J. Cent. South Univ. (2018) 25: 2339-2348

DOI: https://doi.org/10.1007/s11771-018-3918-1

NO adsorption and temperature programmed desorption on K₂CO₃ modified activated carbons

YANG Dai-jun(杨代军)^{1, 2}, MA Xiao-wei(马晓伟)³, LV Hong(吕洪)^{1, 2}, LI Bing(李冰)^{1, 2}, ZHANG Cun-man(张存满)^{1, 2}

1. School of Automotive Studies, Tongji University, Shanghai 201804, China;

2. Clean Energy Automotive Engineering Center, Tongji University, Shanghai 201804, China;

3. Department of Physics and Atmospheric Science, Dalhousie University, Halifax,Nova Scotia B3H 3J5, Canada

Central South University Press and Springer-Verlag GmbH Germany, part of Springer Nature 2018

Abstract: Fuel cell stacks as the automotive power source can be severely poisoned by a trace amount of NO_x in atmosphere, which makes it necessary to provide clean air for fuel cell vehicles. In this work, activating commercial activated carbons with K₂CO₃ for the large enhancement of NO capture was studied. K₂CO₃ modified activated carbons (K₂CO₃ ACs) were prepared by impregnating activate carbons in K₂CO₃ solution under ultrasound treatment, followed by temperature programmed baking at 800 ^oC. The dynamic NO flow tests on K₂CO₃ ACs at room temperature indicated that NO adsorption capacity reached the maximum (96 mg/g) when K₂CO₃ loading was 19.5 wt%, which corresponded to a specific surface area of 1196.1 m²/g and total pore volume of 0.70 cm³/g. The ten-fold enhancement of NO adsorption on K₂CO₃ ACs compared to the unimpregnated activated carbon was mainly attributed to the formation of potassium nitrite, which was confirmed by FTIR and temperature programmed desorption measurements. Regeneration tests of NO adsorption on the optimum sample revealed that 76% of the NO adsorption capacity could be remained after the fourth cycle.

Key words: activated carbon; potassium carbonate; modification; NO adsorption; temperature programmed desorption

Cite this article as: YANG Dai-jun, MA Xiao-wei, LV Hong, LI Bing, ZHANG Cun-man. NO adsorption and temperature programmed desorption on K₂CO₃ modified activated carbons [J]. Journal of Central South University, 2018, 25(10): 2339–2348. DOI: https://doi.org/10.1007/s11771-018-3918-1.

1 Introduction

NO_x (mainly NO and NO₂) toxic gases, mostly emitted during the combustion of fossil fuels (by mobile and stationary sources), can cause severe environmental issues like urban smog, acid rain and tropospheric ozone [1–3]. Fuel cell vehicles are a promising substitute for traditional internal combustion engine (ICE) vehicles due to its high energy efficiency and zero air pollution. However, a subsequent issue associated with the application of fuel cell vehicles is the negative impact of NO_x on proton exchange membrane fuel cells. According to previous studies, the presence of NO_x in low concentration can significantly reduce the power efficiency of fuel cells by poisoning the cathode Pt/C catalyst. For example, 1×10^–6 of NO₂ was able to reduce the voltage of proton exchange membrane fuel cells (PEMFCs) by 10% within 100 h [4]. The exposure to 5×10^–6 NO₂ for 12 h could lead to 55% loss on the current of PEMFCs [5]. NO_x (NO: NO₂=9:1) of 140×10^–6 could cause a 30% reduction in the voltage of PEMFCs within 5 min [6]. Therefore, it is important to study the removal of NO_x emitted in the atmosphere because fuel cell vehicles need to inevitably share the traffic with ICE vehicles in a long term.

