In-situ precipitation zero-valent Co on Co2VO4 to activate oxygen vacancies and enhance bimetallic ions redox for efficient detection toward Hg(II)

Despite the widespread utilization of variable valence metals in electrochemistry, it is still a formidable challenge to enhance the valence conversion efficiency to achieve excellent catalytic activity without introducing heterophase elements. Herein, the in-situ precipitation of Co particles on Co2VO4 not only enhanced the concentration of oxygen vacancies (Ov) but also generated a greater number of low-valence metals, thereby enabling efficient reduction towards Hg(II). The electroanalysis results demonstrate that the sensitivity of Co/Co2VO4 towards Hg(II) was measured at an impressive value of 1987.74 μA μM-1 cm-2, significantly surpassing previously reported results. Further research reveals that Ov acted as the main adsorption site to capture Hg(II). The redox reactions of Co2+/Co3+ and V3+/V4+ played a synergistic role in the reduction of Hg(II), accompanied by the continuous supply of electrons from zero-valent Co to expedite the valence cycle. The Co/Co2VO4/GCE presented remarkable selectivity towards Hg(II), with excellent stability, reproducibility, and anti-interference capability. The electrode also exhibited minimal sensitivity fluctuations towards Hg(II) in real water samples, underscoring its practicality for environmental applications. This study elucidates the mechanism underlying the surface redox reaction of metal oxides facilitated by zero-valent metals, providing us with new strategies for further design of efficient and practical sensors.

Visualizing and sorbing Hg(II) with a cellulose-based red fluorescence aerogel: Simultaneous detection and removal

Both sensing and removal of Hg(II) are important to environment and human health in view of the high toxicity and wide applications of mercury in industry. This study aims to develop a cellulose-based fluorescent aerogel for simultaneous Hg(II) sensing and removal via conveniently cross-linking two nanomaterials cellulose nanocrystals and bovine serum albumin-functionalized gold nanoclusters (BSA-AuNCs) with epichlorohydrin. The aerogel exhibited strong homogeneous red fluorescence at the non-edged regions under UV light due to highly dispersed BSA-AuNCs in it, and its fluorescence could be quenched by Hg(II). Through taking pictures with a smartphone, Hg(II) in the range of 0-1000 μg/L could be quantified with a detection limit of 12.7 μg/L. The sorption isotherm of Hg(II) by the aerogel followed Freundlich model with an equation of Qe = 0.329*Ce1/0.971 and a coefficient of 0.999. The maximum sorption capacity can achieve 483.21 mg/g for Hg(II), much higher than many reported sorbents. The results further confirmed Hg(II) strong sorption and sensitive detection are due to its complexation and redox reaction with the chemical groups in aerogels and its strong fluorescence quenching effect. Due to extensive sources and low cost, cellulose is potential to be developed into aerogels with multiple functions for sophisticated applications.

A new bodipy/pillar[5]arene functionalized magnetic sporopollenin for the detection of Cu(II) and Hg(II) ions in aqueous solution

In this study, a new bodipy/pillar[5]arene functionalized magnetic MS-Sp-P[5]-bodipy microcapsule sensor was prepared based on the use of environmentally friendly for the selective and sensitive detection of Cu(II) and Hg(II) ions in aqueous media. SEM results used in the characterization process of the materials synthesized at each stage confirmed the structural and morphological changes in the pore structure, while other characterization results (FT-IR and XRD) elucidated the role of pillar[5]arene compound and bodipy dye in the synthesis of magnetic microcapsule sensors. The colloidal solution of MS-Sp-P[5]-bodipy (water/ethanol)) showed two fluorescence bands centered at 402 and 540 nm. The detection limits of MS-Sp-P[5]-bodipy for Hg(II) and Cu(II) were calculated to be 0.06 µM and 2.27 µM, respectively (at 540 nm). The linear range of the magnetic sensor for Hg(II) and Cu(II) was found to be in the range of 1-150 µM and 10-150 µM, respectively. The experimental results (response time, pH, temperature, sensitivity and selectivity) demonstrated the applicability and potential of the prepared magnetic microcapsule sensor for the detection of Cu(II) and Hg(II) in water and tap water samples containing heavy metal ions.

A Comprehensive Study on the Effect of Plasticizers on the Characteristics of Polymer Inclusion Membranes (PIMs): Exploring Butyl Stearate as a Promising Alternative

This study investigated the influence of various plasticizers commonly used in the manufacture of polymer inclusion membranes (PIMs), such as 2-nitrophenyl octyl ether (NPOE), phthalates, adipates, and sebacates on the mechanical, thermal, and transport properties of membranes. Additionally, butyl stearate (BTS), chosen for its non-toxic nature compared to phthalates and its cost-effectiveness relative to adipates and sebacates, was evaluated as a plasticizer in PIMs for the first time. All plasticizers were incorporated in PIMs made of either cellulose triacetate (CTA) or poly(vinyl chloride) (PVC) as the base polymers and the task-specific ionic liquid trioctylmethylammonium thiosalicylate (TOMATS) as the carrier. The plasticizers were found to significantly affect the characteristics of membrane hydrophilicity, mechanical flexibility, and thermal stability. Transport experiments using Hg(II) as a model target ion revealed that, for CTA-based PIMs, the plasticizer did not significantly affect transport efficiency. However, for PVC-based PIMs, BTS exhibited better efficiency when compared to NPOE. These findings highlight the potential of BTS as an attractive alternative to currently used plasticizers in PVC-based PIM formulations.

Synthesis of salicylaldehyde tailored PAMAM dendrimers/chitosan for adsorption of aqueous Hg(II): Performance and mechanism

Water pollution caused by Hg(II) exerts hazardous effect to environmental safety and human health. Herein, a family of salicylaldehyde tailored poly(amidoamine) (PAMAM) dendrimers/chitosan composites (G0-S/CTS, G1-S/CTS, and G2-S/CTS) were prepared and used for the removal of Hg(II) from water solution. The adsorption performance of the as-prepared composites for Hg(II) was thoroughly demonstrated by determining various influencing factors. G0-S/CTS, G1-S/CTS and G2-S/CTS exhibited competitive adsorption capacity and good adsorption selective property for Hg(II). The maximum adsorption capacity of G0-S/CTS, G1-S/CTS and G2-S/CTS for Hg(II) were 1.86, 2.18 and 4.47 mmol‧g-1, respectively. The adsorption for Hg(II) could be enhanced by raising initial Hg(II) concentration and temperature. The adsorption process was dominated by film diffusion processes with monolayer adsorption behavior. The functional groups of NH2, CONH, CN, OH, CO and CN were mainly responsible for the adsorption of Hg(II). G0-S/CTS, G1-S/CTS and G2-S/CTS displayed good regeneration property and the regenerate rate maintained 95.00 % after five adsorption-desorption cycles. The as-prepared adsorbents could be potentially used for the efficient removal of Hg(II) from aqueous solution.

Sensitive sensing of Hg(II) based on lattice B and surface F co-doped CeO2: Synergies of catalysis and adsorption brought by doping site engineering

Transition metal oxides are widely used in the detection of heavy metal ions (HMIs), and the co-doping strategy that introducing a variety of different dopant atoms to modify them can obtain a better detection performance. However, there is very little research on the co-doped transition metal oxides by non-metallic elements for electrochemical detection. Herein, boron (B) and fluorine (F) co-doped CeO2 nanomaterial (BFC) is constructed to serve as the electrochemically sensitive interface for the detection of Hg(II). B and F affect the sensitivity of CeO2 to HMIs when they were introduced at different doping sites. Through a variety of characterization, it is proved that B is successfully doped into the lattice and F is doped on the surface of the material. Through the improvement of the catalytic properties and adsorption capacity of CeO2 by different doping sites, this B and F co-doped CeO2 exhibits excellent square wave anodic stripping voltammetry (SWASV) current responses to Hg(II). Both the high sensitivity of 906.99 μA μM-1 cm-2 and the low limit of detection (LOD) of 0.006 μM are satisfactory. Besides, this BFC glassy carbon electrode (GCE) also has good anti-interference property, which has been successfully used in the detection of Hg(II) in actual water. This discovery provides a useful strategy for designing a variety of non-metallic co-doped transition metal oxides to construct trace heavy metal ion-sensitive interfaces.

