Identification of metal binding motifs in protein frameworks to develop novel remediation strategies for Hg2+ and Cr(VI).

Amino acid sequences in metal-binding proteins with chelating properties offer exciting applications in biotechnology and medical research. To enhance their application in bioremediation studies, we explicitly aimed to identify specific metal-binding chelating motifs in protein structures for two significant pollutants, such as mercury (Hg2+) and chromium Cr(V1). For this purpose, we have performed an extensive coordination chemistry approach by retrieving Hg2+ and Cr(V1) binding protein structures from the protein database and validated using the B-factor, a term defining uncertainty of the atoms and with occupancy to obtain the best binding motifs. Our analysis revealed that acidic amino acids like aspartic acid, glutamic acid, and basic amino acids such as cysteine and histidine are predominant in coordinating with these metals. The order of preference in Hg2+-bound structures is predicted to be Cys > His > Asp > Glu, and for Cr(V1) is His > Asp > Glu. Examination of the atomic coordinates and their distance from each metal revealed that the sulfur atoms of cysteine showing more preference towards Hg2+coordination with an atomic distance ranging from 1.5 to 2.9 Å. Likewise, oxygen atoms of aspartic acid, glutamic acid and nitrogen atoms of histidine are within 2 Å of Cr(V1) coordination. Based on these observations, we obtained C-C-C, C-X(2)-C-C-(X)2-C, H-C-H motifs for Hg2+, and D-X(1)-D, H-X(3)-E motif for Cr(V1) to be shared within the coordination space of 3 Å. As a future scope, we propose that the identified metal-binding chelating motifs are oligopeptides and can display on the surface of microorganisms such as Escherichia coli and Saccharomyces cerevisiae for effective removal of natural Hg2+ and Cr(V1) through biosorption. Hence, our results will provide the basis for futuristic bioremediation.

Removal of Mercury Ions from Aqueous Solutions by Crosslinked Chitosan-based Adsorbents: A Mini Review.

Abatement of mercury emissions in air and waters has become a global challenge due to the toxicity of mercury species for life, yet actual remediation techniques are limited. In particular, adsorption of mercury ions onto solids is widely used but most adsorption techniques are not specific, and in turn, removal efficiency is lower. Adsorbents developed so far include activated carbon, clay, bentonite, cellulose and chitosan. Chitosan derivatives have recently attracted research attention for water purification because their molecular frames contain a large amount of -NH2 and -OH groups that can chelate with metal ions specifically. This manuscript reviews recent advances in chitosan-based adsorbents designed to remove mercury ions from wastewater. Focus is placed on their design, synthesis, characterization, adsorption properties, adsorption mechanisms and applications.

A New Molecular Probe for Colorimetric and Fluorometric Detection and Removal of Hg2+ and its Application as Agarose Film-Based Sensor for On-Site Monitoring.

A new molecule incorporating two units of 7-nitro-benzoxadiazole (NBD), bridged by m-xylylenediamine, was synthesized and characterized on the basis of analytical and spectroscopic techniques. The metal ion sensing property of this molecule was studied spectroscopically with a large number of metal ions. This study revealed that it can perform as a dual-channel probe for colorimetric as well as fluorometric detection of Hg2+. In presence of Hg2+, a substantial change in UV-Vis spectrum with the appearance of a new band at 545 nm and a distinct colour change from yellow to red was observed. In the fluorescence spectrum, the intensity of the emission band was substantially quenched only upon addition of Hg2+. No significant interference from any other metal ion used in this study was noted, the limit of detection (LOD) for Hg2+ was found to be 60 and 10 nM for colorimetric and fluorometric detection method, respectively. This new chemosensor was used for removal of Hg2+ from aqueous solution with 92% efficiency. For on-site monitoring and field application, this molecule was immobilized into the agarose based hydrogel film, which was used successfully for detection of Hg2+ in water. The study on reversible behaviour of this chemosensor revealed that it can be recycled in solution as well as in solid phase by treatment with Na2S.

Oxidative stress, metabolic and histopathological alterations in mussels exposed to remediated seawater by GO-PEI after contamination with mercury.

