Hg Adsorption Capacity Research Articles

Metal oxide nanoparticle-modified graphene oxide for removal of elemental mercury

ABSTRACTMercury is an extremely toxic element that is primarily released by anthropogenic activities and natural sources. Controlling Hg emissions, especially from coal combustion flue gas, is of practical importance in protecting the environment and preventing human health risks. In the present work, three metal oxides (MnO2, CuO, and ZnO) were loaded on graphene oxide (GO) sorbents (designated as MnO2-GO, CuO-GO, and ZnO-GO). All three adsorbents were successfully synthesized and were well characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The results indicated that the metal oxide nanoparticles (NPs) successfully decorated the GO. The elemental Hg adsorption capabilities of the three sorbents were subsequently evaluated using an in-house built setup for cold vapour atomic fluorescence spectrophotometry (CVAFS) with argon as the carrier gas for mercury detection. The testing temperature ranged from 50°C to 200°C at intervals of 50°C. MnO2-GO showed an excel lent Hg0 adsorption capacity via chemisorption from 50 to 150°C and a mercury removal efficiency as high as 85% at 200°C, indicating that the MnO2-NP-modified GO is applicable for enhancing gas-phase elemental mercury removal. However, neither CuO-GO nor ZnO-GO performed well. This work provides useful insights into the development of novel sorbent materials for the elemental mercury removal from flue gases.

Study on the Effects of the Pyrolysis Atmosphere on the Elemental Mercury Adsorption Characteristics and Mechanism of Biomass Char

Biochars prepared in three pyrolysis atmospheres of N2, O2, and CO2 were investigated. The pyrolysis characteristics, pore structures, and functional groups of the biochars were characterized by thermogravimetric analysis (TGA), specific surface area and porosity analyses, and Fourier transform infrared (FTIR) spectroscopy. The adsorption mechanism was further explored by the temperature-programmed desorption (TPD) technique in combination with the adsorption kinetics. The results showed that the Hg0 adsorption capacities of the biochars produced in an O2 pyrolysis atmosphere were worse than those of the biochars obtained in a N2 atmosphere, whereas CO2 significantly promoted the adsorption capacity. The biochar prepared in 20% CO2 had the highest adsorption capacity. Three pyrolysis reaction pathways were possible in the O2 atmosphere. In addition, a critical concentration existed between O2 concentrations of 5 and 7%. Above 750 °C, CO2 could react directly with the biochar through the Boudouard reaction...

Selective removal of mercury(II) from water using a 2,2-dithiodisalicylic acid-functionalized graphene oxide nanocomposite: Kinetic, thermodynamic, and reusability studies

2,2-Dithiodisalicylic acid-functionalized magnetic graphene oxide (Fe3O4@DTSA_GO) was used for the selective removal of Hg(II) from aqueous solution. The equilibrium was reached after 10 min and the maximum Hg(II) adsorption capacity of the Fe3O4@DTSA_GO nanocomposite was 283.5 mg g−1. The Hg(II) adsorption ability increased with the pH value of the aqueous solution. Isotherm and kinetic studies revealed the Sips isotherm model and pseudo-second kinetic model to provide the best fit to the experimental results. The positive value of ΔH° indicated endothermic interactions between Hg(II) and Fe3O4@DTSA_GO, while the negative ΔG° revealed a spontaneous reaction and the positive ΔS° an increase of the randomness at the solid–solute interface during the adsorption process. The selective removal of Hg(II) by the nanocomposite confirmed the presence of higher-affinity binding sites for Hg(II) than for Cd(II), Co(II), Zn(II), and Ni(II) ions. Furthermore, the Fe3O4@DTSA_GO nanocomposite exhibited excellent preferential adsorption for Hg(II) spiked in drinking water samples. EDTA 0.01 N was found to be an efficient elution agent for nanocomposite regeneration, with which over 84% of the adsorbed Hg(II) was recovered after five adsorption/desorption cycles.