Study on the cyclic adsorption performance of biomass composite membrane for Hg(II)

Salix psammophila wood flour /polyvinyl alcohol hydrogel composite membrane (SPPM) with high adsorption capacity and good cycle adsorption performance was prepared by wet spinning technology. The SPPM was characterised by the scanning electron microscope (SEM), specific surface area test (BET), energy dispersive spectrum (EDS) thermal gravimetric analysis (TGA), fourier transform infrared spectroscopy (FT-IR), and x-ray photoelectron spectroscopy (XPS). The results showed that the surface of SPPM is rough and porous, with good pore structure and thermal stability, and mercury ions (Hg(II)) have been successfully adsorbed on SPPM. At the same time, the effects of adsorption conditions (Hg(II) initial concentration, pH, adsorption time, and temperature) on the adsorption performance of SPPM were studied. Results from the adsorption experiment showed that the adsorption capacity of SPPM for Hg(II) can reach 426 mg/g. After four adsorption and desorption experiments, the adsorption capacity can reach 375 mg/g, which indicates that SPPM has good cycle adsorption performance. The adsorption kinetics was better described by the Pseudo-second-order kinetic, and their adsorption isotherms were fitted for the Langmuir model. The obtained results showed that SPPM is an available, economical adsorbent and was found suitable for removing Hg(II) from an aqueous solution.

Histamine Recognition by Carbon Dots from Plastic Waste and Development of Cellular Imaging: Experimental and Theoretical Studies

The present work highlights the sustainable approach for the transformation of plastic waste into fluorescent carbon dots (CDs) through carbonization and then they were functionalized with L-cysteine and o-phenylenediamine. CDs which were characterized by different analytical techniques such as X-ray diffraction (XRD), thermogravimetric analysis (TGA), Scanning electron microscopy (SEM), and transmission electron microscopy (TEM) are employed to recognize Cu2+, Fe2+, and Hg2+ ions. The results show that the fluorescence emission was considerably quenched, and it is consistent with the interference and Jobs plots. The detection limit was found to be 0.35µM for Cu(II), 1.38 µM for Hg(II), and 0.51µM Fe(III). The interaction of CDs with metal ions enhances the fluorescence intensity detecting histamine successfully. It shows that plastic waste-based CDs can be applied clinically to detect toxic metals and biomolecules. Moreover, the system was employed to develop the cellular images using Saccharomyces cerevisiae cells with the support of a confocal microscope. Furthermore, theoretical studies were performed for the naphthalene layer (AR) as a model for C-dots, then optimized its structure and analyzed by using the molecular orbital. The obtained TD-DFT spectra coincided with experimental spectra for CDs/M2+/histamine systems.

An efficient fluorescence reversible regulation strategy with single labelled oligonucleotide HEX-OND successively triggered by Hg(II) and Cysteine: The application and mechanism

An efficient fluorescence reversible regulation system with HEX-OND was developed. Then the application potential was explored in probing Hg(II) & Cysteine (Cys) in real samples and the thermodynamic mechanism was further investigated by precise theory analysis combining multiple spectroscopic methods. The results showed that only mere disturbances were observed among 15 and 11 kinds of other substances for the optimal system in detecting Hg(II) & Cys, respectively; The linear ranges of quantification were identified as 1.0 ∼ 14.0 and 2.0 ∼ 20.0 (×10^-8 mol/L) with LODs of 8.75 and 14.09 (×10^-9 mol/L) for Hg(II) and Cys, respectively; no significant deviations were found in the quantification results of Hg(II) in three traditional Chinese herbs and Cys in two samples between the well-understood methods with ours respectively, showing excellent selectivity, sensitivity, and tremendous application feasibility. The detailed mechanism was further verified as that the introduced Hg(II) forced HEX-OND to transform into the Hairpin structure with the apparent equilibrium association constant of 6.02 ± 0.62 × 10¹⁰ L/mol in the bimolecular ratio, leading to the equimolar quencher, consecutive two guanine bases ((G)₂), approaching and spontaneously static-quenching the reporter HEX (hexachlorofluorescein) (equilibrium constant, 8.75 ± 1.97 × 10⁷ L/mol) in the Photo-induced Electron Transfer (PET) way that was driven by the Electrostatic Interaction. The additional Cys destructed the equimolar Hairpin structure with the apparent equilibrium constant of 8.87 ± 2.47 × 10⁵ L/mol through breaking one of the formed T-Hg(II)-T mismatches by association with the involved Hg(II), occasioning (G)₂ apart from HEX and consequently the fluorescence recovery.

Highly efficient and selective Hg(II) adsorbent: ZnS grown on the surface of 4A zeolite and supported on starch aerogels

In this study, ZnS nanoparticles were loaded on the surface of zeolite NaA and embedded in a carbon aerogel to prepare C@zeolite-ZnS, where zeolite NaA was used in order to adsorb Zn²⁺ ions released during ion exchange, and the carbon aerogel had good dispersion as a carrier for ZnS to solve the ZnS agglomeration problem. The morphology and structure of C@zeolite-ZnS were characterized by FT-IR, XRD, SEM, BET, and XPS. C@zeolite-ZnS showed excellent selectivity and high removal rate for Hg(II) ions with a maximum adsorption capacity of 795.83 mg/g. When the pH, adsorption time, and Hg(II) ion concentration were 6, 30 min, and 25 mg/L at 298 K, the corresponding adsorption and removal rates reached 99.90% and 124.88 mg/g, respectively. Thermodynamic studies have shown that the adsorption process is a spontaneous heat absorption process. Furthermore, after up to 10 cycles of adsorption, the adsorbent still exhibited outstanding stability and high adsorption capacity with removal rates exceeding 99%. In conclusion, C@zeolite-ZnS, which is stable and reusable and has the ability to meet industrial emission standards after adsorption of Hg(II) ions, is very promising for industrial applications.

Post-synthetic thiol modification of covalent organic frameworks for mercury(II) removal from water

Various materials have been developed for environmental remediation of mercury ion pollution. Among these materials, covalent organic frameworks (COFs) can efficiently adsorb Hg(II) from water. Herein, two thiol-modified COFs (COF-S-SH and COF-OH-SH) were prepared, through the reaction between 2,5-divinylterephthalaldehyde and 1,3,5-tris-(4-aminophenyl)benzene, followed by post-synthetic modification using bis(2-mercaptoethyl) sulfide and dithiothreitol, respectively. The modified COFs showed excellent Hg(II) adsorption abilities with maximum adsorption capacities of 586.3 and 535.5 mg g^-1 for COF-S-SH and COF-OH-SH, respectively. The prepared materials showed excellent selective absorbability for Hg(II) against multiple cationic metals in water. Unexpectedly, the experimental data showed that both co-existing toxic anionic diclofenac sodium (DCF) and Hg(II) performed positive effect for capturing another pollutant by these two modified COFs. Thus, a synergistic adsorption mechanism between Hg(II) and DCF on COFs was proposed. Moreover, density functional theory calculations revealed that synergistic adsorption occurred between Hg(II) and DCF, which resulted in a significant reduction in the adsorption system's energy. This work highlights a new direction for application of COFs to simultaneous removal of heavy metals and co-existing organic pollutants from water.

Preparation of metal organic frameworks modified chitosan composite with high capacity for Hg(II) adsorption

In this study, a novel modified chitosan composite adsorbent (UNCS) was prepared by crosslinking between chitosan and metal organic frameworks (MOFs) material UiO-66-NH₂ using epichlorohydrin as crosslinker. The influence of the prepared conditions was investigated. The structure and morphology of the composite were characterized by FT-IR, XRD, SEM, TGA, BET and zeta potential analysis. Effects of different variables for adsorption of Hg(II) on this adsorbent were explored. The kinetic studies indicated that the adsorption process followed the pseudo-second-order kinetic model and the adsorption equilibrium could be reached within 2 h. The adsorption was mainly controlled by chemical process. Adsorption isothermal studies illustrated that the adsorption fitted Langmuir isotherm model, implying the homogeneous adsorption on the surface of the adsorbent. The adsorbent exhibited high uptake and the maximum capacity from Langmuir model could reach 896.8 mg g^-1 at pH 6. Thermodynamic studies showed the spontaneous nature and exothermic nature of the adsorption process. Additionally, the removal of Hg(II) on UNCS could achieve over 90 %. The adsorption-desorption cycled experiments indicated the appropriate reusability of the adsorbent. Hence, this adsorbent would be promising for the removal of Hg(II) from wastewater.