The modern technology brought new engineering materials (e.g. nanostructured materials) with advantageous characteristics such as a high capacity to decontaminate water from pollutants (for example metal(loid)s). Among those innovative materials the synthesis of nanostructured materials (NSMs) based on graphene as graphene oxide (GO) functionalized with polyethyleneimine (GO-PEI) had a great success due to their metal removal capacity from water. However, research dedicated to environmental risks related to the application of these materials is still non-existent. To evaluate the impacts of such potential stressors, benthic species can be a good model as they are affected by several environmental constraints. Particularly, the mussel Mytilus galloprovincialis has been identified by several authors as a bioindicator that responds quickly to environmental disturbances, with a wide spatial distribution and economic relevance. Thus, the present study aimed to evaluate the impacts caused in M. galloprovincialis by seawater previously contaminated by Hg and decontaminated using GO-PEI. For this, histopathological and biochemical alterations were examined. This study demonstrated that mussels exposed to the contaminant (Hg), the decontaminant (GO-PEI) and the combination of both (Hg + GO-PEI) presented an increment of histopathological, oxidative stress and metabolic alterations if compared to organisms under remediated seawater and control conditions The present findings highlight the possibility to remediate seawater with nanoparticles for environmental safety purposes.

Real-Time Detection of Markers in Blood.

The real-time selective detection of disease-related markers in blood using biosensors has great potential for use in the early diagnosis of diseases and infections. However, this potential has not been realized thus far due to difficulties in interfacing the sensor with blood and achieving transparent circuits that are essential for detecting of target markers (e.g., protein, ions, etc.) in a complex blood environment. Herein, we demonstrate the real-time detection of a specific protein and ion in blood without a skin incision. Complementary metal-oxide-semiconductor technology was used to fabricate silicon micropillar array (SiMPA) electrodes with a height greater than 600 µm, and the surface of the SiMPA electrodes was functionalized with a self-assembling artificial peptide (SAP) as a receptor for target markers in blood, i.e., cholera toxin (CTX) and mercury(II) ions (Hg). The detection of CTX was investigated in both in vitro (phosphate-buffered saline and human blood serum, HBO model) and in vivo (mouse model) modes via impedance analysis. In the in vivo mode, the SiMPA pierces the skin, comes into contact with the blood system, and creates comprehensive circuits that include all the elements such as electrodes, blood, and receptors. The SiMPA achieves electrically transparent circuits and, thus, can selectively detect CTX in the blood in real time with a high sensitivity of 50 pM and 5 nM in the in vitro and in vivo modes, respectively. Mercury(II) ions can also be detected in both the in vitro and the in vivo modes by changing the SAP. The results illustrate that a robust sensor that can detect a variety of molecular species in the blood system in real time that will be helpful for the early diagnosis of disease and infections.

Studying absorbance properties and mercury remediation capabilities of gold-graphene oxide-iron oxide (Au-GO-Fe3O4) nanoparticle systems.

Mercury pollution is a rampant problem in many economically significant Philippine freshwater ecosystems. Communities dependent on these freshwater sources are therefore at risk for exposure to harmful levels of mercury. Various formulations of a novel gold-graphene oxide-iron oxide (Au-GO-Fe3O4) hybrid nanoparticle system were created and subjected to UV-Vis spectroscopy to determine optimal formulations that would best serve as potential substrates for Surface-Enhanced Raman Spectroscopy (SERS) detection of mercury. Optimal formulations of Au-GO-Fe3O4 were also introduced into mercury-polluted environments to evaluate its ability to remove mercury from both water and biological tissues. Spectroscopic analysis revealed that Fe3O4-rich formulations of Au-GO-Fe3O4 had the greatest potential to boost Raman signal intensities of mercury due to red shifting of absorbance peaks and overall increased absorbance across visible wavelengths resulting in the inclusion of greater areas underneath absorbance peaks. Mercury remediation experiments likewise demonstrated Au-GO-Fe3O4 to significantly reduce average concentrations of mercury from 1.67 to 0.82 ppm in polluted water samples - corresponding to a mercury removal efficiency of 50.9% and a mercury adsorption capacity of 5.89 mg/g. The results highlight the viability of Au-GO-Fe3O4 to function as both substrate for SERS detection of mercury and as effective adsorbent for mercury remediation.

Supramolecular Assembly-Induced Emission Enhancement for Efficient Mercury(II) Detection and Removal.

