Preparation of activated carbon from peanut shell with KOH activation and its application for H2S adsorption in confined space

Journal Pre-proof Preparation of activated carbon from peanut shell with KOH activation and its application in H2 S adsorption: isotherm and kinetic studies Shuang Wang, Hoseok Nam, Hyungseok Nam

PII:

S2213-3437(20)30031-2

DOI:

https://doi.org/10.1016/j.jece.2020.103683

Reference:

JECE 103683

To appear in:

Journal of Environmental Chemical Engineering

Received Date:

14 October 2019

Revised Date:

29 December 2019

Accepted Date:

9 January 2020

Please cite this article as: Wang S, Nam H, Nam H, Preparation of activated carbon from peanut shell with KOH activation and its application in H2 S adsorption: isotherm and kinetic studies, Journal of Environmental Chemical Engineering (2020), doi: https://doi.org/10.1016/j.jece.2020.103683

This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier.

Preparation of activated carbon from peanut shell with KOH activation and its application in H2S adsorption: isotherm and kinetic studies Shuang Wang1, Hoseok Nam2, Hyungseok Nam3*, 1

Mechanical Engineering, Pukyong National University, Busan, 48547, Korea

2

Institute of Economic Research, Kyoto University, Kyoto, 606-8501, Japan

3

Greenhouse Gas Laboratory, Korea Institute of Energy Research, Dajeon, 34129, Republic of Korea

*Corresponding author. Tel.: +82-51-629-6358; E-mail: [email protected] (H. Nam)

ro of

Highlights

Activated carbon filter derived from peanut shell with KOH activation was utilized for H2S removal



Carbonization temperature significantly affected the texture properties of activated carbon



Max H2S adsorption capacity was 98 mg/g using the best activated carbon filter (S BET =1523 m2/g)



Adsorption of H2S followed Langmuir isotherm model and Pseudo-first order kinetic model



Regeneration of used activated carbon filter through heating under argon was available

ABSTRACT

Jo

ur

na

G RAPH I CAL

lP

re

-p



Highlights 

Activated carbon filter derived from peanut shell with KOH activation was utilized for H 2S removal



Carbonization temperature significantly affected the texture properties of activated carbon



Max H2S adsorption capacity was 98 mg/g using the best activated carbon filter (S BET =1523 m2/g)



Adsorption of H2S followed Langmuir isotherm model and Pseudo-first order kinetic model



Regeneration of used activated carbon filter through heating under argon was available

ro of

Abstract Hydrogen sulfide (H2S), as a major air pollutant, poses a serious threat to people`s health, especially in confined spaces. In this study, a porous carbon filter was developed by impregnating a copper on activated carbon derived from peanut shell biomass. The carbonization temperature can significantly affect the texture properties of activated carbon,

-p

and the optimized temperature was 450 ℃. The optimal activated carbon sample (SBET=1523.2 m2/g, Vmicro=0.533 cm3/g) was prepared at a carbonization temperature of 450℃ and KOH

re

activation at 750 ℃. The best adsorption performance was obtained with a copper impregnated optimal activated carbon (Cu/PAC-450) filter, and the maximum adsorption capacity was found

lP

to be 97.63 mg/g. As the initial concentration of H2S increased, the adsorption efficiency decreased. Adsorption isotherm and kinetic studies showed that Langmuir isotherm model was the best-fitted model for the adsorption of H2S on Cu/PAC-450 filter, with a correlation

na

coefficient of 0.9627. The adsorption kinetic process followed the pseudo first order model, and the adsorption mechanism was controlled by intraparticle diffusion along with film diffusion model. The used Cu/PAC-450 filter can be successfully regenerated, and had good

ur

reusability. The Cu/PAC-450 has a very broad prospect for use in household appliances (such as refrigerator, air conditioner, microwave oven, etc.) for indoor air purification. Therefore, this

Jo

study is expected to expand the utilization of agriculture waste for the indoor air purification.

Keywords: peanut shell, activated carbon, H2S, adsorption, isotherm and kinetic.

1. Introduction Hydrogen sulfide (H2S) is a major air pollutant mainly from chemical industrial processes

such as petroleum refining, natural gas processing, coal gasifiers and wastewater treatment [1]. Due to its extremely toxic and corrosive nature, it not only corrodes steel equipment [2], poisons catalyst used in fuel cells [3], as well as contributes to the formation of acid rains [4]; but also poses a threat to human health even at low concentrations [5]. Many techniques have been proposed for the removal of hydrogen sulfide, such as biotrickling filter [6], hydrodesulfurization [7], adsorption [8], and oxidation [9]. Among them, adsorption with activated carbon (AC) seems to be very promising due to its cost-effective, high adsorption capacity, simple design, ease operation, and regeneration [10].

ro of

Activated carbon (AC) is a high surface area porous carbonaceous material with excellent adsorption properties. It is widely used in drinking water purification, industrial and domestic sewage treatment, and environmental remediation. At present, the main precursor source for the AC production is wood [11], but the high cost of wood limits the widespread application of AC to some extent. Therefore, in recent years, a new interest has been growing in the use of

-p

low-cost and readily available lignocellulosic materials such as agricultural waste for the AC preparation [12, 13]. China is the world`s largest peanut producer, and about 5 million tons of

re

peanut shells are produced per year [14]. As a byproduct of peanut production, peanut shells are mainly discarded or burned off in stacks, resulting in resource consumption and

lP

environmental pollution. Fortunately, peanut shells are rich in cellulose, hemicellulose and polymer materials, making it a great potential to be a good precursor for the AC preparation [15], which in turn can solve the problem of resource consumption and environmental pollution.

na

Traditionally, the methods for preparing AC can be classified into chemical activation and physical activation. Compared with physical activation, chemical activation normally produces AC with higher yield and better-developed pore structure [16]. The most commonly used

ur

chemical activators include KOH, NaOH, H3PO4, H2SO4, K2CO3, ZnCl2, etc [17]. Among them, KOH is considered to be a more effective activator when the activated carbon with more

Jo

microporous structure is required [12]. Generally, chemical synthesis of AC via KOH activation can be divided into one-step

activation method and two-step activation method. In the one-step method, a biomass precursor is impregnated with a chemical activator, and then the impregnated biomass precursor is activated/carbonized to produce a biomass-derived AC. However, the two-stop method involves a carbonization process and an activation process. During the carbonization process, the biomass is thermally converted into biochar. The obtained biochar precursor is then

impregnated with the chemical activator, followed by the activation of the impregnated biochar precursor is performed to produce a biochar-derived AC [18]. Although the one-step method shortens the preparation process and reduces energy consumption, due to the lack of a carbonization process to optimize the microstructure of the carbon matrix, the obtained AC has poor texture characteristics, such as lower specific surface area and smaller porosity [19]. Adsorption of phenol using activated carbon derived from rice husk via one- and two-step KOH activation was performed by Fu et al. [19], the results indicated that the two-step method can produce a higher yield, and the AC has higher specific surface area and larger pore volume than the one-step method. As a result, the AC produced by the two-step method showed a

ro of

higher adsorption capacity of phenol. In addition, Yang et al. [20] synthesized activated carbon derived from sludge and coconut shell by one- and two-step KOH-catalyzed pyrolysis for the adsorption of methylene blue (MB). The results showed compared with the one-step method, the AC produced by the two-step method has a higher surface area, a larger total pore volume

