Removal Of Inorganic Mercury Research Articles

Evaluation of olive stone biochar as valuable and inexpensive agro‐waste adsorbent for the adsorption and removal of inorganic mercury from Nile tilapia aquaculture systems

The study's objective was to evaluate using olive stone biochar (OSB), an inexpensive agro-waste product, to adsorb and remove inorganic mercury from Nile tilapia (Oreochromis niloticus) aquaculture systems. First, the OSB's adsorption capacity was evaluated by testing different concentrations: 1, 2 and 3 g L−1 for 0, 24, 48, 72 and 120 h. The concentration of Hg decreased with increasing OSB concentration up to 48 h, with the highest Hg adsorption rate observed at 2 g OSB L−1. An experimental study assessed the OSB's impact on Nile tilapia immune status and growth efficiency. The experiment used 180 Nile tilapia divided into four treatment groups (CONT, OSB, Hg and Hg +OSB), with three replicates per treatment. Fish were fed a normal basal diet twice daily for 60 d. The CONT group served as a control without any treatment. The OSB group was exposed to 2 g OSB L−1 of water, the Hg group was exposed to 0.084 mg Hg L−1, and the Hg +OSB group was exposed to 0.084 mg Hg L−1 with 2 g OSB L−1. Hg exposure caused liver and renal dysfunction and reduced growth performance, haematological indices, total antioxidant capacity, superoxide dismutase and non-specific immune parameters. Adding OSB to the pond water reduced these effects. In conclusion, adding 2 g OSB L−1 to aquarium water and changing it every 48 h mitigates the immunosuppressive effects of sub-chronic mercury toxicity and lowers mercury residues in fish muscle.

Removal of inorganic mercury by selective extraction and coprecipitation for determination of methylmercury in mercury-contaminated soils by chemical vapor generation inductively coupled plasma mass spectrometry (CVG-ICP-MS)

A procedure is developed for selective extraction of methylmercury (CH3Hg+) from heavily Hg-contaminated soils and sediments for determination by chemical vapor generation inductively coupled plasma mass spectrometry (CVG-ICP-MS). Soils artificially contaminated with 40 μg g−1 inorganic mercury (Hg2+) or methylmercury chloride (CH3HgCl) were agitated by shaking or exposing to ultrasounds in dilute hydrochloric acid (HCl) or nitric acid (HNO3) solutions at room temperature. Extractions in HCl (5 or 10% v/v) resulted in substantial leaching of Hg2+ from soils, whereas 5% (v/v) HNO3 provided selectivity for quantitative extraction of CH3Hg+ with minimum Hg2+ leaching. Agitation with ultrasounds in 5% (v/v) HNO3 for about 3 min was sufficient for extraction of all CH3Hg+ from soils. Coprecipitations with Fe(OH)3, Bi(OH)3 and HgS were investigated for removal of residual Hg2+ in soil extracts. Hydroxide precipitations were not effective. Thiourea or l-cysteine added to soil extracts prior to hydroxide precipitation improved precipitation of Hg2+, but also resulted in removal of CH3Hg+. HgS precipitation was made with dilute ammonium sulfide solution, (NH4)2S. Adding 30 μL of 0.35 mol L−1 (NH4)2S to soil extracts in 5% (v/v) HNO3 resulted in removal of all residual Hg2+ without impacting CH3Hg+ levels. Vapor generation was carried out by reacting Hg2+-free soil extracts with 1% (m/v) NaBH4. No significant interferences were observed from (NH4)2S on the vapor generation from CH3Hg+. The slopes of the calibration curves for CH3HgCl standard solutions in 5% (v/v) HNO3 with and without (NH4)2S were similar. Limits of detection (LOD, 3s method) were around 0.08 μg L−1 for 5% (v/v) HNO3 blanks (n = 10) and 0.10 μg L−1 for 5% (v/v) HNO3 + 0.005 mol L−1 (NH4)2S blanks (n = 10). Percent relative standard deviation (%RSD) for five replicate measurements varied between 3.1% and 6.4% at 1.0 CH3HgCl level. The method is validated by analysis of two certified reference materials (CRM); purely Methylmercury sediment (SQC1238, 10.00 ± 0.291 ng g−1 CH3Hg+) and Hg-contaminated Estuarine sediment (ERM – CC580, 75 ± 4 ng g−1 CH3Hg+ and 132 ± 3 μg g−1 total Hg). CH3Hg+ values for SQC1238 were between 13.0 and 13.2 ng g−1, and 79 and 81 ng g−1 for ERM – CC580. Hg-contaminated soils (57–96 μg g−1 total Hg) collected from the floodplains of Oak Ridge, TN were analyzed for CH3Hg+ using the procedure by CVG-ICPMS. CH3Hg+ levels ranged from 30 to 51 ng g−1 and did not correlate with total Hg levels (R2 = 0.01).

