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Removal of mercury (II), elemental mercury and arsenic from simulated flue gas by ammonium sulfide a

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Ping Ning , Xiaolong Guo , Xueqian Wang , Ping Wang , Yixing Ma & Yi Lan

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Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming 650500, China Accepted author version posted online: 12 May 2015.

Click for updates To cite this article: Ping Ning, Xiaolong Guo, Xueqian Wang, Ping Wang, Yixing Ma & Yi Lan (2015): Removal of mercury (II), elemental mercury and arsenic from simulated flue gas by ammonium sulfide, Environmental Technology, DOI: 10.1080/09593330.2015.1043355 To link to this article: http://dx.doi.org/10.1080/09593330.2015.1043355

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Publisher: Taylor & Francis Journal: Environmental Technology DOI: 10.1080/09593330.2015.1043355

Removal of mercury (II), elemental mercury and arsenic from simulated flue gas by ammonium sulfide

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Ping Ning, Xiaolong Guo, Xueqian Wang1*, Ping Wang, Yixing Ma, Yi Lan

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Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming 650500, China

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This work was supported by the National Natural Science Foundation of China (No. 51268021, No. 51368026, U1137603), 863 National High-tech Development Plan Foundation (No. 2012AA062504) and by Applied Basic

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Research Program of Yunnan (No. 2011FB027, No. 2011FA010).

Abstract: A tubular resistance furnace was used as a reactor to simulate mercury and arsenic in smelter flue gases by heating mercury and arsenic compounds. The flue gas containing Hg2+, Hg0 and As was treated with ammonium sulfide. The experiment was conducted to investigate the effects of varying the concentration of ammonium sulfide, the pH value of ammonium sulfide, the temperature of ammonium sulfide, the presence of SO2 and the presence of sulfite ion on removal efficiency. The prepared adsorption products were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy

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(XPS) and scanning electron microscopy (SEM). The results showed that the optimal concentration of ammonium

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sulfide was 0.8mol/L. The optimal pH value of ammonium sulfide was 10, and the optimal temperature of ammonium sulfide was 20oC.Under the optimum conditions, the removal efficiency of Hg2+, Hg0 and As could reach 99%, 88.8%, 98%, respectively. In addition, SO2 and sulfite ion could reduce the removal efficiency of mercury and arsenic from simulated flue gas.

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Key words: Ammonium sulfide; simulated flue gas; Hg2+; Hg0; As

1. Introduction

Heavy metal is a kind of persistence, bioaccumulation and toxic pollutant, which has

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Acknowledgments

a great negative impact on human health and ecological environment. Mercury is one of the most toxic heavy metals. The Minamata Convention on Mercury, a new legally binding global treaty that aims to reduce mercury emission, was signed on Oct. 10, 2013. [1] It means that the control of mercury emissions is becoming more urgent all over the world. Nonferrous metal production plays an important role in mercury emission. [1-3] In China, it has been estimated that about 12-15% of the total mercury 1*

Corresponding author. Email: [email protected]

emission comes from the flue gas of nonferrous metal smelting in 2010. [1,4,5] As the main source mercury pollution in the environment, the mercury in flue gas of nonferrous metal smelting should be effectively controlled. Mercury in the flue gas primarily exists in three forms: elemental (Hg0), oxidized, and particulate-bound mercury. [6] The oxidized and particulate-bound mercury can be effectively removed by wet flue gas desulfurization (FGD) facilities. [6] Elemental mercury (Hg0) is extremely difficult to control because of its high volatility and low solubility. Arsenic

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was also one of the main pollution from the flue gas. [7,8] The forms of arsenic in the

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flue gas are arsenic sulfide, arsenic trisulfide and arsenic trichloride etc, which are

attached on the atmospheric particulates. Arsine gas was directly emitted into the

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At present, most of the countries in the world remove heavy metals from the flue gas mainly by adsorption [10-13] and catalytic oxidation method. [14-16] Especially in recent years, a lot of work has been done by many researchers. [17-19] There are