Increasing the chlorine active sites in the micropores of biochar for improved mercury adsorption

A series of biochars were prepared from rice(RI), tobacco(TO), corn(CO), wheat(WH), millet(MI), and black bean straw(BB). These biochars were used to study the mechanism of elemental mercury(Hg0) adsorption by hydrochloric acid modified biochars. The biochars were modified by 1 M hydrochloric acid (HCl) and then used in a fixed-bed Hg0 adsorption experiment. As would be expected, the results indicated that HCl modification increased the Hg0 adsorption performance of the six biochars. After modification, the Hg0 adsorption efficiency of tobacco biochar increased from 8.2% to 100.0%, and the average Hg0 adsorption capacity of the biochars increased by 61 times. The acid modification dissolved the metal compounds in the biochar, reducing the metal content and increasing the average surface area of the biochar. The average surface area of the raw biochars increased from 29.9 to 110.1 m2/g after HCl modification. The extra surface area was mostly created in the micropores, leading to a significant increase in the amount of micropores. These micropores effectively adsorbed the Cl atoms, which acted as active sites for Hg0. In the adsorption process, Hg0 diffused into the interior of modified biochars via mesopores, and finally the adsorbed Cl in the micropores reacted with Hg0 to form HgCl2.

Modified silica gel surface with chelating ligand for effective mercury ions adsorption

The electron-donating group dithiocarbamate functionalized silica gel (SG-PDC) was prepared and used for adsorption of metal ions from aqueous solution. The modified silica gel was characterized by fourier transform infrared spectroscopy (FT-IR), elemental analysis (EA) and scanning electron microscopy (SEM). It showed excellent adsorption selectivity for Hg(II) ions over other metal ions, such as Cu(II), Cd(II), Pb(II). Kinetics and equilibrium isotherms of Hg (II) sorption were determined in batch equilibrium experiments. The adsorption capacity for Hg (II) of SG-PDC was more than five times as much as that of unmodified silica gel. X-ray photoelectron spectroscopy (XPS) was applied to study the adsorption mechanism and it confirmed that the improvement in mercury adsorption was related to the ligand groups containing S and N atoms anchored on the surface of silica gel. The adsorbent had high reusability after several adsorption–desorption cycles. This study provided a feasible strategy to develop the effective sorbent for Hg (II) ions by covalently modification of silica gel with ligand containing multiple coordination sites.

Promotional effect of CuO loading on the catalytic activity and SO2 resistance of MnOx/TiO2 catalyst for simultaneous NO reduction and Hg0 oxidation

CuO loaded MnOx/TiO2 mixed oxide (CuMnTi) synthesized by an ultrasonic-assisted impregnation method was for the first time employed for simultaneous nitrogen monoxide (NO) reduction and elemental mercury (Hg0) oxidation under selective catalytic reduction (SCR) atmosphere with the presence of NH3. The CuMnTi catalyst exhibited a wide temperature window from 150 to 250 °C for both NO reduction and Hg0 oxidation. At the optimal temperature of 175 °C, CuMnTi reduced 96.4% of the inlet NO and oxidized 100% of the inlet Hg0 at a very high gas hourly space velocity (GHSV) of 40,000 h−1. O2, HCl and NO significantly promoted Hg0 oxidation and offset the adverse effect of detrimental flue gas components such as water vapor, SO2 and NH3. The protection effect of CuO over MnOx reserved enough active sites of CuMnTi for Hg0 oxidation in the presence of NH3 or SO2. Compared with MnOx/TiO2 (MnTi), the superior redox property, enlarged Hg0 adsorption capacity and decent SO2 resistance of CuMnTi ternary system were evidenced to account for its improved catalytic activity. This study indicated future potential for applying CuMnTi catalyst in simultaneous NO reduction and Hg0 oxidation in low-temperature (150–250 °C) and low-rank (sub-bituminous and lignite) coal combustion flue gases.