Synthesis of functional poly(amidoamine) dendrimer decorated apple residue cellulose for efficient removal of aqueous Hg(II)

Water pollution caused by Hg(II) exerts hazardous effect to the environment and public health. The design and fabrication of eco-friendly bioadsorbents for efficient removal of Hg(II) from aqueous solution is a promising strategy. Herein, a series of bioadsorbents were synthesized by the decoration of apple residue cellulose with different generation (G) Schiff base functionalized poly(amidoamine) (PAMAM) dendrimers (SA-G0/CE, SA-G1.0/CE and SA-G2.0/CE). The structures of SA-G0/CE, SA-G1.0/CE and SA-G2.0/CE were characterized and their adsorption performances were determined comprehensively by considering various factors. The maximum adsorption capacity of SA-G0/CE, SA-G1.0/CE and SA-G2.0/CE for Hg(II) are 1.18, 1.73 and 1.88 mmol·g^-1, respectively. The as-prepared bioadsorbents exhibit competitive adsorption capacity as compared with other reported adsorbents. Moreover, they exhibit remarkable adsorption selectivity toward Hg(II) with the coexistence of Ni(II), Cd(II), Mn(II), or Pb(II). The bioadsorbents display satisfactory adsorption performance in real water sample and can be reused with good regeneration property. Adsorption mechanism reveals that the functional groups of OH, -CONH-, CN and NC take part in the adsorption for Hg(II). The work not only opens a pathway to realize the reuse of apple residue, but also provides a promising strategy to construct efficient bioadsorbents for the decontamination of Hg(II) from aqueous solution.

Ultrasensitive green spectrofluorimetric approach for quantification of Hg(II) in environmental samples (water and fish samples) using cysteine@MnO2 dots

Mercury (Hg²⁺ ) is a natural element present in foods such as fish, water and soil. Exposure to mercury leads to severe toxic effects on the nervous, digestive, and immune systems. Here, a novel, green, and environmentally friendly fluorescent probe decorated with cysteine/MnO₂ quantum dots (Cys@MnO₂ QDs) was synthesized. This synthesis was carried out using a simple ultrasound technique with the aid of cysteine for fabricating Cys@MnO₂ QDs to estimate Hg levels in fish and water samples. In this morphological study, Cys@MnO₂ QDs were fully characterized using high-resolution transmission electron microscopy, zeta potential analysis, fluorescence, ultraviolet-visible and infrared spectroscopy. The fluorescence of the synthesized Cys@MnO₂ QDs was significantly quenched by gradually increasing the Hg(II) concentration. The quenching mechanism based on the Hg-S bonds strengthened the utility of the Cys@MnO₂ QDs as a novel luminescent nanoprobe. The estimation of Hg was linear in the concentration range 0.7-100.0 ng mL^-1 with a limit of quantitation equal to 0.30 ng mL^-1 . The Cys@MnO₂ QDs are fluorescent probes with various benefits such as speed, ease of use, cost- effective, and being environmentally friendly; they are easily applied in food manufacturing and for public health improvement.

Ln Based Metal-organic Framework for Fluorescence "Turn Off-On" Sensing of Hg2

A highly luminescent Ln-MOF [La₃(NDC)₄(DMF)₃(H₂O)₄]_n, (NDC = 2, 6 naphthalen dicarboxylic acid) was designed and synthesized. The structure was characterized by x-ray single structure determination, TGA, IR spectra and PXRD and fluorescence spectroscopy. The structure shows high fluorescence intensity based on the presence of lanthanide metal and ligand. In the presence of I^-, the emission can be effectively quenched introducing turn off system. Furthermore, the synthesized Ln-MOF can recognize Hg (II) by showing fluorescence turn-on signal because of the high affinity between Hg (II) and I^-. Moreover, the high selectivity and sensitivity of the synthesized Ln-MOF makes it quit qualified for determination of the low concentration of mercury (2.00 nM).

High-efficiency Hg(II) adsorbent: FeS loaded on a carbon black from pyrolysis of waste tires and sequential reutilization as a photocatalyst

Iron-sulfur nano compounds have been proven to be effective in mercury removal, but the agglomeration, poor dispersion and mobility, and easy oxidation challenges limit their application. Herein, carbon black originating from pyrolysis of waste tires was used as a carrier of nano-FeS to obtain an efficient adsorbent (C@PDA-FeS). It is found that the C@PDA-FeS shows outstanding adsorption ability, excellent selectivity, and high removal rate. A maximum adsorption capacity of 1754 mg/g is obtained, and the residual Hg(II) ion concentration is as low as 3.2 μg/L in the simulated industrial wastewater, which meets the industrial discharge standard under the optimal conditions. Meanwhile, the removal rate of Hg(II) ion can reach 99.8% after up to 10 cycles. More importantly, the C@PDA-FeS still shows good adsorption efficiency, and the removal rate of Hg(II) ion is over 99% (25 mg/L Hg(II) concentration) after 90 days of storage, demonstrating the long-term stability and promising future of the adsorbent. In addition, the waste adsorbent (C@PDA-FeS/HgS) is reused as a photocatalyst to degrade methylene blue, and the corresponding degradation rate is 92.9% (10 mg/L).

A Reversible Optical Sensor Film for Mercury Ions Discrimination Based on Isoxazolidine Derivative and Exhibiting pH Sensing

We developed a new optical sensor for tracing Hg(II) ions. The detection affinity examines within a concentration range of 0-4.0 µM Hg(II). The sensor film is based on Methyl 2-hydroxy-3-(((2S,2'R,3a'S,5R)-2-isopropyl-5,5'-dimethyl-4'-oxotetrahydro-2'H-spiro[cy-clohexane-1,6'-im-idazo[1,5-b]isoxazol]-2'-yl)methyl)-5-methylbenzoate (IXZD). The novel synthesized compound could be utilized as an optical turn-on chemosensor for pH. The emission intensity is highly enhanced for the deprotonated form concerning the protonated form. IXZD probe has a characteristic fluorescence peak at 481 nm under excitation of 351 nm with large Stocks shift of approximately 130 nm. In addition, the binding process of IXZD:Hg(II) presents a 1:1 molar ratio which is proved by the large quench of the 481 nm emission peak of IXZD and the growth of a new emission peak at 399 nm (blue shift). The binding configurations with one Hg(II) cation and its electronic characteristics were investigated by applying the Density Functional Theory (DFT) and the time-dependent DFT (TDDFT) calculations. Density functional theory (DFT) and the time-dependent DFT (TDDFT) theoretical results were provided to examine Hg(II)-IXZD structures and their electronic properties in solution. The developed chemical sensor was offered based on the intramolecular charge transfer (ICT) mechanism. The sensor film has a significantly low limit of detection (LOD) for Hg(II) of 0.025 μM in pH 7.4, with a relative standard deviation RSD_r (1%, n = 3). Lastly, the IXZD shows effective binding affinity to mercury ions, and the binding constant K_b was estimated to be 5.80 × 10⁵ M^-1. Hence, this developed optical sensor film has a significant efficiency for tracing mercury ions based on IXZD molecule-doped sensor film.

Confining Fluorescent Probes in Nanochannels to Construct Reusable Nanosensors for Ion Current and Fluorescence Dual Gating

Here, we confined fluorescent probes to solid nanochannels to construct nanosensors, which not only significantly improved the reusability of the molecular probes, but also achieved ion current and fluorescence dual gating for more reliable detection. The combination of optical and electrical modalities can provide comprehensive spatiotemporal information that can be used to elucidate the sensing mechanism within the nanochannel. As a proof-of-concept experiment, fluorescein isothiocyanate (FITC)−hydrazine (N2H4) was selected to modify nanochannels for the effective detection of Hg2+. Based on spirolactam opening tactics, the system synergistically alters the surface charge and fluorescence intensity in response to Hg2+, establishing a dual open state of current and fluorescence. The newly prepared nanosensor exhibited a fast response (<1 min), high sensitivity, and selectivity towards Hg2+. Importantly, the nanodevice could be recovered by simple N2H4 treatment. Such sensing behavior could be used to implement optoelectronic dual-output XOR logical gates under the management of Hg2+ and N2H4. This strategy is anticipated to find broad applications in other nanochannel-based systems for various sensing applications used for monitoring of pollutants, food additives, and biomolecules.

