized areas. Special attention has been paid to collection and storage of the samples. The dominant arsenic species in aerobic soils was arsenate, with small quantities of arsenite and MMAA in mineralized areas. In anaerobic soils arsenite was found to be the major soluble species. The analysis was done with an HPLC anion-exchange column combined with continuous-flow hydride-generation and atomic-absorption spectrometry. A preconcentration column was incorporated to increase the sensitivity.     

Mercury determination and speciation analysis in surface waters

A sorbent L-cysteine grafted silica gel has been evaluated for separation and enrichment of dissolved inorganic i-Hg(II) and methylmercury CH₃Hg(I) from surface waters at sub-μg L⁻¹ concentrations. Chemical parameters for mercury species enrichment and separation have been optimized. Analytical schemes for the determination of Hg species, using selective column solid phase extraction (SPE) with continuous flow chemical vapor generation atomic absorption spectrometry (CF-CVG-AAS) or inductively coupled plasma-mass spectrometry (ICP-MS) were developed. Possibilities for on-site SPE enrichment were demonstrated as well. The limits of quantification were 1.5 and 5 ng L⁻¹ for dissolved i-Hg(II) and CH₃Hg(I) by CF-CVG-AAS and 1 and 2.5 ng L⁻¹ by ICP-MS with relative standard deviations between 7–12% and 7–14%, respectively. The chemically modified SPE sorbent has demonstrated high regeneration ability, chemical and mechanical stability, acceptable capacity and good enrichment factors. Results for total dissolved mercury were in reasonable agreement with those from independent analyses by direct ICP-MS determinations for river waters and for estuarine water certified reference material.      

Non-chromatographic speciation analysis of chromium in natural waters

The difference in toxicity between Cr(III) and Cr(VI) species is one of the main reasons for the recent developments in analytical procedures for their differentiate. Non-chromatographic methods offer highly convenient tools for this purpose and can be used as a fast and cheap alternative to the chromatographic processes. The present work overviews and discuss different non-chromatographic procedures for speciation of chromium in natural water samples such as coprecipitation, dialysis, solvent and solid phase extraction. This survey will attempt to cover the state of-the art from 2005 to 2010.     

Toward the use of surface modified activated carbon in speciation: selective preconcentration of selenite and selenate in environmental waters

This paper describes a novel application of tetrabutylammonium hydroxide-modified activated carbon (AC-TBAH) to the speciation of ultra-trace Se(IV) and Se(VI) using LC-ICP-DRC-MS. The anion exchange functionality was immobilized onto the AC surface enables selective preconcentration of inorganic Se anions in a wide range of working pHs. Simultaneous retention and elution of both analytes, followed by subsequent analysis with LC-ICP-DRC-MS, allows to accomplish speciation analysis in natural samples without complicated redox pre-treatment. The laboratory-made column of immobilized AC (0.4 g of sorbent packed in a 6 mL syringe barrel) has achieved analyte enrichment factors of 76 and 93, respectively, for Se(IV) and Se(VI), thus proving its superior preconcentration efficiency and selectivity over common AC. The considerable enhancement in sensitivity achieved by using the preconcentration column has improved the method's detection limits to 1.9-2.2 ng L(-1), which is a 100-fold improvement compared with direct injection. The analyte recoveries from heavily polluted river matrix were between 95.3 and 107.7% with less than 5.0% RSD. The robustness of the preconcentration and speciation method was validated by analysis of natural waters collected from rivers and reservoirs in Hong Kong. The modified AC material is hence presented as a low-cost yet robust substitute for conventional anion exchange resins for routine applications.     

Fast speciation analysis of iodophenol compounds in river waters by capillary electrophoresis-inductively coupled plasma-mass spectrometry with off-line solid-phase microextraction

An analytical methodology for the fast separation and determination of iodophenol species in natural water samples was developed using capillary electrophoresis (CE) coupled to inductively coupled plasma-mass spectrometry (ICP-MS). Based on the element-specific and highly sensitive detection provided by ICP-MS, the methodology has been applied to the analysis of 2-iodophenol, 4-iodophenol, and 2,4,6-triiodophenol. The use of solid-phase microextraction (SPME), after proper optimization, improved the signal by a factor of 100 leading to detection limits in the sub microg.L(-1). Different desorption conditions of iodophenol compounds from the SPME microfiber were studied to achieve the optimum preconcentration factor and best analytical performance. Different CE conditions were studied to achieve complete baseline separation of iodophenols in short migration times. Three different CE buffer systems were evaluated using ICP-MS detection. A buffer solution containing 20 mmol.L(-1) 3-(cyclohexylamino)-1-propanesulfonic acid (CAPS) and an applied potential of +22 kV were finally selected leading to a maximum separation time of 6.6 min. A relative standard deviation (%RSD) of about 5.0% for ten consecutive determinations was obtained. Finally, the speciation methodology developed was utilized for the determination of iodophenol compounds in natural water samples.     