New strategies that can simultaneously detect and remove highly toxic environmental pollutants such as heavy metal ions are still in urgent need. Herein, through supramolecular host-guest interactions, a fluorescent supramolecular polymer has been facilely constructed from a newly designed [2]biphenyl-extended pillar[6]arene equipped with two thymine sites as arms (H) and a tetraphenylethylene (TPE)-bridged bis(quaternary ammonium) guest (G) with aggregation-induced emission (AIE) property. Interestingly, supramolecular assembly-induced emission enhancement (SAIEE) could be switched on upon addition of Hg2+ into the above-mentioned supramolecular polymer system to generate spherical-like supramolecular nanoparticles, due to the restriction of intramolecular rotation (RIR)-related AIE feature of G. Significantly, this supramolecular polymer with integrated modalities has been successfully used for real-time detection and removal of toxic heavy metal Hg2+ ions from water with quick response, high selectivity, and rapid adsorption rates, which could be efficiently regenerated and recycled without any loss via a simple treatment with Na2S. The newly developed supramolecular polymer system combines the inherent rigid and spacious cavity of novel extended-pillarene host with the AIE characteristics of TPE-based guest, suggesting a great potential in the treatment of heavy metal pollution and environmental sustainability.

An Anthracene Excimer Fluorescence Probe on Mesoporous Silica for Dual Functions of Detection and Adsorption of Mercury (II) and Copper (II) with Biological In Vivo Applications.

Dual functional activity by the same organic-inorganic hybrid material toward selective metal ion detection and its adsorption has drawn more attraction in the field of sensing. However, most of the hybrid materials in the literature are either for sensing studies or adsorption studies. In this manuscript, a fluorescent active hybrid material SiO2 @PBATPA is synthesized by covalent coupling of anthracene-based chelating ligand N,N'-(propane-1,3-diyl) bis(N-(anthracen-9-ylmethyl)-2-((3-(triethoxysilyl)propyl) amino) acetamide) (PBATPA) within the mesopores of newly synthesized cubic mesoporous silica. The synthetic strategy is designed to form an exclusively intramolecular excimer on a solid surface, which is then used as a sensory tool for selective detection of metal ions through fluorescence quenching by the destruction of excimer upon metal ion binding. The dual functions of sensing and adsorption studies show selectivity toward Hg2+ and Cu2+ among various metal ions with detection limits of 37 and 6 ppb, respectively, and adsorption capacities of 482 and 246 mg g-1 , respectively. This material can be used as a sensory cum adsorbent material in real food samples and living organisms such as the brine shrimp Artemia salina without any toxic effects from the material.

Criminal mercury vapor poisoning using heated tobacco product.

We report an unusual case of mercury vapor poisoning from using a heated tobacco product. The suspect had added grains of mercury into 20 cigarettes in a pack. When a 36-year-old Japanese man inserted one of these cigarettes into the battery powered holder, it was heated to a temperature of 350 °C, and he inhaled vaporized mercury. After using 14 of the cigarettes over 16 h, he noticed he had flu-like symptoms so he visited the hospital. Although no physical abnormalities were revealed, 99 µg/L of mercury was detected in his serum sample. His general condition improved gradually and his whole blood mercury level had decreased to 38 µg/L 5 days later. When the remaining six cigarettes in the pack were examined, many metallic grains weighing a total of 1.57 g were observed. Energy dispersive X-ray fluorescence spectrometry confirmed the grains as elemental mercury. Accordingly, the victim was diagnosed with mercury poisoning. Because the mercury was incorporated into cigarettes, an unusual and novel intoxication occurred through the heating of the tobacco product. Both medical and forensic scientific examination confirmed this event as attempted murder.

Affinity Directed Surface Functionalization of Two Different Metal Nanoparticles by a Natural Ionophore: Probing and Removal of Hg2+ and Al3+ Ions from Aqueous Solutions.

In this work, we report affinity controlled surface modifications of two different metal nanoparticles (MNPs) using a hydrophilic natural ionophore (microbial chelator) aeruginic acid (abbreviated as H2L) that possesses two different types of binding pockets viz. O/O from carboxylic acid group and N/O from a phenol-thiazole moiety. Preferred binding of the former donor set (i.e., O/O) on to the surface of silver nanoparticles (AgNPs) has resulted in a colorimetric nanomaterial HL@AgNPs, which showed naked eye observable easy detection of Hg2+ in aqueous HEPES buffer at pH 7.4, even in the presence of other metal ions. On the other hand, excellent affinity of the phenol-thiazole moiety (i.e., N/O) for iron nanosurfaces (FeNPs) develops a fluorogenic nanomaterial HL@FeNPs. Brilliant emission behavior of this nanomaterial enabled it to be useful for highly selective recognition of Al3+ under identical experimental conditions. Remarkable fluorescence enhancement (122-folds) of HL@FeNPs upon addition of Al3+ remain unchanged even in the presence of other competing metal ions. The nanomaterials HL@AgNPs and HL@FeNPs could even detect the target analytes instantly offering lower detection limits of 2 and 80 nM, respectively. Presence of toxic metal ions as environmental pollutant demands for dual-functional materials capable of performing the task of probing cum removal. Surface functionalizations of the nanomaterials of silver and iron with H2L have also resulted two removal agents that can efficiently and easily extract Hg2+ and Al3+ ions from contaminated water, respectively. We are not aware of any work that highlights the manifold utilization of a microbial chelator (i.e., natural ionophore) in the facile construction of different metal nanoparticles for environmental applications such as detection cum removal of toxic metal ions from aqueous solutions.