Carbon nanotubes magnetic hybrid nanocomposites for a rapid and selective preconcentration and clean-up of mercury species in water samples

Hybrid nanocomposites based on Fe3O4 magnetic nanoparticles (MNPs) coated with different types of carbon nanotubes (CNTs) have been studied for the first time as sorbent materials for magnetic solid phase extraction (MSPE) for mercury speciation analysis. Monomethylmercury (MMHg) was the target mercury species in water samples and the adsorption and desorption processes were optimized based on this species. Single-walled CNT-MNP showed higher adsorption capacity than double-walled or multi-walled CNTs. Then, the magnetic sorbent was retrieved with an external magnet and MMHg was selectively desorbed from it with dichloromethane (DCM) in two steps with vortex agitation. Inorganic mercury was removed during the desorption stage. The rapid adsorption and desorption equilibrium, the magnetic separation of the sorbent, and the simple and fast synthesis of CNT-MNPs without any additional modification of the CNTs simplified and shortened the extraction procedure. The extract was submitted to derivatization of the mercury species by ethylation (with an optional nitrogen stream evaporation of the organic phase) and injection into a gas chromatograph coupled to an atomic fluorescence detector (GC-pyro-AFS). The overall procedure provides the preconcentration of MMHg up to 150 times and the removal of inorganic mercury at the same time. The procedural limits of detection (LOD) and quantification (LOQ) were 5.4 and 17.9pgmL−1, respectively. Moreover, magnetic nanocomposites can be reused at least 7 times without losing their efficiency. The methodology was validated in tap, dam and river water samples to evaluate the performance under real conditions with recoveries from 79% to 97% of spiked MMHg.

Effectiveness of gold nanoparticle-coated silica in the removal of inorganic mercury in aqueous systems: Equilibrium and kinetic studies

The adsorption of inorganic mercury, Hg (II), in aqueous solution has been investigated to evaluate the effectiveness of synthesized gold (Au) nanoparticle-coated silica as sorbent in comparison with activated carbon and Au-coated sand. The synthesis of the Au-coated silica was confirmed by x-ray diffraction (Bragg reflections at 38.2°, 44.4°, 64.6°, and 77.5°) and the Au loading on silica surface was 6.91±1.14 mg/g. The synthesized Au-coated silica performed an average Hg adsorption efficiency of ~96 (±2.61) % with KD value of 9.96 (±0.32) L/g. The adsorption kinetics of Hg(II) on to Au-coated silica closely follows a pseudo-second order reaction where it is found out to have an initial adsorption rate of 4.73 g/μg/min/ and overall rate constant of 4.73 × 10(-4) g/μg/min/. Au-coated silica particles are effective in removing Hg (II) in aqueous solutions due to their relatively high KD values, rapid adsorption rate, and high overall efficiency that can even decrease mercury levels below the recommended concentrations in drinking water.

Removal of inorganic mercury from aquatic environments by multi-walled carbon nanotubes.