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two main methods to remove mercury from the flue gas. One is adsorption by chemically modified activated carbon, [20–23] and the disadvantage of this method is high cost. The other method is oxidation/absorption method. Namely, the main task of this method is to enhance the oxidation capacity of Hg0 to Hg2+, and then removing

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Hg2+ by wet-FGD. The oxidants for approaching Hg0 include halogens, halides [24–27]

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and catalysts (e.g, SiO2/TiO2/V2O5, [28] CeO2/TiO2, [29,30] MnOx–CeO2/TiO2, [31] CuCl2/α-Al2O3, [32] CuO–MnO2–Fe2O3/γ-Al2O3, [33] CuCl2/TiO2 [34] and define SCR [35]). However, most of them either have higher economical costs or may

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release hazardous products which can pollute the environment. Therefore, the development of low costs and low pollution technology for mercury removal is still necessary and urgent. In recent years, several treatment methods have been developed

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atmosphere to cause pollution. [9]

for the removal of arsenic from water. The common methods adopted for the treatment of arsenic from water include flotation, [36] precipitation with sulfide, [3740] coagulation, [41] adsorption [42,43] and filtration and ion exchange [44]. But the study on removal of arsenic from the flue gas is less. Sulfide method is mainly used for removing heavy metals from waste water, but the study on removal of heavy metals from the flue gas is less. This paper focuses on the study of removal of bivalent mercury (Hg2+), elemental mercury (Hg0) and arsenic (As) in simulated flue gas by (NH4)2S solution. The method is based on the precipitation reactions between S2- and Hg2+, Hg0, As in simulated flue gas to

generate HgS, As2S3, As2S5 precipitation. It is also beneficial to recycle mercury and arsenic and realize the economic cycle. The basic research and theoretical basis can be provided to the engineering application of removal of toxic metals from simulated flue gas. 2. Material and methods 2.1.

The simulation experiment of smelting flue gas

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The solide-state mercuric chloride (HgCl2) and mercury (Hg) were put into the

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Tubular resistance furnace (SLG1200-60, 220V, 4000W). After that, the gaseous

bivalent (Hg2+) and gaseous mercury (Hg0) were generated when the Tubular

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sodium (Na3AsO4•H2O) was heated at 105ºC for 48 h to get dry diarsenic pentoxide (As2O5). The As2O5 and arsenic trioxide (As2O3) were put into the Tubular resistance

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furnace and heated to 1000ºC, and then gaseous arsenic (As) was generated. The carrier gases were the mixture of nitrogen and sulfur dioxide with a constant flow rate of 200 mL/min. Under the above conditions, the concentrations of Hg2+, Hg0 and As could reach 10~30 mg/m3, 10-30 mg/m3 and 2~7 mg/m3 in the simulated flue gas,

2.2.

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respectively, which were consistent with the composition of actual smelting gas. Removal of heavy metals from simulated flue gas using ammonium sulfide

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The experimental device for using ammonium sulfide to remove Hg2+, Hg0 and As in simulated flue gas is shown in Fig. 1. In this study, all of the experimental

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simulated flue gas was the flue gas of single heavy metal. The corresponding tail gas absorption solution of Hg2+ and Hg0 was acidic solution of KMnO4, and the corresponding tail gas absorption solution of As was HNO3/HCl mixture (3:1, v/v).

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resistance furnace was heated to 450ºC and 40ºC, respectively. The arsenic acid three

[45] The purification plant containing ammonium sulfide solution was cleaning device. If the temperature of outlet flue gas was too high, it was better to first go through a quench tower. And then the cooled gas could come to the (NH4)2S solution.

