Hg Adsorption Capacity Research Articles

A chelating polymer resin: synthesis, characterization, adsorption and desorption performance for removal of Hg(II) from aqueous solution

A chloromethylated polystyrene-N-methyl thiourea chelating resin (DMTUR) was successfully prepared by the reaction of chloromethylated polystyrene beads (PS-Cl) with N-methyl thiourea (DMTU). The DMTUR exhibited a high selective adsorption toward Hg(II) in the mixture of different metal ions containing Cu(II), Hg(II), Cd(II), Pb(II), Cr(III) and Ni(II), and the adsorption capacity of Hg(II) approached a maximum with a value of 347 mg/g at pH = 4.0. Moreover, the batch kinetic study showed that the adsorption behavior of Hg(II) presented as a pseudo-second-order manner. And the adsorption isotherms fitted well with Langmuir model, and the maximum uptake of Hg(II) could reach to be 476 mg g−1 at 35 °C. The thermodynamics study ensured the adsorption process essentially as favorable and endothermic. Finally, an eluent of 4 M HNO3 solution could completely remove the adsorbed Hg(II) and the adsorption capacity allowed a high level at least five cycles. As aforementioned appealing properties, the DMTUR with simple technology, high adsorption capacity, significant selectivity and good regenerability may have a potential application in industrial scale as a treatment of enriched Hg(II) in wastewater.

Modification of PPTA-based polymeric waste and adsorption properties for metal ions

Novel composite adsorbents PPTA-AOx were synthesized by grafting polyacrylonitrile onto poly(p-phenylene terephthalamide) (PPTA) followed by converting the acrylonitrile into the amidoxime (AO) groups. Their structures were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, elemental analysis, transmission electron microscopy, etc. Scanning electron microscopy analysis and pore structure analysis manifested that PPTA-AOx adsorbents are all composed of nanoparticles aggregation. The as-synthesized PPTA-AOx adsorbents showed good adsorption capacity for Hg2+ with a maximum adsorption capacity of 2.50 mmol g−1. The pseudo-second-order model can reasonably describe the adsorption kinetics of the three adsorbents for Hg2+. Langmuir model provided better fit for the isothermal adsorption of Hg2+ on PPTA-AO1 and PPTA-AO2, while the Freundlich model was better for PPTA-AO3. The adsorption process might involve both chemisorption and physisorption. According to the calculated thermodynamic parameters, it can be concluded that the adsorption is an endothermic, spontaneous and entropy-driven process.

Adsorption of mercury from aqueous solution on synthetic polydopamine nanocomposite based on magnetic nanoparticles using Box–Behnken design

Abstract The aim of this study is to examine the possibility of using synthesized functional polydopamine@Fe3O4 nanocomposite (PDA@Fe3O4) with magnetic response and a special surface area as the most effective adsorbent to remove the mercury (Hg(II)) from aqueous solution in batch process (in batch mode/ in batch phase/ in bach processing/ in a batch process). The structural characterization of this nanocomposite was performed by XRD, TEM, TGA and FTIR analyses. Response surface methodology was used to optimize the Hg(II) adsorption capacity mg/g with three experimental factors using Box–Behnken design (BBD). The optimum conditions included: pH 5.36, Hg(II) initial concentration 98.65 mg/g, contact time 5.17 h. The maximum adsorption capacity of Hg(II) in batch administrations was 307 mg/g.

High-Performance Hg(II) Removal Using Thiol-Functionalized Polypyrrole (PPy/MAA) Composite and Effective Catalytic Activity of Hg(II)-Adsorbed Waste Material

