Properties and suitability of liquid electrode plasma optical emission spectrometry (LEP-OES) for the determination of potassium, lithium, iron, and zinc in aqueous sample solutions

Abstract The effects of different parameters and the nitric acid concentration on the sensitivity and repeatability of elemental analysis were characterized for liquid electrode plasma optical emission spectrometry (LEP-OES). In addition, internal standardization for LEP-OES was investigated. The developed LEP-OES method was used for the determination of lithium, potassium, iron, and zinc in aqueous solutions and in samples with high acid concentrations after microwave-assisted digestion. The results were compared with those obtained by inductively coupled plasma — optical emission spectrometry. The sensitivity was improved when the plasma parameters were optimized. In addition, some improvement in the accuracy and reproducibility of the results was achieved when internal standardization by gold was employed. However, due to the strong matrix effects, the calibration standards should be made as similar as possible to the sample matrix

Effects of bromides of potassium and ammonium on some crops

Abstract In this work, the response of wheat (Triticum aestivum L.), rye (Secale cereale L.), oat (Avena sativa L.), and pea (Pisum sativum L.) to bromides of potassium (KBr) and ammonium (NH4Br) was studied. All plants were capable of accumulating high concentrations of bromine (Br). However, the Br accumulation depended on the Br compounds presented in the growth medium and plant species. The highest Br concentrations were observed in leaves and roots of the seedlings germinated in the medium spiked with KBr. Oat accumulated more Br than other plants and the lowest Br accumulation was observed in pea. The bioaccumulation of Br resulted in suppression of plant biomass and concentrations of several essential nutrients (K, Na, Ca, Mg, Zn and Cl). The most negative effects were caused by NH4Br. Probably, this action was due to cumulative effects of Br- and NH4+. Among other plant species, the most tolerant to bromides was oat and the most sensitive was wheat

Nano-TiO₂ catalyzed UV-LED sample pretreatment method for decomposition of humic substances in natural water samples

Abstract A photocatalytic digestion device consisting of an ultraviolet light emitting diode (UV-LED) and a nano-TiO2 coated catalyst rod was designed and used for the decomposition of humic substances in natural water samples prior to inorganic elemental analysis. The aim was to develop a green sample pretreatment method by utilizing energy efficient and environmental friendly UV-LED technology. The effects of different experimental variables including pH, UV-LED irradiation time, and hydrogen peroxide concentration were studied using a statistical experimental design. Dissolved organic carbon (DOC) removal was studied as the response. Dissolved organic carbon can interfere in some analytical measurements (for example in electrochemical analysis methods) and after digestion, the possible interfering effects are minimized. The recoveries for some spiked elements (As, Bi, Cd, Co, Cu, Ge, Ni, Pb, Sb, Se and Tl) were studied. It was found that in optimal DOC removal conditions, the recoveries for cadmium, cobalt, nickel and selenium were good. However, lower recoveries for some hydride forming elements were observed, indicating element losses, possibly due to adsorption phenomenon

Bioavailability and toxicity of bromine and neodymium for plants grown in soil and water

Abstract Information about biological significance and possible phytotoxicity of many trace elements is still scarce. Bromine and neodymium are among the poorly investigated trace elements. In the research, greenhouse experiment was conducted to study the effects of bromide of neodymium on wheat seedlings grown in soil and water. The wheat seedlings were capable of accumulating large amounts of both Br and Nd. Compared to the soil-grown plants, the water-grown plants accumulated higher concentrations of the trace elements. The bioaccumulation of Br and Nd resulted in statistically significant variations in the concentrations of several elements. The concentrations of P, Cl, and Ca in roots and Cl in leaves of the plants grown in the contaminated water and the concentration of I in roots of the soil-grown plants decreased. In the water-grown seedlings, the concentrations of Na and P were higher and concentrations of Mg and K were lower than those in the seedlings grown in soil. In leaves of the plants grown in water, the concentration of Cl was lower than that in leaves of the soil-grown plants. In roots of the water-grown plants, the concentration of Zn was higher, and in leaves, it was lower compared with Zn content in roots and leaves of the plants grown in soil. The K/Na ratios were 4 (leaves) and 20 (roots) times higher in the soil-grown plants, while the Ca/Mg ratios were 8–19 times higher in the water-grown plants. Marked distinctions were also observed in relationships between different elements in the soil-grown and water-grown plants

Determination of ethyl xanthate in aqueous solution by high performance liquid chromatography–inductively coupled plasma–tandem mass spectrometry and spectrophotometry

Abstract Xanthates are commonly used collectors in flotation processes but are highly toxic to the aquatic environment. However, there are few methods for reliable determination of low xanthate concentrations in water samples. In this work, a sensitive, selective, and fast method is presented for the determination of potassium ethyl xanthate (KEX). KEX was determined by high-performance liquid chromatography–inductively coupled plasma–mass spectrometry (HPLC-ICP-MS/MS) directly and as diethyl dixanthogen [(EX)₂] after oxidation with triiodide. The HPLC method was optimized for (EX)₂ and the separated compounds were detected by ICP-MS/MS. The ICP-MS/MS was used in mass-shift mode using O₂ as the cell gas and S⁺ was measured as SO⁺ to reduce spectral interferences. Detection limits of 88 µg L⁻¹ for KEX and 20 µg L⁻¹ for (EX)₂ calculated from the peak area were obtained using mass-shift ³²S⁺ → ³²S¹⁶O⁺. No significant matrix effects were present when spiking experiments of (EX)₂ were done to a sample collected from the tailings of a flotation process. The developed method demonstrates the potential of the HPLC-ICP-MS/MS for the determination of ethyl xanthate. This method may be extended to analyzing other xanthates and similarly structured sulfur containing collectors