-p

and a greater adsorption capacity of MB. Therefore, this indicated that the carbonization process is necessary for the preparation of AC, when a high-quality AC with a well-developed

re

microporous structure and a high specific surface area is required. According to Zhao et al. [21] and Angin et al. [22], pyrolysis temperature was the most significant factor affecting the

lP

physical and chemical properties of biochar as a precursor of activated carbon, among the pyrolysis temperature, heating rate, residence time, and feedstock source. The pyrolysis temperature for the pyrolysis of different biomass was mainly in the temperature range of 300

na

– 600 ℃ [22, 23]. Hence, in this work, in order to evaluate the effect of pyrolysis temperature on the texture properties of biochar and AC, different temperatures of 350, 450, and 550 ℃ were set for the preparation of AC. In addition, the activation temperature for the preparation

ur

of AC was set to 750 ℃ according to the KOH activation mechanism reported in detail by Otowa et al. [24].

Jo

Several studies on the adsorption of H2S using various adsorbents have been reported so

far. Yang et al., [25] reported the adsorption of H2S using N-modified coal based AC supported ZnO adsorbent. N-modification not only increased the basicity of the water film condensed in the pores, promoting the dissociation of H2S and H2O, but also affected the electronic structure of ZnO, accelerating the rate of lattice diffusion. As a result, it was found that the maximum breakthrough sulfur capacity was 62.5 mg/g. Surra et al., [26] prepared AC using maize cob waste with CO2 physical activation for the adsorption of H2S. The textural properties of AC was found to be SBET = 820 m2/g, Vmicro = 0.32 cm3 /g, and H2S uptake capacity was 15.5 mg/g.

Removal of H2S using ZnO-CuO supported commercial AC at room temperature was performed by Balsamo et al., [27]. The high dispersion of the metal oxide phase contributed to the interaction with the AC, and the functionalized AC exhibited a strongly enhanced adsorption capacity of H2S. Furthermore, the formation of the reaction product (metal sulphides and/or elemental sulphur) indicated that H2S adsorption process was accompanied by an oxidation reaction. However, so far, studies on the adsorption of H2S by AC derived from peanut shells have not been reported. In this work, the peanut shells were carbonized at different temperatures of 350, 450 and

ro of

550 ℃ for 30 min, and then the biochar was activated at 750 ℃ for 2 hours with KOH activation. The obtained activated carbon was used to prepare a porous carbon filter by impregnating a copper catalyst on peanut shell activated carbon (Cu/PAC) for the adsorption of contaminants. In recent years, indoor air pollution has gradually become a hot spot of concern because it affects people`s health and quality of life more directly and more persistently [28]. Hydrogen

-p

sulfide is an important component of indoor air pollutants, mainly from food residues, sulfurcontaining domestic sewage and household waste. Therefore, the prepared Cu/PAC filter was

re

used to adsorb H2S in a confined space for indoor air purification. Several specific objective of this study are a) the obtained PAC was characterized by SEM, TGA, DTA, Proximate and

lP

elemental analysis, N2 adsorption-desorption isotherm to investigate the effect of carbonization temperature on the textural properties of AC; b) H2S adsorption tests were performed using Cu/PAC filter and PAC filter to evaluate their adsorption efficiency; c) isotherm and kinetic

na

models were used to analyze the H2S adsorption equilibrium data, in order to understand and optimize the adsorption process; and d) the used Cu/PAC filter was regenerated and readsorbed H2S to assess its potential for reuse. This study is expected to expand the utilization

ur

of agricultural waste for air pollutant removal, especially for indoor air purification.

Jo

2. Materials and methods

2.1. Preparation of activated carbon The peanut shell used in this study was cleaned with an ultrasonic washer, and then dried

in an oven at 110 ℃ for 12 hours. The dried peanut shell was ground into powder, then immersed in a HCl (2 mol/L) solution to remove impurities, and finally oven dried again at 110 ℃ for 12 hours. About 18 g the prepared peanut shell powder was placed in a stainless steel reactor (36 mm inner diameter × 90 mm length), and then placed into the center of the furnace

tube as show in Figure 1. Then the prepared sample was carbonized at 350, 450 and 550 ℃ for 30 min under a flow of 2 ml/min of argon. Repeated carbonization experiment several times and collected the biochar (carbonized peanut shell). A KOH chemical activation was carried out with collected biochars at 350, 450 and 550 ℃ to prepare peanut shell activated carbon (PAC). First, around 30 g of collected biochar was immersed in 500 ml of 7 M KOH solution, followed by heating and stirring for 2 hours. The KOH impregnated biochar was filtered and then dried in an oven at 110 ℃ for 2 days. Then, the KOH-impregnated biochar was activated at 750 ℃ for 2 hours under a flow of 2 ml/min of argon using the same reactor and electric furnace. According to Mohammed et al. [29], the residence time for the activation was

ro of

important, and 2 hours was the optimal residence time. After cooling to room temperature, obtained sample was washed and neutralized with distilled water, and then oven dried at 110 ℃ for 2 days. The dried sample was ground and sieved into 70 µm powder. Finally, the prepared peanut shell activated carbon powders at different carbonization temperatures of 350, 450 and

Jo

ur

na

lP

re

-p

550 ℃ were defined as PAC-350, PAC-450 and PAC-550, respectively.

Figure 1. Schematic diagram of the preparation of activated carbons from peanut shells.

2.2. Preparation of activated carbon filter A PET filter (77×77 mm) purchased from the local market was used to make AC filter, and

the manufacturing process was as follows: first, PAC (22 wt.% of total weight) mixed with organic binder (34 wt.% of total weight), and copper (CuCl2.2H2O, 97.5%) catalyst (22 wt.% of total weight) was dissolved in distilled water (22 wt.% of total weight), and then the AC slurry and the dissolved copper catalyst were mixed for 10 min as shown in Figure 2 (a). Second, a PET filter was immersed into the AC slurry, then pass through a squeezer, and finally dried naturally for 24 hours as shown in Figure 2 (b). Prior to the adsorption experiment, the naturally dried AC filter was again oven dried at 90℃ for 20 min, which was optimal curing conditions determined from our previous study [30].

ro of

2.3. Adsorption and regeneration experiments

In order to simulate a narrow confined space, a transparent plastic box (0.1m3) was designed and fabricated as adsorption apparatus for the adsorption test as shown in Figure 2 (c). Two Cu/PAC filters were installed on the electric fans located in the center of the chamber.