Problems related with highly toxic mercury emissions from industrial effluents are one of the great concerns in the world of environmental science and technology. The primary aim of this present work is the remediation of hazardous pollutant Hg (II) from aqueous medium via a thiol-functionalized (mercaptoacetic acid) conducting polypyrrole (PPy/MAA) composite. The synthesized composite exhibited high Hg(II) adsorption capacity as the incorporated mercapto functionality plays a vital role for the strong binding affinity toward Hg(II) ions. To understand the adsorption properties of the developed polymer composite, a series of batch adsorption experiments were performed by altering the adsorption parameters. A maximum adsorption capacity (qmax) of 1736.8 mg/g at 25 °C was obtained using the Langmuir isotherm. The adsorption data showed better fitting to the pseudo-second-order rate equation for Hg(II) adsorption. A plausible adsorption mechanism is suggested on the basis of XPS results of major elements present in the adsorbent. To apply to catalytic reactions, the use of waste-derived mercury-adsorbed material (termed as PPy-MAA/Hg (II)) is also addressed here for further application of organic transformation. Here, we described the catalytic reaction with phenylacetylene in the presence of 5 mol % PPy-MAA/Hg (II) catalyst at 90 °C for 6 h. This method provides a straightforward formation of acetophenone in 55% yield. Thus, PPy/MAA not only effectively eliminates toxic Hg(II) ions from water but also is successfully applied for the catalytic organic transformation after adsorption.

Removal of mercury ions from aqueous solution by thiourea-functionalized magnetic biosorbent: Preparation and mechanism study

A novel magnetic bio-material (MCIT) was synthesized via coupling reaction and functional modification after load of Fe3O4 nano-particle on the puckered surface of cyclosorus interruptus (CI). The synthesized material was characterized by fourier transform infrared (FTIR), field emission scanning electron microscope (FE-SEM), X-ray photoelectron spectroscopy (XPS) and X-ray powder diffractometer (XRD). The influence factors like pH, temperatures, contact time, initial concentration and cycle times on the adsorption of Hg (II) in aqueous solution were studied. Adsorption isotherm, kinetics, selectivity and mechanism were investigated. The results indicated that the isotherm model well agreed with monolayer adsorption model. The adsorption process could be divided into three steps, which included a fast step controlled by chemical adsorption, a slow step limited by intraparticle diffusion and an equilibrium stage. The maximum adsorption capacity of Hg (II) was 385.3mg/g at 318K. MCIT possessed high reusability (retained 93% after five successive cycles) and sharply magnetic nature (9.5emu/g), which endowed it easy and efficient separation from aqueous solution.

Novel Fe-Ce-O mixed metal oxides catalyst prepared by hydrothermal method for Hg0 oxidation in the presence of NH3

In this study, novel Fe-Ce-O mixed metal oxides were prepared by hydrothermal method. The Fe(0.3)-Ce-O catalyst showed excellent Hg0 oxidation performance in the presence of NH3, with high N2 selectivity (90% at 300°C) for NH3 oxidation. NH3-TPD indicated that a large concentration of acid sites appeared after CeO2 modification by Fe. The large surface area and Oα/(Oα+Oβ) ratio and the good Hg0 adsorption capacity were beneficial for Hg0 oxidation over the Fe(0.3)-Ce-O catalyst in the presence of NH3. Moreover, it was proposed that Hg0 was adsorbed in preference to NH3 on weak acid sites. Thus, the weak acid sites were crucial in Hg0 oxidation in the presence of NH3.

Sulfur-modified chitosan hydrogel as an adsorbent for removal of Hg(II) from effluents

Sulfur-modified chitosan hydrogel (SMCH) was successfully synthesized by grafting dimethyl 3,3′-dithiodipropionate onto chitosan and then crosslinking with N,N′-methylene diacrylamide (MBA). The structure and properties of chitosan and sulfur-modified chitosan (SMC) were characterized and analyzed by Fourier transform infrared spectroscopy (FT-IR), Nuclear magnetic resonance (1H NMR), X-ray diffraction (XRD) and Thermogravimetric analysis (TGA). Meanwhile, chitosan hydrogel and SMCH were characterized by Scanning electron microscope (SEM). In addition, static adsorption Hg(II) ions properties of chitosan hydrogel and SMCH were also investigated. The FT-IR and 1H NMR manifested that SMC was synthesized successfully. The XRD and TGA showed that the crystallinity and thermal stability of SMC decreased. SEM showed that the SMCH had much more pores and bigger specific surface area than chitosan hydrogel. The result of adsorption experiment indicated that the SMCH showed noticeable improvements in the adsorption capacity of Hg(II), and had the highest adsorption capacity (187.5 mg/g) at pH 5.0. The equilibrium was achieved at 40 min. And the maximum adsorption capacities were 186.9 mg/g of SMCH.