Determination of xanthates as Cu(II) complexes by high-performance liquid chromatography:inductively coupled plasma tandem mass spectrometry

Abstract The present study provides a novel, selective analysis method for the determination of low xanthate concentrations. The rising concern over the environmental effects of xanthates demands the development of analysis methods which this study answers. Complex formation in aqueous solution between xanthates and an excess of Co(II), Ni(II), Pb(II), Cd(II), Cu(II), and Zn(II) ions was utilized to selectively determine xanthates by high-performance liquid chromatography–inductively coupled plasma tandem mass spectrometry for the first time. The complexes that were formed were extracted to ethyl acetate using liquid–liquid extraction and separated by high-performance liquid chromatography technique before the quantitative determination of metal ions and sulfur in the xanthate complexes. Good separation and high measurement sensitivity were achieved using Cu(II) as the complex metal ion. The analysis method was optimized for the determination of sodium isopropyl xanthate and sodium isobutyl xanthate with detection limits of 24.7 and 13.3 μg/L, respectively. With a linear calibration range of 0.1–15 mg/L and a total analysis time of 4–5 min, the present method is a fast and sensitive option for selective xanthate determination

The effect of experimental conditions on the formation of dixanthogen by triiodide oxidation in the determination of ethyl xanthate by HPLC–ICP-MS/MS

Abstract The rising concern over the environmental impact of xanthates, especially in the arctic region, has increased the need to study these traditional flotation reagents in greater detail. The environmental concern relates mostly to the formation of carbon disulfide (CS₂) and the heavy metal complexes of xanthates. Due to the unstable nature and multiple reaction mechanisms of xanthates, their reliable determination at low concentration levels is difficult. In this study, a xanthate pretreatment method was optimized and applied for the determination of ethyl xanthate (EX⁻) by high performance liquid chromatography–inductively coupled plasma tandem mass spectrometry (HPLC–ICP-MS/MS). Ethyl xanthate was oxidized to diethyl dixanthogen ((EX)₂) by triiodide (I₃⁻) in aqueous solution and the formed (EX)₂ was extracted into n-hexane. Important experimental parameters, including pH, I₃⁻ amount, and oxidation time, were optimized and the detection limit of 0.29 mg L⁻¹ for potassium ethyl xanthate was obtained. During the optimization experiments, it was found that the oxidation reaction resulted in multiple products, decreasing the efficiency of (EX)₂ formation and, therefore, the sensitivity of the method. The proposed method was applied to wastewater samples with recoveries of 105–106%. This study provides a selective method for the determination of ethyl xanthate and introduces novel information on the parameters affecting the oxidation of xanthates

Mineralogical and surface chemical characterization of flotation feed and products after wet and dry grinding

Abstract Wet processing after crushing is common practice in mineral processing circuits involving flotation but the need for more efficient water management has increased interest towards dry processing. In this study the effects of both wet and dry grinding on flotation of one sulphidic and one non-sulphidic ore were compared. Bench scale flotation tests were carried out and various microscopic and spectroscopic methods such as FESEM and XPS were used in characterization of flotation feeds and products. Bulk surface charge properties were tested with mass titration. Clear differences in surface properties and flotation results were observed from the wet and dry grinding methods, which encourages further research. Wet grinding was beneficial for the energy efficiency for both ores and promoted the selectivity of flotation particularly with sulphidic ore. The wear of the mill and grinding media seemed more extensive in wet grinding. Dry grinding produced more fine particles tightly attached to the surfaces, caused by the higher surface charge of the dry ground ore especially with non-sulphidic ore

Characterisation of used traction sand for utilization aspects in earth construction based on the requirements of Finnish environmental legislation

Abstract Finland launched a new Government Decree, the so-called MARA-regulation, on the utilization of certain wastes in earth construction on 1.1.2018. This statutory regulation sets limit values for the solubility of heavy metals (Sb, As, Ba, Cd, Cr, Cu, Pb, Mo, Ni, Se, Zn, V, Hg), chloride, sulphate, fluoride and dissolved organic carbon, as well as for organic substance (petroleum hydrocarbons, benzene, naphthalene, TEX (toluene, ethylbenzene and xylene), PAH-, phenolic- and PCB-compounds). In this case study, the concentrations of these harmful substances in the used traction sand collected in the city of Kemi, Northern Finland, were lower than their limit values set in the MARA-regulation. Therefore, this residue is a potential material to be used at earth construction sites such as in roads and roadways, in field and embankment structures, as well as in floor structures of industrial or storage buildings. However, if the used traction sand is to be utilized for these kinds of civil engineering purposes, an environmental permit is still needed because this material is not yet included in the scope of the MARA-regulation. This paper also gives an overview of the relevant Finnish environmental legislation on the utilization of wastes as an earth construction material

Evaluation of time-gated Raman spectroscopy for the determination of nitric, sulfuric and hydrofluoric acid concentrations in pickle liquor

Abstract The focus of this study was to assess the feasibility of time-gated Raman spectroscopy for stainless steel pickle liquor acid quantification. Pickle liquor is used for dissolving metal surface impurities during the pickling process. The pickle liquor samples consisted mainly of 11–89 g/L HNO₃, 20–160 g/L H₂SO₄, 5–57 g/L HF and stainless steel residue. Raman peaks correlating with the different acids were identified in both aqueous and pickle liquor solutions. The linearity between Raman scattering intensity and acid concentration was studied. Multivariate PLSR calibration for pickle liquor HNO₃, H₂SO₄ and HF quantification was also investigated. Time-gated Raman spectroscopy was found to be a promising technique for pickle liquor HNO₃ and H₂SO₄ quantification