Engineering linkage as functional moiety into irreversible thiourea-linked covalent organic framework for ultrafast adsorption of Hg(II)

Development of novel functionalized covalent organic frameworks (COFs) as adsorbent for removal of mercury from environment is of great significance, but the conventional strategies for functionalizing COFs always sacrifice porous properties and suppress the exposure of functional sites, which goes against the rapid adsorption of Hg(II). Here, we show the rational design and preparation of the first thiourea-linked COFs via engineering the COFs linkage as functional moiety for ultrafast and selective adsorption of Hg(II). Two thiourea-linked COFs JNU-3 and JNU-4 were prepared via tautomerism reaction of 1,3,5-triformylphloroglucinol with 1,4-phenylenebis(thiourea) and 1,4-biphenylenebis(thiourea), respectively. The thiourea serves as not only linkage to connect the building block into irreversible crystalline structure, but also functional moiety to give no occupation of the COF pore and full exposure to Hg(II) with strong affinity, offering the JNU-3 and JNU-4 large adsorption capacity (960 and 561 mg g^-1, respectively) and ultrafast kinetics (equilibrium time of 10 s) for Hg(II). The proposed strategy for the design of functional COFs with inherent linkage as functional moiety largely promotes the performance of COFs for diverse applications.

Study on Mercury Adsorption and Desorption on Different Modified Biochars

To develop high-performance biochar adsorbents, the adsorption ability and rate of untreated (BC-CK) and six modified biochars with amino (BC-NH), epoxy (BC-C₂H₂O), ethoxy (BC-C₂H₅O), hydrosulfuryl (BC-SH), selenium (BC-Se), and chitosan (BC-Chitosan) on Hg(II) and MeHg were investigated by simulated experiment. The results indicated that the some modified biochars (BC-NH, BC-C₂H₂O, BC-C₂H₅O and BC-Chitosan) showed lower adsorption capacity than the untreated, possibly due to the decreased specific surface area and pore volume. Whereas, BC-SH and BC-Se was improved immensely by forming stable -SH-Hg and Hg-Se with the adsorption capacity 1.26 and 1.51 times as much as BC-CK, respectively. In spite of that, Hg desorption capacities and rates of all biochars were extremely low, exhibiting great adsorption stability of biochars on Hg in another way. In addition, BC-Chitosan performed the highest adsorption speed. These provided insights on the adsorption effectiveness for Hg in the aqueous solution that was critical for evaluating the application of modified biochars.

Enzyme-free fluorescence determination of uric acid and trace Hg(II) in serum using Si/N doped carbon dots

A new fluorescence probe method for the detection of Hg(II) in serum was established, which has the detection limit of 3.57 nM and quantification limit of 5 nM, based on the electrostatic induced agglomeration quenching and complexation between Hg(II) and silicon-nitrogen-doped carbon nanodots (Si/N-CDs). Furthermore, the fluorescence probe also showed the satisfactory results in the determination of Hg(II) in human serum. Subsequently, take advantage of the uric acid (UA) to recover the fluorescence of the Si/N-CDs-Hg(II) complex probe, another enzyme-free ways to determine UA was developed. The complex probe can selectively detect the UA content in the 0.5-30 μM range, and its detection limit can reach 0.14 μM, which has successfully detected the UA in total serum, and the results were no significant difference comparing with the controls.

Label-free Hg(II) electrochemiluminescence sensor based on silica nanoparticles doped with a self-enhanced Ru(bpy)32+-carbon nitride quantum dot luminophore

Herein, a label-free, self-enhanced electrochemiluminescence (ECL) sensing strategy for divalent mercury (Hg(II)) detection was presented. First, a novel self-enhanced ECL luminophore was prepared by combining the ECL reagent tris(2, 2'-bipyridyl) dichlororuthenium(II) hexahydrate (Ru(bpy)₃²⁺) and its co-reactant carbon nitride quantum dots (CNQDs) via electrostatic interactions. In contrast to traditional ECL systems where the emitter and its co-reactant underwent an intermolecular reaction, the self-enhanced ECL system exhibited a shortened electron-transfer distance and enhanced luminous efficiency because the electrons transferred from CNQDs to oxidized Ru(bpy)₃²⁺ via an intramolecular pathway. Furthermore, the as-prepared self-enhanced ECL material was encapsulated in silica (SiO₂) nanoparticles to generate a Ru-QDs@SiO₂ luminophore. Based on the different affinity of Ru-QDs@SiO₂ nanoparticles for single-stranded DNA (ssDNA) and Hg(II)-triggered double-stranded DNA (dsDNA), a label-free ECL biosensor for Hg(II) detection was developed as follows: in the absence of Hg(II), ssDNA was adsorbed on Ru-QDs@SiO₂ surface via hydrogen bond, electrostatic, and hydrophobic interaction. Thus, quenched ECL signal was observed. On the contrary, in the presence of Hg(II), stable dsDNA was formed and carried the ssDNA separating from Ru-QDs@SiO₂ surface, resulting in most of Ru-QDs@SiO₂ existing in their free state. Therefore, a recovered ECL intensity was obtained. On this basis, Hg(II) was measured by the proposed method in the range of 0.1 nM-10 μM, with a detection limit of 33 pM. Finally, Hg(II) spiked in water samples was measured to evaluate the practicality of the fabricated biosensor.

Novel amidinothiourea-modified chitosan microparticles for selective removal of Hg(II) in solution

Glutaraldehyde-crosslinked chitosan microparticles (CGP) prepared via the inversed-phase emulsification were successively modified by epichlorohydrin (ECH) and amidinothiourea (AT) as novel adsorbent (CGPET) for selective removal of Hg(II) in solution. FTIR, EA, XPS, SEM-EDX, TG, DTG, and XRD results indicated that CGPET had ample -NH₂ and CS, relative rough surface, mean diameter of ~40 μm, great thermal stability, and crystalline degree of 2.4%, beneficial to the uptake of Hg(II). The optimum parameters (pH 5, dosage 1 g/L, contact time 4 h, and initial concentration 150 mg/L) were acquired via batches of adsorption experiments. Adsorption behavior was well described by the Liu isothermal and pseudo-second-order kinetics models, and the maximum adsorption capacity was 322.51 mg/g, surpassing many reported adsorbents. Regeneration and coexisting-ion tests demonstrated that CGPET had outstanding reusability (R_r > 86.89% at the fifth cycle) and selectivity (R_s > 93%). Besides, its potential adsorption sites and mechanisms were proposed.

Amino-assisted AHMT anchored on graphene oxide as high performance adsorbent for efficient removal of Cr(VI) and Hg(II) from aqueous solutions under wide pH range

The adsorbents with high adsorption capacity for simultaneously removing Cr(VI) and Hg(II) from aqueous solutions under broad working pH range are highly desirable but still extremely scarce. Here, a novel adsorbent with multidentate ligands was facilely fabricated by covalently bonding 4-amino-3-hydrazino-5-mercapto- 1,2,4-triazole on graphene oxide via the Schiff's base reaction. The maximum adsorption capacities of Cr(VI) and Hg(II) on the current adsorbent were 734.2 and 1091.1 mg/g, which were 14.36 and 5.61 times higher than that of the pure graphene oxide, respectively, exceeding those of most adsorbents previously reported. More interestingly, Cr(VI) and Hg(II) concentrations were decreased from 2 mg/L to 0.0001 mg/L for Hg(II) and 0.004 mg/L for Cr(VI), far below the WHO recommended threshold for drinking water. Moreover, the adsorbent shows an excellent performance for simultaneous removal of Cr(VI) and Hg(II) with more than 99.9% and 98.6% removal efficiencies in aqueous solutions. Finally, the adsorbent was successfully applied in dealing with the real industrial effluent, implying huge potential in industrial application. This work offers a new possibility for the removal of the metallic contaminants by rational designing target groups and ligands.