Synthesis and application of TiO2/SiO2/Fe3O4 nanoparticles as novel adsorbent for removal of Cd(II), Hg(II) and Ni(II) ions from water samples

In the current study, SiO2/Fe3O4 core–shell nanoparticles functionalized with TiO2, using a simple method and application for removal of Cd(II), Hg(II) and Ni(II) ions from aqueous solution. The structure of the resulting product was confirmed by X-ray diffraction spectrometry, transmission electron microscopy (TEM), pHpzc and Brunauer, Emmett and Teller methods. The average diameter of TiO2/SiO2/Fe3O4 nanoparticles according to TEM was obtained around 48 nm. In batch tests, the effects of pH, initial metal concentration, contact time and temperature were studied. Adsorption of metal ions was studied from both kinetics and equilibrium point of view. Maximum adsorption capacity of Cd(II), Hg(II) and Ni(II) on TiO2/SiO2/Fe3O4 nanoparticles was 670.9, 745.6 and 563.0 mg g−1, respectively. Adsorption–desorption results showed that the reusability of nanoparticles was encouraging. This adsorbent was successfully applied to removal Cd(II), Hg(II) and Ni(II) ions in real samples including tap water, electronic wastewater and medical wastewater.

Ag-Mo modified SCR catalyst for a co-beneficial oxidation of elemental mercury at wide temperature range

V2O5-MoO3-TiO2 (V-Mo-Ti) is often used as a selective catalytic reduction catalyst for NOx from coal-fired flue gas. The performance of a V-Mo-Ti catalyst for the oxidation of elemental mercury (Hg0) was investigated. It was found that Mo was resistant toward sulfur dioxide and can enhance the Hg0 adsorption capacity. Ag was employed to enhance the Hg0 oxidation reaction and can enlarge reaction temperature window. Doping with Ag can significantly enhance the oxidation of Hg0, and adding only 0.5% Ag can keep Hg0 oxidation efficiency to approximately 90% with 5ppmHCl, with an increase of 20–40% compared to that of V-Mo-Ti catalyst. Besides, the reaction temperature window of catalyst was enlarged from 150 to 400°C. TEM and XPS characterization data indicated that Ag nanoparticles were loaded on the Mo/V-Ti carrier, maintaining Ag-Mo/V-Ti at a higher oxidation state. Furthermore, the TPR and Deacon reaction tests suggested that the Ag dopant might enhance the redox behavior, which facilitates the Deacon or semi-Deacon reactions for HCl activation. In addition, Hg0 desorption and breakthrough experiments and mercury valence state change experiments were carried out to investigate the Hg0 catalytic oxidation mechanisms at various temperature ranges.

A systematic review on the efficiency of cerium-impregnated activated carbons for the removal of gas-phase, elemental mercury from flue gas.

In the present systematic review, we aimed to collect and analyze all the relevant evidence on the efficiency of cerium-impregnated versus virgin-activated carbons (ACs) for the removal of gas-phase elemental mercury (Hg0) from the flue gas of coal-fired power plants and to assess the effect of different calcination and operational parameters on their efficiency. A total of eight relevant papers (out of 1193 hits produced by the search) met the eligibility criteria and were included in the study. Results indicated that the Hg0 adsorption capacity of cerium-impregnated ACs is significantly higher than that of virgin ACs, depending highly on the impregnation and operational parameters. It was noticed that although cerium-impregnated ACs possessed smaller surface areas and pore volumes, their Hg0 removal efficiencies were still higher than their virgin counterparts. An increased Hg0 removal efficiency was in general found by increasing the operational adsorption temperature as high as 150-170°C. Studies also indicated that NO, SO2, and HCl have promoting impacts on the Hg0 removal efficiency of Ce-impregnated ACs, while H2O has an inhibitory effect.