Arsenic solubility, mobility and speciation in the deposits from a copper production waste storage

The sediments in large pond for discharge of waste products of metallurgical activity were studied with respect to the valence forms of arsenic and its mobility. A sequential extraction procedure for arsenic compounds was applied and optimized according to the nature of analyzed products. During the first stage, the content of water-soluble arsenic compounds was determined, during the second—HCl-soluble forms and during the third—compounds soluble in sodium hydroxide. The optimum conditions for leaching arsenic from sediments (sample weight, concentration and volume of extractants, time of treatment) were established for each fraction.Speciation studies for determining As(III) and As(V) were carried out in the obtained arsenic extracts. The ability of the proposed sequential extraction procedure to specify the valence forms of inorganic arsenic was evaluated using model samples with added As(III) and As(V) and the recovery of spikes has been assessed. It was found that oxidation of As(III) and processes of sorption and sedimentation of As(V) proceed upon dissolution. A depth profiling was performed of the content of diverse forms of Às in two sites. The content of water-soluble As does not exceed 7.4% of total As in the sediments, As(III) being lower than 7.4% of that of the extracted As. The bulk of arsenic compounds (above 78% As) is dissolved in 2M HCl, and As(V) was found to be more than 94% of extracted arsenic. The analytical features of the procedure are as follow: precision, evaluated through the repeatability w > 0.96 and accuracy, estimated by the recovery above 93%, calculated on the basis of a twice repeated analysis of a series of 9 samples.     

Automatic ultramicro determination of iodine in natural waters

An automatic spectrophotometric reaction rate method is described for the ultramicro determination of iodine in natural waters. The method is based on the catalytic effect of iodine on the reduction of cerium(IV) by arsenic(III). The time required for a small fixed (about 0.06 unit) change in absorbance is measured automatically and related to the iodine concentration. Speed and the small size of the sample needed are the main advantages over other methods. Iodine in water in the range 1 to 15 μg/l in a total volume ot 4 ml is determined with errors smaller than ±0.3 μg /l.     

Analytical determination of microelements in well waters

Well water analysis was carried out starting with liquid samples which have been evaporated to dryness. The salt deposit crust has ensured an enrichment in microelements which were approximately determined by emission spectroscopy. Once the order of magnitude was established, the exact measurements were carried out based on the following techniques: mass spectrometry, atomic absorption spectrophotometry, activation with slow neutrons, and γ-spectrometry. The results obtained are the average values of at least three methods employed. *** DIRECT SUPPORT *** A1353055 00005     

The stability of selected herbicides preconcentrated from estuarine river waters on solid-phase extraction disks

Summary The stability of atrazine, simazine, alachlor, metolachlor, and deethylatrazine on C₁₈ Empore disks has been determined. Estuarine water (100 mL) spiked at 3 g L^–1 with the target pesticide mixture was preconcentrated on the disks; the disks were then stored at –20°C, 4°C, and at room temperature for periods up to three months and were analyzed by gas chromatography with nitrogen-phosphorus detection. Complete recovery was observed after storage at –20°C throughout the period of the study. Losses up to maximum of 10% were observed after storage at 4°C. Higher losses (up to 24% for alachlor) occurred only at room temperature; the coefficient of variation for these determinations (8–11%) was also higher than that for the others (3–5%). The stability of the pesticides was dependent on the water matrix, on storage temperature, and on properties such as vapor pressure and water solubility.     

Fate of antibacterial spiramycin in river waters

Spiramycin, a widely used veterinary macrolide antibiotic, was found at traceable levels (nanograms per litre range) in Po River water (N-Italy). The aqueous environmental fate of this antibiotic compound was studied through drug decomposition, the identification of the main and secondary transformation products (TPs), assessment of mineralisation and the investigation of drug TPs toxicity. Initially, laboratory experiments were performed, with the aim of stimulating the antibacterial transformation processes followed in aquatic systems. The TPs were identified through the employment of the liquid chromatography (LC)-mass spectrometry technique. Under illumination, spiramycin degraded rapidly and transformed into numerous organic (intermediate) compounds, of which 11 could be identified, formed through five initial transformation routes. These laboratory simulation experiments were verified in situ to check the mechanism previously supposed. Po River water was sampled and analysed (by LC-high-resolution mass spectrometry) at eight sampling points. Among the previously identified TPs, five of them were also found in the river water. Three of them seem to be formed through a direct photolysis process, while the other two are formed through indirect photolysis processes mediated by natural photo sensitisers. The transformation occurring in the aquatic system involved hydroxylation, demethylation and the detachment of forosamine or mycarose sugars. Toxicity assays using Vibrio fischeri proved that even if spiramycin did not exhibit toxicity, its transformation proceeded through the formation of toxic products.     

Ionic membrane technologies for the recovery of valuable chemicals from waste waters

An overview of various processes is provided in which use of ionic membranes and related technologies (dialysis, electrodialysis, electrolysis, etc.) enable the recovery of valuable chemicals. The most relevant literature in the field is surveyed and some elucidating case studies are discussed, also accounting for the results of some research programmes carried out in our laboratories.