To effectively remove heavy metal Hg(II) from water bodies, a novel adsorbent of MgAl-layered double hydroxide (LDH) was designed and functionalized with Schiff base. The characterization results of the adsorbent (MgAl-LDH@SiO2-AG) show that the Schiff base polymer was successfully coated onto the outside surface of MgAl-LDH with hexagonal structure. The theoretical maximum adsorption capacity to Hg(II) is 228.46 mg/g at pH 7 and 298 K. The different pH solutions were investigated from pH 2 to 8, and the optimal capacity of MgAl-LDH@SiO2-AG toward Hg(II) achieves 268.7 mg/g at pH = 7.2, T = 36.8 °C, C0 = 32.1 mg/L and dosage = 0.083 g/L. In reality, the adsorbent not only exhibits efficient removal of Hg(II) in various water bodies, including lake water, river water, effluent from sewage treatment plant, but also has an excellent selectivity in electroplating wastewater containing different heavy metal ions. Low contents of TN and TP in real wastewater have less effect on the removal of Hg(II). Moreover, the prepared adsorbent had a good reusability and stability. The reaction mechanism mainly involves chelation with nitrogen/oxygen-containing groups and the predominant participation of nitrogen atoms in the Schiff base functional group. The removal of Hg(II) relies on the pseudo-second-order kinetics and Langmuir model, and is an endothermic and spontaneous chemical reaction. The present work offers a practical method for preparing highly effective adsorptive materials with the LDH composites and for the treatment of heavy metal Hg(II) from water bodies.

Water pollution has become a serious issue, and mercury(II) ion (Hg(II)) is highly toxic even at low concentrations. Therefore, Hg(II) concentration should be strictly monitored. This study evaluated pyrazoline compounds as fluorescence chemosensor agents for Hg(II) detection. These compounds were prepared from vanillin via etherification, Claisen-Schmidt, and cyclocondensation reactions, to yield benzothiazole-pyrazoline-styrene hybrid compounds. The hybrid compound without styrene was successfully synthesized in 97.70% yield with limit of detection (LoD) and limit of quantification (LoQ) values of 323.5 and 1078 μM, respectively. Conversely, the hybrid compound was produced in 97.29% yield with the LoD and LoQ values of 8.94 and 29.79 nM, respectively. Further spectroscopic investigations revealed that Hg(II) ions can either chelate with three nitrogen of pyridine, pyrazoline, and benzothiazole structures or two oxygen of vanillin and styrene. Furthermore, the hybrid compound was successfully applied in the direct quantification of Hg(II) ions in tap and underground water samples with a validity of 91.63% and 86.08%, respectively, compared with mercury analyzer measurement. The regeneration of pyrazoline was also easily achieved via the addition of an ethylenediaminetetraacetic acid solution. These findings show the promising application of the benzothiazole-pyrazoline-styrene hybrid compound for Hg(II) monitoring in real environmental samples.

Herein, efficient and potential chelating α-aminophosphonate based sorbents (AP-) derived from three different amine origins (aniline/anthranilic acid/O-phenylenediamine) to form AP-H, carboxylated and aminated enhanced aminophosphonate as AP-H, AP-COOH, and AP-NH2 were synthesized via a facile method. The structure of the synthesized sorbents was elucidated using different techniques; elemental analysis (CHNP/O), FT-IR, NMR (1H-, 13C and 31P NMR), TGA and BET. The fabricated sorbents were exploited for Hg(II) removal from aqueous solution via sorption properties. Isotherm fitted by Langmuir equation: the maximum sorption capacities at optimum pH 5.5, and T:25 ± 1 °C, were found to be 1.33, 1.23, and 1.15 mmol Hg g-1 for AP-COOH, AP-NH2, AP-H, respectively, which is roughly correlated with the active sites density and the hard/soft characteristics of adsorbents\' reactive groups. Metal-ligand binding affinities are qualitatively rationalized in terms of hard and soft acids and bases (HSAB) theory. The interaction of Hg(II) (soft) has a stronger affinity to AP-COOH can be considered a softer base compared with reference material (AP-H) over than AP-NH2 (hard). This sequence result showed opposite trends consistent with their reciprocal properties according to the steric effect modulates and the specific surface area. Thermodynamics analysis for absolute values of ΔH°, ΔS° and ΔG° afford the selectivity towards Hg(II) sorption with the following order: AP-COOH > AP-NH2 >AP-H. Elution and regeneration was carried out by HCl solution and recycled for a minimum of five cycles, the sorption and desorption efficiencies are greater than 91%. Such sorbents exhibit good durability, stability and promising potential for Hg(II) removal. Finally, a new modelling technique for quantitative non-linear description and comparison of equivalent geographical positions in 3D space of extended relationships. Exothermic and spontaneous behavior were observed using a proposed Floatotherm that included the Van\'t Hoff parameters model.