As shown in Figure 1, when valve 1 and valve 2 were opened and valve 3, valve 4 were closed, the simulated flue gas directly went into the tail gas absorption equipment (1) for 15 min. When valve 1,valve 2 were closed and valve 3, valve 4 were opened, the flue gas went into the tail gas absorption equipment (2) for 15 min after passing through the bottles containing ammonium sulfide solution. The concentrations of Hg2+, Hg0 and As (CL) in the tail gas absorption solution were

determined using Cold Vapor Atomic Absorption Mercury Analyzer (JKG-205, worked at 220V, 15-20mA, the temperature was between 10 and 30ºC), Double Optical Digital Mercury Analyzer (SG-921, worked at 220V, 6-10mA, the temperature was between 10 and 40ºC) and Flame Atomic Absorption Spectrophotometry (CAAM-2001E, worked at 150-350V, 8-12mA, the temperature was between 10 and 30ºC), respectively. The concentration of Hg2+ from the tail gas was calculated by the concentration of Hg2+ in the acidic solution of KMnO4 by

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equation (1). And the concentration of As from the tail gas was calculated by the

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concentration of As in the HNO3/HCl mixture by equation (1). Finally, the concentration of Hg0 from the tail gas was determined by the Double Optical Digital

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The concentrations of heavy metals in simulated flue gas (mg/m3) were calculated by the following equation (1): C LVL 1000Qt

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C=

(1)

Where, CL was the concentration of heavy metals in the tail gas absorption solution (mg/L); VL was the volume of the tail gas absorption solution (mL); Q was the gas flow (mL/min); t was simulated flue gas collection time (min). (C 0 − C n ) × 100% C0

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η=

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And the Hg2+, Hg0 and As removal efficiency were calculated by the equation (2): (2)

Where, C0 was the initial concentration of heavy metals in simulated flue gas

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without the absorption of ammonium sulfide solution (mg/m3), Cn was the residual concentration of heavy metals in simulated flue gas after the absorption of ammonium sulfide solution (mg/m3).

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Mercury Analyzer online.

2.3.

The experimental principle

2.3.1. Mercury removal principle As shown in the equations (3-4), the pH value of ammonium sulfide solution decreased from 12 to 3 in the process of adsorption, which was due to the existence of sulfur dioxide in simulated flue gas. As shown in the equations (5-6), the reaction product between sulfur dioxide and ammonium sulfide were hydrogen sulfide (H2S) and sulfur (S), and they can react with mercury (Hg0) to form mercuric sulfide precipitate. These are the major principle for the removal of Hg0. Mercury ions (Hg2+)

reacted with sulfide ions (S2-) to generate stable mercuric sulfide precipitate under the condition of weak alkaline, [46] and the Hg2+ removal principle can be fully explained by the equation (7).

6SO2 + 4(NH4 )2 S+ 3H2O → 3(NH4 )2 S2O3 + 2 NH4HSO3 + 2H2S

(3)

S2O32− + 2 HSO3− → 2S + 2SO4 2− + H 2O

(4)

Ksp = 4.0 ×10−53

(5)

Hg 0 + H 2 S → HgS ↓ + H 2

Ksp = 4.0 ×10−53

(6)

Ksp = 4.0 ×10−53

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Hg 2+ + S 2− → HgS ↓

(7)

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2.3.2. Arsenic removal principle

Since the entire absorption process is gradually from alkaline to acidic, so the arsenic removal process is divided into two parts: Under alkaline conditions:

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As2O3 + 6OH − → 2 AsO33− + 3H 2O

As2O5 + 3H 2O → 2H3 AsO4 Under acidic conditions:

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2 H 3 AsO3 + 3H 2 S → As2 S3 ↓ +6 H 2O

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2 H 3 AsO4 + 5H 2 S → As2 S5 ↓ +8H 2O

(8) (9)

(10) (11)

After the above procedures, As2S5, As2S3 and HgS were precipitated out. Finally,

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the arsenic and mercury could be recycled through some treatment. 2.4.

Sample characterization

SEM was used to study the surface morphology of the precipitation of mercury and

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Hg 0 + S → HgS ↓

arsenic. The nitrogen adsorption isotherms at 77.35 K were determined on a multispot nitrogen adsorption meter NOVA2000e (Quantachrome Corp). Scanning electron microscopy (SEM) produced by the Japanese Hitachi electronic and field emission of S4800. EX-350 Energy Dispersive X-ray Microanalyzer and HORIBA EMAX Energy were used in this work. Fourier transform infrared spectra (FTIR) were

recorded on a Mattson 5000 FTIR spectrometer in the range between 4000 and 300 cm−1. XRD was employed to investigate the crystal structures of the precipitation of mercury and arsenic. XRD analysis was conducted on a Rigaku diffraction meter (D/MAX-2200), which was operated under the conditions of 36 kV and 30 mA using

Nifiltered Cu Kα radiation (λ=0.15406 nm) at a rate of 2o/min from 2θ=10~80o. Plus, powdered samples were directly analyzed without pretreatment. The instrument X photoelectron spectroscopy (XPS) used America Thermo ESCALAB 250Xi X photoelectron spectroscopy, in which the X-ray source was operated with an Al Kα anode with a photo-energy of hv 1486.6 eV.

