Mechanism Of Hg Research Articles

Whole-Waste synthesis of Kilogram-Scale Macropores adsorbent materials for Wide-Range oil and heavy metal removal

The rapid pace of social development leads to the generation of significant quantities of oily wastewater and heavy metal ions, posing severe threats to the environment and human health. Therefore, finding cost-effective and efficient adsorbent materials is crucial. In the present study, a porous organic polymer based on waste cooking oil was synthesized as a macropores material called POP-WCO, allowing for preparation in kilogram quantities (more than one kilogram in a single batch). This material effectively removes oil and heavy metals, exhibiting excellent hydrophobic and superoleophilic properties, enabling the adsorption of various common oils within 22 s. POP-WCO is designed to swiftly remove and recover eight common oils through simple mechanical extrusion, maintaining a consistent oil recovery efficiency of 94% after 10 cycles. It can effectively treat and recover oil spills at sea through static and continuous adsorption. In addition, the POP-WCO material removes over 99% of the heavy metal mercury, showing exceptional resistance to acid, alkali, and salt, as well as economic value. The mechanism of Hg(II) adsorption by POP-WCO has been confirmed through density functional theory (DFT) calculations and X-ray photoelectron spectroscopy (XPS) analysis, elucidating the microdynamics process of the adsorption mechanism. This research presents an important strategy for achieving resource sustainability by transforming waste into valuable materials.

Revealing Insights into the Mechanism of Hg0 Removal over MnO2 Hollow Sphere Adsorbents: Effect of Calcination Temperatures

In this study, MnO2 hollow spherical adsorbents were synthesized using the template approach, and the impacts of calcination temperatures on their physicochemical parameters and Hg0 removal ability were investigated. The adsorbent calcined at 300 °C (labeled as Mn300) demonstrated the highest performance; at 200 °C, the Hg0 removal efficiency reached over 90%. The presence of surface acid sites promoted the physisorption of Hg0 and compensated for the relatively weak oxidative ability, which made much of the Hg0 susceptible to capture on the adsorbent surface and consequently explained Mn300’s superior Hg0 capture capacity. The Mars–Maessen mechanism helped to understand the Hg0 capture pathways over Mn300, with Mn4+ and chemisorbed oxygen serving as the active species to oxidize Hg0 to HgO. Finally, Mn300 demonstrated reasonable recyclability and a rather weak gas-component adaptability, indicating that additional modification is required to improve the practical use of the adsorbent.

Adsorption behavior and mechanism of Hg(II) on highly stable Zn-based metal organic frameworks

A novel adsorbent (MTZ-MOFs) was synthesized by a one-step reaction of zinc nitrate hexahydrate and 1-(2-dimethylaminoethyl)-1H-5-mercaptotetrazole to remove mercury from waste water. The results showed that MTZ-MOFs had excellent selectivity and repeatability for Hg(II), the optimum pH was 3.0, the maximum adsorption capacity was 872.8 mg/g, and the process was a spontaneous exothermic reaction. The adsorption behavior was chemisorption, which conformed to the pseudo-second-order kinetic and Freundlich isothermal model. Moreover, the adsorption mechanism showed that the adsorption process mainly depended on ion exchange and chelation, and the synergistic action of S and N atoms played a key role. So, MTZ-MOFs were an efficient adsorbent for mercury ion removal.

Effect of Pyrolysis Temperature on Removal Efficiency and Mechanisms of Hg(II), Cd(II), and Pb (II) by Maize Straw Biochar