Decontamination of Hg(II) from aqueous solution using polyamine-co-thiourea inarched chitosan gel derivatives

Ethylenediamine (EDA), triethylenetetramine (TETA) and tetraethylenepentamine (TEPA) had been successfully introduced into the structure of thiourea (TC) modified chitosan (CS) by using formaldehyde as linkage, respectively. The resulted materials, TC-CS, TC-EDA-CS, TC-TETA-CS, and TC-TEPA-CS were characterized and employed as adsorbents in batch experiment for the Hg(II) removal. We have found the modification enhanced the Hg(II) adsorption significantly in comparison with raw CS. Hg(II) adsorption amounts for all adsorbents increased gradually and reached maxima at pH≥4.0. The adsorption of Hg(II) achieved an equilibrium state within 12h with the process drove by the pseudo-second-order model. The ionic strength had no remarkable inhibition effect on Hg(II) adsorption. While the Hg(II) adsorption capacities of the adsorbents were strongly related with the modifier types and the length of the incorporating amino ligands. Langmuir model described Hg(II) adsorption well with the maximum adsorption capacities of prepared adsorbents in order of TC-EDA-CS (217.1mg/g)>TC-CS (164.8mg/g)>TC-TETA-CS (149.7mg/g)>TC-TEPA-CS (140.6mg/g) at room temperature. The FT-IR and XPS investigations implied that Hg(II) ion adsorption mechanism was characterized by a complexation reaction process. Adsorbents could be readily regenerated and had great reusability potential in Hg(II) ions capture from aqueous solution.

Highly selective adsorption of Hg(II) by the monodisperse magnetic functional chitosan nano-biosorbent

Aminothiourea functionalized magnetic chitosan nano-biosorbent (AT-MCS), a new kind of bio-adsorbent, has been first synthesized by covalently linking the chitosan and NH2-Fe3O4 with glutaraldehyde and functionalized with aminothiourea group. The resulting bio-absorbent was characterized by means of the Fourier transform infrared spectra (FT-IR), transmission electron microscope (TEM), X-ray diffraction (XRD), elemental analysis, and vibrating sample magnetometer (VSM). With the excellent mono-dispersive ability in aqueous phase, the obtained bio-sorbent showed not only the good adsorption capacity for Hg(II) on high initial concentration, but also the strong removal ability on low concentration. The maximum adsorption amount was up to 246 mg g−1, and the removal percentage reached 98.7% at initial concentration of 10 mg L−1. Moreover, the nano-biosorbent has a unique selectivity for Hg(II) among the mixed metal ions solution and exhibits good regeneration performance.

Preparation of chitosan/amine modified diatomite composites and adsorption properties of Hg(II) ions.

A green functional adsorbent (CAD) was prepared by Schiff base reaction of chitosan and amino-modified diatomite. The morphology, structure and adsorption properties of the CAD were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy and Brunauer Emmett Teller measurements. The effect of pH value, contact time and temperature on the adsorption of Hg(II) ions for the CAD is discussed in detail. The experimental results showed that the CAD had a large specific surface area and multifunctional groups such as amino, hydroxyl and Schiff base. The optimum adsorption effect was obtained when the pH value, temperature and contact time were 4, 25 °C and 120 min, respectively, and the corresponding maximum adsorption capacity of Hg(II) ions reached 102 mg/g. Moreover, the adsorption behavior of Hg(II) ions for the CAD followed the pseudo-second-order kinetic model and Langmuir model. The negative ΔG0 and ΔH0 suggested that the adsorption was a spontaneous exothermic process.

Combined effects of Ag and UiO-66 for removal of elemental mercury from flue gas

The zirconium metal-organic framework material UiO-66 was doped with Ag nanoparticles and investigated for the removal of elemental mercury (Hg0) in flue gas. Physical and chemical characterization of the adsorbents showed that adding Ag did not change the crystal structure and morphology of the UiO-66. Ag doping can improve the redox activity of UiO-66, and the adsorbent exhibited high thermal stability and surface area. Hg0 removal experiments indicated that UiO-66 exhibited the higher performance compared with P25 and activated carbon, and the addition of Ag exhibited a significant synergistic effect with the UiO-66, which had highest Hg0 adsorption capacity (3.7 mg/g) at 50 °C. Furthermore, the Hg0 removal mechanism was investigated, revealing that Hg0 is removed by the formation of an Ag amalgam and channel adsorption at low temperature, and through Ag-activated oxygen oxidation and channel capture at high temperature.