The influence of concentration on removal of heavy metals from simulated

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3.1.

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3. Results and discussions flue gas

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and running costs of sulfide method. High concentration of (NH4)2S solution would not only lead to high S2- concentration in the solution, but also increase the processing

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costs. However, too low concentration of (NH4)2S solution would also reduce the removal efficiencies of heavy metals from simulated flue gas, which may lead to the higher concentration of heavy metals at the outlet.

In this research, the influence of (NH4)2S concentration on removal efficiency of heavy metals from simulated flue gas was examined. Different concentrations of

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(NH4)2S solution (0, 0.2, 0.4, 0.8 and 1.2 mol/L) were used for absorbing and

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removing Hg2+, Hg0, As from simulated flue gas, and then the optimum concentration of (NH4)2S solution was determined. When the concentration of (NH4)2S solution was increased from 0 to 0.2 mol/L,

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the removal efficiency of Hg2+ increased from 80.5% to 89.2%. Similarly, the removal efficiency of Hg0 also increased from 71.6% to 81.9%, and the removal efficiency of As varied from 81.8% to 87.5%. As we can see from the Fig. 2, the

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The concentration of (NH4)2S solution has an important effect on removal efficiency

removal efficiencies of Hg2+, Hg0, As were increased as the concentration of (NH4)2S solution increased. When the concentration of (NH4)2S solution increased from 0 to 0.8 mol/L, the removal efficiencies of Hg2+, Hg0 and As could reach 96%, 85% and 95.2%, respectively. We can see from equations (3-11), when the concentration of (NH4)2S solution increased, the concentration of S2-, S and H2S increased too. They could react with Hg2+, Hg0, As and generated HgS, As2S3, As2S5 precipitation. This was the reason why the removal efficiencies increased as the concentration of (NH4)2S solution increased. All in all, the removal efficiencies of Hg2+, Hg0 and As

using (NH4)2S solution were relatively high. Considering removal efficiencies and economic benefits, the optimum concentration of (NH4)2S solution used for removing Hg2+, Hg0, As from simulated flue gas was 0.8 mol/L. At each concentration, the order of the three heavy metals removal efficiencies were: Hg2+ > As > Hg0.[18,47-49] It indicated that (NH4)2S likely reacted with Hg2+ and formed precipitation. This was in accord with the Ksp (solubility product constant) of two kinds of metal: HgS< As2S3. The influence of pH value on removal of heavy metals from simulated flue

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3.2. gas

As shown in equations (12-13),[50] a part of S2- combined with H+ and formed

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the use efficiency of S2-. Because the pKp2 value for equation (13) was nearly twice the pKp1 value for equation (12), the reaction between S2- and H+ was easier than the

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reaction between HS- and H+. Therefore, the pH value of (NH4)2S solution also had an important influence on the removal efficiencies of heavy metals in flue gas. +

⎯⎯ → S 2− + H + HS − ←⎯ ⎯

 HS −   H +  Kp1 =  H2S  S 2 −   H +  Kp 2 =   HS − 

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⎯⎯ → HS + H H 2 S ←⎯ ⎯ −

pKp1 = 6.99

pKp2 = 14

(12) (13)

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In this study, the influence of pH value of (NH4)2S solution on removal efficiencies of heavy metals from simulated flue gas was also investigated. Different pH value of (NH4)2S solution (2, 4, 6, 8 and 10) were used for absorbing and

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removing Hg2+, Hg0 and As from simulated flue gas, and then the optimum pH value of (NH4)2S solution was determined. The experimental data showed that the pH value of ammonium sulfide solution