-p

In order to set up an initial H2S concentration of 400 ppm, One liter of standard gas (H2S 4.02% and N2 balance) was injected into the enclosed chamber at a temperature of 20 ℃ and a humidity

re

of 60%, as determined from our previous study [30]. Then the electric fans were operated and the concentration of H2S was measured at 10, 20 and 30 min using a syringe type detector.

lP

After adsorption test, the used Cu/PAC filter was heated in electric furnace at 220 ℃ for 30 min with a flow of 2 ml/min of argon, which was the best regeneration conditions determined from our previous study [12]. The regenerated activated carbon filter was used to re-adsorb H2S gas

na

under the same conditions, and the regeneration and re-adsorption processes were repeated five

Jo

ur

times to evaluate the reusability of the Cu/PAC filter.

Figure 2. Schematic diagrams of (a) mixing of process of activated carbon, (b) manufacturing process of activated carbon filter, and (c) H2S adsorption experimental setup [12].

2.4. Analytical methods The FE-SEM (Scanning Electron Microscope; TESCAN (Czech), VEGA) was used to observe the surface morphology of peanut shell and PACs. The thermogravimetric analyzer (TGA 7, Perkin Elmer, USA) was used to investigate the volatilization properties of PACs. The proximate analysis was performed to investigate the VCM (volatile combustible mater), FC (fixed carbon), and Ash contents in accordance with ASTM D3173, D3175, and E1755. A Flash 2000 CHNS/O elemental analyzer (Thermo Fisher Scientific) was used to determine the C, H, N and S element contents.The N2 adsorption-desorption isotherm was performed at 77 K

ro of

using a surface area analyzer (Quantachrome autosorb-iQ). The specific surface area of PACs was calculated by using the Brunauer–Emmett–Teller (BET) method based on the data of the N2 adsorption–desorption isotherm, and the pore size distribution of PACs was calculated using the non-local density functional theory (NLDFT) method based on the data of the N2

-p

adsorption–desorption isotherm. Impregnated catalyst (copper) and adsorbed H2S molecules on the Cu/PAC filter were determined using SEM-EDS (Hitachi S-2400 with Kevex Ltd., Sigma).The functional groups on the surface of Cu/PAC filter before and after adsorption

re

experiment were identified with Fourier Transform Infrared (FTIR) spectrophotometer (Perkin elmer (U.S.A), Spectrum X). All experiments and analyses were performed at least twice or

lP

more and the average values are reported in the results section. The adsorption capacity of the Cu/PAC filter was calculated with Equation (1). mg,adsorbate g,adsorbent

na

Adsorption capacity (

)=

𝑉𝐶 𝑤

×

𝑀𝑊 𝑉𝑀

× (𝐶𝑖 − 𝐶𝑓 )

where Vc (m3): experimental chamber volume

ur

w (g): mass of adsorbent

Jo

MW (34 g/mol): H2S molar mass Vm (24 l/mol): gas molar volume at 20 ℃ Ci or f (ppm): initial or final concentration of H2S gas

(1)

3. Results and discussion 3.1. Characterization of activated carbon TGA and DTA analyses were carried out at a heating rate of 10 ℃/min in a N2 atmosphere to investigate the thermal behavior of peanut shell and PACs, and the results were shown in Figure 3 (a) and (b), respectively. It can be seen that the TGA curves of all samples consist of three stages in the temperature range of 20 – 800 ℃. The first stage of peanut shell curve at 20 – 120 ℃ was attributed to the evaporation of moisture (about 5.0%). Major weight loss (approx. 92.0%) occurred in the second stage of 120 – 480 ℃, and it was due to the decomposition of

ro of

hemicelluloses and cellulose. Thereafter, about 3.0% of the lignin remained almost constant. A similar result was found by Zhang et al. [31], who reported that the decomposition of hemicelluloses and cellulose mainly occurred at 125 – 400 ℃. For the PAC curves at different temperatures, the first stage of moisture evaporation occurred at 20 – 250 ℃ for PAC-350 (about

-p

5% weight loss) and PAC-450 (about 5% weight loss), and 20 – 200 ℃ for PAC-550 (about 7% weight loss), respectively. The second stage for the decomposition of hemicelluloses and cellulose took place at 250 – 520 ℃ for PAC-350, 250 – 500 ℃ for PAC-450, and 200 – 460 ℃

re

for PAC-550, respectively. During the second stage, a lot of heat was absorbed for the decomposition of lignocelluloses, resulting in a major weight loss of 85% for PAC-350, 80%

lP

for PAC-450, and 68% for PAC-550, respectively. The high endothermic peaks in the DAT curves confirmed that the decomposition of hemicellulose and cellulose mainly occurred at 450 ℃ for PAC-350, 440 ℃ for PAC-450, and 350 ℃ for PAC-550, respectively. This can be

na

explained by the fact that activated carbon with higher carbonization temperature contains less lignocelluloses, and therefore requires a lower endothermic peak for the decomposition of

ur

lignocelluloses.

PAC-350

60

PAC-550 PAC-450

40

DTA (uV)

80

PAC-550

90

Jo

weight percent (%)

100

60 PAC-450

30 0

Peanut shell

20

(a)

0 0

100

Peanut shell

(b)

-30

PAC-350 200

300

400

500

600

700

800

0

100

200

o

Temperature C

Figure 3. (a) TGA and (b) DTA analyses of peanut shell and PACs.

300 400 500 o Temperature ( C)

600

700

800

Proximate and elemental analysis of peanut shell and PACs were performed, and the results were summarized in Table 1. For peanut shell, the FC content was found to be 16.33%, and the ash content was as low as 8.16%. In addition, the carbon content in peanut shells was very high, and it can be confirmed as high as 46.82% by elemental analysis. Based on this information, it can be concluded that peanut shell has great potential to become an excellent AC precursor. After carbonization and activation, the VCM content dropped sharply from 75.51% in peanut shell to 12.77% – 21.28% in PACs. In contrast, the FC content increased sharply from 16.33% in peanut shell to 48.94% - 72.34 % in PACs. Ash also increased from 8.16% in peanut shell

ro of

to 14.89% - 29.79% in PACs. The reduction of VCM and increase of FC were due to the decomposition of hemicellulose and cellulose during carbonization and activation. It wat worth noting that as the carbonization temperature increased, the FC content in PACs reduced, while the ash content in PACs increased. This was attributed to decarboxylation and CO2 release

-p

during KOH activation at 750 ℃. In addition, the significant reduction in oxygen content of PACs was due to the major dehydration (removal of hydroxyl groups, -OH) and minor

re

decarboxylation (removal of carboxyl groups, -COOH) reactions during carbonization and activation. The changes in the properties (composition and element) was supported by the

lP

elemental atomic ratio of O/C and H/C.