Although selective catalytic reduction (SCR) of NO_x with NH₃ is effective at relatively high temperatures [7, 8], NO_x removal by sorbents like activated carbons (ACs) is still desirable at ambient temperature considering the low cost and easy replacement [9–13]. K₂CO₃, as an environmentally benign reagent, can chemically activate various carbonaceous raw materials to be ACs (as K₂CO₃ ACs) with well-defined pore structures [14–24]. The consumption of carbon by K₂CO₃ at high temperatures is able to create macropores and/or large mesopores [16]. In addition, the intercalation of potassium vapors at temperatures above 700 °C will further enlarge the graphitic layers of carbon and lead to well-developed micropores and/or small mesopores [25, 26]. K₂CO₃ ACs have been widely studied, but their ability for NO_x capture was rarely reported [27]. AL-RAHBI et al [27] studied waste tire derived ACs and found that K₂CO₃ modification was less effective for NO adsorption than KOH modification due to the poorly developed porous structure. On the other hand, several types of K₂CO₃ ACs were reported to have higher specific surface areas and better porosities than KOH modified activated carbons (KOH ACs) [28–30].

In this work, K₂CO₃ ACs containing different potassium loadings were characterized with TGA- mass spectrometry and N₂ adsorption porosimetry. The NO dynamic flow tests on K₂CO₃ ACs were compared. The temperature programmed desorption and regeneration cycles on the optimum sample were also studied.

2 Experimental

2.1 Sorbent preparation

A type of commercial activated carbon (denoted as AC hereinafter, from Sinopharm Chemical Reagent Co., Ltd.) was first heat-treated in a furnace at 600 °C for 1 h in nitrogen atmosphere to remove possibly contained volatiles. Meanwhile, a series of 0.1 mol/L to 1.5 mol/L K₂CO₃ solutions were prepared by dissolving the calculated amount of K₂CO₃ (Shanghai Guanghua Technology Co., Ltd) in 100 mL deionized (DI) water. 25 g AC was immersed in 100 mL K₂CO₃ solution with vigorous stir for 2 h at 45 °C, and the solution was then treated by ultrasound for 1 h. Subsequently, the solution was drained and the AC powder was dried in a vacuum oven at 100 °C for 24 h. The K₂CO₃ loading ratios (wt% AC) were determined by measuring the weight differences of ACs before and after impregnation.

The temperature programmed heat treatment of dehydrated K₂CO₃-containing ACs was performed to promote the reaction between K₂CO₃ and carbon. The heat treatment was carried out in a fixed-bed reactor with a diameter of 1.5 cm and a bed depth of 3 cm (also served for the dynamic NO flow tests). A tape heater (960 W) was wrapped outside of the reactor and the temperature of the reactor was controlled by a temperature controller. The samples were calcined at 800 °C in helium with a heating rate of 10 °C /min, followed by dwelling at 800 °C for 1 h and then slowly cooled down to room temperature. Finally, five samples (labeled as KC-1 to KC-5) associated with the original AC sample were reserved in a desiccator. The textural properties of all the samples are listed in Table 1.

Table 1 Textural properties of AC and K₂CO₃ ACs (S_T: total specific surface area; S_M: micropore specific surface area; V_T: total pore volume)

2.2 Sorbent characterization

N₂ adsorption-desorption isotherms of AC and K₂CO₃AC samples were collected with a micromeritics ASAP 2020 at 77 K. Samples were degassed at 300 °C for 5 h before the measurements. The specific surface areas of all samples were determined based on the data points at P/P₀ from 0.05 to 0.3 by the brunauer-emmett-teller (BET) method, the micropore surface areas were calculated by dubinine radushkevich (DR) equation and the total pore volumes were determined from the amount of nitrogen adsorbed at the relative pressure of 0.98.

Thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) were carried out using a TASC414 (NETZSCH). Samples loaded in an alumina crucible were heated from 25 °C to 1000 °C with a rate of 10 °C/min in helium atmosphere and the effluent gases were detected by a mass spectrometer (IMSQ4-GP, ABB).

Fourier transform infrared spectroscopy (FTIR) spectra of K₂CO₃ AC samples were collected with an EQUINOXSS/HYPERION2000 (Bruker) in the range from 400–4000 cm^–1.