Synthesis of polyamine‐bridged polysilsesquioxanes and their adsorption properties for heavy metal ions

Four types of polyamine‐bridged polysilsesquioxane adsorbents were prepared via a facile sol‐gel method using pre‐synthesized ethanediamine (EDA)‐ and diethylenetriamine (DETA)‐bridged monomers containing soft organic bridge. Infrared spectra (IR), scanning electron microscope (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TG), elemental analysis, and nitrogen gas adsorption–desorption were used to characterize their structures. Porogen hexadecyl tyimethyl ammonium bromide (CTAB) was found to be efficient in increasing the porosity of the absorbents. Adsorption experiments at different temperatures showed that the obtained absorbents exhibited relatively high adsorption capacities for Hg(II). Pseudo second‐order model is more suitable for describing the adsorption kinetics in the temperature range of 15–35°C. Compared with Freundlich models, Langmuir isotherm was better to describe the adsorption process of Hg(II) for all adsorbents. Finally, the thermodynamic parameters demonstrated that the adsorption reaction was endothermic and spontaneous. © 2017 American Institute of Chemical Engineers Environ Prog, 36: 1089–1099, 2017

Hg selective adsorption on polypropylene-based hollow fiber grafted with polyacrylamide

A novel polypropylene hollow fiber membrane with a new function of selective adsorption of mercury ions in aqueous solutions was successfully prepared. The surface of the polypropylene hollow fiber membrane was initially modified with polydopamine by surface polymerization, and subsequently grafted with polyacrylamide (PAM) polymer brush via the surface initiated atom transfer radical polymerization (SI-ATRP) technique (thereafter named as PP-PAM). This study investigated the adsorption performance of Hg(II) ions by PP-PAM and the effect of various influencing factors on Hg(II) ion adsorption. The experiment indicated that the Hg(II) adsorption capacity of the PP-PAM increased with the increase of the pH, and the Hg(II) adsorption kinetics was consistent with the pseudo-second-order kinetic model. The adsorption isotherm followed the Langmuir model, with the maximum adsorption capacity calculated to be 0.854 mmol/g for Hg(II) ions. The adsorption study in multi-component system indicated that PP-PAM preferentially adsorbs Hg(II) over Pb(II) ions, with significant adsorption capacity difference of the two heavy metal ions. This study provided an efficient method for the preparation of the adsorptive polypropylene hollow fiber membrane, which expands its application for the selective removal of heavy metal ions.

Influences of Copper(II) Chloride Impregnation on Activated Carbon for Low-Concentration Elemental Mercury Adsorption from Simulated Coal Combustion Flue Gas

In this study, the Hg0 adsorption equilibrium and kinetics of a coconut-shell-based activated carbon impregnated with CuCl2 were examined with respect to their resulting physical and chemical properties. Integrating the results from N2 adsorption isotherm at 77 K, scanning electron microscopy, elemental analysis, X-ray photoelectron spectroscopy, and Hg0 adsorption experiments under N2 and simulated coal-combustion flue gases conditions, it was found that HCl pretreatment could enhance Hg0 adsorption of crude activated carbon; the Hg0 adsorption capacities of crude and HCl-pretreated activated carbon under N2 condition were 95.8 and 225.4 µg g–1, respectively. Additionally, CuCl2 impregnation further increased the adsorption capacity of crude. The Hg0 adsorption capacity of crude activated carbon with 8% CuCl2 impregnation was 631.1 µg g–1. However, the equilibrium Hg0 adsorption capacity decreased when Cu loading exceeded 8 wt%, suggesting that adequate forms of surface Cu, O and Cl interacting with flue gas components and Hg0, as well as the presence of pores with specific size ranges allowing rapid transport of the Hg molecules into the interior of the activated carbon and as energy sinker govern the overall chemisorption process. Pseudo-second-order kinetic model could best describe the adsorption behaviors of tested samples under both test conditions, indicating that Hg0 adsorbed on the activated carbon surface could be explained by bimolecular reaction mechanisms.

