A system for the direct determination of the nonvolatile organic carbon, dissolved organic carbon, and inorganic carbon in water samples through inductively coupled plasma atomic emission spectrometry

Applications of Plasma-Liquid Systems: A Review

Plasma-liquid systems have attracted increasing attention in recent years, owing to their high potential in material processing and nanoscience, environmental remediation, sterilization, biomedicine, and food applications. Due to the multidisciplinary character of this scientific field and due to its broad range of established and promising applications, an updated overview is required, addressing the various applications of plasma-liquid systems till now. In the present review, after a brief historical introduction on this important research field, the authors aimed to bring together a wide range of applications of plasma-liquid systems, including nanomaterial processing, water analytical chemistry, water purification, plasma sterilization, plasma medicine, food preservation and agricultural processing, power transformers for high voltage switching, and polymer solution treatment. Although the general understanding of plasma-liquid interactions and their applications has grown significantly in recent decades, it is aimed here to give an updated overview on the possible applications of plasma-liquid systems. This review can be used as a guide for researchers from different fields to gain insight in the history and state-of-the-art of plasma-liquid interactions and to obtain an overview on the acquired knowledge in this field up to now.

Development and validation of an in situ and real-time quantification method for bicarbonate, carbonate and orthophosphate ions by ATR FT-IR spectroscopy in aqueous solutions

Bicarbonate salts are used in various industrial processes and could even serve as an alternative source of carbon in bioprocesses involving photosynthetic organisms. Industrial productions require efficient monitoring and control to ensure that their output will meet target specifications. To this end, a simple and rapid in situ quantification method was developed for bicarbonate, carbonate and phosphate ions using Attenuated Total Reflectance-Fourier Transform Infrared (ATR FT-IR) spectroscopy combined with partial least squares (PLS). The resulting multivariate approach allows the simultaneous determination of inorganic carbon and orthophosphate ions concentrations in aqueous solutions (R2 > 0.98, root-mean-square-errors of the cross validation RMSECV < 3.3%). Validation of the method was achieved through replicability and repeatability tests. Univariate calibration graphs are linear over a concentration range of 150 mM (R2 > 0.9990). Quantification limits for those ions were in the 6.9-17.2 mM range, as determined from univariate models. The multivariate model was successfully applied to a microalgal culture of Scenedesmus obliquus using bicarbonate as the carbon source and a phosphate buffer to maintain the pH. This analytical technique did not require extraction or chemical treatment and no sample preparation is needed. The results demonstrate the potential of ATR FT-IR method to study inorganic carbon and phosphate species during a bioprocess.

Effective degradation of phenol via Fenton reaction over CuNiFe layered double hydroxides

A series of CuNiFe layered double hydroxides (LDHs) with various Cu/Ni molar ratios were synthesized as catalysts for Fenton degradation of phenol. It is found that Cu⁺, Cu²⁺, Ni²⁺, Ni³⁺ and Fe³⁺ are present on LDHs, owing to an electron transfer from Ni²⁺ to Cu²⁺ via metal-oxo-metal bridges. At lower Cu/Ni ratios, the highly dispersed MO₆ octahedra and the electron donation effect of Ni facilitate such electron transfer and thus increase the percentage of Cu⁺. The catalytic activity increases with the decrease in Cu/Ni ratio. The most active Cu_0.5Ni_2.5Fe LDH can mineralize 98.9% phenol at ambient pH and less excessive H₂O₂ dosage ( [Formula: see text] /M_phenol = 37). Even at the H₂O₂ dosage close to the theoretical value, around 90% phenol can be mineralized. The structure-activity correlation indicates Cu⁺ which can readily react with H₂O₂ to produce hydroxyl radicals may dominate the reaction. The regeneration of Cu⁺ could be achieved by the electron transfer between Cu²⁺ and Ni²⁺ in LDHs. Moreover, Fe³⁺ can also act as Fenton-like active sites. The special structure of CuNiFe LDHs could offer surface-enriched and easily regenerated Cu⁺ species, leading to the complete mineralization of phenol and the efficient use of H₂O₂.

Continuous and Inexpensive Monitoring of Nonpurgeable Organic Carbon by Coupling High-Efficiency Photo-oxidation Vapor Generation with Miniaturized Point-Discharge Optical Emission Spectrometry

Currently, no applicable analyzers are available to accomplish online continuous monitoring of organic pollution, which is one of the most important factors contributing to water shortages around the world, particularly in developing countries. In this work, a sensitive, miniaturized, inexpensive, and online nonpurgeable organic carbon (NPOC) analysis system was developed for continuous monitoring of such organic pollution. This system consists of a specially designed high-efficiency UV photo-oxidation vapor generation (HE-POVG) reactor and a miniaturized, low-power (7 W) point-discharge microplasma optical emission spectrometer (PD-OES). Organics present in sample or standard solutions are pumped to the HE-POVG and efficiently converted into CO₂, which is separated and further transported to the PD-OES for NPOC analysis via highly sensitive detection of carbon atomic emission at 193.0 nm. Under optimal conditions, a limit of detection of 0.05 mg·L^-1 (as C) is obtained, with precision better than 5.0% (relative standard deviation) at 5 mg·L^-1. This system overcomes many shortcomings associated with conventional chemical oxygen demand or total organic carbon analyzers such as long analysis time, use of expensive and toxic chemicals, production of secondary toxic waste, requirement of large, power consuming and expensive instrumentation and difficulties implementing continuous online monitoring. The system was successfully applied to sensitive and accurate determination of NPOC in various water samples and for continuous monitoring of such organic pollution in tap water.

A set up of a modern analytical laboratory for wastewaters from pulp and paper industry

The introduction of analytical techniques allowing rapid, selective, sensitive, and reliable determination of aqueous pollutants is of crucial importance for the protection of the environment. This critical review summarizes the advanced analytical techniques suggested over the last ten years together with already established methods, and evaluates whether they are fit for wastewater quality assessment considering the area of application, interferences, limit of detection, calibration function, and precision. The key parameters of wastewater quality assessment are: total organic carbon (TOC), chemical oxygen demand (COD), biochemical oxygen demand (BOD), organochlorines (AOX), nitrogen, phosphorus, sulfur, and toxicity. Chromatography and capillary electrophoresis, photocatalytic oxidation with semiconductor nanofilms and atomic emission spectrometry, optical fibre sensors and chemiluminescence, amperometric mediated biosensors and microbial fuel cells, respirometry and bioluminescence measurements are just part of the proposed wastewater analyst's toolkit. The diversity of fundamental phenomena and the captivating elegance of interdisciplinary applications involved in the development of wastewater analytical techniques should attract the interest of a wide scientific audience including analytical chemists, chemical physicists, microbiologists and environmentalists. To conclude, we suggest a laboratory set up for the analysis of wastewaters from the pulp and paper industry.