Powder X-ray diffraction patterns of the original AC and K₂CO₃ AC samples were collected using a D/max-2550PC operated at a voltage of 40 kV and a current of 100 mA. The system is equipped with a Cu K_a radiation source (wavelength = 1.5408). Typical conditions were a scan rate of 0.02 (°)/step and a dwell time of 1.2 s/step.

2.3 Dynamic adsorption-temperature programmed desorption

The dynamic NO adsorption and temperature programmed desorption (TPD) were carried out in the same fixed-bed reactor as depicted earlier. Standard 5% NO and nitrogen (99.99%) were mixed via a four-way valve to form the NO challenge gas stream ((5200±50)×10^–6). The flow rates were controlled by mass flow controllers (Alicat Scientific). The overall flow rate was 60 mL/min. The NO adsorption capacity was calculated based on the integration of dynamic flow test curves. The mixed challenge gas stream was introduced through the reactor and the intensities of NO in the effluent gas stream were detected by mass spectrometer (IMSQ4-GP, ABB).

In TPD measurements, each sample after NO adsorption was heated to 800 °C with a rate of 10 °C/min in helium atmosphere, and the effluent gas stream was also monitored by mass spectrometry.

The regeneration tests were performed by repeating NO adsorption and desorption on the sample which exhibited the highest NO adsorption capacity. In the desorption process, the selected sample was heated to 700 °C with a rate of 10 °C/min in helium atmosphere.

2.4 Adsorption equations

The calculated NO adsorption efficiency and adsorption capacity on activated carbon adsorbents are shown in Eqs. (1)–(3). In this work, T_s was defined as the interval between adsorption beginning and the time when effluent volume concentration of NO (C) returned to 95% of its original concentration (C₀). Equivalent breakthrough time (T^*) is deduced from an ideal adsorption state of NO, in which the concentration of NO increased to its original value immediately.

                             (1)

                       (2)

                      (3)

where η is NO adsorption efficiency, Q_a is the specific adsorption capacity for NO, q₀ is the flow rate (mL/min), M is the molecular weight of NO and w is the loading weight of adsorbents.

3 Results and discussion

3.1 Characterization of K₂CO₃ modified activated carbons (K₂CO₃ ACs)

A commercial AC sample was chosen for K₂CO₃ impregnation and its textural data are listed in Table 1. The AC sample was impregnated into K₂CO₃ solutions of variable concentrations from 0.1 to 1.5 mol/L, respectively, followed by ultrasound treatment. After being dried, the AC surface will be covered by K₂CO₃. During the temperature programmed heat treatment, K₂CO₃ can react with carbon via a solid-solid reaction, forming potassium vapor and CO [23].

Figure 1 shows the TGA and DSC curves of unimpregnated AC and K₂CO₃ ACs in the temperature range of 1000 °C. As can be seen in Figure 1(a), the mass of AC remained constant until approximately 500 °C, afterwards it gradually decreased about 10 wt% in the temperature range from 500 °C to 1000 °C, due to the presence of certain volatiles. K₂CO₃ exhibited two sharp weight losses: one below 100 °C and the other at around 900 °C, corresponding to the dehydration and decomposition of K₂CO₃ respectively. Two endothermic peaks at 84 °C and 890 °C can be seen in Figure 1(b). K₂CO₃ ACs lost more weight than AC in the whole temperature range and the mass loss increased with the increasing K₂CO₃ loading from KC-1 to KC-4. No sharp endothermic peaks were observed on samples KC-1, KC-2 and KC-3, likely attributed to the reaction between K₂CO₃ and carbon. KC-4 and KC-5 showed almost overlapped mass loss below 800 °C, indicating that both samples contained similar amount of K₂CO₃ that can react with carbon (i.e., overloaded K₂CO₃ impregnation in KC-5). The endothermic peak at 150 °C for both samples was related to the dehydration of K₂CO₃. The decomposition of extra K₂CO₃ in KC-4 and KC-5 was indicated by the broad endothermic peaks at 830 and 810 °C, respectively.