New thiamine functionalized silica microparticules as a sorbent for the removal of lead, mercury and cadmium ions in aqueous media

The existence of heavy metal ions in aqueous media is one of the biggest environmental pollution problems and thus the removal of heavy metals is a very important procedure. In this work, a new adsorbent was synthesized by modifying 3-aminopropyl-functionalized silica gel with thiamine (vitamin B1) and characterized. The influence of the uptake conditions, such as pH, contact time, initial feed concentration and foreign metal ions, on the binding capacity of thiamine-functionalized silica gel sorbent (M3APS) were investigated. Maximum obtained adsorption capacities for Pb(II), Hg(II) and Cd(II) were 39.4?0.2, 30.9?0.5 and 9.54?0.4 mg g-1 M3APS, respectively, at pH 5.0. The observed selectivity of M3APS for these metal ions was the following: Pb(II) > Hg(II) > Cd(II). Adsorption isotherm models were also applied to the adsorption process. As a result, the Langmuir isotherm model gave the best fit for the adsorption of metal ions on M3APS. The Gibbs energy change (?G) for the adsorption of Pb(II), Hg(II) and Cd(II) were calculated to predict the nature of adsorption process. Having such satisfactory adsorption results, M3APS is a potential candidate adsorbent for Pb(II) and Hg(II) removal from aqueous media.

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.

Mercury Removal by Magnetic Biochar Derived from Simultaneous Activation and Magnetization of Sawdust.

Novel magnetic biochars (MBC) were prepared by one-step pyrolysis of FeCl3-laden biomass and employed for Hg0 removal in simulated combustion flue gas. The sample characterization indicated that highly dispersed Fe3O4 particles could be deposited on the MBC surface. Both enhanced surface area and excellent magnetization property were obtained. With the activation of FeCl3, more oxygen-rich functional groups were formed on the MBC, especially the C═O group. The MBC exhibited far greater Hg0 removal performance compared to the nonmagnetic biochar (NMBC) under N2 + 4% O2 atmosphere in a wide reaction temperature window (120-250 °C). The optimal pyrolysis temperature for the preparation of MBC is 600 °C, and the best FeCl3/biomass impregnation mass ratio is 1.5 g/g. At the optimal temperature (120 °C), the Fe1.5MBC600 was superior in both Hg0 adsorption capacity and adsorption rate to a commercial brominated activated carbon (Br-AC) used for mercury removal in power plants. The mechanism of Hg0 removal was proposed, and there are two types of active adsorption/oxidation sites for Hg0: Fe3O4 and oxygen-rich functional groups. The role of Fe3O4 in Hg0 removal was attributed to the Fe3+(t) coordination and lattice oxygen. The C═O group could act as act as electron acceptors, facilitating the electron transfer for Hg0 oxidation.

Kinetic studies of mercury adsorption in activated carbon modified by iodine steam vapor deposition method

The objective of this study was to develop a high efficiency activated carbon (AC) sorbent for mercury removal. The vapor deposition method was used to modify the raw AC. This method is relatively easy to carry out and uniformly modifies the AC. The results of this study indicate that AC modified by iodine steam vapor deposition has much better Hg capturing capacity than AC modified by bromide deposition under the same experimental conditions. London dispersion forces and exposure of the sorbent surfaces play important roles in elemental mercury (Hg0) adsorption. Adsorption kinetic behavior was also studied under different experiment conditions. Results indicated that the pseudo-second model was the best fit to the actual mercury adsorption behavior onto AC-I2 sorbent. The effect of adsorbent mass and gas flow rate on adsorption behavior were examined. Results indicated that increasing the sorbent mass led to an increase in Hg adsorption capacity, while increasing the gas flow rate resulted in a significant decrease in Hg adsorption capacity. Decreases in Hg adsorption capacity were likely due to a shorter contact time and lower partial pressure reducing the number of contact opportunities between the Hg atoms and the sorbent surface. Finally, a general dynamic equation was determined that can be used to help predict Hg adsorption curve of AC-I2 sorbent without completing a real fixed-bed Hg adsorption experiment.