BackgroundMercury is considered as a toxic heavy metal in aquatic environments due to accumulation in bodies of living organisms. Exposure to mercury may lead to different toxic effects in humans including damages to kidneys and nervous system.Materials and methodsMulti-walled carbon nanotubes (MWCNTs) were selected as sorbent to remove mercury from aqueous solution using batch technique. ICP instrument was used to determine the amount of mercury in solution. Moreover, pH, contact time and initial concentration of mercury were studied to determine the influence of these parameters on the adsorption conditions.ResultsResults indicate that the adsorption strongly depended on pH and the best pH for adsorption is about 7. The rate of adsorption process initially was rapid but it was gradually reduced with increasing of contact time and reached the equilibrium after 120 min. In addition, more than 85 % of initial concentration of 0.1 mg/l was removed at 0.5 g/l concentration of sorbent and contact time of 120 min. Meanwhile, the adsorption process followed the pseudo second-order model and the adsorption isotherms could be described by both the Freundlich and the Langmuir models.ConclusionThis study showed that MWCNTs can effectively remove inorganic mercury from aqueous solutions as adsorbent.

Removal of inorganic mercury and methylmercury from surface waters following coagulation of dissolved organic matter with metal-based salts

The presence of inorganic mercury (IHg) and methylmercury (MeHg) in surface waters is a health concern worldwide. This study assessed the removal potential use of metal-based coagulants as a means to remove both dissolved IHg and MeHg from natural waters and provides information regarding the importance of Hg associations with the dissolved organic matter (DOM) fraction and metal hydroxides. Previous research indicated coagulants were not effective at removing Hg from solution; however these studies used high concentrations of Hg and did not reflect naturally occurring concentrations of Hg. In this study, water collected from an agricultural drain in the Sacramento–San Joaquin Delta was filtered to isolate the dissolved organic matter (DOM) fraction. The DOM was then treated with a range of coagulant doses to determine the efficacy of removing all forms of Hg from solution. Three industrial-grade coagulants were tested: ferric chloride, ferric sulfate, and polyaluminum chloride. Coagulation removed up to 85% of DOM from solution. In the absence of DOM, all three coagulants released IHg into solution, however in the presence of DOM the coagulants removed up to 97% of IHg and 80% of MeHg. Results suggest that the removal of Hg is mediated by DOM-coagulant interactions. There was a preferential association of IHg with the more aromatic, higher molecular weight fraction of DOM but no such relationship was found for MeHg. This study offers new fundamental insights regarding large-scale removal of Hg at environmentally relevant regarding large-scale removal of Hg at environmentally relevant concentrations.

Removal of inorganic mercury from aqueous solutions by biomass of the marine macroalga Cystoseira baccata

The ability of Cystoseira baccata algal biomass to remove Hg(II) from aqueous solutions is investigated. The mercury biosorption process is studied through batch experiments at 25 °C with regard to the influence of contact time, initial mercury concentration, solution pH, salinity and presence of several divalent cations. The acid–base properties of the alga are also studied, since they are related to the affinity for heavy metals. The studies of the pH effect on the metal uptake evidence a sharp increasing sorption up to a pH value around 7.0, which can be ascribed to changes both in the inorganic Hg(II) speciation and in the dissociation state of the acid algal sites. The sorption isotherms at constant pH show uptake values as high as 178 mg g −1 (at pH 4.5) and 329 mg g −1 (at pH 6.0). The studies of the salinity influence on the Hg(II) sorption capacity of the alga exhibit two opposite effects depending on the electrolyte added; an increase in concentration of nitrate salts (NaNO 3, KNO 3) slightly enhances the metal uptake, on the contrary, the addition of NaCl salt leads to a drop in the sorption. The addition of different divalent cations to the mercury solution, namely Ca 2+, Mg 2+, Zn 2+, Cd 2+, Pb 2+ and Cu 2+, reveals that their effect on the uptake process is negligible. Finally, the equilibrium sorption results are compared with predictions obtained from the application of a simple competitive chemical model, which involves a discrete proton binding constant and three additional constants for the binding of the main neutral inorganic Hg(II) complexes, Hg(Cl) 2, HgOHCl and Hg(OH) 2, to the algal surface sites.