In situ remediation efficacy of hybrid aerogel adsorbent in model aquatic culture of Paramecium caudatum exposed to Hg(II)

Silica-gelatin hybrid aerogel of 24 wt% gelatin content is an advanced functional material suitable for the high performance selective adsorption of aqueous Hg(II). The remediation efficacy of this adsorbent was tested under realistic aquatic conditions by exposing cultures of Paramecium caudatum to Hg(II) and monitoring the model cultures by time-lapse video microscopy. The viability of Paramecium was quantified by analyzing the pixel differences of the sequential images caused by the persistent movement (motility) of the cells. The viability of Paramecium displays a clear exposure-response relationship with Hg(II) concentration. Viability decreases with increasing Hg(II) concentration when the latter is higher than 125 μg L^-1. In the presence of 0.1 mg mL^-1 aerogel adsorbent, the viability of the cells decreases only at Hg(II) concentrations higher than 500 μg L^-1, and 220 min survival time was measured even at 1000 μg L^-1 Hg(II). The effective toxicity of Hg(II) is lower in the presence of the aerogel, because the equilibrium concentration of aqueous Hg(II) is low due to adsorption, thus Paramecium cells do not uptake as much Hg(II) as in the un-remediated cultures. Video imaging of Paramecium cultures offers a simple, robust and flexible method for providing quantitative information on the effectiveness of advanced materials used in adsorption processes for water treatment.

Expanded Diversity and Phylogeny of mer Genes Broadens Mercury Resistance Paradigms and Reveals an Origin for MerA Among Thermophilic Archaea

Mercury (Hg) is a highly toxic element due to its high affinity for protein sulfhydryl groups, which upon binding, can destabilize protein structure and decrease enzyme activity. Prokaryotes have evolved enzymatic mechanisms to detoxify inorganic Hg and organic Hg (e.g., MeHg) through the activities of mercuric reductase (MerA) and organomercury lyase (MerB), respectively. Here, the taxonomic distribution and evolution of MerAB was examined in 84,032 archaeal and bacterial genomes, metagenome assembled genomes, and single-cell genomes. Homologs of MerA and MerB were identified in 7.8 and 2.1% percent of genomes, respectively. MerA was identified in the genomes of 10 archaeal and 28 bacterial phyla previously unknown to code for this functionality. Likewise, MerB was identified in 2 archaeal and 11 bacterial phyla previously unknown to encode this functionality. Surprisingly, homologs of MerB were identified in a number of genomes (∼50% of all MerB-encoding genomes) that did not encode MerA, suggesting alternative mechanisms to detoxify Hg(II) once it is generated in the cytoplasm. Phylogenetic reconstruction of MerA place its origin in thermophilic Thermoprotei (Crenarchaeota), consistent with high levels of Hg(II) in geothermal environments, the natural habitat of this archaeal class. MerB appears to have been recruited to the mer operon relatively recently and likely among a mesophilic ancestor of Euryarchaeota and Thaumarchaeota. This is consistent with the functional dependence of MerB on MerA and the widespread distribution of mesophilic microorganisms that methylate Hg(II) at lower temperature. Collectively, these results expand the taxonomic and ecological distribution of mer-encoded functionalities, and suggest that selection for Hg(II) and MeHg detoxification is dependent not only on the availability and type of mercury compounds in the environment but also the physiological potential of the microbes who inhabit these environments. The expanded diversity and environmental distribution of MerAB identify new targets to prioritize for future research.

Hg(II) sensing, catalytic, antioxidant, antimicrobial, and anticancer potential of Garcinia mangostana and α-mangostin mediated silver nanoparticles

This study reports synthesis of Garcinia mangostana fruit pericarp (unwanted waste material) and α-mangostin mediated silver nanoparticles (AgNPs). These AgNPs were efficiently produced using 1:10 (extract and salt) ratio under stirring and heating, which was confirmed by surface plasmon resonance (SPR) band in UV-Visible spectroscopic analysis, and size of 73-91 nm determined by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The synthesized AgNPs were used for Hg(II) detection in tap water, where the limits of detection and quantification were 2.6 μM and 8.9 μM, respectively. Furthermore, the subject AgNPs showed promising catalytic activity in the reduction of dyes and food colours including Congo red (CR), methylene blue (MB), malachite green (MG), methyl orange (MO), para-nitrophenol (PNP), rhodamine B (RdB), zarda yellow (ZY), deep green (DG), and bright red (BR). The synthesized AgNPs were also evaluated for their antioxidant, antimicrobial, and anticancer properties, where α-mangostin and its nanoparticles (Mang-AgNPs) exhibited promising IC₅₀ values of 14.1 and 13.5 μg/mL, respectively against DU-145 cell line validated by in silico molecular docking study. This study is the first report highlighting the application of AgNPs of G. mangostana fruit pericarp extracts, and α-mangostin in Hg(II) detection, dyes degradation, and anticancer potential against DU-145. Finding of this study suggested the suitability of AgNPs as promising solid biosensor in Hg(II) metal detection, dyes reduction, and target in anticancer drug development.

Ultrafast removal of ppb levels of Hg(II) and volatile Hg(0) using post modified metal organic framework

A novel MOF based adsorbent was prepared by functionalization of MIL 88A with mercapto ethanol to yield MIL88A-SH and evaluated for the removal of Hg(II) in water and Hg(0) in air. The prepared MOFs were characterized by field emission scanning electron microscope (FESEM), Transmission electron microscopy (TEM), Brunauer- Emmett-Teller (BET), Fourier transform infrared spectroscopy (FTIR), and zeta X-ray photoelectron microscopy (XPS). The reaction rate was found to be very fast and within 15 min 95.5% Hg(II) was removed. The kinetics data followed pseudo second order model with rate constant values at 1.19 and 2.38 g/μg/min for MIl88A and MIL88A-SH respectively. A very high adsorption capacity in the order 1111.1 mg/g of Hg(II) was found using MIL88A-SH as adsorbent. The uptake was found to be constant in a wide range of pH from 5 to 9. Furthermore, in the presence other interfering metal ions, viz., Cu(II), As(V), Cd(II), Cr(VI), Pb(II), Zn(II), MIL88A-SH demonstrated an excellent adsorption for Hg(II). Around 45.6 mg/g of Hg(0) was found to be adsorbed by MIL88A-SH. XPS, FTIR and XRD studies suggested insitu oxidation Hg(0) to Hg(II) and complexation of Hg(II) with thiol groups during adsorption. Applicability on removal of Hg(II) at ppb levels from drinking water, fast kinetics, wide pH range, a very high sorption capacity, Hg(0) removal, selectivity and recyclability makes MIL88A-SH an efficient adsorbent to tackle mercury contamination.

Cross-linked sulfydryl-functionalized graphene oxide as ultra-high capacity adsorbent for high selectivity and ppb level removal of mercury from water under wide pH range

It is highly desirable but remains extremely challenging to develop a facile strategy to prepare adsorbent for dealing with heavy metal pollution in water. Here, we report a facile approach for preparing sulfydryl-functionalized graphene oxide (S-GO) by cross-linking method with an unprecedented adsorption capacity and ultrahigh selectivity for efficient Hg(II) removal. The adsorbents exhibit a prominent performance in capturing Hg(II) from wastewater with a record-high adsorption capacity of 3490 mg/g and rapid kinetics to reduce Hg(II) contaminants below the discharge standard of drinking water (2 ppb) within 60 min under a wide pH range even in the coexistent of other interfering metal ions. In addition, the adsorbents can be also easily recycled and reused multiple times with no apparent decline in removal efficiency. Considering the broad diversity, we developed also a magnetic Fe₃O₄/S-GO adsorbent by a simple chemical cross-linking reaction to achieve rapid separation of S-GO from their aqueous solution. In addition, the adsorbents were successfully applied in dealing with the practical industrial wastewater. The results indicate the potential of rationally designed sulfydryl-functionalized graphene oxide for high performance Hg(II) removal.

Fabrication of thiophene-chitosan hydrogel-trap for efficient immobilization of mercury (II) from aqueous environs

The fabrication of thiophene-chitosan (TCS) hydrogel has been carried out to show the excellent binding performance of Hg(II) from an aqueous solution of heavy metal ions in presence of thiophene moiety within the hydrogel network. Thiophene moiety has been implanted within chitosan, a wild bio-resources, through a facile Schiff base condensation strategy with 2-thiophenecarboxaldehyde to develop a three-dimensional network of TCS hydrogel. The parameters influencing adsorption capacity such as pH, volume of functional agent, contact time, amount of the hydrogel are included to broaden the in-depth study for the adsorption window of Hg(II) followed by the desorption and reusability performance of TCS. The results indicate that the TCS hydrogel for Hg(II) followed pseudo-second-order kinetics. Ethylenediaminetetraacetic acid (EDTA), acts as a better eluent compared to HCl to desorb Hg(II) and even after recurring adsorption/desorption cycles, removal efficacy of TCS hydrogel could be retained.