Enhanced Hg(II) Adsorption by Monocarboxylic-Acid-Modified Microalgae Residuals in Simulated and Practical Industrial Wastewater

In this study, three kinds of monocarboxylic acids, formic, acetic, and propionic acids, are first applied to modified microalgae residuals (M1-RD, M2-RD, and M3-RD, respectively) after lipid extraction, aiming to enhance the adsorption capacity and selective binding ability for Hg(II) ions in simulated wastewater. The effect of pH, temperature, and initial Hg(II) concentration was investigated to identify the optimum adsorption conditions. Batch adsorption tests showed that the maximum adsorption efficiency obtained was 96.7% for M1-RD, 91.1% for M2-RD, and 84.4% for M3-RD at pH 4.05 compared to 48.5 and 57.6% for raw and residual microalgae at pH 5.01, respectively. The adsorption capacity of raw, residual, and modified microalgae increased with the increase of the temperature. Langmuir and Freundlich isotherm model tests showed that the maximum equilibrium adsorption capacity among three modified adsorbents reached 63 ± 3 mg/g for M1-RD, in contrast to 17 ± 1 and 25 ± 2 mg/g for raw and residual microa...

Adsorption-assisted decontamination of Hg(ii) from aqueous solution by multi-functionalized corncob-derived biochar.

Mercury (Hg) contamination of wastewater streams as a result of anthropogenic activities is a great threat to living organisms due to its acute toxicity. Therefore, current research is focused on the development of effective remediation technologies to protect human health and the environment. In this study, a novel chemical modification route was applied for the multi-functionalization of biochar in order to make it more efficient and selective for Hg(ii) removal from aqueous solution. The amino-grafted modified biochar (AMBC) having multifunctional groups on its surface was successfully synthesized through the activation of excessively available carboxylic groups (–COOH) on pre-oxidized biochar (BC–COOH). The maximum Hg(ii) adsorption capacity for the optimized amino-BC2 sample was 14.1 mg g−1, which was almost twice as that for pristine biochar (BC, 7.1 mg g−1). SEM, FTIR, and XPS techniques were applied for the confirmation of chemically grafted amino groups as well as the presence of residual –COOH groups on the biochar surface. Based on the batch adsorption data, adsorption kinetics and isotherms as well as XPS results, it was concluded that the Hg(ii) removal mechanism was purely driven by chemisorption such as electrostatic interaction, surface complexation, ion exchange with no precipitation and crystalline material being adsorbed on the adsorbent surface. These research findings not only provide a suitable adsorbent for decontamination of Hg(ii) from aqueous solution but also offer a new route for the multi-functionalization of biochar in order to make environment-friendly and inexpensive adsorbents.

Removal of Elemental Mercury from Simulated Flue Gas over Peanut Shells Carbon Loaded with Iodine Ions, Manganese Oxides, and Zirconium Dioxide

A low-cost material with high adsorption and oxidation ability for Hg0 capture is needed, whereas it is hard to prepare by present methods. Here, halide ions (I–) and metal oxides (MnOx and ZrO2) were both loaded on peanut shells carbon to synthesize 6Mn-6Zr/PSC-I3. Various characterizations and experiments were used to investigate the physiochemical properties and Hg0 removal performances. The sample exhibited an abundant pore structure and the active components dispersed well on its surface. The excellent total Hg0 removal efficiency (more than 90%) was obtained in a wide reaction temperature range (150–300 °C) under a N2 + 6% O2 atmosphere. Moreover, the Hg0 adsorption capacity in 1440 min was 5587.0 μg·g–1 and the Hg0 oxidation efficiency after reaching adsorption equilibrium was more than 30%. Further, the reaction mechanism at 150 °C was proposed. The main chemical adsorption sites of carbon-iodine groups dominate Hg0 removal at the initial reaction stage. As reaction progresses, chemical adsorption...