Elimination of inorganic mercury from waste waters using crandallite‐type compounds

AbstractThe removal of inorganic mercury from waste water streams arising from mines, using an artificial amorphous compound of the crandallite type synthesized in our laboratory, Ca0.5Sr0.5Al3(OH)6(HPO4) (PO4), has been investigated. This compound exhibits an extremely wide range of ionic substitutions: Ca2+ and Sr2+ were interchanged with Hg2+, so the mercury content of the waste water, ranging from 70 to 90 ppm, was reduced to less than 0.1 ppm. The process has been studied under batch conditions. The crandallite showed a high capacity for the exchange of mercury from mercuric nitrate solutions, 1.555 meq g−1. The ion‐exchange equilibrium isotherms for Hg2+ were correlated by the Langmuir equation. The recovery of mercury from Hg‐crandallite using HCl solutions and thermal treatment was also studied. Optimum recuperation of mercury is achieved by chemical reaction with HCl solution (pH 2.25). At these conditions, 75% of the mercury is recovered as the HgCl42− complex in a simple batch process, and the crandallite (in the protonic form) can be reused.© 2003 Society of Chemical Industry

Removal of Inorganic Mercury from Aqueous Solutions by Carbonized Waste Newsprint Fiber

The ability of carbonized waste newsprint fiber to remove Hg(II) from aqueous solutions by physicochemical adsorption was investigated. Defiberized waste newsprint was carbonized in a nitrogen atmosphere at temperatures ranging 600 to 900°C for 3 h. Research parameters included carbonization temperature, initial solution pH, contact time, solution temperature, and initial concentration of Hg(II). The studies showed the adsorbents to be an efficient adsorbent for removing Hg(II) from aqueous solutions. Of the parameters studied, carbonization temperature and initial solution pH were considered to be the most crucial. The amount of Hg(II) adsorbed onto the adsorbent increased with increasing carbonization temperature in the pH range 3 to 9, while it decreased as the temperature increased at pH 11. The extent of the adsorption was also dependent upon the contact time, solution temperature, and initial concentration of Hg(II). The adsorption data were well fitted to both the Freundlich and Langmuir isotherms. Desorption studies imply the occurrence of strong interaction of the Hg(II) species with the active sites on the surface of the adsorbent.

Removal of inorganic mercury from mine waste water by ion exchange

Removal of inorganic mercury from mine waste water by ion exchange

Removal of inorganic mercury from mine waste water by ion exchange

The present study has been undertaken to investigate a process that might remove inorganic mercury from mine waste water streams by use an ion exchange resin system. A number of commercial resins have been evaluated as ion exchangers and the mercury content of the waste water, ranging from 70 to 90 ppm, is reduced to a permitted level of 34 ppb. Dowex XZS-1, a strong cationic ion exchanger in a gel Form, has the most pronounced selectivity for mercury. The loaded resin was regenerated efficiently using HCl solutions, due to increased competition between Hg and hydronium ions and formation of an HgCl 4 2− ionic complex. © 2000 Society of Chemical Industry

Differentiation of Mercury and Methylmercury by Direct In-situ Derivatization and Supercritical Fluid Extraction

A novel method of in-situ conversion of inorganic mercury to organic mercury combined with the supercritical fluid extraction of the organic mercury by supercritical carbon dioxide is proposed. The removal of inorganic mercury and/or organic mercury from cellulose matrix was accomplished with very good efficiency. An analytical procedure including this or a similar method can be the base-point for the further mercury speciation in solid samples.

Removal of inorganic mercury from water by bituminous coal

Sorption of inorganic mercury in water onto bituminous coal and activated carbon was investigated in the laboratory. Some coal samples were observed to be comparable to activated carbon in mercury sorption. Chemical pretreatment of coal, e.g. nitric acid oxidation, sulfonation, and sulfurisation further improved the sorption capacity. Column studies indicated the feasibility of using coal for removing mercury from water supplies or industrial wastewater.