Removal of toxic mercury from petroleum oil by newly synthesized molecularly-imprinted polymer

Advancements in mercury detection using surface-enhanced Raman spectroscopy (SERS) and ion-imprinted polymers (IIPs): a review

Mercury (Hg) contamination remains a major environmental concern primarily due to its presence at trace levels, making monitoring the concentration of Hg challenging. Sensitivity and selectivity are significant challenges in the development of mercury sensors. Surface-enhanced Raman spectroscopy (SERS) and ion-imprinted polymers (IIPs) are two distinct analytical methods developed and employed for mercury detection. In this review, we provide an overview of the key aspects of SERS and IIP methodologies, focusing on the recent advances in sensitivity and selectivity for mercury detection. By examining the critical parameters and challenges commonly encountered in this area of research, as reported in the literature, we present a set of recommendations. These recommendations cover solid and colloidal SERS substrates, appropriate Raman reporter/probe molecules, and customization of IIPs for mercury sensing and removal. Furthermore, we provide a perspective on the potential integration of SERS with IIPs to achieve enhanced sensitivity and selectivity in mercury detection. Our aim is to foster the establishment of a SERS-IIP hybrid method as a robust analytical tool for mercury detection across diverse fields.

Ion-Imprinted Polymeric Materials for Selective Adsorption of Heavy Metal Ions from Aqueous Solution

The introduction of selective recognition sites toward certain heavy metal ions (HMIs) is a great challenge, which has a major role when the separation of species with similar physicochemical features is considered. In this context, ion-imprinted polymers (IIPs) developed based on the principle of molecular imprinting methodology, have emerged as an innovative solution. Recent advances in IIPs have shown that they exhibit higher selectivity coefficients than non-imprinted ones, which could support a large range of environmental applications starting from extraction and monitoring of HMIs to their detection and quantification. This review will emphasize the application of IIPs for selective removal of transition metal ions (including HMIs, precious metal ions, radionuclides, and rare earth metal ions) from aqueous solution by critically analyzing the most relevant literature studies from the last decade. In the first part of this review, the chemical components of IIPs, the main ion-imprinting technologies as well as the characterization methods used to evaluate the binding properties are briefly presented. In the second part, synthesis parameters, adsorption performance, and a descriptive analysis of solid phase extraction of heavy metal ions by various IIPs are provided.

Ultratrace mercury speciation analysis in rice by in-line solid phase extraction - liquid chromatography - atomic fluorescence spectrometry

For the first time, Hg²⁺ and methylmercury speciation analysis was accomplished by in-line SPE-LC-AFS. After modification with 0.1 mL of 0.001% (m:v) sodium diethyldithiocarbamate, a C₁₈ microcolumn retained Hg²⁺ and MetHg in rice extract within 3 min; the captured Hg species were separated within 12 min in 0.25% (v:v) 2-mercaptoethanol + 60 mmol L^-1 (m:v) ammonium acetate + 4% (v:v) acetonitrile. Under optimized conditions, the detection limits were 0.3 ng L^-1 for Hg²⁺ and 0.2 ng L^-1 for MetHg, respectively, with 10 mL injection vs. 0.1 mL eluent; in-line SPE achieved ∼ 100x enrichment. Method precision and accuracy were satisfactory at < 2% relative standard deviations (RSDs) for 20 ng L^-1 of Hg²⁺ and MetHg and 95-102% recoveries for real rice samples. In-line SPE obviated human involvement and avoided invalid transportation between interfaces, rendering this SPE-LC-AFS method easy, compact, robust, yet sensitive in mercury speciation analysis to uphold food safety.