DENSITY FUNCTIONAL STUDY OF ELEMENTAL MERCURY ADSORPTION ON X (X=Mn, Si, Ti, Al, AND Zn)-DOPED CuO (110) SURFACE

Copper oxide (CuO) is proved to be a potential adsorbent for elemental mercury in the flue gas emitted from coal-fired power plant. However, the O-terminated CuO(110) surface has relatively week adsorption capacity for Hg. In this work, the doped method is applied to enhance the mercury adsorption capacity of O-terminated CuO(110). Mn, Si, Ti, Al and Zn are selected as the doped atom. It is found that only Zn-doped CuO (110) surfaces have the higher adsorption energy than the pure O-terminated CuO(110) surface. The mercury adsorption capacity is a complex issue, which depends on a combination of oxygen and doped element. The results suggest that the lower electropositive doped element is favorable for the improvement of mercury adsorption capacity. However, the lower electronegativity of oxygen atoms does not facilitate the mercury capture, which is different from the organic material. Cu and doped metal element, rather than oxygen atom, mainly determine mercury adsorption capacity of O-terminated CuO(110) surface, which leads to the lower adsorption capacity of the O-terminated CuO(110) surface than the Cu-terminated CuO(110) surface. The conclusions can also offer a valuable reference for the other metal oxide regarding mercury capture.

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.

Preparation and characterization of polyphenylene sulfide–based chelating resin–functionalized 2‐amino‐1,3,4‐thiadiazole for selective removal Hg(II) from aqueous solutions

A novel chelating resin (PPS‐ATD) containing N and S elements was prepared through the chloromethylation of polyphenylene sulfide resin and subsequent functionalization with 2‐amino‐1,3,4‐thiadiazole (ATD). The structure of PPS‐ATD was systematically characterized and analyzed by the Fourier transform infrared spectroscopy, elemental analysis, thermogravimetric analysis, scanning electron microscope, and energy dispersive spectrometer. The adsorption performance of PPS‐ATD was evaluated by batch methods at different pH, temperature, adsorption time, and initial concentration, and the results showed that the PPS‐ATD exhibited high adsorption capacity (197.79 mg·g−1 at 298 K) and selectivity for Hg(II). The adsorption of PPS‐ATD for Hg(II) was well fitted by the Langmuir isotherm model, and the adsorption process was endothermic. After 5 consecutive regeneration cycles, no obvious loss in the adsorption capacity of the PPS‐ATD was found, which implied that the PPS‐ATD had great application prospects in the treatment of mercury‐containing wastewater.

Adsorption/reduction of Hg(II) and Pb(II) from aqueous solutions by using bone ash/nZVI composite: effects of aging time, Fe loading quantity and co-existing ions.

In this research, a versatile and highly efficient method for the stabilization of nanoscale zerovalent iron particles (nZVI) on the surface of ostrich bone ash (OBA) was presented as a novel inorganic adsorbent (OBA/nZVI) for the removal of Hg(II) and Pb(II) ions from aqueous solutions, even after 1year of storage under room conditions. The removal behavior of the OBA/nZVI was assessed as a function of the initial pH, contact time, initial pollutants concentration, temperature, amount of adsorbent, effect of competitive metal ions, and ionic strength. The synthesized adsorbent was characterized by several techniques including N2 adsorption at -196°C, FT-IR spectroscopy, scanning electron microscopy, X-ray diffraction, and zeta potential. The results confirmed that the OBA is a good candidate as support of nZVI. The maxima adsorption capacity for Hg(II) and Pb(II) ions found from experimental results were 170 and 160mgg-1, when the loading quantities of Fe were 20%. The equilibrium sorption data obeyed a Langmuir-Freundlich isotherm type model. The kinetic data of the adsorption followed the mechanism of the pseudo-second-order model. The thermodynamic experiments indicated that the removal of metal ions were feasible, endothermic, and spontaneous. It can be found that fresh and aged OBA/nZVI maintained its usability even after five cycles in the order: fresh (OBA/nZVI)-Hg(II) > fresh (OBA/nZVI)-Pb(II) > aged (OBA/nZVI)-Hg(II) > aged (OBA/nZVI)-Pb(II), which indicate that OBA/nZVI can be regenerated as adsorbent. The existence of Fe in the OBA/nZVI was proved by SEM-EDX results and X-ray diffraction analysis also confirmed adsorption/reduction of some of the Hg(II) to Hg0 and Pb(II) to Pb0.