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HS- and H2S. H+ combined with S2- and formed HS- and H2S, which would decrease

had played an important role in removal of heavy metals from simulated flue gas. As shown in Fig. 3, the removal efficiencies of Hg2+, Hg0 and As decreased as the pH value of (NH4)2S solution increased from 2 to 6, while the removal efficiencies of heavy metals increased as the pH value increased from 6 to 10. The range of removal efficiencies for Hg2+, Hg0 and As were 92.8%-98.5%, 80.3%-88.6% and 90.1%96.9%, respectively. When the pH value was between 4 and 6, the removal efficiencies reduced to a minimum level. When the solution was strong acidic, gaseous heavy metals could be dissolved into ions. Ions state of arsenic and mercury

reacted with sulfur ions and formed arsenic trisulfide (As2S3) and mercury sulfide (HgS) precipitation, and then the precipitation was dissolved in the solution. So most

of the Hg and As removed from simulated flue gas were dissolved in the solution under the strong acidic conditions. When the solution was strong alkaline, one part of heavy metals from simulated flue gas reacted with sulfur ions and formed As2S3 and HgS precipitation, and another part of heavy metals stay in the solution due to cooling and realized solid-gas separation. No matter under acidic or alkaline condition, the

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removal efficiencies of Hg2+, Hg0, As were all above 89%. However, ionic heavy

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metal which was formed under acidic condition need to conduct further treatment. Additionally, alkaline condition was advantageous to remove Hg0 from simulated flue

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simulated flue gas. In this research, the optimum pH value of (NH4)2S solution was 10. 3.3.

The influence of temperature on removal of heavy metals from simulated

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flue gas

In addition to the concentration and pH value of (NH4)2S solution, the temperature also had important effect on the removal efficiencies of heavy metals. At the optimum concentration and pH value of (NH4)2S solution, water bath was used to control absorption of heavy metals using ammonium sulfide solution at

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different temperatures (10, 20, 30, 40 and 50oC), which could study the effect of

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temperature on removal efficiency and determine the optimum temperature of (NH4)2S solution.

As shown in Fig. 4, when the temperature increased from 10oC to 20oC, all of the

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removal efficiencies of Hg2+, Hg0 and As also increased. When the temperature was increased from 20oC to 50oC, the removal efficiencies of heavy metals were not significantly increased, and some were even decreased slightly. The fluctuation range

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gas. Therefore, alkaline condition was more suitable for removing heavy metals from

of removal efficiencies of Hg2+, Hg0 and As were 97.2%-97.7%, 87.2%-86% and 97.1%-97.5%, respectively. When the temperature increased from 10oC to 50oC, the Hg0 volatilization and H2S volatilization were the main reason why the removal efficiencies of Hg2+, Hg0 and As were decreased. Considering the removal efficiencies and economic benefits, the optimum temperature of removal As and Hg

from simulated flue gas by (NH4)2S solution was 20oC. 3.4.

The influence of SO2 on removal of heavy metals from simulated flue gas

At the optimum concentration, pH value and temperature of (NH4)2S soultion, different concentration of SO2 (0%, 0.5%, 1%, 6%, 10%) were used to study the effect of SO2 on removal efficiencies of heavy metals. The experimental data showed that the concentration of SO2 had an impact on removal efficiencies of heavy metals from simulated flue gas. The removal efficiencies of heavy metals from simulated flue gas containing different SO2 concentrations were studied. As the concentration of SO2 from simulated flue gas was

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increased, the removal efficiencies of Hg2+, Hg0, As decreased from 98.7%, 87.2%,

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and 96.3% to 95.1%, 70.6%, and 93%, respectively (Fig. 5). When the concentration of SO2 in simulated flue gas increased, the removal efficiencies of Hg2+ and As

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metals and S2- was inhibited in the process of experiment. As the concentration of SO2 increased, the removal efficiency of Hg0 initially increased and then decreased. H2S, which was the resultant of reaction between (NH4)2S and SO2, was advantageous to

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remove Hg0 from simulated flue gas in the initially stage of reaction. As the reaction gradually continued, there was no more S2- could react with SO2 and form H2S, which resulted in a decrease on the removal efficiency of gaseous Hg0. Therefore, the existence of SO2 had an inhibitory effect on removal of heavy metals from simulated

The influence of sulfite ion on removal of heavy metals from simulated flue gas

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3.5.