Pyrolysis temperature significantly affects the properties of biochar, which in turn can affect the removal of heavy metal ions and the underlying mechanism. In this work, biochars from the pyrolysis of maize straw at 300, 400, and 500 °C (BC300, BC400, and BC500, respectively) and wheat straw at 400 °C (WBC400) were investigated. The influence of production temperature on the adsorption of Hg2+, Cd2+, and Pb2+ by maize straw biochar was investigated by the characterization of the biochars and by adsorption tests. The adsorption capacities of maize and wheat straw biochar were compared in an adsorption experiment. Biochar BC400 showed the best physical and chemical properties and had the largest number of surface functional groups. The pseudo-second-order kinetic model was more suitable for describing the adsorption behavior of metal ions to biochar. The Langmuir model better fit the experimental data. Biochar BC400 had a higher adsorption speed and a stronger adsorption capacity than WBC400. The sorption of Pb2+ and Hg2+ to maize straw biochar followed the mechanisms of surface precipitation of carbonates and phosphates and complexation with oxygenated functional groups and delocalized π electrons. The adsorption mechanism for Cd2+ was similar to those of Hg2+ and Pb2+, but precipitation mainly occurred through the formation of phosphate. In the multi-heavy-metal system, the adsorption of Cd2+ by BC400 was inhibited by Pb2+ and Hg2+. In summary, BC400 biochar was most suitable for the adsorption effect of heavy metals in aqueous solution.

Experimental and Mechanistic Study of Synergistic Removal of Hg by Evaporation from Desulfurization Wastewater

The flue evaporation of desulfurization wastewater can solve the problem that it is difficult to remove some heavy metal ions and chloride ions by conventional methods. A large amount of chloride ions in desulfurization wastewater can also promote the catalytic oxidation removal of Hg in the flue gas. The migration character of chloride ions in the flue evaporation process of desulfurization wastewater was studied by using the coal-fired thermal state experimental platform. The concentrations of Hg0 and Hg2+ in the flue gas at the inlet and outlet of selective catalytic reduction denitration (SCR), electrostatic precipitator (ESP), and wet desulfurization (WFGD) devices were tested, and the synergistic removal of traditional pollutant removal equipment by flue evaporation of desulfurization wastewater was analyzed. The influence of Hg and the effect of the evaporation of desulfurization wastewater at different positions on the removal of Hg in the flue gas were compared and analyzed, and the catalytic mechanism of Hg on the SCR surface was further revealed. The results show that 10% chloride ions enter the flue gas after the desulfurization wastewater evaporates. The content of chlorine elements and evaporation temperature influence the evaporation of desulfurization wastewater. The mechanism of SCR catalytic oxidation of Hg0 was explored; oxygen atoms have catalytic oxidation effects on Hg0 at different positions in the V2O5 molecule in SCR; and chloride ions can enhance the catalytic oxidation of Hg0 by V2O5. The intermediate product HgCl is generated, which is finally converted into HgCl2. The oxidation efficiency of Hg0 in electrostatic precipitation (ESP) is increased from 3% to 18%, and the removal efficiency of Hg is increased from 5% to 10%. The removal efficiency of Hg2+ in WFGD is basically maintained at approximately 85%. In addition, a small amount of Hg2+ was restored to Hg0 in WFGD. The removal efficiency of Hg0 in the flue gas of evaporative desulfurization wastewater before SCR is 65%, and the removal efficiency of gaseous Hg is 62%. When the evaporative desulfurization wastewater before ESP, the synergistic removal efficiency of Hg0 is 39%, and the gaseous Hg removal efficiency is 39%, and the removal efficiency of Hg is 40%. Evaporation of the desulfurization wastewater before SCR was more conducive to the coordinated removal of Hg by the device.

New Insight into the Characteristics and Mechanism of Hg0 Removal by NaClO2 in Limestone Slurry

New Insight into the Characteristics and Mechanism of Hg⁰ Removal by NaClO₂ in Limestone Slurry

Metabolomics coupled with integrated approaches reveal the therapeutic effects of higenamine combined with [6]-gingerol on doxorubicin-induced chronic heart failure in rats