Sample

na

Table 1. Proximate and elemental analysis of peanut shell, PACs, rice husk [11], and cocoa AC [24]. Proximate analysis (wt. %) Elemental analysis (%) FC

Ash

C

H

N

O*

O/C

H/C

Peanut shell

75.51

16.33

8.16

46.82

6.58

0.8

37.64

0.60

1.69

PAC-350

12.77

72.34

14.89

72.87

0.83

0.59

10.82

0.11

0.14

18.75

60.42

20.83

68.39

0.72

0.36

9.70

0.10

0.13

21.28

48.94

29.79

59.92

0.78

0.20

9.31

0.12

0.16

PAC-450

Jo

PAC-550

ur

VCM

The scanning electron microscopy images of peanut shell and PACs was shown in Figure

4. An irregular and non-porous surface was observed with peanut shell as shown in Figure 4 (a). For PACs at different carbonization temperature, a highly distributed interconnected hierarchically porous structure with a size range of 1 – 7 µm was clearly observed with PACs as illustrated in Figure 4 (b), (c) and (d). Here, KOH activation played a significant pole in

promoting the formation of a well-developed porous structure on the surface of the PACs. This is fundamental for the adsorption process, because it makes the active sites more accessible and allows diffusion of adsorbate molecules [32]. It should be noted that as the carbonization temperature increased, the surface of PAC became smoother and the pores became cleaner. This was because the lower carbonization temperature cannot completely remove some of the residues (such as coal tar, and coke) generated during the carbonization process, resulting in its remaining in the pore structure of PAC after KOH activation as shown in Figure 4 (b). However, the higher temperature also caused some demerits such as excessive pore size and even collapse of pore structure as shown in Figure 4 (d). Therefore, this indicates that the carbonization

ro of

temperature can highly affected the texture properties of the activated carbon.

Jo

ur

na

(b) PAC-350

lP

re

-p

(a) Peanut shell

(c) PAC-450

(d) PAC-550

Collapse

ro of

Figure 4. SEM images of (a) peanut shell, (b) PAC-350, (c) PAC-450, and (d) PAC-550.

In order to investigate the specific surface area and pore size distribution of PACs, the N2 adsorption-desorption isotherms was performed at 77 K, and the pore size distribution of PACs was calculated by DFT methodology. As shown in Figure 5 (a), all PACs curves displayed

-p

IUPAC type-I isotherms. Steep N2 adsorption at very low relative pressure (P/P O < 0.005) indicates the presence of a large number of micropores (< 2 nm). However, in the case of a

re

P/PO range of 0.5 – 0.9, a very minor hysteresis loop was observed with PAC-350 and PAC550, which means that there is a very small number of mesopores (2 – 50 nm). This was supported by the DFT pore size distribution as illustrated in Figure 5 (b). As can be seen from

lP

Table 2, PAC-450 was found to be the best sample due to its highest BET surface area and largest total pore volume and micropores volume, followed by PAC-550 and PAC-350. This is

na

consistent with the SEM analysis above, i.e, carbonization temperature is a significant parameter on texture properties of AC. In addition, it can be concluded from Table 3 that the

Jo

ur

peanut shell is a good activated carbon precursor and KOH is an excellent activator.

400 300 200

PAC-350 PAC-450 PAC-550

100

(a) 0.2

0.4 0.6 0.8 Relative pressure (P/Po)

-p

PAC-350 PAC-450 PAC-550

0.16 meso

re

micro

macro

lP

0.08

0.00

1.0

(b)

10 Pore width (nm)

100

ur

1

na

3

Incremental pore volume (cm /g)

0 0.0

ro of

3

Quantity adsorbed (cm /g STP)

500

Jo

Figure 5. (a) N2 adsorption-desorption isotherms and (b) DFT pore size distribution (PSD) profiles.

Table 2. Textural properties of PACs

PAC-350 PAC-450 PAC-550

SBET (m2/g) 1325.5 1523.2 1493.5

Vtotal (cm3/g) 0.611 0.736 0.735

Vmicro (cm3/g) 0.475 0.533 0.519

Table 3. Comparison of specific surface area (BET) and pore volume of activated carbon from different biomass by different activators.

Activator

SBET (m2/g)

Vtotal (cm3/g)

Vmicro(cm3/g) References

Peanut shell

KOH

1523.2

0.736

0.533

This work

Peanut shell

CO2

1060

0.802

0.422

[33]

Peanut shell

H3PO4

952.6

0.881

0.278

[34]

Garlic peel

KOH

1262

0.700

0.65

[35]

Unburnt coal

KOH

1520

0.834

0.670

[36]

Cocoa shell

Steam

1042

0.542

0.486

[10]

ro of

Precursors

3.2 Adsorption of H2S

Figure 6 shows the H2S adsorption results using PACs and Cu/PACs filters. It can be seen

-p

that all PACs filters exhibited similar undesirable adsorption efficiencies. Although the adsorption efficiency of all Cu / PACs filters was greatly improved compared to PACs filters, only Cu/PAC-450 filter can completely remove H2S gas within 30 minutes. This indicates that

re

adsorption efficiency not only depend on copper catalyst, but also on the texture properties of

Filter curing: 90oC, 20 min

Measurement: hum.60%, temp.20oC

na

400 300 200

Jo

100

ur

H2S concentration, ppm

500

lP

activated carbon.

PAC-350 PAC-450 PAC-550 Cu/PAC-350 Cu/PAC-450 Cu/PAC-550

0

0

10 20 Measurement time, min

30

Figure 6. Adsorption of H2S by PACs filter and Cu/PACs filter.

Based on the above results, the Cu/PAC-450 filter was selected as sample for the following

analysis. The Cu/PAC-450 filter before and after adsorption was analyzed with SEM-EDS to identify the presence of copper catalysts, and adsorbed H2S molecules in the porous structure of activated carbon. It also help to observe the surface morphology of Cu/PAC-450 before and after adsorption. Before the adsorption, high peak of copper (24.12 wt.%) was identified with Cu/PAC-450 filter, indicating the presence of copper on the surface of Cu/PAC-450 filter as shown in Figure 7 (a). In addition, a relatively loose irregular surface with many pores was observed on the SEM of Cu/PAC-450 filter. These pores were still very clean at high magnification SEM image. After the adsorption, a very obvious high peak of “S” (6.74 wt.%) was determined with used Cu/PAC-450 filter as shown in Figure 7 (b). This strongly confirmed

ro of

that the H2S molecules were adsorbed by the Cu/PAC-450 filter. This was also supported by the SEM image of the used Cu/PAC-450 filter. A relatively compact surface with less pores was found, and the adsorbed H2S molecules was can be clearly observed under the

Jo

ur

na

lP

re

-p

magnification SEM image of the used Cu/PAC-450 filter.

(a)

(b)

ro of

Figure 7. SEM-EDS analysis of (a) new Cu/PAC-450, and (b) Cu/PAC-450 after H2S removal.