Surface modification of bio-char by dielectric barrier discharge plasma for Hg0 removal

Bio-char (BC) samples were modified by the dielectric barrier discharge (DBD) plasma method to enhance the adsorption capacity for gaseous mercury (Hg0). The discharge gases and treatment time were studied for their influences on surface modification. Surface characteristics of BCs were investigated using nitrogen adsorption method and X-ray photoelectron spectroscopy (XPS) analysis. Hg0 adsorption performance of BCs was tested in a bench-scale fixed bed reactor. The results indicated that surface area and pore volume of samples decreased slightly with the plasma treatment. Oxygen-containing functional groups (OCFGs) especially CO groups increased on carbon surface as a result of the reaction with reactive intermediates. Adsorption data showed that BCs with DBD plasma treatment had higher mercury removal efficiency compared with that of raw BC. Oxygen and water vapor were favorable to surface modification in the process of DBD treatment in this study. Chemisorption was believed to be predominant in Hg0 adsorption process and carbonyl and ester groups might play the key roles. Compared with commercial activated carbons, the modified BC showed an excellent adsorption performance, implying that DBD plasma treatment was a potential surface activation technology to improve Hg0 adsorption capacity on bio-char adsorbents.

Characteristics of a biomass-based sorbent trap and its application to coal-fired flue gas mercury emission monitoring

A novel sorbent trap based on rice husk char (RHC) was developed. Scanning electron microscopy and Brunauer–Emmett–Teller analysis revealed that the raw RHC possesses a developed pore structure and has potential for mercury adsorption after brominated impregnation (RHC-HBr). The performance of both the raw and impregnated sorbents for Hg capture was investigated in a fixed bed system and compared with the performance of commercial activated carbon (AC). RHC-HBr showed a remarkable Hg adsorption capacity (57.84μg/g) comparable with commercial AC. The RHC-HBr sorbent passed the analytical bias test for mercury detection when spiked by Hg0 and HgCl2 under both the lower and upper concentration levels. Field verification test of the biomass-based sorbent traps was performed in a 6 kWth fluidized-bed combustion (FBC) system. The Ontario Hydra Method (OHM) was applied as the reference method for evaluating HgT(g) measured by the sorbent traps. The field verification test showed that RHC-HBr sorbent traps perform with almost the same accuracy as AC-based sorbent traps, with 97.5±2.9% field recovery rate, 3.2% breakthrough rate, and 0.6% relative deviation. HgT(g) field sampling based on the biomass-based traps was performed in a utility 660MW coal-fired unit in parallel with the OHM under two different operational loads (100% and 75%). Mercury migration and the removal characteristics of the existing air pollution control devices (APCDs) were evaluated using the biomass-based sorbent traps. The final Hg emissions from the stack were determined to be 0.65 and 1.54μg/Nm3 for 100% and 75% operational loads, respectively, indicating that a high load operation condition could be beneficial for mercury control by existing APCDs.

Removal of mercury(II) and cadmium(II) ions from synthetic wastewater by a newly synthesized amino and thiolated multi-walled carbon nanotubes

Functionalization of multi-walled carbon nanotubes can be carried out by introducing amino and thiol functional groups onto the nanotube sidewalls. This functionalized multi-walled carbon nanotubes can be used as a new type of efficient metal ions adsorbent from aqueous solutions. In this study, batch and column adsorption experiments were carried to evaluate the adsorption capacities of single and binary system mercury and cadmium. In the single system, the maximum adsorption capacity of 204.64 and 61.10mg/g were obtained for mercury and cadmium, respectively, while for binary systems, the values of 35.89 and 14.09mg/g were achieved for mercury and cadmium, respectively. Column breakthrough curves were obtained and described by Yan and Thomas models. The bigger Thomas rate constant (kTh) (120.77ml/min/mg for Cd(II) and 9.44ml/min/mg for Hg(II)) indicated that the intensity of adsorption of Cd(II) onto thiolated MWCNTs was higher compared to Hg(II). However, the value of maximum adsorption capacity (qe) for Hg(II) (39.75mg/g) was bigger than that of Cd(II) (9.72mg/g) in continuous system.