BackgroundThis study was aimed to investigate the therapeutic effects and potential mechanism of higenamine combined with [6]-gingerol (HG/[6]-GR) against doxorubicin (DOX)—induced chronic heart failure (CHF) in rats.Materials and methodsTherapeutic effects of HG/[6]-GR on hemodynamics indices, serum biochemical indicators, histopathology and TUNEL staining of rats were assessed. Moreover, a UHPLC-Q-TOF/MS-based serum metabolic approach was performed to identify the metabolites and possible pathways of HG/[6]-GR on DOX-induced CHF.ResultsHG/[6]-GR had effects on regulating hemodynamic indices, alleviating serum biochemical indicators, improving the pathological characteristics of heart tissue and reducing the apoptosis of myocardial cells. Serum metabolisms analyses indicated that the therapeutic effects of HG and [6]-GR were mainly associated with the regulation of eight metabolites, including acetylphosphate, 3-Carboxy-1-hydroxypropylthiamine diphosphate, coenzyme A, palmitic acid, PE(O-18:1(1Z)/20:4(5Z,8Z,11Z,14Z)), oleic acid, lysoPC(18:1(9Z)), and PC(16:0/16:0). Pathway analysis showed that HG/[6]-GR on CHF treatment was related to twelve pathways, including glycerophospholipid metabolism, fatty acid metabolism, pantothenate and CoA biosynthesis, citrate cycle (TCA cycle), pyruvate metabolism, and arachidonic acid metabolism. Serum metabolites and metabolic pathways regulated by HG/[6]-GR appear to be related to energy metabolism.ConclusionMultivariate statistical analysis has provided new insights for understanding CHF and investigating the therapeutic effects and mechanisms of HG/[6]-GR, which influencing the metabolites and pathways related to energy metabolism pathway.

Adsorption behavior and mechanism of Hg (II) on a porous core-shell copper hydroxy sulfate@MOF composite

Herein, a porous core-shell copper hydroxy sulfate@metal-organic framework decorated by 2,5-dimercapto-1,3,4-thiadiazol (DMTZ) was synthesized via a facile self-template strategy for the capture of Hg2+. The strategy of assembling MOF shell on copper hydroxy sulfate (CHS) core avoided the self-nucleation of MOF(Cu3(BTC)2) in the solution and complex multistep procedures by means of in situ transformation the metal source CHS into well-defined Cu3(BTC)2 crystal. The structure and properties of the DMTZ modified CHS@Cu3(BTC)2 (CHS@Cu3(BTC)2-DMTZ) was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR), thermogravimetric analysis (TGA) and N2 sorption–desorption isotherms (BET). The adsorption behavior followed Langmuir adsorption model and the maximum adsorption capacities for the removal of Hg2+ was up to 627.6 mg g−1. 99.96% Hg2+ was rapidly captured by CHS@Cu3(BTC)2-DMTZ within 10 min from 40 mg L-1 to 0.014 mg L-1. Meanwhile, not only X-ray photoelectron spectroscopy (XPS) but also Raman spectra verified the selective and strong interaction between Hg2+ and thiol/nitrogen-containing functional groups of DMTZ on CHS@Cu3(BTC)2-DMTZ. These results manifested that this novel thiol-functionalized MOF adsorbent had superior adsorption capacity and selective for Hg2+.

Insight into the effect of SO2 on the Hg0 removal performance over a 1V-8Ce/AC sorbent at low temperatures

The influences of SO2 on Hg° removal over the 1V-8Ce/AC sorbent were systematically investigated at low temperatures. The experimental results showed that SO2 has a dual effect on Hg° removal, that is, SO2 has both a promoting effect and an inhibiting effect on Hg° removal. The SO2 transient response experiment indicated that SO2 could not only react with Hg° to promote the removal of Hg° but also react with the active components and poison the sorbent. O2 is indispensable for the removal of Hg°, which can offset the adverse effects caused by SO2 and H2O. HCl exhibited an obvious promoting effect on Hg° removal in the presence of SO2. The 1V-8Ce/AC sorbent exhibited good sulfur resistance and excellent stability (EHg = 90.04 %) after a 24 h reaction performed under the 1000 ppm SO2 condition at 150 °C. In addition, the Hg-TPD and XPS methods were used to assist in studying the effect of SO2 on Hg° removal over the 1V-8Ce/AC sorbent. Finally, the mechanism of Hg° removal in an SO2 atmosphere was also explored, which showed that Hg° was removed by two possible pathways over the 1V-8Ce/AC sorbent.