Effects of Pseudomonas alkylphenolica KL28 on immobilization of Hg in soil and accumulation of Hg in cultivated plant.

OBJECTIVE: The available content of mercury (Hg) in farmland soil is directly related to the safety of agricultural products. Meanwhile, humans may accumulate high concentrations of Hg through the food chain, resulting in health damage. Regarding the remediation technologies of Hg-contaminated soil, research and development is mainly concentrated on the immobilisation of Hg in soil and efficient extraction by accumulators. Therefore, in this work, the highly Hg-tolerant strain Pseudomonas alkylphenolica KL28 was used to study the removal effect of Hg in a solution, immobilization effect of Hg in soil, and its effect on growth, Hg accumulation and photosynthetic characteristics of Brassica campestris L. RESULTS: KL28 could effectively remove Hg2+ in the solution, with the removal ratio of 96.0% at 24 h. This strain could reduce decreases in shoots' and roots' dry weights by 31% and 16%, respectively, at a Hg concentration of 20 mg/L. The available Hg in the soil decreased to 4.7-9.4% in 8 days treated with KL28 bacterial solution at a dosage of 100 L/hm2. Meanwhile, with increases in Hg concentrations, Fv/Fm, Y(II), Y(I) and Y(NPQ) in the leaves of B. campestris showed a downward trend while Y(ND) and Y(NO) displayed an upward trend. Under the stress of 20 mg/L Hg2+, KL28 could reduce the Fv/Fm from 11.2 to 6.1%. CONCLUSIONS: KL28 could effectively remove Hg in the solution, immobilize Hg in soil, promote growth, decrease Hg accumulation and affect photosynthetic characteristics of B. campestris, indicating its potential use in Hg contaminated soils.

Green Hydrothermal Synthesis of N-doped Carbon Dots from Biomass Highland Barley for the Detection of Hg2.

Totally water-soluble N-doped Carbon dots (N-CDs) were synthesized by a green hydrothermal method from biomass using Highland barley as a carbon source and ethanediamine as nitrogen source. TEM and XRD showed the graphitic amorphous structure and narrow diameter distribution of these N-CDs. N-doping to the crystal lattice and carrying many hydrophilic groups on the surface of N-CDs were verified by XPS and FT-IR. The as-synthesized N-CDs emitted strong blue fluorescence at 480 nm and owned a relatively high quantum yield of 14.4%. The product also could sensitively and selectively detect Hg2+ ions in the range of 10-160 µM and the limit of detection was equal to 0.48 µM.

Mercury removal from municipal secondary effluent with hydrous ferric oxide reactive filtration.

This study evaluated the ability of hydrous ferric oxide reactive filtration (HFO-RF) to remove mercury (Hg) from municipal secondary effluent at four study sites. Pilot HFO-RF systems (136 m3 /day) at two sites demonstrated total Hg concentration removal efficiencies of 96% (inflow/outflow mean total Hg: 43.6/1.6  ng/L) and 80% (4.2/0.8 ng/L). A lightly loaded medium-scale HFO-RF system (950 m3 /day) had a concentration removal efficiency of 53% (0.98/0.46 ng/L) and removed 0.52 mg/day of total Hg and 2.2 µg/day of methyl-Hg. A full-scale HFO-RF system (11,400 m3 /day) yielded a total Hg concentration removal efficiency of 97% (87/2.7 ng/L) and removed an estimated 0.36 kg/year of Hg. Results suggest that the quality of secondary effluent, including dissolved organic matter content, affects achievable minimum total Hg concentrations in effluent from HFO-RF systems. Low HFO-RF effluent concentrations (<1 ng/L) can be expected when treating secondary effluent from suspended-growth biological treatment systems. PRACTITIONER POINTS: Trace levels of mercury in municipal secondary effluent can negatively impact receiving waters. Hydrous ferric oxide reactive filtration (HFO-RF) can remove mercury from municipal secondary effluent to levels below the Great Lakes Initiative discharge standard of 1.3 ng/L. Mercury removal to low concentrations (< 1 ng/L) using HFO-RF appears to be associated with secondary effluents with low dissolved organic matter content. HFO-RF can also remove total phosphorus and turbidity to low concentrations.

