Determination of Trace Levels of Mercury in Effluents and Wastewaters

Concern about mercury pollution of the environment and the inapplicability of natural water methods necessitated development of a procedure for determining parts per billion mercury in effluents and wastewaters containing large amounts of organic matter. The sample is digested with sulfuric and nitric acids to destroy the organic matter, and the ionic mercury is reduced to the elemental state by stannous ion. Then the digestate is aerated with a stream of air to carry the mercury vapor through a heated line into a quartz cell positioned in an atomic absorption spectrophotometer for measurement. Analyses of effluents and aqueous samples gave good recoveries of added mercury. Effluents, wastewaters, water supplies, and aqueous samples secured within manufacturing plants have been analyzed. With minor modification, the procedure has been applied to manufacturing materials such as vinylpyridine, latex, sizing, dyes, caustic, and hydro.     

Artifact formation of methyl mercury during aqueous distillation and alternative techniques for the extraction of methyl mercury from environmental samples

 Aqueous distillation as a pre-extraction step for monomethyl mercury (MMHg) in waters and sediments is the most common method because it eliminates negative interferences in the aqueous ethylation procedure. However, the distillation procedure generates a positive MMHg artifact as a result of the action of naturally occurring organic substances on inorganic Hg in the sample. Methylation of Hg(II) does not occur in deionized water samples, indicating that the artifact is not due to the distillation itself or the reagents added (ammonium pyrrolidine dithiocarbamate, HCl), but rather to naturally occurring organic matter. Methylation of Hg(II) spikes ranged from 0.001% for rainwater and oligotrophic lake water to 0.08% for brown, humic-rich water. Methylation of Hg(II) spikes in sediments ranged from 0.005 to 0.1%, with the highest conversions in wetland peat. In most water samples, the artifact is not significant, as the ambient concentration of MMHg is 1–10% of the total, well above the contribution due to the artifact. The artifact may be significant in sediments and in Hg-contaminated water samples, where the measured fraction of MMHg is less than 1% of the total. The best of six alternative techniques involves leaching with KBr/H₂SO₄/CuSO₄ and extraction into CH₂Cl₂, followed by back extraction into water, and subsequent ethylation. Received: 7 October 1996/Revised: 10 February 1997/Accepted: 16 February 1997     

Artifact formation of methyl mercury during aqueous distillation and alternative techniques for the extraction of methyl mercury from environmental samples

 Aqueous distillation as a pre-extraction step for monomethyl mercury (MMHg) in waters and sediments is the most common method because it eliminates negative interferences in the aqueous ethylation procedure. However, the distillation procedure generates a positive MMHg artifact as a result of the action of naturally occurring organic substances on inorganic Hg in the sample. Methylation of Hg(II) does not occur in deionized water samples, indicating that the artifact is not due to the distillation itself or the reagents added (ammonium pyrrolidine dithiocarbamate, HCl), but rather to naturally occurring organic matter. Methylation of Hg(II) spikes ranged from 0.001% for rainwater and oligotrophic lake water to 0.08% for brown, humic-rich water. Methylation of Hg(II) spikes in sediments ranged from 0.005 to 0.1%, with the highest conversions in wetland peat. In most water samples, the artifact is not significant, as the ambient concentration of MMHg is 1–10% of the total, well above the contribution due to the artifact. The artifact may be significant in sediments and in Hg-contaminated water samples, where the measured fraction of MMHg is less than 1% of the total. The best of six alternative techniques involves leaching with KBr/H₂SO₄/CuSO₄ and extraction into CH₂Cl₂, followed by back extraction into water, and subsequent ethylation. Received: 7 October 1996/Revised: 10 February 1997/Accepted: 16 February 1997     

Determination of very low levels of inorganic and organic mercury in natural waters by cold-vapor atomic absorption spectrometry after preconcentration on a chelating resin

Inorganic and organic mercury at ng l^?1 levels in fresh waters are collected simultaneously on a column of a dithiocarbamate-treated resin and quantitatively eluted with slightly acidic aqueous thiourea solution. Mercury vapor is generated from inorganic mercury by reduction with alkaline SnCl₂ solution, and from inorganic and organic mercury with a CdCl₂SnCl₂ solution, for determination by cold-vapor atomic absorption spectrometry. The range of determination is 0.2–5,000 ppt (ng l^?1) for 20-l water samples.     

Preconcentration of inorganic mercury and organic mercury with solvent extraction for neutron activation analysis

A preconcentration method combined with neutron activation technique for the analysis of organic and inorganic mercury in waste water samples at ppb levels is presented. The inorganic mercury is extracted in CCl₄ solution with lead diethyldithiocarbamate reagent and the organic mercury is extracted in C₆H₆ solution. Interfering activities of sodium and bromine are removed from the irradiated samples by this procedure. Two different solvent extraction procedures are also described in detail.     