Detection of Hg(II) in adsorption experiment by a lateral flow biosensor based on streptavidin-biotinylated DNA probes modified gold nanoparticles and smartphone reader

The increased occurrence of Mercury (Hg II) contaminant has caused environmental and health concerns worldwide. Removal of Hg(II) from water is of significant interest, in particular if these can be coupled in a manner of detection. Here, a novel activated carbon (AC) adsorbent and a fast detection device to form a closed-cycle strategy was developed. The synthesis of conjugates of streptavidin-biotinylated DNA probes modified gold nanoparticle was used with lateral flow biosensors for Hg(II) detection. A quantification was completed via a self-developed smartphone app and its limit of detection was 2.53 nM. Moreover, AC was activated with a new activating agent of diammonium hydrogen phosphate. The adsorbent was characterized and determined to have an amorphous microporous structure with a high surface area (1076.5 m² g^-1) and demonstrated excellent removal efficiency (99.99%) and adsorption capacity (∼100 mg g^-1) for Hg(II). The kinetics of the pseudo-second-order model and the mechanisms of electrostatic adsorption, ion exchange, and complex reactions are provided. The proposed closed-cycle strategy can be useful for early, fast, and mobile detection of Hg (II) pollution, followed by its effective removal during water treatment.

The biosorption of mercury by permeable pavement biofilms in stormwater attenuation

This study reports on the evaluation of the equilibrium, thermodynamics and kinetics of mercury (II) biosorption using a living biofilm, developed on a nonwoven polypropylene and polyethylene geotextile, typically used within the structure of Sustainable Drainage System (SuDS) devices. Batch biosorption assays were carried out with variables such as pH, initial concentrations, contact time, temperature and biofilm incubation time. Langmuir, Freundlich and Dubinin Radushkevich (D-R) models were applied to the equilibrium data which revealed the maximum biosorption capacities and efficiencies at pH 5.5 with a contact time of 120 min at 25 °C. With 20 mg L^-1 added Hg (II), living biofilm samples with incubation times of 1, 7, 14, 21 and 28 days, biosorption values were 101.31 (55.72%), 24.41 (67.12%), 16.81 (61.37%), 9.70 (62.57%) and 13.34 (65.38%) mg g^-1, respectively. Free mean biosorption energy from the D-R model was between 2.24 and 2.36 kJ mol^-1 for all biofilm development incubation times, that revealed the physical biosorption mechanism for Hg(II). The thermodynamic studies showed that the Hg(II) biosorption of living biofilm was thermodynamically feasible and had a spontaneous and exothermic nature. Kinetic parameters revealed that Hg(II) biosorption onto living biofilm had a good correlation with a pseudo second-order kinetic model. FTIR spectra after biosorption suggested that amine, hydroxyl and carboxyl groups were the main functional groups available and responsible for Hg(II) biosorption onto living biofilm. Experimental data suggested that a living biofilm developed on a nonwoven polypropylene and polyethylene geotextile can be efficient in the removal of mercury ions from contaminated urban and industrial runoff.

Dynamic Structure and Stability of DNA Duplexes Bearing a Dinuclear Hg(II)-Mediated Base Pair

Quantum mechanical (QM) and hybrid quantum mechanical/molecular mechanical (QM/MM) molecular dynamics simulations of a recently reported dinuclear mercury(II)-mediated base pair were performed aiming to analyse its intramolecular bonding pattern, its stability, and to obtain clues on the mechanism of the incorporation of mercury(II) into the DNA. The dynamic distance constraint was employed to find initial structures, control the dissociation process in an unbiased fashion and to determine the free energy required. A strong influence of the exocyclic carbonyl or amino groups of neighbouring base pairs on both the bonding pattern and the mechanism of incorporation was observed. During the dissociation simulation, an amino group of an adenine moiety of the adjacent base pair acts as a turnstile to rotate the mercury(II) ion out of the DNA core region. The calculations provide an important insight into the mechanism of formation of this dinuclear metal-mediated base pair and indicate that the exact location of a transition metal ion in a metal-mediated base pair may be more ambiguous than derived from simple model building.

Selective Fluorometric Analysis of Hg(II) in Industrial Waste Water Samples

The highly selective and sensitive fluorometric method has been developed for trace level determination of Hg(II) is based on photo-induced electron transfer between rhodamine-6G dye and metal complex. Quenching in fluorescence intensity by fluorescence resonance energy transfer (FRET) is due to interaction between metal ion complex and dye. The fluorescence emitted was measured at 510 and 550 nm, for excitation and emission wavelengths respectively. Possible interferences present in water samples, which could affect the analytical response are studied and determined. The calibration graph was dynamically linear from 0.002 to 0.05 mgL^-1 of Hg(II) with limit of detection 7 × 10^-4 mgL^-1 and limit of quantitation 1.9 × 10^-3 mgL^-1. The Stern-Volmer constant (K_SV) calculated for the quenching of R-6G with Hg (II) was 8.47 Lmg^-1 s^-1 at optimized reaction conditions. The proposed FRET based fluorometric method was applied successfully in different industrial wastewater samples with satisfactory outcome.

Anammox biofilm system under the stress of Hg(II): Nitrogen removal performance, microbial community dynamic and resistance genes expression

The existence of heavy metals in wastewater has obtained more attention due to its high toxicity and non-degradability. In this study, we investigated the changes of anaerobic ammonium oxidation (Anammox) system under long-term invasion of Hg(Ⅱ). The results indicated that the total nitrogen removal efficiency (TNRE) dropped to around 55 % as Hg(Ⅱ) concentration went up to 20 mg L^-1. But the functional bacteria rapidly developed some resistant abilities and maintained a stable TNRE of 65 % till the end of test. The maximum relative expression fold change of merA, merB, merD and merR were 468.8476, 23.7383, 5.0321 and 15.2514 times, respectively. The high positive correlation between the expression abundance of metal resistance genes and the concentrations of Hg(Ⅱ) revealed the resistant mechanisms of microorganisms to heavy metals. Moreover, the protective strategy based on extracellular polymeric substances also contributed to the stability of Anammox system.

A Fluorescent Chemosensor Based on Schiff Base for the Determination of Zn2+, Cd2+and Hg2

Metal complexes were obtained by the reaction of zinc, cadmium and mercury(II) salts with Schiff base HL (N(salicylidene)benzylamine). HL was synthesized by the condensation reaction of benzylamine and 2-hydroxybenzaldehyde. The fluorescence properties of the Schiff base and its metal complexes were studied in ethanol-water solutions. HL was examined for its utility as a fuorescent chemosensor for the determination of Zn²⁺, Cd²⁺ and Hg²⁺ in aqueous samples. The HL chemosensor was found to be sensitive to Zn²⁺, Cd²⁺ and Hg²⁺ than some metal ions and its complexes emitted strong fluorescence at 452 nm for Zn²⁺ at 474 nm for Cd²⁺ and at 491 nm for Hg²⁺, respectively. It was determined that HL forms complexes with a ratio of 2:1 for Zn²⁺ and Hg²⁺ and with a ratio of 1:1 for Cd²⁺ by Job plots. For the detection of Zn²⁺, Cd²⁺ and Hg²⁺ in aqueous samples, pH, solvent type and ligand concentration were optimized for an analytical method based on HL chemosensor. HL gave a wide range of linearity with Zn²⁺, Hg²⁺ and Cd²⁺, the limit of detection was found to be 2.7 × 10^-7 M, 7.5 × 10^-7 M and 6.0 × 10^-7 M, respectively.

Highly sensitive turn-on detection of mercury(II) in aqueous solutions and live cells with a chemosensor based on tyrosine

Herein, we reported a novel fluorescent chemosensor (DY) based on dansyl group and tyrosine by solid phase peptide synthesis (SPPS) for the detection of mercury(II) ions with excellent selectivity among 17 different metal ions. As designed, DY exhibited a sensitive fluorescence "turn-on" response to Hg²⁺ with low detection limits of 22.65 nM. A stoichiometric ratio (2: 1) of chemosensor DY and Hg²⁺ ions was determined by a Job's plot, fluorescent titration and the ESI-MS spectra. Especially, the reversible of DY-Hg with EDTA establishes the reuse of DY, and the circulation effect was very good. Furthermore, the wide pH range of 6-10 makes it capable of application in biological systems. Moreover, DY has been successfully applied to the detection of Hg²⁺ ions and EDTA in living HeLa and HK2 cells based on low cytotoxicity and good membrane permeability.