Figure 1 TGA (a) and DSC (b) of AC and K₂CO₃ ACs

The mechanism of K₂CO₃ modificaion to prepare ACs mainly follows an overall reaction in Eq. (4) and more detailed reactions in Eqs. (5) to (8) [17, 18]:

                 (4)

                      (5)

                          (6)

                   (7)

                     (8)

The emission of CO during K₂CO₃ modification can differ from variable K₂CO₃ loadings in AC. Figure 2 shows the effluent evolution of CO in helium flow, which was detected by mass spectrometry following the TGA measurement of samples KC-1 to KC-5. The appearance of CO at 580 °C was mainly due to the decomposition of K₂CO₃ to K₂O and CO₂ as in Eq. (5). Meanwhile, CO₂ can be reduced by carbon to form CO (Eq. (6)). The net reaction is shown in Eq. (7). Notably, K₂CO₃ in AC displays much lower decomposition temperature than its pure phase, which is 890 °C as indicated in Figure 1(b). This agrees with the observation in the literature [31]. When temperature was above 700 °C, K₂O can be further reduced by carbon to metallic potassium, resulting in the formation of more CO (Eq. (8)). In general, the potassium deposited among carbon layers should be washed out in order to create more micropores. Herein, potassium will be retained, which has significantly enhanced the NO adsorption capacity as discussed in the next section. Comparing the CO evolution of the 5 samples with variable potassium contents, it is evident that the intensity of CO increased with the amount of K₂CO₃ in AC. Indeed, larger amount of K₂CO₃ will consume more carbon, consistent with the increasing mass loss from KC-1 to KC-5 as shown in Figure 1. It is noted that each sample, except for KC-1, exhibited a broad peak in the range of 650–700 °C. As discussed above, more CO will be produced below 700 °C in Eq. (7) than in Eq. (8). In particular, KC-5 shows a higher peak at about 800 °C, which is in agreement with the sharp mass loss and the endothermic peak of KC-5 at 810 °C in Figure 1. This is likely due to the overloading of K₂CO₃, in which case the excessive part of K₂CO₃ did not react thoroughly with carbon at low temperatures.

Figure 2 Effluent evolution of CO for K₂CO₃ ACs following TGA measurement

The porosity of AC can be largely affected by the potassium loading because the pores were partially or fully filled with potassium ions after heat treatment [32]. Figure 3 shows the N₂ adsorption–desorption isotherms of the unimpregnated AC and K₂CO₃ ACs. The isotherm of AC contains a hysteresis loop between P/P⁰ = 0.4 and 1 due to the capillary condensation of flat particle mesopores (2–50 nm), which is consistent with the characteristics of type IV isotherm (IUPAC) [33]. As the potassium loading increased, the hysteresis loop became smaller and nearly invisible for KC-5, indicative of less mesopores in AC. The porosity data of K₂CO₃ ACs are shown in Table 1. The total and micropore specific surface areas (S_T and S_M) as well as the total pore volume (V_T) were largely reduced by the increased amount of K₂CO₃. However, the proportion of micropores among the total pores became higher, as reflected by the increasing ratio of S_M/S_T ratio. In the impregnation process, K⁺ and CO₃^2- ions had easier access to mesopores and macropores, so large pores can be etched more severely by K₂CO₃ with heat treating [32].