A new fluorescent probe TPE-GHK was synthesized containing a tetrastyrene (TPE) derivative as fluorophore and classical tripeptide (Gly-His-Lys-NH2) as a receptor based on the aggregation-induced emission (AIE) mechanism. TPE-GHK displayed high selectivity and rapid fluorescent \"turn-on\" response to Hg2+ among other competitive metal ions. The 2:1 complex binding mechanism of TPE-GHK toward Hg2+ was verified by fluorometric titration, Job\'s plots, and ESI-HRMS spectra. The fluorescent emission showed a good linear response in the range of 0-1.0 μM with the low detection limit of 28.6 nM. Meanwhile, TPE-GHK exhibited the excellent biocompatibility and low toxicity and was successfully applied in monitoring Hg2+ in living CAKI 2 cells, which demonstrated its potential application in environment and biological science. More importantly, TPE-GHK could be used to detect Hg2+ in two real water samples and also was successfully designed as test strips.

In the field of nanotechnology, nanoadsorbents have emerged as a powerful tool for the purification of contaminated aqueous environments. Among the variety of nanoadsorbents developed so far, magnetite (Fe3O4) nanoparticles have drawn particular interest because of their quick separation, low cost, flexibility, reproducibility, and environmentally benign nature. Herein, we describe a new strategy for the synthesis of Fe3O4 nanoclusters, which is based on the use of naturally available edible mushrooms (Pleurotus eryngii) and environmentally benign propylene glycol as a solvent medium. By tuning the temperature, we successfully convert Fe3O4 nanoparticles into Fe3O4 nanoclusters via hydrothermal treatment, as evidenced by transmission electron microscopy. The Fe3O4 nanoclusters are functionalized with an organic molecule linker (dihydrolipoic acid, DHLA) to remove hazardous Hg(II) ions selectively. Batch adsorption experiments demonstrate that Hg(II) ions are strongly adsorbed on the material surface, and X-ray photoelectron and Fourier transform infrared spectroscopy techniques reveal the Hg(II) removal mechanism. The DHLA@Fe3O4 nanoclusters show a high removal efficiency of 99.2 % with a maximum Hg(II) removal capacity of 140.84 mg g-1. A kinetic study shows that the adsorption equilibrium is rapidly reached within 60 min and follows a pseudo second-order kinetic model. The adsorption and separation system can be readily recycled using an external magnet when the separation occurs within 10 s. We have studied the effect of various factors on the adsorption process, including pH, concentration, dosage, and temperature. The newly synthesized superparamagnetic DHLA@Fe3O4 nanoclusters open a new path for further development of the medical, catalysis, and environmental fields.

In this study, a new tannic acid cross-linking cellulose/polyethyleneimine functionalized magnetic composite (MCP) as a biomass adsorbent of Hg(II) ions was prepared. The morphology and structure of MCP were characterized with FT-IR, TG, XRD, SEM and TEM. The effect of the different factors such as pH, contact time, initial Hg(II) ion concentration, and adsorption temperature on the adsorption behavior was investigated. The results showed that MCP exhibited an excellent selectivity and reutilization, fast removal rate, and very high adsorption capacity. The corresponding adsorption capacity and removal rate of could reach 99.00% and 247.51 mg/g when the pH value, adsorption time, Hg(II) ion concentration were 5, 180 min and 100 mg/L at 293 K. The kinetics followed the pseudo-second-order, which indicated that the adsorption behavior of MCP for Hg(II) ion belonged to the chemical adsorption process and external diffusion. The thermodynamic study showed that the adsorption process was a spontaneous and exothermic process. After the fifth adsorption-desorption experiment, it still had better adsorption performance and reutilization. All in all, MCP with highly stable and efficient, as well as excellent reusability will be a candidate for industry-level applications from wastewater with Hg(II) ions.

Carbon dots and gold nanoclusters co-encapsulated by zeolitic imidazolate framework-8 (CDs/AuNCs@ZIF-8) have been obtained at room temperature. The composite has been applied to the ratiometric fluorescence determination of mercury(II). The composite shows fluorescence emission maxima at 440 and 640 nm under 360 nm excitation, due to the CDs and AuNCs, respectively (associated quantum yields were 18% and 17%, respectively). In the presence of Hg2+, the fluorescence at about 640 nm is quenched, while the fluorescence at about 440 nm is unaffected. The CDs/AuNCs@ZIF-8 composite allows the sensitive detection of Hg2+, with the fluorescence intensity ratio (I640/I440) decreasing linearly with Hg2+ concentration over the range 3-30 nM. The fluorescence emission of the composite changes color from red to blue with increasing Hg2+ under UV excitation, which can easily be discerned visually. This visual detection of Hg2+ is due to the high fluorescence quantum yields of the CDs and AuNCs and the ~ 200 nm separation between the two emission maxima. Graphical abstract (A) Schematic diagram showing the operating principle of the determination for Hg(II). (B) Digital graph of the solutions in absence and presence of 30 nM Hg(II) under a portable UV lamp.