Dual optoelectronic visual detection and quantification of spectroscopically silent heavy metal toxins: A multi-measurand sensing strategy based on Rhodamine 6G as chromo or fluoro ionophore

A novel colorimetric chemo-sensor for the simultaneous visual detection and quantification of spectroscopically silent heavy metal toxins viz. cadmium, lead and mercury has been developed. This is based on the proposed sequential ligand exchange (SLE) mechanism of iodide from Pb-I⁻-Rhodamine 6G ion associate with citrate (without affecting ion associates of Cd and Hg) and subsequently from Cd-I⁻-Rhodamine 6G ion associate with EDTA (without affecting Hg-I⁻-Rhodamine 6G). Multi-measurand detection and quantification by colorimetry is possible as the individual toxins gives identical bathochromic shifts in aqueous solution, i.e. from 530 to 575 nm on formation of ternary ion associates in singular, binary and ternary mixtures. The visual detection provides a simple, quick and sensitive detection method in addition to quantification via spectrophotometry with Sandell sensitivities of 1.1, 15 and 2.5 μg dm⁻² for cadmium, lead and mercury, respectively. The developed procedure has been successfully tested for the analysis of environmental (cast alkali, lead acid battery and zinc manufacturing industry effluents) samples. Furthermore, the multi-measurand quantification of the above-mentioned heavy metal toxins based on fluorescence quenching and use of Pyronine G as chromo-ionophore instead of Rhodamine 6G is also described.     

Investigations of oxidative UV photolysis

Summary Oxidative UV photolysis according to DIN standard 38406 E 16 [1] has been investigated as a sample preparation method for voltammetry. UV photolysis has decisive advantages compared with mineral acid digestion owing to the simple procedure and the very low blank values, which in turn are due to the minimal reagent addition required. For UV photolysis with a high pressure mercury lamp, an apparatus has been used that employs a new type of sample cooling and that allows the simultaneous irradiation of 12 samples. The sample preparation for the voltammetric determination of zinc, cadmium, lead, copper, nickel and cobalt has been optimized using a model water solution and subsequently tested with real matrices. The type of organic matrix and the irradiation temperature determine the irradiation time required. To digest aromatic compounds, it is advantageous to work at reaction temperatures of ca. 90°C. The application of UV photolysis centers on water samples slightly polluted with organic compounds; however, it can also be used with more heavily polluted wastewaters. As the digestion times are at most 60 min, the method is of interest for routine analysis.     

Liquid Anion Exchange Studies and Separation of Mercury

Abstract

A new method is developed for the extractive separation of mercury from associated elements. Mercury is quantitatively extracted from 0.5 M acetic acid solution by aliquat 336 S, which acts as a liquid anion exchanger. The metal ion from the organic phase is stripped with sodium hydroxide solution and determined in the aqueous phase complexometrically. The extracted species is [2(R₄N⁺), Hg(OAc)₄ ^?2]. A working procedure for the selective separation of mercury from zinc, cadmium, nickel, cobalt, copper, bismuth and manganese is described.     

Simultaneous determination of mercury and selenium in biological materials by radiochemical neutron activation analysis

A simple and sensitive radiochemical neutron activation analysis (RNAA) method has been developed for the simultaneous determination of mercury and selenium in biological materials. The radiochemical procedure is based upon the digestion of irradiated samples with sulphuric and nitric acids followed by subsequent extractions of mercury and selenium into toluene, first of mercury from 7.5 M H₂SO₄-0.01M HBr media and after of selenium from 7M H₂SO₄-1 M HBr media. After washing of the organic phases with similar media, the mercury bromide was back-extracted into 0.034M EDTA in 5% aqueous ammonia and the selenium bromide into 0.14M H₂O₂ in aqueous solution. The¹⁹⁷Hg and the⁷⁵Se were counted on a Ge(Li) detector. The precision and accuracy of the method was checked by analysing NBS Standard Reference Materials: orchard leaves and bovine liver.     

Ozone as Releasing Agent: The Determination of Trace Mercury in Organic Matrices by Cold Vapor Atomic Absorption

Abstract

Ozonization of aqueous solutions of organomercurials and mercury salts in organic complexing agents is recommended for releasing the mercury for direct determination by cold vapor atomic absorption. The combination of ozonization and subsequent reduction by sodium borohydride is particularly effective.     