Synthesis of Poly(2-aminothiazole)-Coated Polystyrene Particles and Their Excellent Hg(II) Adsorption Properties

Synthesis of conjugated polymer-coated latex particles is an effective method to improve the poor processability of conjugated polyheterocycles. The key to success is to control the overlayer thickness so it is less than the size of the solvated layer of polymeric stabilizer. This paper presents a protocol to coat polymer latex particles with poly(2-aminothiazole) (PAT), which is a relatively new heterocyclic conjugated polymer. The protocol is based on chemical oxidative polymerizations of 2-aminothiazole using copper chloride as the oxidant at a fixed oxidant/monomer molar ratio of 0.5 in aqueous media in the presence of poly(N-vinyl-2-pyrrolidone)-functionalized polystyrene (PS) latex. The effects of monomer concentration, PS concentration, and polymerization temperature on the morphology of the PAT-coated PS composite particles were investigated by SEM and TEM, and the resulting composite particles characterized by FTIR and XPS. Optimization of the initial monomer concentration allowed colloidally stable PAT-coated PS composite particles to be formed at ambient temperature, and the PAT loading was easily adjusted by varying the initial PS concentration. The Hg(II) adsorption properties of selected PAT-coated PS composite particles were assessed preliminarily. The maximum adsorption capacity at 25 °C reached 440.25 mg/g, which is much higher than many other adsorbents.

Removing tetracycline and Hg(II) with ball-milled magnetic nanobiochar and its potential on polluted irrigation water reclamation

The feasibility of ball-milled magnetic nanobiochars (BMBCs) derived from wheat straw for adsorptive removal of tetracycline (TC) and Hg(II) from aqueous solution was assessed against that of pristine magnetic biochars (PMBCs). Ball milling conversion of PMBCs into BMBCs greatly improved TC and Hg(II) removal, and ≥ 99% TC and Hg(II) were adsorbed by BMBC prepared at 700 °C (BMBC700) within 12 h. The maximum adsorptive removal capacities of BMBC700 for TC and Hg(II) were 268.3 and 127.4 mg/g, respectively. The amounts of TC and Hg(II) removed by BMBC700 decreased gradually as the ionic strength of the solution increased, but increased as the solution temperature increased from 25 to 45 °C. The further FTIR and XPS analysis confirmed removal of TC was predominately regulated by the combination of electrostatic interactions, hydrogen bonds, and Cπ-Cπ interaction, while, the adsorption of Hg(II) was mainly governed by several mechanisms, including electrostatic attractions, Hg-Cπ bond formation, and surface complexation. Overall, BMBC700 presented great potential for TC and Hg(II) removal from polluted irrigation water and exhibited acceptable recyclability performance as well as magnetic separation advantage in use.

Remediation of mercury contaminated soil, water, and air: A review of emerging materials and innovative technologies

Mercury contamination in soil, water and air is associated with potential toxicity to humans and ecosystems. Industrial activities such as coal combustion have led to increased mercury (Hg) concentrations in different environmental media. This review critically evaluates recent developments in technological approaches for the remediation of Hg contaminated soil, water and air, with a focus on emerging materials and innovative technologies. Extensive research on various nanomaterials, such as carbon nanotubes (CNTs), nanosheets and magnetic nanocomposites, for mercury removal are investigated. This paper also examines other emerging materials and their characteristics, including graphene, biochar, metal organic frameworks (MOFs), covalent organic frameworks (COFs), layered double hydroxides (LDHs) as well as other materials such as clay minerals and manganese oxides. Based on approaches including adsorption/desorption, oxidation/reduction and stabilization/containment, the performances of innovative technologies with the aid of these materials were examined. In addition, technologies involving organisms, such as phytoremediation, algae-based mercury removal, microbial reduction and constructed wetlands, were also reviewed, and the role of organisms, especially microorganisms, in these techniques are illustrated.

Coumarin-based Hg2+ fluorescent probe: Fluorescence turn-on detection for Hg2+ bioimaging in living cells and zebrafish

The need in developing fluorescent probes for trace metal ion detection in biological samples has been an important issue. Herein, a reaction-based fluorescent probe PIC containing a perimidine moiety was designed and synthesized for Hg²⁺ detection. The probe can selectively distinguish Hg²⁺ with 42-fold fluorescent enhancement from the other metal ions at physiological pH. This probe can detect Hg²⁺ with the detection limit of 1.08 μM. The sensor PIC can be applied to real-time detection of Hg²⁺ in cells with blue emission.

A cytosine-rich hairpin DNA loaded with silver nanoclusters as a fluorescent probe for uranium(IV) and mercury(II) ions

A dually responsive fluorescent probe for determination of U(IV) and mercury(II) ions was synthesized. The probe consists of a cytosine-rich hairpin DNA loaded with silver nanoclusters (DNA-AgNCs). The fluorescence of the AgNCs is found to be quenched by UO₂(II) at pH 5.0 and Hg(II) at pH 7.0 due to combined static and dynamic quenching. Under the optimal conditions, the green fluorescence of the DNA-AgNCs, best measured at excitation/emission wavelengths of 420/525 nm, decreases in the 4.0 to 75 pM UO₂(II) concentration range, and in the 0.3 to 8.0 nM Hg(II) concentration range. The respective detection limits are as low as 1.8 pM and 0.1 nM. The method was successfully applied to the determination of UO₂(II) and Hg(II) in (spiked) pond and taps waters and in soil extracts. Graphical abstract A label-free DNA was designed to synthesize green-fluorescent silver nanoclusters (AgNCs) and used for rapid dual detection of uranyl ions (UO₂(II)) at pH 5.0 and of mercury ions (Hg(II)) at pH 7.0 in environmental samples.

Amino- and Thiol- Polysilsesquioxane Simultaneously Coating on Poly(p-Phenylenetherephthal Amide) Fibers: Bifunctional Adsorbents for Hg(II)

A double reagents simultaneous functionalization (DRSF) was used to prepare porous polysilsesquioxane with NH₂ and SH bifunctional groups (PAMPSQ) coated poly(p-phenylenetherephthal amide) (PPTA) fibers adsorbents (PPTA-AM), via in situ condensations with aminopropyltriethoxysilane (APTES) and mercaptopropyltriethoxysilane (MPTES). The PAMPSQ coated on the PPTA surface was in the form of nanoparticles and its morphology varied with the proportion of the reactants. The PAMPSQ exhibited loose open meso- or macroporous features. The functional groups utilization of PAMPSQ was much higher than those of polysilsesquioxane on the mono-functional adsorbents with thiol or amino groups. The selective adsorption of PPTA-AM adsorbents for Hg(II) in binary component metal ion systems indicated their potential application in environmental remediation. The adsorption mechanism of Hg(II) onto PPTA-AM was proposed.

Mercury speciation, transformation, and transportation in soils, atmospheric flux, and implications for risk management: A critical review

Mercury (Hg) is a potentially harmful trace element in the environment and one of the World Health Organization's foremost chemicals of concern. The threat posed by Hg contaminated soils to humans is pervasive, with an estimated 86 Gg of anthropogenic Hg pollution accumulated in surface soils worldwide. This review critically examines both recent advances and remaining knowledge gaps with respect to cycling of mercury in the soil environment, to aid the assessment and management of risks caused by Hg contamination. Included in this review are factors affecting Hg release from soil to the atmosphere, including how rainfall events drive gaseous elemental mercury (GEM) flux from soils of low Hg content, and how ambient conditions such as atmospheric O₃ concentration play a significant role. Mercury contaminated soils constitute complex systems where many interdependent factors, including the amount and composition of soil organic matter and clays, oxidized minerals (e.g. Fe oxides), reduced elements (e.g. S^2-), as well as soil pH and redox conditions affect Hg forms and transformation. Speciation influences the extent and rate of Hg subsurface transportation, which has often been assumed insignificant. Nano-sized Hg particles as well as soluble Hg complexes play important roles in soil Hg mobility, availability, and methylation. Finally, implications for human health and suggested research directions are put forward, where there is significant potential to improve remedial actions by accounting for Hg speciation and transportation factors.