Aqueous Hg(II) immobilization by chitosan stabilized magnetic iron sulfide nanoparticles

Stabilized iron sulfide (FeS) nanoparticles have been proven effective in the adsorption of Hg from the water environment. However, previous work with these nanoparticles determined that the separation from the treated water was difficult and time-consuming. In this study, nanoscale FeS-Fe3O4 nanocomposites were firstly synthesized with chitosan as the stabilizer (CTO-MFeS). Then, the Hg adsorption capacity and mechanism were studied. Results showed that the size of the prepared nanoparticles was about 20nm and the specific surface area was 21.3m2/g. Hg removal by the CTO-MFeS nanoparticles involved both adsorption and precipitation. Further investigation with XPS showed that Hg2+ was adsorbed on the surface of the CTO-MFeS nanoparticles and reacted with CTO-MFeS to form HgS and [Fe(1−x)Hgx]S. It was also found as pH decreased below 4, the adsorption capacity of CTO-MFeS was significantly reduced that might be due to the dissolving of Fe. Additionally, the presence of Cl− resulted in the transformation of Hg2+ to HgClx2-x (x=1, 2, 3, 4) that competed with OH in solution for Hg2+ and therefore inhibited the adsorption of Hg. Our findings provide additional information that may be useful for a theoretical basis for Hg treatment in water environment.

A ligand anchored conjugate adsorbent for effective mercury(II) detection and removal from aqueous media

In this study, a novel mesoporous conjugate adsorbent (MCA) was fabricated by directly anchoring the organic ligand of 2-hydroxyacetophenone-4N-pyrrolidine thiosemicarbazones (HAPT) onto highly ordered mesoporous ZSM-5 for efficient and selective mercury (Hg(II)) ions capturing from aqueous solution. The effect of solution pH, interference of foreign metal ions, contact time, initial Hg(II) ions concentration, and elution-regeneration of the MCA were evaluated in the case of detection and removal operations. The MCA was exhibited an obvious color change from colorless to yellow in the presence of Hg(II) ions at optimum pH conditions. In addition, the Hg(II) ions was detected and removed from water samples with naked-eye observations. The sensitive detection was determined under specific optimum conditions and the lower detection limit was determined by the MCA was 3.69 µg/L of Hg(II) ions. The foreign ions effect was evaluated and the MCA was exhibited high selectivity towards the Hg(II) ions with optimum color formation and the Hg(II) ions can be detected easily on-site Hg(II) ions monitoring. The adsorption efficiency was determined in terms of initial Hg(II) ions concentration. The data well fitted with the Langmuir isotherm model, and the maximum adsorption capacity of Hg(II) ions was 172.61 mg/g by the MCA. Moreover, the adsorption results of the MCA were compared with the other forms of different materials. The effective eluent of 0.10 M thiourea-0.10 M HCl was used to elute the Hg(II) ions from the MCA, and the MCA was simultaneously regenerated into the initial form for next process without significant loss in its initial performance. The data clarified that the MCA is an efficient and eco-friendly for simultaneous detection and removal of Hg(II) ions from wastewater samples.

Use of a non-thermal plasma technique to increase the number of chlorine active sites on biochar for improved mercury removal

Biochar, known as a byproduct of biomass pyrolysis, was prepared from rice straw (R6), tobacco straw (T6), corn straw (C6), wheat straw (W6), millet straw (M6), and black bean straw (B6) in high purity nitrogen at 600°C. Chlorine (Cl) non-thermal plasma was used to increase Cl active sites on biochar to promote the mercury removal efficiency. The physio-chemical properties of biochar were characterized by proximate analysis, ultimate analysis, BET, SEM, TGA, FTIR, and XPS. Modification by chlorine plasma increased the Hg0 removal efficiency of the biochar from around 8.0% to 80.0%. The Hg0 adsorption capacity of T6 was 36 times higher after Cl2 plasma modification. Plasma caused the biochar surface to become porous and promoted the thermal stability of the biochar. Sulfur (S) content remained in the range of 0.5–0.7%, elemental/organic sulfur and sulfide were converted to sulfate during plasma treatment. The relative intensity of the oxygen functional groups (CO, CO and C(O)OC) were enhanced, while the content of oxygen (O) in biochar decreased. The main reason for the improved mercury removal efficiency by modified biochars was attributed to the increased number of CCl groups on the surface of the biochars induced by Cl2 plasma. The CCl groups functioned as activated sites and promoted the Hg0 removal efficiency.