Determination of sixteen polycyclic aromatic hydrocarbons in aqueous and solid samples from an Italian wastewater treatment plant

A robust procedure for the determination of 16 US EPA PAHs in both aqueous (e.g. wastewaters, industrial discharges, treated effluents) and solid samples (e.g. suspended solids and sludge) from a wastewater treatment plant (WWTP) is presented. Recovery experiments using different percentages of organic modifier, sorbents and eluting solvent mixtures were carried out in Milli-Q water (1000 mL) spiked with a mixture of the PAH analytes (100 ng/L of each analyte). The solid phase extraction (SPE) procedures applied to spiked waste water samples (1000 mL; 100 ng/L spiking level) permitted simultaneous recovery of all the 16PAHs with yields >70% (6-13% RSD). SPE clean up procedures applied to sewage and stabilized sludge extracts, showed percent recoveries in the range 73-92% (7-13% RSD) and 71-89% (7-12% RSD), respectively. The methods were used for the determination of PAHs in aqueous and solid samples from the WWTP of Fusina (Venice, Italy). Mean concentrations, as the sum of the 16PAHs in aqueous and suspended solid samples, were found to be approx. in the 1.12-4.62 microg/L range. Sewage and stabilized sludge samples contained mean PAH concentrations, as sum of 16 compounds, in the concentration range of 1.44-1.26 mg/kg, respectively. Extraction and clean up procedures for sludge samples were validated using EPA certified reference material IRM-104 (CRM No. 912). Instrumental analyses were performed by coupling HPLC with UV-diode array detection (UV-DAD) and fluorescence detection (FLD).     

Screening of Fish Tissue for Methyl Mercury Using the Enzyme Invertase in a Solvent Interface

This paper describes a simple and rapid screening system for the extraction and determination of methyl mercury in tissue samples from fish. A novel clean-up procedure based on the use of two immiscible phases, an organic one containing methyl mercury and an aqueous one containing invertase, was developed. Methyl mercury was selectively extracted from the organic into the aqueous phase by its irreversible reaction with thiol groups of invertase, and the resulting inhibition of enzymatic activity served as a measure of methyl mercury concentration. Enzyme activity was measured with a spectrophotometric method using 3,5-dinitrosalicylic acid as a reagent. After parameter optimisation including pH, substrate concentration, and enzyme reaction time, it was possible to determine methyl mercury in the ppb range with this technique. Concentrations as low as 10ppb of methyl mercury in the extract, corresponding to 0.2ppm of methyl mercury in fish, were detected. The proposed procedure was successfully demonstrated as a simple screening method for methyl mercury in fish samples.     

Factor Analysis for Assigning Sources of Groundwater Pollution

Abstract

Factor Analysis (FA) is applied to tentatively establish either jhe sources of pollution in the groundwater in a delimited zone in Catalonia which has been polluted by permeation with non-controlled wastewaters or the groundwater evolution with time in this area. Three types of chemical analysis were considered: general parameters indicating the chemical quality of water, inorganic micropollutants and organic micropollutants. These analyses were carried out with forty-five samples collected in three different periods, and eleven parameters were considered. From the final solutions of the FA method applied several factors were retained for the different sampling periods and these factors were related to different sources of pollution. FA has proved to be more useful when punctual pollution incidents takes place rather than when groundwater evolution with time is studied.     

Direct colorimetric visualization of mercury (Hg) based on the formation of gold nanoparticles

It is critical to be able to detect and quantify Hg²⁺ ions under aqueous conditions with high sensitivity and selectivity. The technique presented herein provides a direct way for simple colorimetric visualization of Hg²⁺ ions in aqueous solution, based on the formation of gold nanoparticles through the Hg²⁺ catalyzed HAuCl₄/NH₂OH reaction. The outstanding selectivity and sensitivity result from the well-known amalgamation process that occurs between mercury and gold. The entire procedure takes less than 20 min. The limit of detection (2 ppb) shows excellent potential for monitoring ultralow levels of mercury in water samples.     

Flow injection spectrophotometric determination of copper in petroleum refinery wastewaters

This paper reports a new strategy for flow injection spectrophotometric Cu (II) determination in petroleum refinery wastewaters, exploring its reaction with sodium diethyldithiocarbamate (DDTC), without solvent extraction step, thus avoiding the use of harmful organic solvents. The influence of several chemical and flow variables was studied as well as the possible interferences. Under optimized conditions, the flow system was able to process 63 samples per hour, with a detection limit of 23 ng ml⁻¹ and a RSD of 2.1% at the 0.2 μg ml⁻¹ level. In order to attest the accuracy of the methodology, seven samples of effluents were analyzed by the proposed method and the results were compared with that obtained by FAAS. It was observed that the physical interferences verified in the FAAS procedure, which only permits its use by the standard addition method, were not present in the FIA procedure. The results obtained by FIA method were not statistically different from that obtained by FAAS-standard addition method. Also, the analysis of three spiked samples provided recovery percentages between 93 and 103%.     

