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•Pyrrole-1-carboxylic acid (Py-CO2) was synthesized and applied for modification of pencil graphite electrodes (PGE).•Electropolymerization of Py-CO2 created a sensing film for ...selective metal extraction and determination.•The modified electrode, PPy-CO2@PGE, provided excellent sensitivity and selectivity for detection of Pb2+ and Cd2+.•Accurate analysis of Pb2+ and Cd2+ in several natural water sources was demonstrated and independently verified.
A pencil graphite electrode (PGE) was modified by the electropolymerization of pyrrole-1-carboxylic acid (Py-CO2) to form a sensing film of poly(pyrrole-1-carboxylic acid) (PPy-CO2) for the sensitive determination of Pb2+ and Cd2+ by differential pulse anodic stripping voltammetry (DPASV). The porous structure of the PPy-CO2 film uniformly distributes a carboxylate group throughout the coating to selectively coordinate and preconcentrate metal ions. The polymer film was characterized by cyclic voltammetry (CV), scanning electron microscopy (SEM), and energy dispersive X-ray (EDS) and Fourier transform infrared (FTIR) spectroscopy. Under the optimized conditions (analyte solution pH: 6.0, extraction time: 15 min, reduction potential: −1.1 V and reduction time: 160 s), a linear relationship between peak current and metal concentration was obtained from 0.1 to 1 nM for Pb2+ and Cd2+ with detection limits of 0.018 and 0.023 nM, respectively. Simultaneous analysis of Pb2+ and Cd2+ was performed in the presence of the possible interfering ions Cr3+, Bi3+, Cu2+, Fe2+, Zn2+ and Co2+ and in complex matrices. The performance of the PPy-CO2@PGE demonstrated excellent intra-day repeatability, long-term reproducibility over a seven-week period and was utilized for the determination of Pb2+ and Cd2+ in a variety of natural water samples with the results independently verified by inductively coupled plasma-mass spectrometry.
Produced water (PW), a waste byproduct of oil and gas extraction, is a complex mixture containing numerous organic solubles and elemental species; these constituents range from polycyclic aromatic ...hydrocarbons to naturally occurring radioactive materials. Identification of these compounds is critical in developing reuse and disposal protocols to minimize environmental contamination and health risks. In this study, versatile extraction methodologies were investigated for the untargeted analysis of PW. Thin-film solid-phase microextraction with hydrophilic–lipophilic balance particles was utilized for the extraction of organic solubles from eight PW samples from the Permian Basin and Eagle Ford formation in Texas. Gas chromatography–mass spectrometry analysis found a total of 266 different organic constituents including 1,4-dioxane, atrazine, pyridine, and PAHs. The elemental composition of PW was evaluated using dispersive solid-phase extraction followed by inductively coupled plasma–mass spectrometry, utilizing a new coordinating sorbent, poly(pyrrole-1-carboxylic acid). This confirmed the presence of 29 elements including rare earth elements, as well as hazardous metals such as Cr, Cd, Pb, and U. Utilizing chemometric analysis, both approaches facilitated the discrimination of each PW sample based on their geochemical origin with a prediction accuracy above 90% using partial least-squares-discriminant analysis, paving the way for PW origin tracing in the environment.
The demand for the recovery of valuable metals and the need to understand the impact of heavy metals in the environment on human and aquatic life has led to the development of new methods for the ...extraction, recovery, and analysis of metal ions. With special emphasis on environmentally friendly approaches, efforts have been made to consider strategies that minimize the use of organic solvents, apply micromethodology, limit waste, reduce costs, are safe, and utilize benign or reusable materials. This review discusses recent developments in liquid- and solid-phase extraction techniques. Liquid-based methods include advances in the application of aqueous two- and three-phase systems, liquid membranes, and cloud point extraction. Recent progress in exploiting new sorbent materials for solid-phase extraction (SPE), solid-phase microextraction (SPME), and bulk extractions will also be discussed.