Development and optimization of an immunoassay for the detection of Hg(II) in lake water

In this paper, an indirect competitive enzyme-linked immunosorbent assay (IC-ELISA) has been developed and optimized to detect Hg(II) in tap water and lake water based on a monoclonal antibody (mAb-A24). Some stabilizing additives (Gelatin, bovine serum albumin [BSA], polyvinyl alcohol [PVA], and polyvinyl pyrrolidone [PVP]) and surfactant (Tween-20) have been investigated thoroughly in the optimization process. Under the optimal condition, the 50% half maximal inhibitory concentration (IC50) and limit of detection (LOD) were 1.68 and 0.079 ng/ml, respectively. These anti-Hg mAbs also have some affinity with methyl mercury (CH3Hg) and with no cross-reactivity with other thirteen metal ions. The developed method has shown satisfactory recovery of Hg(II), ranged between 91% and 116%, from tap water and lake water. Therefore, this immunoassay can be used to detect trace Hg(II) in environment water.

Selective Adsorption toward Hg(II) and Inhibitory Effect on Bacterial Growth Occurring on Thiosemicarbazide-Functionalized Chitosan Microsphere Surface

The work presented here aims to fabricate dual-purpose adsorbent with adsorption selectivity for Hg(II) and antibacterial activity. TSC-PGMA-MACS microspheres were first constructed via esterification of malic acid (MA) with chitosan (CS) and through successively grafting glycidyl methacrylate (GMA) and thiosemicarbazide (TSC) onto MACS microsphere surfaces. Fourier transform infrared spectroscopy, elemental analysis, energy-dispersive X-ray spectrometry, X-ray diffraction, differential scanning calorimetry, thermogravimetry, differential thermogravimetry, scanning electron microscopy, and Brunauer-Emmett-Teller results provided ample evidence that new mesoporous adsorbent, with 35.340 m² g^-1 of specific surface area and abundant -NH₂ and C═S, was successfully fabricated and had loose crystalline, thermodynamically stable, and well-defined architectures, beneficial for Hg(II) adsorption and bacterial cell killing. Optimal adsorption parameters were determined via varying pH, time, concentrations, and temperatures, and pH 6.0 was chosen as an optimal pH for Hg(II) adsorption. Adsorption behavior, described well by pseudo-second-order kinetic and Langmuir isotherm models, and thermodynamic parameters implied a chemical, monolayer, endothermic, and spontaneous adsorption process, and the maximum adsorption capacity for Hg(II) was 242.7 mg g^-1, higher than most of the available adsorbents. Competitive adsorption exhibited excellent adsorption selectivity for Hg(II) in binary-metal solutions. Besides, TSC-PGMA-MACS microspheres had outstanding reusability even after five times recycling, with adsorption capability loss <14%. Several potential adsorption sites and bonding modes were proposed. Notably, TSC-PGMA-MACS microspheres before and after adsorption were of high antibacterial activity against Escherichia coli and Staphylococcus aureus (MICs, 2 and 0.25 mg mL^-1), superior to CS powders, and possible antibacterial mechanisms were also summarized. Altogether, dual-purpose TSC-PGMA-MACS microspheres might be promising adsorbent for contaminated water scavenging.

Photoinduced reduction of high concentration Hg(II) to Hg2Cl2 from acid wastewater with the presence of fulvic acid under anaerobic conditions

In order to recover mercury from high concentration Hg(II) acid wastewater, UV irradiation was used to reduce Hg(II) to Hg₂Cl₂ with the presence of fulvic acid and chloride ion. When simulated wastewater with Hg(II) concentration of 1000 mg L^-1 was treated, > 90% of Hg(II) removal efficiency was achieved under the condition of extra Cl^- dosage of 5 g L^-1, FA dosage of 2 g L^-1, pH of 3.0 and 120 min of UV irradiation. Kinetics study showed that the photoreduction process could be well described by pseudo-first order kinetic mode, and the Hg(II) reduction rate was tested to be 0.0422 min^-1. Characterization results indicated that FA-Hg(II) complexes were firstly formed and then broken down into smaller molecules after the UV treatment, in which process highly reductive species (i.e. COO, COOH) were produced. These reductive species mediated the reduction of Hg(II). With the presence of Cl^-, Hg₂Cl₂ was practically the only detected Hg-based product in the photoreduction process. This technique was also employed to treat COD_Cr analysis wastewater (initial Hg(II) concentration > 1000 mg L^-1). With 90 min of reaction, most of the Hg(II) was removed from the system leaving less than 30% that could be further treated by chemical participation or adsorption method.

A highly selective fluorescence sensing platform for nanomolar Hg(II) detection based on cytosine derived quantum dot

Inspired by low toxicity and good biocompatibility of biomass derived quantum dot (QD), we herein developed a cytosine derived quantum dot, namely cyt-dot, via a one-step hydrothermal synthesis. The as-prepared cyt-dot emits blue fluorescence (FL) containing abundant oxygen (20.6at.%) and nitrogen (24.1at.%) contents. The cyt-dot based sensing platform shows exclusive selectivity for Hg(II) while being insensitive towards Fe(III) and Ag(I), which are important interference that usually cannot be ruled out. The detection limit for Hg(II) is of 11nM, which is very close to the guideline value of 10nM allowed by the U.S. Environmental Protection Agency in drinking water. In real water sample analyses, the present sensing platform can fulfil satisfied recoveries ranging from 100% to 108%. Besides, the acidity of solution has almost no effect on the sensing performance of the cyt-dot in a pH range of 5-8, suggesting its potential applications in sensing and bio-imaging.

An ultrasensitive conformation-dependent colorimetric probe for the detection of mercury(II) using exonuclease III-assisted target recycling and gold nanoparticles

An ultrasensitive conformation-dependent colorimetric assay has been developed for the detection of mercury(II) ions. It is based on the use of exonuclease III (Exo III)-assisted target recycling and gold nanoparticles (AuNPs). In the absence of Hg(II), the hairpin-shaped DNA probe (H-DNA) binds to AuNPs and stabilizes them in solutions of high ionic strength. In the presence of Hg(II), on the other hand, the sticky termini of the H-DNA form a rigid DNA duplex stem with a blunt 3'-terminus. Thus, Exo III is activated as a biocatalyst for selective and stepwise removal of mononucleotides from the 3'-terminus of the H-DNA. As a result, Hg(II) is released from the T-Hg(II)-T complexes. The guanine-rich sequences released from the H-DNA are then self-assembled with potassium ion to form a stable G-quadruplex conformation. In solutions of high ionic strength, this results in aggregation of AuNPs and a color change from red to blue which can be seen with bare eyes. The method is highly sensitive and selective. It has a linear response in the 10 pM to 100 nM Hg(II) concentration range, and the detection limit is as low as 3.2 pM (at an S/N ratio of 3). The relative standard deviation at a level of 0.5 nM of Hg(II) is 4.9% (for n = 10). The method was applied to the detection of Hg(II) in spiked environment water samples, with recoveries ranging from 92% to 106%. Graphical abstract A conformation-dependent colorimetric system was fabricated for label-free detection of mercury(II) by utilizing exonuclease III(Exo III)-assisted target recycling and gold nanoparticles (AuNPs).

Insights into the mercury(II) adsorption and binding mechanism onto several typical soils in China

To better understand the Hg(II) adsorption by some typical soils and explore the insights about the binding between Hg(II) and soils, a batch of adsorption and characteristic experiments was conducted. Results showed that Hg(II) adsorption was well fitted by the Langmuir and Freundlich. The maximum adsorption amount of cinnamon soil (2094.73 mg kg^-1) was nearly tenfold as much as that of saline soil (229.49 mg kg^-1). The specific adsorption of Hg(II) on four soil surface was confirmed by X-ray photoelectron spectroscopy (XPS) owing to the change of elemental bonding energy after adsorption. However, the specific adsorption is mainly derived from some substances in the soil. Fourier transform infrared spectroscopy (FTIR) demonstrated that multiple oxygen-containing functional groups (O-H, C=O, and C-O) were involved in the Hg(II) adsorption, and the content of oxygen functional groups determined the adsorption capacity of the soil. Meanwhile, scanning electron microscopy combined with X-ray energy dispersive spectrometer (SEM-EDS) more intuitive revealed the binding of mercury to organic matter, metal oxides, and clay minerals in the soil and fundamentally confirmed the results of XPS and FTIR to further elucidate adsorptive phenomena. The complexation with oxygen-containing functional groups and the precipitation with minerals were likely the primary mechanisms for Hg(II) adsorption on several typical soils. This study is critical in understanding the transportation of Hg(II) in different soils and discovering potential preventative measures.