Synthetic sodalite doped with silver nanoparticles: Characterization and mercury (II) removal from aqueous solutions.

In this work, a novel silver nanoparticles-doped synthetic sodalitic composite was synthesized and characterized using advanced characterization methods, namely TEM-EDS, XRD, SEM, XRF, BET, zeta potential, and particle size analysis. The synthesized nanocomposite was used for the removal of Hg2+ from 10 ppm aqueous solutions of initial pH equal to 2. The results showed that the sodalitic nanocomposites removed up to 98.65% of Hg2+, which is ∼16% and 70% higher than the removal achieved by sodalite and parent coal fly ash, respectively. The findings revealed that the Hg2+ removal mechanism is a multifaceted mechanism that predominantly involves adsorption, precipitation and Hg-Ag amalgamation. The study of the anions effect (Cl-, NO3-, C2H3O2-, and SO42-) indicated that the Hg2+ uptake is comparatively higher when Cl- anions co-exist with Hg2+ in the solution.

Application of Iron-Based Materials for Remediation of Mercury in Water and Soil.

Mercury contamination in soil and water has become a major concern to environmental quality and human health. Among the existing remediation technologies for mercury pollution control, sorption via iron-based materials has received wide attention as they are environmental friendly and economic, and their reactivity is high and controllable through modulating the morphology and surface properties of particulate materials. This paper aimed to provide a comprehensive overview on environmental application of a variety of iron-based sorbents, namely, zero valent iron, iron oxides, and iron sulfides, for mercury remediation. Techniques to improve the stability of these materials while enhancing mercury sequestration, such as nano-scale size control, surface functionalization, and mechanical support, were summarized. Mechanisms and factors affecting the interaction between mercury and iron-based materials were also discussed. Current knowledge gaps and future research needs are identified to facilitate a better understanding of molecular-level reaction mechanisms between iron-based materials and mercury and the long-term stability of the immobilized mercury.

Visible-Light-Driven Janus Microvehicles in Biological Media.

A light-driven multifunctional Janus micromotor for the removal of bacterial endotoxins and heavy metals is described. The micromotor was assembled by using the biocompatible polymer polycaprolactone for the encapsulation of CdTe or CdSe@ZnS quantum dots (QDs) as photoactive materials and an asymmetric Fe3 O4 patch for propulsion. The micromotors can be activated with visible light (470-490 nm) to propel in peroxide or glucose media by a diffusiophoretic mechanism. Efficient propulsion was observed for the first time in complex samples such as human blood serum. These properties were exploited for efficient endotoxin removal using lipopolysaccharides from Escherichia coli O111:B4 as a model toxin. The micromotors were also used for mercury removal by cationic exchange with the CdSe@ZnS core-shell QDs. Cytotoxicity assays in HeLa cell lines demonstrated the high biocompatibility of the micromotors for future detoxification applications.

Removal of mercury from contaminated saline wasters using dithiocarbamate functionalized-magnetic nanocomposite.

In this study, an efficient adsorbent was proposed for the removal of mercury from saline water contaminated with mercury ions. Fe3O4 nanoparticles were modified using tetraethylenepentamine and carbon disulfide to incorporate dithiocarbamate functional group on the surface of the adsorbent. CHNS analysis confirmed successful modification of magnetic nanoparticles. The XRD pattern of adsorbent indicated a proper match with the standard XRD pattern of cubic Fe3O4. The saturation magnetization of final adsorbent was 27 emu g-1. The morphology of bare and silica-coated Fe3O4 and final product were investigated using FE-SEM analysis. For optimizing the adsorption process, response surface methodology was applied, which was resulted in a significant quadratic model. The effect of adsorbent dosage and initial concentration of Hg (II) was much more significant than that of pH. Different concentrations of dissolved solids up to 2000 mg L-1 had no adverse effect on the adsorption process due to the strong interaction between dithiocarbamate functional group of adsorbent and Hg (II). The least values of RMSE (0.0950) and χ2 (0.0009) were observed for Radke-Prausnitz, Redlich-Peterson, and UT isotherms. Maximum adsorption capacities calculated using Langmuir and UT models were 109.5 and 95.07 mg g-1, respectively. The investigation of adsorption isotherm was conducted at the pH range of 2.0-6.5. The results showed an increase in the adsorption capacity by increasing pH. Thermodynamic studies demonstrated that the nature of the adsorption process was spontaneous and endothermic. Recovery of adsorbent was successfully carried out using HCl 0.5 mol L-1. The prepared adsorbent was successfully applied for mercury removal from a real groundwater.