A nanocomposite of graphene oxide (GO), yttrium oxide (Y2O3) nanoparticles, and Nafion was prepared and used to modify a glassy carbon electrode (GCE) by a simple drop casting technique. The modified ...electrode sensor was then used for the electrochemical detection of l-3,4-dihydroxyphenylalanine (l-DOPA). Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) were used for the characterization of the modified electrode. Square wave voltammetry (SWV) and cyclic voltammetry (CV) were also employed for electrochemical detection of l-DOPA and characterization of the modified electrode. The effect of SWV parameters, ratio of GO:Y2O3 in the composite, and the electrolyte solution pH on the oxidation peak currents were examined to optimize experimental conditions. The results of the optimization steps revealed the best experimental parameters based on the current response for oxidation of l-DOPA were 55 mV for pulse amplitude, 10 mV for step potential, 30 Hz for frequency, 2:1 for the GO:Y2O3 ratio, and 3.5 for pH. Under these conditions, the GCE modified with GO-Y2O3 showed a linear current response for oxidation of l-DOPA in the range of 0.5–350 μM with a limit of detection (LOD) of 0.05 μM, a limit of quantification (LOQ) of 0.17 μM, and a heterogeneous rate constant (k°) of 1.07 × 10−2 cm s−1. Increased sensitivity compared to a GO modified electrode was clearly observed. The electrode also exhibited selectivity towards l-DOPA in the presence of common interferences such as ascorbic and uric acid, and excellent stability and reproducibility over time. Finally, the modified electrode was utilized for the detection of l-DOPA in biological samples.
Poly(caffeic acid) was synthesized and utilized for the extraction and determination of rare earth elements (REEs), thorium, and uranium. Oxidative polymerization of caffeic acid, a low-cost ...plant-based material, in the presence of ethylenediamine produced a granular, air-stable, and cross-linked polymer. The polymer is highly oxygenated and together with the amino group from ethylenediamine efficiently coordinates and preconcentrates these critical elements from aqueous media. Extraction was dependent on solution pH, amount of sorbent, and extraction time, while the concentration and flow rate of the desorption solution governed the recovery efficiency. Removal and recovery efficiencies greater than 98 and 90%, respectively, and low levels of detection ranging from 0.1 to 2.9 ng/L were achieved. Determination of these strategic elements in the presence of potentially interfering ions as well as in complex matrices such as well water and produced water samples also was demonstrated. The capacity of poly(caffeic acid) was determined with lanthanum as a representative REE to be 161.7 mg/g, establishing the promise of poly(caffeic acid) for larger-scale extractions in addition to the ability to screen sources for the presence of REEs.
Conducting materials (CMs) for analytical applications have enormously increased due to their unique physical and chemical properties and their ability to interact with various analytes. This ...dissertation focuses on applications of various types of CMs and their composites for electrochemical detection of biomolecules and preconcentration and recovery of rare earths elements (REEs) and heavy metals (HMs). In chapter 1, the background, synthesis and reported applications of CMs in the development of electrode sensors and sorbent materials for sample preparation, separation and detection of various analytes are discussed. The second chapter discusses the preparation and electrochemical application of a nanocomposite of graphene oxide (GO), yttrium oxide (Y2O3) nanoparticles and Nafion. The prepared nanocomposite, GO-Y2O3 was utilized to modify a glassy carbon electrode (GCE) by a simple drop-casting technique. This modified electrode was utilized for electrochemical detection of 3,4-dihyroxy-L-phenylalanine (L-DOPA). Improved sensitivity was clearly observed compared to a GO modified electrode and a bare electrode. The electrode also demonstrated selectivity towards L-DOPA in the presence of ascorbic acid and uric acid, the two most common interfering compounds for L-DOPA detection in biological media. The modified electrode demonstrated excellent stability, reproducibility, low detection limits, a wide linear range and applicability in biological samples.In chapter 3, a new sorbent was developed by N-functionalization of pyrrole with dry ice (solid CO2) to produce pyrrole-1-carboxylic acid (Py-CO2). The obtained monomer was polymerized using chemical polymerization to produce an air-stable, water-insoluble, porous, granular dark powder of poly(pyrrole-1-carboxylic acid) (PPy-CO2). This new polymeric material was evaluated on the analytical scale for the dispersive solid-phase extraction (D-SPE) of a range of metal ions and found to efficiently extract REEs, Th and heavy metals (Cr, Fe, Cd and Pb). The impact of various experimental parameters, such as solution pH, amount of sorbent, extraction time and effect of desorption flow rates, were investigated and optimized using ultrasound-assisted dispersive solid-phase extraction (UAD-SPE) with ICP-MS analysis. Maximum efficiency for metal ion sorption and recovery was achieved at solution pH 6.0, using 10 mg of sorbent, an extraction time of 5 min and desorption conditions of 1 mL of 2 M nitric acid at a desorption flow rate of 0.25 mL min-1. The experimental results demonstrated excellent linear ranges, low detection limits, reproducibility and applicability to various water samples for trace level determination of many elements. PPy-CO2 exhibited enhanced affinity for the sorption of REEs, Th and heavy metals (Cr, Fe, Cd and Pb) compared to unfunctionalized PPy due to the incorporation of carboxylate functional groups onto the polymer backbone.In chapter 4, the excellent sorption efficiency of PPy-CO2 in retaining, preconcentrating and recovery of a wide range of metal ions was used to evaluate the elemental composition of eight produced water (PW) samples obtained from Permian Basin and Eagle Ford formation in Texas. PW is the largest stream of waste water produced during oil and gas production and contains a complex chemical composition. In this project, PW samples were subjected to the UAD-SPE procedure developed in chapter 3 followed by ICP-MS analysis. In total, 29 different metals were found to be present in PW samples. PPy-CO2 efficiently preconcentrated and recovered REEs and heavy metals from the complex PW samples. ICP-MS analysis confirmed the presence of trace lanthanum, cerium and other REEs along with toxic heavy metals Cd, Cr and Pb in most of the PW samples. In addition, the experimental findings demonstrated the PW also contained a wide range and various levels of Mg, Mn, Zn, Se, Rb, Ag, Cs, Ba, V, Cu, Ga and U. In many cases, the levels were found to be much higher than the recommend upper limits for livestock drinking water and irrigation water. The data from elemental analysis will be combined with a study defining the organic soluble components found in the analysis of PW using thin-film solid-phase microextraction (TF-SPME) and processed using statistical analysis tools to evaluate the common and unique characteristics between the geographical locations of the PW samples.
The salinization of soil is responsible for the reduction in the growth and development of plants. As the global population increases day by day, there is a decrease in the cultivation of farmland ...due to the salinization of soil, which threatens food security. Salt-affected soils occur all over the world, especially in arid and semi-arid regions. The total area of global salt-affected soil is 1 billion ha, and in India, an area of nearly 6.74 million ha−1 is salt-stressed, out of which 2.95 million ha−1 are saline soil (including coastal) and 3.78 million ha−1 are alkali soil. The rectification and management of salt-stressed soils require specific approaches for sustainable crop production. Remediating salt-affected soil by chemical, physical and biological methods with available resources is recommended for agricultural purposes. Bioremediation is an eco-friendly approach compared to chemical and physical methods. The role of microorganisms has been documented by many workers for the bioremediation of such problematic soils. Halophilic Bacteria, Arbuscular mycorrhizal fungi, Cyanobacteria, plant growth-promoting rhizobacteria and microbial inoculation have been found to be effective for plant growth promotion under salt-stress conditions. The microbial mediated approaches can be adopted for the mitigation of salt-affected soil and help increase crop productivity. A microbial product consisting of beneficial halophiles maintains and enhances the soil health and the yield of the crop in salt-affected soil. This review will focus on the remediation of salt-affected soil by using microorganisms and their mechanisms in the soil and interaction with the plants.
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