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flue gas.

Sulfite ion (SO32-) was also investigated to study the influence on removal of heavy

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metals using (NH4)2S solution. [51] Different amounts of SO32- (0, 0.05, 0.1, 0.15 and 0.2 mol/L) were added to ammonium sulfide solution to absorb heavy metals, which was used to study the effect of sulfite ion on removal efficiency.

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decreased. Due to the reaction between (NH4)2S and SO2, the reaction between heavy

When increasing SO32- concentration in ammonium sulfide solution from 0 to

0.01 mol/L, the removal efficiencies of Hg2+, Hg0 and As were increased from 98%, 85.7% and 96.6% to 98.5%, 86.9% and 97.2%, respectively (Fig. 6). As the concentration of sulfite ion was increased from 0.01 mol/L to 0.2 mol/L, the removal efficiencies of Hg2+, Hg0 and As were decreased from 98.5%, 86.9% and 97.2% to 96.9%, 82.7% and 95.2%. It was concluded that the existence of sulfite ion also had an inhibitory effect on removal of heavy metals from simulated flue gas.

4. Characterization of materials 4.1.

FTIR analysis

The FTIR spectra of arsenic and mercury precipitates are shown in Fig. 7 and Fig. 8. According to Mineral atlas of infrared spectra by Peng WS, [52] the band in spectra with wavenumber range 378 cm-1 in Fig. 7 (a) correspond to vibration of As2S3, peak at 605 cm-1 which was attributed to As2O3. [53] The band at 375 cm-1 in Fig. 7 (b)

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could be assigned to As2S5, and peak at 620 and 1400 cm-1 could be related to

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(NH4)2SO4. By the Fig. 8 (c, d), the band in spectra with wavenumber range 345 cm-1 were attributed to HgS.

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XRD analysis

By the Fig. 9 (e), the precipitates generated by the reaction between (NH4)2S and As3+ in simulated flue gas was mainly dominated by As2O3 and As2S3. However, the

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content of As2S3 was less than that of As2O3. This fully showed that the main absorption mechanism of As3+ from simulated flue gas using (NH4)2S solution was physical absorption. Chemical deposition played a minor role in this process. According to analyze the Fig. 9 (f), the main precipitates produced by the reaction of (NH4)2S and As5+ in simulated flue gas were (NH4)2SO4, As2S5, and the content of

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As2O5 was little. Accordingly, it showed that the chemical deposition was the

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absorption mechanism of As5+ from simulated flue gas using (NH4)2S solution. As Fig. 10 (g, h) shown, the main resultant of reaction between (NH4)2S and Hg2+, Hg0 was HgS. [54] Therefore, the main absorption mechanism of Hg from simulated flue gas

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using (NH4)2S solution was chemical absorption. 4.3.

XPS analysis

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4.2.

To further confirm the structures of homogeneously prepared adsorption products, XPS was employed and the results are shown in Fig 11 and Fig 12. From Fig 11 (i, j), it could be deduced that the trivalent arsenic precipitation contains As, S and O, and the pentavalent arsenic precipitation contains As, S and O. As shown in the Fig. 12 (k, l), it could be deduced that the mercury (II) and elemental mercury precipitation both contain Hg and S. [55,56] This result is consistent with that by FTIR and XRD. 4.4.