Figure 8 shows the FTIR spectra of Cu/PAC-450 filter before and after H2S adsorption. Before the adsorption, the peaks at 720 and 874 cm-1 were assigned to C-H stretching vibration.

-p

The band at 1018 and 1083 cm-1 was attributed to C-O bond stretching in alcohols and ethers. The peaks at 1244, 1340 and 1404 cm-1 were possible due to the C-O, C-H or C-C stretching

re

vibrations [37]. The peaks at 1708, 2356 and 2897 cm-1 were assigned to C=O stretching of carboxylic acid, C-C stretch vibration of alkyne group, C-H stretching vibration, respectively. The wide bands at 3338 and 3444 cm-1 were due to the O-H stretching. After adsorption,

lP

compared with the Cu/PAC-450 filter before adsorption, it was obvious that the peaks at 720, 874, 1018 and 1083 cm-1 have a very large shift in transmittance, indicating that the C-H and C-O groups were significantly involved in the H2S adsorption process. In addition, the

na

transmission of the bands at 2356, 2897, 3338, and 3444 cm-1 fluctuated very little, indicating that the C-C, C-H, and O-H groups are also involved in the H2S adsorption process. However,

ur

no change was found at the peaks of 1224, 1340, 1404 and 1708 cm-1, showing the relevant

Jo

functional groups did not affect the H2S adsorption process.

100 1340 1404 2356

90

2897

1708 874 1083

75

Before H2S adsorption

1018

70 65 500

3444

1244

85 80

3338

After H2S adsorption 720

1000

1500

2000

2500

3000

3500

-1

wave number (cm )

ro of

Transmittance (%)

95

4000

-p

Figure 8. FTIR spectra of Cu/PAC-450 filter before and after H2S adsorption.

3.3 Adsorption of H2S using Cu/PAC-450 at different initial concentration

re

In order to investigate the effect of initial concentration on the adsorption of H 2S onto Cu/PAC-450 filter, adsorption tests were carried at different initial concentrations of 200, 400,

lP

600, 800, and 1000 ppm under the optimal conditions (Hum. 60%, and Temp. 20 ℃), and the result was shown in Figure 9. It can be seen that removal rate decreases with increase of initial H2S concentration, from 99.75% to 55.15%. Especially after the initial concentration exceeds

na

400 ppm, the removal rate drops sharply. The reason for the decrease in removal rate may be that the adsorbent has low availability to adsorbate molecules at high concentrations, because

ur

the active sites on the surface of adsorbent are completely occupied by the adsorbate molecules [38]. In addition, high concentration may cause adsorbate molecules to compete for adsorptive

Jo

sites, resulting in a decrease in removal rate. On the other hand, the adsorption capacity (qe) increased as the initial concentration increases. This can be attribute to the enhanced driving force at high initial concentration. However, it should be noted that the adsorption capacity (qe) hardly increased after the initial concentration of 800 ppm, indicating that the limit of adsorption initial concentration was 800 ppm.

100

90 80 80 70

qe (mg/g)

Removal rate (%)

100

60

60 40 200

400

600

800

1000

Initial concentration (ppm)

ro of

50

-p

Figure 9. Effect of initial concentrations on the removal rate and adsorption capacity of H2S on Cu/PAC-450 filter.

re

3.4 Adsorption isotherm studies

Adsorption isotherm is critical to the relationship between the mass of adsorbed H2S

lP

molecules adsorbed per unit mass of adsorbent (Cu/PAC-450 filter) and the concentration of adsorbate residues in solution when equilibrium is reached. In this work, the adsorption isotherm experiments were carried out with varying initial concentration of 200, 400, 600, 800,

na

and 1000 ppm under the best conditions (Hum. 60%, Temp. 20 ℃). The obtained isotherm data were fitted to two representative adsorption isotherm models of Langmuir and Freundlich models using OriginPro 8 software. The best-fitted adsorption isotherm model can be

ur

determined by a higher correlation coefficient (R2) and a lower error values.

Jo

Langmuir model is expressed as follows [39]: 𝑞𝑒 =

𝑞𝑚 𝐾𝐿 𝐶𝑒 1+𝐾𝐿 𝐶𝑒

(2)

Where qe (mg/g) is the adsorption capacity at equilibrium, qm (mg/g) is the maximum monolayer adsorption capacity, KL (L/mg) is the constant of Langmuir related to the affinity, Ce (mg/L) is the concentration at equilibrium. The separation factor (RL) is as follows:

1

𝑅𝐿 = 1+𝐾

(3)

𝐿 𝐶𝑜

Where Co (mg/L) is the initial concentration of H2S (from 200 to 1000 ppm). The significance of RL value is as follows: adsorption is irreversible (RL=0), adsorption is favorable (01). As can be seen from Table 4, the RL was between 0.45 and 0.99, indicating that the adsorption of H2S onto Cu/PAC-450 filter was favorable. Freundlich model is given as follows [39]: 1⁄ 𝑛

𝑞𝑒 = 𝐾𝐹 𝐶𝑒

ro of

(4)

Where KF ((mg/g)(L/ mg)1/n) is the constant of Freundlich related to the bonding energy, and n is the Freundlich exponent which is used to measure the intensity of adsorption. The significance of n value is as follows: adsorption process is chemical (n<1), linear (n=1), or

-p

physical (n>1). From Table 4, n is 10.03, which indicates that the adsorption of H2S on Cu/PAC450 was a physical process.

re

The adsorption isotherm data were fitted to the isotherm modes and processed by nonlinear regression as shown in Figure 10. The constants, correlation coefficient (R2), and value errors

lP

[SSE: (sum of squared errors), RMSE: (root mean squared error)] was obtained and summarized in Table 4. It can be seen that Langmuir provided a higher correlation coefficient (R2 = 0.9627) compared to Freundlich model (R2= 0.9164). The SSE and RMSE obtained from

na

Langmuir were lower than that from Freundlich. In addition, the qm (95.66 mg/g) provided by Langmuir was very close to the qexp (97.63 mg/g) provided by the experiment. Based on these

ur

results, Langmuir was the best-fitted adsorption isotherm model for the adsorption of H 2S on Cu/PAC-450 filter. The applicability of Langmuir model confirmed that the monolayer

Jo

coverage and homogeneous nature of adsorption of H2S molecules on Cu/PAC-450 filter. Compared with other works on adsorption of H2S using biochars, Marchelli et al. [40]

conducted the adsorption of H2S using gasification biochar derived from a mixture of different wood chips under different operative conditions. The maximum H2S adsorption capacity of 6.88 mg/g was obtained with the biochar produced at 1173 K using dual-stage reactor technology. Sun et al. [41] prepared biochar derived from black liquor (BL) using fluidized bed at 450 ℃ for the adsorption of H2S, and the maximum H2S adsorption capacity was found to be 70 mg/g. Adsorption of H2S using biochar derived from macroalgae at a pyrolysis

temperature of 800 ℃ was performed by Han et al. [42], the maximum H2S adsorption capacity was reported to be 5.8 mg/g. Therefore, the maximum H2S adsorption capacity of 97.63 mg/g in this work was higher than those in the above literatures, indicating that peanut shell has good potential to become a promising adsorption material for the adsorption of toxic gas.