The bioremediation potentials and mercury(II)-resistant mechanisms of a novel fungus Penicillium spp. DC-F11 isolated from contaminated soil

Bioremediation of Hg-contaminated soil using microbe-based strategies is a promising and efficient method as it is inexpensive and not harmful to the environment. In this study, a novel Hg(II)-volatilizing fungus Penicillium spp., DC-F11 was isolated and showed bioremediation potential for reducing Hg(II) phytotoxicity, total Hg, and exchangeable Hg in Hg(II)-polluted soil. Subsequently, the mechanisms of Hg(II) volatilization and resistance involved were investigated using multiple complementary techniques. The fungal cells could detoxify Hg(II) by extracellular sequestration via adsorption and precipitation. Moreover, a comparative transcriptome analysis uncovered the primary intracellular adaptive responses of the DC-F11 to Hg(II) stress, including mer-mediated detoxification system, thiol compound metabolism, and oxidative stress defense and damage repair metabolism. These results showed that the resistance of DC-F11 to Hg(II) was generally a multisystem collaborative process. Here, we report, for the first time, that the mer-mediated detoxification system was responsible for Hg(II) volatilization in fungus. These findings provide a better understanding of the mechanisms involved in Hg(II) volatilization and resistance that occur in fungi and also provide a strong theoretical basis for the future application of fungi in the bioremediation of Hg-polluted environments.

The adsorption property and mechanism for Hg(II) and Ag(I) by Schiff base functionalized magnetic Fe3O4 from aqueous solution

Schiff-base functionalized magnetic Fe3O4 were prepared by feasible one-pot subsequent homogeneous method (Fe3O4@SiO2–HO–S) and heterogeneous method (Fe3O4@SiO2-HE-S), respectively. The as-prepared adsorbents were used for the adsorption of aqueous Hg(II) and Ag(I). The effects of solution pH, time, temperature, coexisting metal ions, and initial metal ion concentration on the adsorption were investigated. The as-synthesized adsorbents were characterized by transmission electron microscope, scanning electron microscope, and X-ray photoelectron spectroscopy. The effect of solution pH indicates the optimal adsorption pH is 6. The adsorption equilibrium time are 180 and 220 min for both Hg(II) and Ag(I) under the concentration of 0.002 and 0.004 mol L−1, respectively. The adsorption kinetic process is proved to be dominated by film diffusion process and follows pseudo-second-order kinetic model. The adsorption isotherm process is proceeded by chemical mechanism and can be described by Langmuir model. Thermodynamic parameters indicate that the adsorption process is spontaneous, endothermic, and entropy increase. Adsorption selectivity demonstrates Fe3O4@SiO2-HE-S and Fe3O4@SiO2–HO–S exhibit good adsorption selectivity for Hg(II). The adsorption mechanism demonstrates the N atoms of Schiff base functional group mainly dominate the adsorption of Fe3O4@SiO2-HE-S and Fe3O4@SiO2–HO–S for metal ions. The regeneration property indicates the adsorbents can be reused with practical value.

Mercury and dissolved organic matter dynamics during snowmelt runoff in a montane watershed, Provo River, Utah, USA

The mechanisms of Hg and dissolved organic matter (DOM) transport from watersheds to streams remain unclear, especially in snowmelt dominated montane systems. We characterized total Hg concentrations and DOM characteristics during snowmelt by weekly and/or monthly sampling at three locations in the upper Provo River, northern Utah, over two water years (2016 and 2017). Total Hg concentrations increased from <1 ng/L during baseflow to >7 ng/L during the snowmelt period (April–June), with decreasing concentrations from upstream to downstream. Filtered THg concentrations accounted for 65–75% of the unfiltered concentrations, suggesting that Hg is primarily transported in the dissolved phase. Annual THg loading in the upper Provo River was approximately 1 kg/yr, with ~90% of the flux occurring during the snowmelt period. Filtered THg concentrations were strongly correlated with in-situ fluorescence DOM (fDOM) measurements, allowing for the development of high-resolution proxy THg concentrations. Further, DOM characteristics, evaluated using excitation-emission matrices (EEMs) and parallel factor analysis (PARAFAC), identified the dominance of soil humic and fulvic acid fractions of DOM during runoff. Total Hg concentrations were low in snowpack but elevated in ephemeral streams during snowmelt runoff, indicating that Hg originated from shallow soil water rather than snow. Concentration—discharge relationships revealed clockwise hysteresis patterns, suggesting that Hg was flushed from soils on the rising limb of the hydrograph. Our results demonstrate that a majority of Hg transport occurs with a flux of DOM during the short snowmelt season as shallow soils are flushed by meltwater. The snowmelt-driven Hg pulse is a substantial source to downstream reservoirs and potentially contributes to a fish consumption advisory.