Polyamide magnetic palygorskite for the simultaneous removal of Hg(II) and methyl mercury; with factorial design analysis.

A novel efficient adsorbent was prepared by the modification of magnetic palygorskite (MPG) by polyamide via the interfacial polymerization of trimesoyl chloride with m-phenylenediamine. The prepared magnetic palygorskite modified with polyamide (MPGP) material was appraised for its removal of the Hg(II) and CH3Hg species from aqueous solutions. The developed adsorbent was characterized using spectroscopic techniques. The adsorption ability of the MPGP sorbent was systematically investigated by using the batch method. Factorial design analysis was applied to study the effect of different batch parameters on the adsorption yield of both mercury species. These factors include mercury concentration, initial pH, sorbent amount and contact time. The equilibrium data coincided with the Langmuir adsorption isotherm indicating the maximum adsorption capacity of the MPGP was determined as 211.93 mg/g for Hg(II) and 159.73 mg/g for CH3Hg. The kinetic mechanism of the adsorption of both mercury species was well defined by the pseudo-second-order while the adsorption processes demonstrated spontaneity and an exothermic character at the studied temperatures. The cycling adsorption/desorption tests made by using a 1 mol/L HCl solution demonstrated that the MPGP had good reusable performance up to seven cycles. Based on the results it can be suggested that the synthesized MPGP sorbent can be handled for the elimination of Hg(II) and CH3Hg from wastewater effluents.

Synthetic coal fly ash-derived zeolites doped with silver nanoparticles for mercury (II) removal from water.

Coal fly ash-derived zeolites have attracted considerable interest in the last decade due to their use in several environmental applications such as the removal of dyes and heavy metals from aqueous solutions. In this work, coal fly ash-derived zeolites and silver nanoparticles-impregnated zeolites (nanocomposites) were synthesized and characterized by TEM/EDX, SEM/EDX, XRD, XRF, porosimetry (BET), particle size analysis (PSA) and zeta potential measurements. The synthesized materials were used for the removal of Hg2+ from aqueous solutions. The results demonstrated that nanocomposites can remove 99% of Hg2+, up to 10% and 90% higher than the removal achieved by the zeolite and the parent fly ash, respectively. Leaching studies further demonstrated the superiority of the nanocomposite over the parent materials. The Hg2+ removal mechanism is complex, involving adsorption, surface precipitation and amalgamation.

Efficient mercury removal from wastewater by pistachio wood wastes-derived activated carbon prepared by chemical activation using a novel activating agent.

Ammonium nitrate (NH4NO3) with explosive characteristics at high temperatures was used as a novel activating reagent to prepare a surface-engineered activated carbon derived from pistachio wood wastes (PWAC). PWAC was characterized and compared with commercial activated carbon (CAC) by textural and morphological properties, surface chemistry, crystal structure, and surface elemental composition. The results indicated that the optimal conditions of PWAC preparation to obtain the highest mercury adsorption capacity were pyrolysis temperature (800 °C), pyrolysis time (2 h), and impregnation ratio (5%). PWAC was of highly regular-shaped and well-developed pores and possessed a large surface area (1448 m2/g) and high total pore volume (0.901 cm3/g). The batch experiments indicated that the adsorption process of Hg(II) was strongly dependent on the solution pH and reached fast equilibrium at approximately 30 min. PWAC (202 mg/g) exhibited a significantly higher maximum adsorption capacity than commercial activated carbon (66.5 mg/g). Adsorbent-adsorbate dispersion interaction plays a major role in the adsorption mechanism, compared to the minor role played by pore filling and reduction mechanism. Overall, ammonium nitrate can be considered a newer activating reagent to prepare promising and low-cost PWAC for effectively Hg(II) removal from water media.