Detection and Inhibition of an Organic Interference in the Indigo Method for Ozone

Abstract

Aqueous samples of organic solutes often exhibit a delayed reaction in the indigo test for dissolved ozone which is similar to the reaction of ozone itself. This phenomenon has made timing critical in aqueous ozone measurements and has been observed in both laboratory situations with high organic carbon:ozone ratios and in a potable water treatment plant with low organic carbon:ozone ratios. Organic hydroperoxides, singlet oxygen, and Fenton's reagent but not triplet oxygen, hydrogen peroxide, nor p-benzoquinone were found to interfere. Addition of phenolic antioxidants was found to inhibit the interference. These results extend the utility of the indigo method to solutions of high organic carbon concentration.     

Determination of Polychlorinated Biphenyls in Paper Mill Effluents and Process Streams

Abstract

Special techniques have been found necessary for isolating PCB's from cellulose fiber-containing effluents and process streams and for determining PCB's in effluents from paper mills using recycled fiber. Sources of potential PCB loss from aqueous solutions are revealed and means of avoiding these losses are proposed.

Significant amounts of PCB remained on cellulose fibers following separatory funnel extraction of a fiber-water suspension with hexane or methylene chloride-hexane. Reflux of the fibers with alcoholic KOH was necessary to remove the remaining PCBs. PCB losses due to volatilization from aqueous solution occurred during analysis, but these were minimized by working in a cool environment and covering the Sample with a layer of hexane. The presence of cellulose fibers in PCB-containing effluents enhanced the effluents' stability during storage.

Chromium trioxide oxidation was found to be valuable in cleaning up extracts from paper mill effluents. Perchlorination is apt to yield misleading results.     

Optimization of An On-Line Precolumn Preconcentration Method for the Determination of Polycyclic Aromatic Hydrocarbons (PAHs) in Water Samples (River and Sea Water)

Abstract

A new on-line precolumn preconcentration method for the determination of EPA priority pollutants (PAHs) in river and sea water has been developed. The retention time for each PAH in the precolumn has been determined for several percentages of organic solvent (acetonitrile) in the sample. This is very important because recoveries show a great dependence on this parameter.

The proposed procedure, combined with HPLC and spectrofluorimetric detection, reaches very low detection limits (subnanograms per liter) and it has been applied to river and sea water samples with good results.     

Analysis and study of the distribution of polar and non-polar pesticides in wastewater effluents from modern and conventional treatments

The analysis of a wide range of pesticides in wastewaters (WWs) undergoing different treatments (both modern and conventional) has been studied. The need for optimizing specific extraction methods for each WW effluent based on their physico-chemical characteristics has been considered. A distribution study was performed to establish if the filtration step before extraction is a correct procedure since pesticides can be more prone to be in the aqueous or the solid phase, depending on their hydrophobicity. This evaluation demonstrated that pesticides are distributed between the aqueous phase and the suspended particulate matter (SPM; e.g. pyrethroids are only found in the SPM). The proposed methodologies involved the determination of 39 polar and 139 non-polar pesticides using solid-phase extraction (SPE) and pressurized-liquid extraction (PLE) for the extraction of the aqueous phase and the SPM, respectively. Ultra high pressure liquid chromatography and gas chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS, GC-MS/MS) were used in the determination stage. WW samples from four different technologies were evaluated: membrane bioreactor, extended aeration, maturation pond and anaerobic pond. Validation data for the four effluents studied were generated, obtaining adequate precision values (estimated as % relative standard deviation, RSD) in almost all cases (<25%). The methods showed limits of detection at 0.01-0.20μgL(-1) and limits of quantification from 0.02 to 0.50μgL(-1). The proposed methods were applied to the analysis of real samples collected from an experimental WW treatment plant, detecting non-polar and polar pesticides at concentrations in the range 0.02-1.94μgL(-1) and 0.02-0.33μgL(-1), respectively.     

Separation and preconcentration of mercury in water samples by ionic liquid supported cloud point extraction and fluorimetric determination

We have developed a cloud point extraction procedure based on room temperature ionic liquid for the preconcentration and determination of mercury in water samples. Mercury ion was quantitatively extracted with tetraethyleneglycol-bis(3- methylimidazolium) diiodide in the form of its complex with 5,10,15,20-tetra-(4-phenoxyphenyl)porphyrin. The complex was back extracted from the room temperature ionic liquid phase into an aqueous media prior to its analysis by spectrofluorimetry. An overall preconcentration factor of 45 was accomplished upon preconcentration of a 20?mL sample. The limit of detection obtained under the optimal conditions is 0.08?μg mL^?1, and the relative standard deviation for 10 replicate assays (at 0.5?g mL^?1 of Hg) was 2.4%. The method was successfully applied to the determination of mercury in tap, river and mineral water samples.