In the current work, Cu(I)1.28Cu(II)0.36Se nanoparticles were synthesized via a simple procedure and were applied for the first time for recognition, adsorption, enrichment, and detection of Hg(II) ions. The experimental results show that 99.9% Hg(II) could be adsorbed by Cu(I)1.28Cu(II)0.36Se nanoparticles within just 30 s, and the Hg(II) concentration could be lowered down to a super-low level of 0.01 ppb. Cu(I)1.28Cu(II)0.36Se nanoparticles also demonstrate high selectivity to Hg(II) and Ag(I) among nine representative metal ions. The enrichment experiments show that Hg(II) of ultratrace concentration could be enriched significantly by Cu(I)1.28Cu(II)0.36Se nanoparticles, and thus, the detection limit of Hg(II) based on inductively coupled plasma emission spectroscopy-mass spectrometry would be pushed down by 2 orders of magnitude. These outstanding features of Cu(I)1.28Cu(II)0.36Se nanoparticles could be well accounted for in terms of the solubility product principle and the high affinity between selenium and mercury. Cu(I)1.28Cu(II)0.36Se nanoparticles were also found to have peroxidase-like activity, which could be inhibited by Hg(II) but not by Ag(I). This unique characteristic coupled with the solubility product principle successfully allows recognition and detection of Hg(II) even in the presence of Ag(I), which has a similar pKsp to Hg(II). As a result, the qualitative and quantitative analyses of Hg(II) could be performed by the naked eye and UV-visible spectroscopy, respectively. The current results indicate that Cu(I)1.28Cu(II)0.36Se nanoparticles not only have great potential in various aspects of dealing with Hg(II) pollution but would also shed light on discovering new nanomaterials to address other heavy metal ions.

Mercury is one of the most hazardous pollutants, and mercury pollution is a serious hazard to our environment. Herein, we designed and synthesized a new peptide-based fluorescent chemosensor (L) based on a Fmoc-Lys (Fmoc)-OH backbone conjugated with two Serines and dansyl groups using solid phase peptide synthesis (SPPS) technology. L exhibited highly selective and excellent sensitive detection of Hg2+ ions in 100% aqueous solutions through fluorescence quenching. The chemosensor L forms a 2:1 stoichiometry with high binding constants (4.89×106M-1) and the detection limit for Hg2+ ions of the proposed assay was 7.59nM. In addition, the recovery test results of Hg2+ concentration in actual water samples showed that the quantitative detection of Hg2+ ions can be realized in two water samples. Moreover, L showed low cytotoxicity and excellent membrane permeability in HK2 cells, which has been successfully applied for monitoring Hg2+ ions in living LNCaP cells.

Currently, magnetic mesoporous silica nanospheres have been employed widely as adsorbents due to their large surface area and easy recovery. Herein, the functionalized magnetic mesoporous silica/organic polymers nanocomposite (MMSP) was fabricated by the grafted poly(m-aminothiophenol) embedded the aminated magnetic mesoporous silica nanocomposite based on Fe3O4 magnetic core, which was shelled by mesoporous silica and further modified by (3-aminopropyl) triethoxysilane. The adsorption properties of as-developed MMSP were systematically explored by altering the experimental parameters. The results indicated that the adsorption capacity and removal percentage of the MMSP could reach 243.83 mg/g and 97.53% within only 10 min at pH 4.0, and the coexisting ions had no significant effect on the selective Hg(II) ions removal from aqueous solutions, meanwhile, the adsorbent recovered by a magnet still exhibited good adsorption performance after recycled 5 times. In addition, by analyzing experimental data, the adsorption process of Hg(II) ions belonged to spontaneous exothermic adsorption, and the possible adsorption mechanisms were proposed based on the pseudo-second-order model and Langmuir model. After adsorption study, the waste material adsorbed Hg(II) was developed as an efficient catalyst for transformation of phenylacetylene to acetophenone with yield of 97.06%. In this study, we designed an efficient and selective material for Hg(II) ions remove and provided a treatment of the post-adsorbed mercury adsorbent by converting the waste into an excellent catalyst, which reduced the economic and environmental impact from conventional adsorption techniques.