100

40

Experimental Langmuir Freundlich

20

100

200

300 Ce (ppm)

400

500

re

0

ro of

60

-p

qe (mg/g)

80

lP

Figure10. Adsorption isotherm of Langmuir and Freundlich models.

Table 4. Isotherm constants and regression correlation coefficients for the H2S adsorption onto the Cu/PAC-450 filter.

Jo

ur

Langmuir

Freundlich

Parameters qexp (mg/g) qm (mg/g) KL (L/mg) R2 RL SSE RMSE KF ((mg/g)(L/mg)1/n) n R2 SSE RMSE

na

Isotherm models Experimental

Values 97.63 95.66 1.75 0.9627 0.45~0.99 256.32 9.36 55.11 10.03 0.9164 523.11 11.11

3.5 Adsorption kinetic and mechanism studies Adsorption kinetics are critical for describing the rate of adsorption, studying the mechanism of adsorption process, and the rate-limiting step. In this work, the adsorption kinetic

experiments were carried out by adding different initial concentrations (H2S: 200, 400, 600, 800, and 1000 ppm) to experimental apparatus at a humidity of 60% and a temperature of 20 ℃, respectively. The rate of adsorption was measured at varying contact times (0-15 min for 200 ppm, 0-30 for 400ppm, 0-400min for 600, 800, and 1000 ppm) until equilibrium was reached. The obtained kinetic data were fitted to three adsorption kinetic models such as pseudo-first order, pseudo-second order and intraparticle diffusion models. The non-linear equation of pseudo first order model is as follows: 𝑞𝑡 = 𝑞𝑒 (1 − exp(−𝑘1 𝑡))

(5)

ro of

Where qt (mg/g) is the adsorption capacity at time (t, min), qe (mg/g) is the adsorption capacity at equilibrium, k1 (min-1) is the rate constant of pseudo first order.

The non-linear equation of pseudo second order is as follows: 𝑞2 𝑘2 𝑡

𝑞𝑡 = 1+𝑞𝑒

-p

𝑒 𝑘2 𝑡

(6)

re

Where k2 (g/(mg min)) is the rate constant of pseudo second order. The equation of intraparticle diffusion model is as follows: 1⁄ 2

+𝐶

lP

𝑞𝑡 = 𝑘𝑝 𝑡

(7)

Where kp (mg/(g mg1/2)) is the rate constant of intraparticle diffusion model, and C is the

na

intercept.

Figure 11 were fitting results of the adsorption kinetic data for pseudo first order and

ur

pseudo second order models. The constants, correlation coefficient (R2) and value errors (SSE and RMSE) were listed in Table 5. It can be seen that the adsorption pseudo second order model does not seem to be suitable for modelling the adsorption of H2S on Cu/PAC-450 filter due to

Jo

its lower R2 and larger difference between the experimentally obtained adsorption capacity (qe,exp) and the calculated equilibrium adsorption capacity (qe, theo) as compared to the pseudo the pseudo first order model. Since the above two kinetic models were insufficient to interpret the mechanism of adsorption because of its lack of rate-limiting step. Therefore, the adsorption kinetic data was further fitted with an intraparticle diffusion model to explore the mechanism of adsorption and the rate-limiting step, as shown in Figure 12. The adsorption process commonly consists of

three stages: 1. The (i) the transfer of H2S molecule from bulk solution to the external surface of Cu/PAC-450 filter (Film diffusion), (ii) the transfer of H2S molecule from the external surface into the interior pores of the Cu/PAC-450 filter (Intraparticle diffusion) and (iii) Adsorption of H2S molecules onto the interior surface of the Cu/PAC-450 filter (Adsorption) [43]. If the plot of qt vs t1/2 is linear line and passes through the origin, the intraparticle diffusion is the rate-limiting step [43]. However, from Figure 12, no plot was a linear line and passed through the origin, which indicated that the intraparticle diffusion model is not the sole ratelimiting step, and the adsorption can also be controlled by the boundary layer. In addition, as can be seen from Table 6, the R2 at different initial concentrations was smaller than other kinetic

ro of

models such as pseudo-first order and pseudo-second order kinetics, and the value of C was relative large. This also indicated that the intraparticle diffusion model is not the only ratelimiting step, and the adsorption was controlled by the intraparticle diffusion combined with

-p

other kinetic model such as film diffusion (boundary layer).

80

35 200 ppm

400 ppm

70

re

30

60

25

qt (mg/g)

lP

qt (mg/g)

50

20 15 10

Experimental Pseudo-first order Pseudo-second order

0

0

na

5

3

6

9

12

40 30 20

Experimental Pseudo-first order Pseudo-second order

10 0

15

0

5

10

Time (min)

100

Jo

60

0

100

800 ppm

60 40

Experimental Pseudo-first order Pseudo-second order 200 Time (min)

300

400

Experimental Pseudo-first order Pseudo-second order

20 0

0

30

80

40

20

25

100

qt (mg/g)

80

qt (mg/g)

120

ur

600 ppm

15 20 Time (min)

0

100

200 Time (min)

300

400

120

1000 ppm

100

qt (mg/g)

80 60 40 Experimental Pseudo-first order Pseudo-second order

20 0

0

100

200 Time (min)

300

400

ro of

Figure 11. Adsorption kinetic studies with different concentrations.

Table 5. Pseudo-first order and Pseudo-second order kinetic studies on the adsorption of H2S on Cu/PAC-450 filter.

34.41 70.82 88.75 97.63 97.63

qe,theo (mg/g)

k1 (min-1)

R2

SSE

RMSE

qe,theo (mg/g)

k2 (g/(mg min))

R2

SSE

RMSE

33.65 70.09 86.46 95.41 94.45

0.23 0.24 2.44E-2 2.51E-2 2.38E-2

0.9856 0.9946 0.9795 0.9879 0.9851

25.21 31.31 162.57 149.69 152.51

2.25 2.28 4.38 3.33 4.06

44.53 81.23 96.78 106.93 105.68

4.61E-3 3.66E-3 3.33E-4 3.01E-4 3.05E-4

0.9732 0.9921 0.9762 0.9831 0.9809

173.55 46.58 171.89 162.32 160.35

4.36 2.31 4.53 3.57 4.24

100

na

200 400 600 800 1000

ur

80

qt (mg/g)

Pseudo second order

-p

200 400 600 800 1000

Pseudo first order

re

qe,exp (mg/g)

lP

Ci (ppm)

60

Jo

40

20

0

0

3

6

9 12 1/2 t (min)

15

18

21

Figure 12. Intraparticle diffusion model for the adsorption of H 2S on Cu/PAC-450.