Immobilization of mercury and arsenic in a mine tailing from a typical Carlin-type gold mining site in southwestern part of China

Abstract The potential of chicken manure and ferrous sulfate in immobilizing both mercury (Hg) and arsenic (As) in a tailing collected from Danzhai gold (Au) mine in southwestern part of China was investigated. A laboratory leaching experiment was conducted firstly to study the effectiveness of 30 tons ha−1 to 90 tons ha−1 chicken manure, or its combination with 1.5 tons ha−1 to 15 tons ha−1 ferrous sulfate, on the mobilization of Hg and As in the tailing. Results showed that the sole application of chicken manure at dose of 30 tons ha−1 to 90 tons ha−1 to the tailing removed approximately 94%–99% and 49%–85% of Hg and As, respectively, from the leachate over three months. These reductions might be attributed to the formation of hardly soluble Hg sulfides (e.g., HgS) and As sulfides in the tailing. Addition of chicken manure and ferrous sulfate to the tailing decreased Hg and As concentrations by 60%–85% and 31%–60%, respectively, in the leachate as compared to sole treatment of chicken manure. The mechanisms of Hg and As removal might be linked to their adsorption by iron oxides and chicken manure. The co-application of 30 tons ha−1 chicken manure and 15 tons ha−1 ferrous sulfate to the tailing showed promising results in reducing Hg and As concentrations as compared to the other treatments. The results from field trial showed that about 73% of Hg and 82% of As were removed from the leachate by the selected amendments (30 tons ha−1 chicken manure and 15 tons ha−1 ferrous sulfate), as compared to the control. In summary, the co-application of 30 tons ha−1 chicken manure and 15 tons ha−1 ferrous sulfate was promising in mitigating risk of both Hg and As from tailings, and the knowledge provided might deepen our understanding of mobilization of Hg and As in the tailing in Carlin-type gold mining regions.

Mechanism of Hg(II), Cd(II) and Pb(II) ions sorption from aqueous solutions by Aspergillus niger spores

ABSTRACTRecent work has focused on the removal of Pb2+, Hg2+, and Cd2+ by using an organ of Aspergillus niger – spores, which were spherical particles with small diameter (2 µm) characterized by negative charge. Results shown that the biosorption of Pb2+, Hg2+, and Cd2+ from aqueous solutions using spores was analyzed at varying biosorbent dosages, pH levels, contact times and initial heavy metal concentrations. The maximum biosorption capacities of Pb2+, Hg2+, and Cd2+ were 23.9, 27.2, and 21.5 mg/g at a natural pH with the initial concentration were 30 mg/L, respectively. The sequence of biosorption capacity for cationic heavy metals was Pb2+>Cd2+>Hg2+. Spores exhibited a short biosorption equilibrium time of 60 min at a pH range of 4.0–6.0, and the main biosorption mechanism was electronic attraction, ion exchanges and complexation(involved in C = C, C-H, C-O, N-H), the data fit well in the pseudo-second-order kinetic equation and the Freundlich isotherm. In addition, Spores can grow on many kinds of moist agriculture waste without any added nutrition. The results showed that spores could be considered as a potential biosorbent for the removal of cationic heavy metals from aqueous solutions.