Rational Design of an Ion-Imprinted Polymer for Aqueous Methylmercury Sorption

Methylmercury (MeHg+) is a mercury species that is very toxic for humans, and its monitoring and sorption from environmental samples of water are a public health concern. In this work, a combination of theory and experiment was used to rationally synthesize an ion-imprinted polymer (IIP) with the aim of the extraction of MeHg+ from samples of water. Interactions among MeHg+ and possible reaction components in the pre-polymerization stage were studied by computational simulation using density functional theory. Accordingly, 2-mercaptobenzimidazole (MBI) and 2-mercaptobenzothiazole (MBT), acrylic acid (AA) and ethanol were predicted as excellent sulfhydryl ligands, a functional monomer and porogenic solvent, respectively. Characterization studies by scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) revealed the obtention of porous materials with specific surface areas of 11 m2 g-1 (IIP-MBI-AA) and 5.3 m2 g-1 (IIP-MBT-AA). Under optimized conditions, the maximum adsorption capacities were 157 µg g-1 (for IIP-MBI-AA) and 457 µg g-1 (for IIP-MBT-AA). The IIP-MBT-AA was selected for further experiments and application, and the selectivity coefficients were MeHg+/Hg2+ (0.86), MeHg+/Cd2+ (260), MeHg+/Pb2+ (288) and MeHg+/Zn2+ (1510), highlighting the material's high affinity for MeHg+. The IIP was successfully applied to the sorption of MeHg+ in river and tap water samples at environmentally relevant concentrations.

Artificial Neural Network Approach for Modelling of Mercury Ions Removal from Water Using Functionalized CNTs with Deep Eutectic Solvent

Multi-walled carbon nanotubes (CNTs) functionalized with a deep eutectic solvent (DES) were utilized to remove mercury ions from water. An artificial neural network (ANN) technique was used for modelling the functionalized CNTs adsorption capacity. The amount of adsorbent dosage, contact time, mercury ions concentration and pH were varied, and the effect of parameters on the functionalized CNT adsorption capacity is observed. The (NARX) network, (FFNN) network and layer recurrent (LR) neural network were used. The model performance was compared using different indicators, including the root mean square error (RMSE), relative root mean square error (RRMSE), mean absolute percentage error (MAPE), mean square error (MSE), correlation coefficient (R²) and relative error (RE). Three kinetic models were applied to the experimental and predicted data; the pseudo second-order model was the best at describing the data. The maximum RE, R² and MSE were 9.79%, 0.9701 and 1.15 × 10^-3, respectively, for the NARX model; 15.02%, 0.9304 and 2.2 × 10^-3 for the LR model; and 16.4%, 0.9313 and 2.27 × 10^-3 for the FFNN model. The NARX model accurately predicted the adsorption capacity with better performance than the FFNN and LR models.

Molecularly Imprinted Polymers for Removal of Metal Ions: An Alternative Treatment Method

Aquatic and terrestrial environment and human health have been seriously threatened with the release of metal-containing wastewater by the rapid growth in the industry. There are various methods which have been used for removal of ions from the environment, such as membrane filtration, ion exchange, membrane assisted liquid extraction and adsorption. As a sort of special innovation, a polymerization technique, namely molecular imprinting is carried out by specific identification for the target by mixing it with a functional monomer. After the polymerization occurred, the target ion can be removed with suitable methods. At the end of this process, specific cavities, namely binding sites, are able to recognize target ions selectively. However, the selectivity of the molecularly imprinted polymer is variable not only because of the type of ligand but also charge, size coordination number, and geometry of the target ion. In this review, metal ion-imprinted polymeric materials that can be applied for metal ion removal from different sources are discussed and exemplified briefly with different metal ions.

Determination of subnanomolar levels of mercury (II) by using a graphite paste electrode modified with MWCNTs and Hg(II)-imprinted polymer nanoparticles

Mercury ion-imprinted polymer nanoparticles (Hg-IP-NPs) were synthesized via precipitation polymerization by using itaconic acid as a functional monomer. A carbon paste electrode was impregnated with the synthesized Hg-IP-NPs and MWCNTs to obtain a highly sensitive and selective electrode for determination of Hg(II). Mercury ion is first accumulated on the electrode surface via an open circuit procedure. After reduction of Hg(II) ions to its metallic form at a negative pre-potential, square wave anodic stripping voltammetry was applied to generate the electrochemical signal. The high affinity of the Hg-IP-NPs for Hg(II) was substantiated by comparing of the signals of electrodes with imprinted and non-imprinted polymer. The beneficial effect of MWCNTs on the voltammetric signal is also demonstrated. Under the optimized conditions and at a typical working potential of +0.05 V (vs. Ag/AgCl), the electrode has a linear response in the 0.1-20 nmol L^-1 Hg(II) concentration range and a 29 pM detection limit. The electrochemical sensitivity is as high as 1441 A·M^-1·cm^-2 which is among the best values known. The electrode was applied to the determination of Hg(II) in water samples. Graphical abstract Schematic representation of the sensor electrode modified with mercury-imprinted polymer nanoparticles, and the recognition and voltammetric determination steps.