SEM observation

In this study, the electron microscopy of the precipitates generated by the reaction between heavy metals and (NH4)2S were done for a better analysis the absorption effects and mechanism of heavy metals from simulated flue gas using (NH4)2S solution. The (NH4)2S solution absorbed Hg2+, Hg0 from the flue gas and formed HgS precipitation. As shown in the Fig. 13 (m), the particles of HgS precipitation had relatively uniformly feathers. [57] And it was not difficult to observe that the tiny

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HgS precipitation was attached to the (NH4)2SO3 molecules in the Fig. 13 (n). As

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shown in the Fig. 14 (o, p), the precipitates of arsenic were in different sizes and

unevenly distributed. It was implied that only a small fraction of As could react with

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particulate which could not react with (NH4)2S. They directly deposited in (NH4)2S solution. This was the reason why the As were uneven and irregular in the scanning electron micrograph. Therefore, the removal mechanism of Hg from simulated flue

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gas was mainly chemical deposition, and the removal mechanism of arsenic from flue gas was mainly physical adsorption. This result is consistent with FTIR, XRD and XPS analysis above.

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5. Conclusion

Considering removal efficiency and economic benefits, the optimal concentration,

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temperature and pH value of ammonium sulfide solution were 0.8 mol/L, 20oC and 10, respectively. Under the optimum conditions, the concentration of Hg2+, Hg0 and As in the treated flue gas could be reduced to 0.25 mg/m3, 0.45 mg/m3, 0.23 mg/m3,

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respectively. And the removal efficiencies of Hg2+, Hg0 and As from simulated flue gas could reach 99%, 88.8%, 98%, respectively. The results of FTIR, XRD, XPS and SEM showed that the removal mechanism of Hg from simulated flue gas was mainly

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(NH4)2S and generated precipitation. Most of the As from simulated flue gas was

chemical deposition and the removal mechanism of arsenic from flue gas was mainly physical adsorption. All in all, the theories and results prove that ammonium sulfide is an efficient and low-cost adsorbent for arsenic and mercury from simulated flue gas.

In addition, the existence of SO2 and SO32- had an inhibitory effect on removal of Hg2+, Hg0 and As from simulated flue gas. References [1] Ma YP, Qu Z, Xu HM, Wang WH, Yan NQ. Investigation on mercury removal method from flue gas in the

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Fig.1 Schematic of the experimental apparatus

Fig.2 The influence of concentration on removal of heavy metals from simulated flue gas.

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Fig. 3 The influence of pH value on removal of heavy metals from simulated flue gas.(concentration of

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Fig.4 The influence of temperature on removal of heavy metals from simulated flue gas.(concentration of

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ammonium sulfide was 0.8mol/L, pH value of ammonium sulfide was 10)

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ammonium sulfide was 0.8mol/L)

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Fig.5 The influence of SO2 on removal of heavy metals from simulated flue gas.(concentration of ammonium

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Fig.6 The influence of sulfite ion on removal of heavy metals from simulated flue gas. (concentration of

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ammonium sulfide was 0.8mol/L, pH value of ammonium sulfide was 10, temperature of ammonium sulfide was 20oC)

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sulfide was 0.8mol/L, pH value of ammonium sulfide was 10, temperature of ammonium sulfide was 20oC)

a Trivalent arsenic precipitation

b Pentavalent arsenic precipitation

Fig.7 The precipitation of arsenic of Fourier transform infrared spectroscopy analysis

d elemental mercury precipitation

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c mercury(II) precipitation

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e Trivalent arsenic precipitation

f Pentavalent arsenic precipitation

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Fig.9 The precipitation of arsenic of X ray diffraction analysis

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Fig.8 The precipitation of mercury(II) of Fourier transform infrared spectroscopy analysis

g mercury(II) precipitation

h elemental mercury precipitation

Fig.10 The precipitation of mercury of X ray diffraction analysis

i Trivalent arsenic precipitation

j Pentavalent arsenic precipitation

Fig.11 The precipitation of arsenic of X-ray photoelectron spectroscopy analysis

l elemental mercury precipitation

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k mercury(II) precipitation

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Fig.13 The precipitation of mercury of scanning electron microscope analysis

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Fig.12 The precipitation of mercury of X-ray photoelectron spectroscopy analysis

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Fig.14 The precipitation of arsenic of scanning electron microscope analysis

Removal of mercury (II), elemental mercury and arsenic from simulated flue gas by ammonium sulphide.

A tubular resistance furnace was used as a reactor to simulate mercury and arsenic in smelter flue gases by heating mercury and arsenic compounds. The...
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