The enhancement of CuO modified V2O5-WO3/TiO2 based SCR catalyst for Hg° oxidation in simulated flue gas

CuO modified V2O5-WO3/TiO2 based SCR catalysts prepared by improved impregnation method were investigated to evaluate the catalytic activity for elemental mercury (Hg°) oxidation in simulated flue gas at 150–400 °C. Nitrogen adsorption, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were used to characterize the catalysts. It was found that V0.8WTi-Cu3 catalyst exhibited the superior Hg° oxidation activity and wide operating temperature window at the gas hourly space velocity (GHSV) of 3 × 105 h−1. The BET and XRD results showed that CuO was well loaded and highly dispersed on the catalysts surface. The XPS results suggested that the addition of CuO generated abundant chemisorbed oxygen, which was due to the synergistic effect between CuO and V2O5. The existence of the redox cycle of V4+ + Cu2+ ↔ V5+ + Cu+ in V0.8WTi-Cu3 catalyst enhanced Hg° oxidation activity. The effects of flue gas components (O2, NO, SO2 and H2O) on Hg° oxidation over V0.8WTi-Cu3 catalyst were also explored. Moreover, the co-presence of NO and NH3 remarkably inhibited Hg° oxidation, which was due to the competitive adsorption and reduction effect of NH3 at SCR condition. Fortunately, this inhibiting effect was gradually scavenged with the decrease of GHSV. The mechanism of Hg° oxidation was also investigated.

Preparation of new diatomite-chitosan composite materials and their adsorption properties and mechanism of Hg(II).

A new composite absorbent with multifunctional and environmental-friendly structures was prepared using chitosan, diatomite and polyvinyl alcohol as the raw materials, and glutaraldehyde as a cross-linking agent. The structure and morphology of the composite absorbent, and its adsorption properties of Hg(II) in water were characterized with Fourier transform infrared (FT-IR) spectra, scanning electron microscope (SEM), X-ray diffraction (XRD), Brunauer Emmett Teller (BET) measurements and ultraviolet–visible (UV–Vis) spectra. The effect of the pH value and contact time on the removal rate and absorbance of Hg(II) was discussed. The adsorption kinetic model and static adsorption isotherm and regeneration of the obtained composite absorbent were investigated. The results indicated that the removal of Hg(II) on the composite absorbent followed a rapid adsorption for 50 min, and was close to the adsorption saturation after 1 h, which is in accord with the Langmuir adsorption isotherm model and the pseudo-second-order kinetic model. When the pH value, contact time and the mass of the composite absorbent was 3, 1 h and 100 mg, respectively, the removal rate of Hg(II) on the composite absorbent reached 77%, and the maximum adsorption capacity of Hg(II) reached 195.7 mg g−1.

Thyroid hormone related gene transcription in southern sand flathead (Platycephalus bassensis) is associated with environmental mercury and arsenic exposure

Arsenic (As) and mercury (Hg) are ubiquitous elements known to disrupt thyroid function in vertebrates. To explore the underlying mechanisms of Hg and As on the fish thyroid system, we investigated the associations between muscle concentrations of Hg and As with thyroid-related gene transcription in flathead (Platycephalus bassensis) from a contaminated estuary. We sampled fish at several sites to determine the hepatic expression of genes including deiodinases (D1 and D2), transthyretin (TTR), thyroid hormone receptors (TRα and TRβ) and related them to Hg and As levels in the same individuals. Negative correlations were observed between Hg levels and D2, TTR, TRα and TRβ, whereas positive associations were found between As concentrations and TTR and TRβ. These results suggest that Hg and As exposures from environmental pollution affect the regulation of genes important for normal thyroid function in fish. These thyroid-related genes could be used as biomarkers for monitoring environmental thyroid-hormone disrupting chemicals.