Table 6. Intraparticle diffusion model results for the adsorption of H2S on Cu/PAC-450.

Intraparticle diffusion model Kp (mg/(g mg1/2)) R2 1.27 0.4556 3.15 0.6657 4.15 0.8098 5.31 0.8406 4.52 0.8542

Co (ppm) 200 400 600 800 1000

C 12.66 22.22 20.06 17.68 21.95

3.6 Regeneration

ro of

The spent Cu/PAC-450 filter for H2S removal was regenerated by heating it in an electric furnace under an argon flow. The optimized condition regeneration was determined to be 230 ℃ for 30 min according to our previous study [12]. In order to investigate the reusability of the Cu/PAC-450 filter, the used Cu/PAC-450 filter was regenerated and re-adsorbed for multiple

-p

times. As can be seen from Figure 13, although the removal rate weakly decreased as the recycle time increased, the removal rate was higher than 90%, indicating that the regeneration

re

of Cu/PAC-450 filter was acceptable. This can greatly improve the economics and competitiveness of the Cu/PAC-450 filter, thereby increasing its potential in practical

lP

applications. This filter is ideal for use in some household appliances (such as refrigerator, air conditioner, microwave oven, etc.) for indoor air purification. Simply insert the filter into the

na

household appliances to achieve a good air purification.

ur

80

Jo

Removal rate (%)

100

60 40 20 0

1

2

3 Recycle time

4

5

Figure 13. H2S removal using 30-min residence time regenerated Cu/PAC-450 filter in the five cycles after regeneration.

4. Conclusions In this work, a porous activated carbon filter was developed using peanut shells as agricultural waste for the removal of H2S gas in a confined space. The carbonization temperature had a significant effect on the specific surface area and porosity of activated carbon, and the best carbonization temperature was found to be 450 ℃. The best activated carbon sample (SBET=1523.2 m2/g, Vmicro=0.533 cm3/g) was obtained at a carbonization temperature of 450 ℃

ro of

and an activation temperature of 750 ℃ with KOH activation. The best adsorption performance was obtained with a Cu/PAC-450, and the maximum adsorption capacity was 97.63 mg/g. Adsorption result at different initial concentration of H 2S indicated that as the initial concentration increased, the removal rate decreased, and the limit of initial concentration was

-p

800 ppm. Adsorption isotherm and kinetic models were used to analyze the adsorption of H2S on the Cu/PAC-450 filter. The results showed that Langmuir isotherm model was the best fit in

re

describing the adsorption of H2S on the Cu/PAC-450, with a correlation coefficient of 0.9627. The adsorption kinetic process followed the pseudo first order model, and the adsorption

lP

mechanism was controlled by the intraparticle combined with film diffusion model. In addition, regeneration study indicated that the spent Cu/PAC-450 filter can be successfully regenerated and had good reusability. Due to the Cu/PAC-450 filter had some advantages including low

na

cost, simple design, convenient operation, high adsorption performance, and good regenerability, it has wide application prospects in household appliances (refrigerators, air conditioners, etc.) for indoor air purification. Therefore, this study is expected to expand the

ur

utilization of agriculture waste for the indoor air purification.

Jo

Declaration of Interest Statement Hydrogen sulfide (H2S), as a major air pollutant, poses a serious threat to people`s health, especially in confined spaces. However, so far, few studies has been reported on the removal of H2S using a porous activated carbon filter (Cu/PAC) derived from peanut shell biomass. Langmuir isotherm model was the best fit in describing the adsorption of H 2S on the Cu/PAC, and the adsorption kinetics followed the pseudo first order model. The Cu/PAC filter has excellent adsorption capacity (97.63 mg/g), and has good regeneration and reusability. Hence,

due to the Cu/PAC filter had some advantages such as low cost, simple design, convenient operation, high adsorption performance, and good regenerability, it has broad application prospects in household appliances (refrigerators, air conditioners, etc.) for indoor air purification. Therefore, this study is expected to expand the utilization of agriculture waste for the indoor air purification. We confirm that this manuscript is our original work and has not been published elsewhere, nor is it under consideration by another journal. All co-authors have approved the manuscript

ro of

and there is no competition and conflict of interest to report

References

[1] D. Stirling, The Sulfur Problem: Cleaning up Industrial Feedstocks, Royal Society of Chemistry, Cambridge, 2000.

-p

[2] S. Nam, K.B. Hur, N.H. Lee, Environ. Eng. Res. 16 (2011) 159-164.

[3] S. Rasi, J. Lantela, J. Rintala, Energy Convers. Manag. 52 (2011) 3369-3375

re

[4] P. O'Neill, Environmental Chemistry, second ed., Chapman and Hall, London, 1993.

lP

[5] U.S. Occupational, Safety and Health Administration (OSHA), Fact Sheet: Hydrogen Sulfide, (2005) (Accessed 21 September 2017), https://www.osha.gov/OshDoc/ data_Hurricane_Facts/hydrogen_sulfide_fact.html. [6] Khanongnuch R., Capua F. D., Lakaniemi A. M., Rene E. R., Lens P. N. L., H2S removal and microbial community composition in an anoxic biotrickling filter under autotrophic and

na

mixotrophic conditions, Journal of Hazardous Materials 367 (2019) 397–406

ur

[7] J.A. Kadijani, E. Narimani, Simulation of hydrodesulfurization unit for natural gas condensate with high sulfur content, Appl. Petrochemical Res. 6 (2016) 25–34, https://doi.org/10.1007/s13203-015-0107-0. [8] Oliveira L. H. d., Meneguin J. G., Pereira M. V., et al., H2S adsorption on NaY zeolite,

Jo

Microporous and Mesoporous Materials 284 (2019) 247–257 [9] Chaiprapat S., Mardthing R., Kantachote D., Karnchanawong S., Removal of hydrogen sulfide by complete aerobic oxidation in acidic biofiltration, Process Biochemistry 46 (2011) 344–352 [10] Wang S, Nam H, Nam H, 2019. Utilization of cocoa activated carbon for TMA and H2S gas removals in a confined space and its techno-economic analysis and life cycle analysis. Environmental Progress & Sustainable Energy DOI:10.1002/ep.13241 [11] L. Khezami, A. Chetouani, B. Taouk, R. Capart, Production and characterization of activated carbon from wood components in powder: cellulose, lignin, xylan, Powder

Technology 157 (2005) 48–56. [12] Nam H., Wang S., Jeong H. R., TMA and H2S gas removals using metal loaded on rice husk activated carbonfor indoor air purification, Fuel 213 (2018) 186-194 [13] Gebreegziabher T. B., Wang S., Nam H., Adsorption of H2S, NH3and TMA from indoor air using porous corncobactivated carbon: Isotherm and kinetics study, Journal of Environmental Chemical Engineering 7 (2019) 103234 [14] M. Wu, R. Li, X. He, H. Zhang, W. Sui, M. Tan, Microwave-assisted preparation of peanut shell-based activated carbons and their use in electrochemical capacitors, New. Carbon. Mater 30 (2015) 86-91

ro of

[15] Z.A. AL-Othman, R. Ali, M. Naushad, Hexavalent chromium removal from aqueous medium by activated carbon prepared from peanut shell: adsorption kinetics, equilibrium and thermodynamic studies, Chemical Engineering Journal 184 (2012) 238–247.

