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Spectrophotometric determination of nitrate in hypersaline waters after optimization based on the Box-Behnken design
摘要： Monitoring dissolved nitrate (NO3?) concentrations is essential for conservation efforts in aquatic ecosystems. Spectrophotometric methods are a widely accepted approach for NO3? analysis. They detect NO3? as a colored diazo complex after reduction to nitrite (NO2?) and its consequent reaction with the so-called Griess reagent. This method is commonly used for freshwater and saline water samples, even though it requires applying a heavy metal in powder form (cadmium) or high concentrations of heavy metal salts (vanadium-III), as a reductant. There has been little discussion about applying these methods for hypersaline samples. This study optimizes an existing method for use in high saline conditions based on the Griess reaction. Five factors were studied: incubation temperature, reaction time, concentration of EDTA, concentration of trisodium citrate, and concentration of reductant (VCl3). Optimal conditions were obtained by using the Box-Behnken design and included using VCl3 17.5 mM, trisodium citrate 70 mM, and an incubation temperature of 60 °C for 40 min. These conditions provided a linear range from 0.55 μM to 50 μM NO3?. The method showed a moderate precision (ranging from 4.3% to 15.4%). The proposed protocol was tested with hypersaline natural samples and showed recovery rates between 92.6% and 100.1%. This protocol for NO3? determination is the first specifically described for hypersaline samples.
关键词： Hypersaline water,Nitrate analyses,Griess reaction,Vanadium chloride,Box-Behnken design
更新于2025-09-23 15:22:29
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Direct Trace Element Determination in Oil and Gas Produced Waters with Inductively Coupled Plasmaa??Optical Emission Spectrometry: Advantages of High Salinity Tolerance
摘要： Waters co-produced during petroleum extraction are the largest waste streams from oil and gas development. Reuse or disposal of these waters is difficult due to their high salinities and the sheer volumes generated. Produced waters may also contain valuable mineral commodities. While an understanding of produced water trace element composition is required for evaluating the associated resource and waste potential of these materials, measuring trace elements in brines is challenging due to the dilution requirements of typical methods. Alternatively, inductively coupled plasma-optical emission spectrometry (ICP-OES) has shown promise as being capable of direct measurements of trace elements within produced waters with minimal dilution. Here we evaluate direct ICP-OES trace element quantification in produced waters for seventeen trace elements (As, Al, Ba, Be, Cd, Cr, Co, Cu, Hg, Mo, Ni, Pb, Rb, Sb, U, V and Zn) within fifteen produced waters from five U.S. continuous reservoirs. The total analytical uncertainties associated with the trace element levels determined using ICP-OES were estimated to be better than ± 30% (2s) except for Rb, which could not be determined due to ionisation interferences. The ICP-OES results are compared with trace element levels determined using inductively coupled plasma-mass spectrometry from the same samples. Our results demonstrate the potential for direct analysis of high salinity waters using ICP-OES with minimal dilution and provide trace element concentrations in waters from several important U.S. petroleum-generating reservoirs where available data are sparse.
关键词： ICP-OES,elemental analysis,hypersaline matrix,produced waters,unconventional oil and gas
更新于2025-09-16 10:30:52
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Applying facilely synthesized CuO/CeO <sub/>2</sub> photocatalyst to accelerate methylene blue degradation in hypersaline wastewater
摘要： Textile and dye effluents have strong color, unstable pH and COD, a lot of inorganic salt, and high biotoxicity. It is difficult and inefficient to remove dyes from high‐saline wastewater by traditional methods. In this study, a simple synthetic CuO/CeO2 photocatalyst is used to achieve high efficiency photodegradation of methylene blue in high salt wastewater. The p‐type CuO/n‐type CeO2 heterojunction photocatalyst is synthesized by a modified hydrothermal‐calcination method. The XRD and XPS reveal the successful synthesis of CuO/CeO2 composite. The SEM and TEM images show that the sample consists of large amounts of well‐dispersed CuO nanosphere loading on the CeO2 layers. DRS exhibits the absorption band (about 510 nm) and the band gap energy (2.43 eV) of the CuO/CeO2 composite. Compared with pure CuO, CeO2, and TiO2 (P25), the prepared CuO/CeO2 can increase the mineralization rate of MB by 18.19%~33.74%. More than 80% of MB can be effectively removed in the wastewater containing 5~80 g/L NaCl with a wide pH value range of 2.11~9.02, and the degradation processes follow the pseudofirst‐order reaction kinetics. Active species trapping experiments confirm that the degradation of methylene blue is mainly attributed to hydroxyl radical; besides, O2?? and hole (h+) also play important roles. Chlorine ions have dual effects in photocatalytic reactions. This work could provide a new approach to construct new heterojunction photocatalysts and a deeper insight for the treatment of hypersaline dye wastewater.
关键词： methylene blue,dye wastewater,hypersaline,UV/H2O2,CuO/CeO2,photocatalysis
更新于2025-09-10 09:29:36