Hg(II) reduction by siderite (FeCO3)

In groundwater, chemical reactions of Hg(II) with mineral surfaces play an important role in determining the concentration of mercury that is mobile and bioavailable. In this study, we investigated Hg(II) reduction by the ferrous carbonate mineral, siderite (FeCO3), to better understand reductive transformation of mercury in anoxic carbonate-bearing waters. Kinetic experiments and X-ray adsorption spectroscopy (XAS) were conducted to examine the rate and mechanism of Hg(II) reaction with siderite. Hg(II) was reacted with synthesized siderite mineral at various concentrations and the subsequently formed Hg(0) was measured to assess the extent of mercury reduction by siderite. Our experimental data showed that Hg(II) reduction by siderite resulted in the loss of Hg when reacted with siderite mineral suspensions concurrent to formation of gaseous Hg(0). Hg(II) reduction occurred within minutes and reaction rates increased with increasing siderite surface area. XAS analysis confirmed that Hg(II) was reduced to Hg(0) and revealed that reduced mercury was sorbed to siderite surfaces suggesting that electron transfer reactions occur at siderite/water interface. The results of our study suggest that Hg(II) reduction by siderite is a kinetically favorable pathway for the mercury mobilization in ferruginous carbonate-bearing waters.

High removal efficacy of Hg(II) and MeHg(II) ions from aqueous solution by organoalkoxysilane-grafted lignocellulosic waste biomass

An effective organoalkoxysilanes-grafted lignocellulosic waste biomass (OS-LWB) adsorbent aiming for high removal towards inorganic and organic mercury (Hg(II) and MeHg(II)) ions was prepared. Organoalkoxysilanes (OS) namely mercaptoproyltriethoxylsilane (MPTES), aminopropyltriethoxylsilane (APTES), aminoethylaminopropyltriethoxylsilane (AEPTES), bis(triethoxysilylpropyl) tetrasulfide (BTESPT), methacrylopropyltrimethoxylsilane (MPS) and ureidopropyltriethoxylsilane (URS) were grafted onto the LWB using the same conditions. The MPTES grafted lignocellulosic waste biomass (MPTES-LWB) showed the highest adsorption capacity towards both mercury ions. The adsorption behavior of inorganic and organic mercury ions (Hg(II) and MeHg(II)) in batch adsorption studies shows that it was independent with pH of the solutions and dependent on initial concentration, temperature and contact time. The maximum adsorption capacity of Hg(II) was greater than MeHg(II) which respectively followed the Temkin and Langmuir models. The kinetic data analysis showed that the adsorptions of Hg(II) and MeHg(II) onto MPTES-LWB were respectively controlled by the physical process of film diffusion and the chemical process of physisorption interactions. The overall mechanism of Hg(II) and MeHg(II) adsorption was a combination of diffusion and chemical interaction mechanisms. Regeneration results were very encouraging especially for the Hg(II); this therefore further demonstrated the potential application of organosilane-grafted lignocellulosic waste biomass as low-cost adsorbents for mercury removal process.

Tuning the Adsorption of Elemental Mercury by Small Gas-Phase Palladium Clusters: First-Principles Study.

Density functional theory (DFT) calculations were performed to study the nature of interaction of elemental mercury (Hg) with small palladium clusters (Pdn, n = 1-6) using generalized gradient approximation method. Results of these calculations showed stronger binding of Hg with Pd2 cluster, which, therefore, was chosen for further investigation as presented in the latter part of the third section of this report. This extended study explains the binding mechanism of Hg with alloys of Pd dimers, PdM (M = Pd, Pt, Cu, Ag, Au) in neutral, cationic, and anionic states. Interaction energy of Hg with palladium dimer follows the trend Pd2+ > Pd2 > Pd2-. For all of the above PdM complexes, the strength of Hg binding is found to be highest in their cationic states. Mixing of Pt and Au enhances the reactivity of the cationic Pd2 dimers, decreases it for their neutral counterparts, and does not affect much in the anionic states. Natural bond orbital (NBO) analysis indicates that Hg binding takes place because of the charge transfer from its s-orbitals primarily to the d-orbitals of M atoms followed by back-donation of charges from their s-orbitals to the p-orbitals of Hg atom. Moreover, the amount of charge transfer from Hg(s)→M(d) correlates with the Hg binding energy in Hg-PdM0,± complexes. Binding of Hg in cationic Hg-PdM complexes conjointly depends on energies of the lowest unoccupied molecular orbitals of the PdM+ dimers as well as NBO partial charges on adsorbed Hg.