-p

[16] Macia-Agullo J.A., Moore B.C., Cazorla-Amoros D., Linares-Solano A., 2004. Activation of coal tar pitch carbon fibres: Physical activation vs. chemical activation, Carbon 42, 1367– 1370

re

[17] S. Kamariya, J. Pandya, S. Charola, Preparation and characterization of activated carbon from agricultural waste, peanut shell by chemical activation, Int. J. Trend Res. Dev. 3 (2012) 138–141.

lP

[18] Oginni, O., Singh, K., Oporto, G., Dawson-Andoh, B., McDonald, L., Sabolsky, E., 2019. Influence of one-step and two-step KOH activation on activated carbon characteristics. Bioresour. Technol. Rep. 7, 100266.

na

[19] Fu Y., Shen Y., Zhang Z., Ge X., Chen M., Activated bio-chars derived from rice husk via one- and two-step KOH-catalyzed pyrolysis for phenol adsorption, Science of the Total Environment 646 (2019) 1567–1577

ur

[20] Yang B., Liu Y., Liang Q., et al., Evaluation of activated carbon synthesized by one-stage and two-stage co-pyrolysis from sludge and coconut shell, Ecotoxicology and Environmental Safety 170 (2019) 722–731

Jo

[21] Zhao B., O`Connor D., Zhang J., et al., Effect of pyrolysis temperature, heating rate, and residence time on rapeseed stem derived biochar, Journal of Cleaner Production 174 (2018) 977-987 [22] Angin D., Effect of pyrolysis temperature and heating rate on biochar obtained from pyrolysis of safflower seed press cake, Bioresource Technology 128 (2013) 593–597 [23] Goswami R., Shim J., Deka S., et al., Characterization of cadmium removal from aqueous solution bybiochar produced from Ipomoea fistulosa at different pyrolytictemperatures, Ecological Engineering 97 (2016) 444–451 [24] Otowa T, Tanibata R, Itoh M. 1993. Production and adsorption characteristics of

MAXSORB: high-surface-area active carbon. Gas Sep Purif 7: 241–5 [25] Yang C., Yang S., Fan H., Wang Y., Ju S., Tuning the ZnO-activated carbon interaction through nitrogen modification for enhancing the H2S removal capacity, Journal of Colloid and Interface Science 555 (2019) 548–557 [26] Surra E., Nogueira M. C., Bernardo M., Lapa N., Esteves I., Fonseca I., New adsorbents from maize cob wastes and anaerobic digestate for H2S removal from biogas, Waste Management 94 (2019) 136–145 [27] Balsamo M., Cimino S., de Falco G., Erto A., Lisi L., ZnO-CuO supported on activated carbon for H2S removal at room temperature, Chemical Engineering Journal 304 (2016) 399– 407

ro of

[28] Ezzati M., Indoor Air Pollution: Developing Countries, International Encyclopedia of Public Health (Second Edition) 2017, 201-206 [29] Mohammed J, Nasri NS, Zaini MAA, Hamza UD, Ani FN. Adsorption of benzene and toluene onto KOH activated coconut shell based carbon treated with NH 3. Int Biodeterior Biodegrad 2015;102:245–55

-p

[30] Wang S, Nam H, Kim H, Nam K., 2016. Cocoa activated carbon to remove VOCs (TMA, H2S). 13th International Symposium on the Genetics of Industrial Microorganisms (GIM2016 WUHAN), 277

re

[31] Zhang S., Tao L., Zhang Y., et al., The role and mechanism of K2CO3 and Fe3O4 in the preparation of magnetic peanut shell based activated carbon, Powder Technology 295 (2016)

lP

152–160

[32] G.L. Dotto, C. Buriol, L.A.A. Pinto, Diffusional mass transfer model for the adsorption of food dyes on chitosan films, Chem. Eng. Res. Des. 92 (2014) 2324–2332.

na

[33] Wu M., Guo Q., Fu G., Preparation and characteristics ofmedicinal activated carbon powders by CO2 activation of peanut shells, Powder Technology 247 (2013) 188–196

ur

[34] Zhong Z-Y., Yang Q., Li X-M., et al., Preparation of peanut hull-based activated carbon by microwave-induced phosphoric acid activation and its application in Remazol Brilliant Blue R adsorption, Industrial Crops and Products 37 (2012) 178– 185

Jo

[35] Huang G., Liu Y., Wu X., Cai J., Activated carbons prepared by the KOH activation of a hydrochar from garlic peel and their CO2 adsorption performance, New Carbon Materials, 2019, 34(3): 2 47-257 [36] Wu F-C., Wu P-H., Tseng R-L., Juang R-S., Preparation of activated carbons from unburnt coal in bottom ash with KOH activation for liquid-phase adsorption, Journal of Environmental Management 91 (2010) 1097–1102 [37] Georgin J., Dotto G. L., Mazutti M. A., Foletto E. L., Preparation of activated carbon from peanut shell by conventional pyrolysis and microwave irradiation-pyrolysis to remove organic dyes from aqueous solutions, Journal of Environmental Chemical Engineering 4 (2016) 266–

275 [38] J.M.M. Vianney, K. Muthukumar, Studies on dye decolorization by ultrasound assisted electrocoagulation, Clean – Soil, Air, Water 44 (3) (2016) 232–238. [39] Foo K. Y., Hameed B. H., 2010. Insights into the modeling of adsorption isotherm systems, Chemical Engineering Journal 156, 2–10 [40] Marchelli F., Cordioli E., Patuzzi F., et al., Experimental study on H2S adsorption on gasification char under different operative conditions, Biomass and Bioenergy 126 (2019) 106– 116

ro of

[41] Sun Y., Zhang J. P., Wen C., Zhang L., An enhanced approach for biochar preparation using fluidized bed and its application for H2S removal, Chemical Engineering and Processing 104 (2016) 1–12 [42] Han X., Chen H., Liu Y., Pan J., Study on removal of gaseous hydrogen sulfide based on macroalgae biochars, Journal of Natural Gas Science and Engineering 73 (2020) 103068

Jo

ur

na

lP

re

-p

[43] Jothirani R., Kumar P. S., Saravanan A., Narayan S. A., Dutta A., Ultrasonic modified corn pith for the sequestration of dye from aqueous solution, Journal of Industrial and Engineering Chemistry 39 (2016) 162–175