Figure 3 N₂ adsorption–desorption isotherms of AC and K₂CO₃ ACs

3.2 NO adsorption and temperature programmed desorption (TPD)

The removal of NO is herein highlighted because it is more difficult to be captured than NO₂, which is soluble in water [34]. Figure 4(a) shows the adsorption efficiencies (η) of NO on the unimpregnated AC and K₂CO₃ ACs, which derived from their dynamic NO flow tests. The capture of NO by all the samples can be distinguished by comparing the decreasing rates of adsorption efficiencies. The unimpregnated AC exhibited poor NO adsorption efficiency, as reflected by the quick drop to less than 10% dring the beginning 40 minutes. The affinity of NO onto AC was mostly attributed to the physical adsorption in the carbon pores. As NO reached the surface of AC, it can interact with oxygen complex (the oxygen content in AC is 22.5 wt%) to form NO₂ as described by Eq. (9) [35]. NO₂ may be directly captured in the micropores of AC or converted to some surface complex such as C-NO₂, C-ONO, C-ONO₂ [36, 37]. When potassium was loaded as K₂CO₃ ACs, NO adsorption was apparently improved due to the occurrence of chemisorption. At the K₂CO₃ loading of 9.5 wt% (KC-1), the adsorption efficiency decreased to ~20% in 100 min and then more slowly to ~5% after 700 min. A higher K₂CO₃ loading at 19.5 wt% (KC-2) further promoted NO adsorption. The adsorption efficiency was about 40% at 200 min and declined to 15% after 800 min. Unfortunately, loading more potassium from KC-3 to KC-5 turned to lower the NO uptake as reflected by the decreasing NO adsorption efficiency. The overall adsorption capacities versus potassium contents of all 6 samples were calculated and shown in Figure 4(b). The amount of NO adsorbed increased drastically with potassium loadings for AC, KC-1 and KC-2. KC-2 demonstrates the highest NO adsorption capacity of 96 mg/g, which is nearly 10 times higher than the unimpregnated AC, indicating NO adsorption was mainly dominated by the chemisorption. This also explained the decline trend on NO capture as potassium loading increased. Overloaded potassium can block the pores and reduce the effective surface area of AC. Hence further enhancement on the uptake of NO was hindered.

                      (9)

Figure 4(b) also displays the NO adsorption results on KOH AC samples that derived from our previous results [38]. It is evident that both K₂CO₃ and KOH modified ACs exhibited nearly overlapped trends in NO adsorption with the potassium loading. The production of K₂CO₃ was often associated with the heat treatment of ACs by KOH, during which KOH reacts with carbon to form K₂CO₃ at above ~400 °C and until the reaction is finished near 600 °C [39]. In this respect, K₂CO₃ heat treatment is superior to KOH treatment for NO removal by AC considering KOH is a strong base.

Figure 4(c) displays the effluent NO₂ concentration in the NO adsorption test of KC-2. The inlet NO challenge gas stream contained ~6×10^–6 NO₂, which was completely adsorbed from the onset of the flow test. Subsequently, the breakthrough occurred quickly and the NO₂ concentration returned to the original level (6×10^–6)in 3 h. The evolution of NO₂ suggested that NO₂ was mostly adsorbed by the sorbents if significant amount was produced (the concentration of NO in the stream was ~5000×10^–6). For all reactions, the presence of active oxygen and potassium sites was believed to be very important and AC was proposed as a catalyst in the reaction process [40]. When potassium was consumed adequately by NO and NO₂, the breakthrough occurred.

The mechanism of NO/NO₂ adsorption on K₂CO₃ ACs is believed to be related to the formation of potassium nitrate and/or nitrite in the presence of oxygen functional groups [32, 41, 42]. According to previous studies, the possible reactions are summarized in Eq. (10) to Eq. (12). NO can be converted into NO₂ as discussed earlier in Eq. (9), and NO₂ will then react with potassium to form potassium nitrite (Eq. (10)) or potassium nitrate considering potassium was dispersed in the graphitic layers after K₂CO₃ modification. In the latter case, NO₂ will either directly react with potassium nitrite to nitrate and release NO (Eq. (11)) or be oxidized followed by reaction with potassium (Eq. (12)). However, attempt to identify crystalline potassium nitrite or nitrate was unsuccessful.Figure 5(a) shows the powder XRD patterns of AC and KC-2 before and after NO adsorption. The parent AC exhibits two broad peaks at 2θ=24° and 43°, corresponding to the amorphous carbon [43]. After being activated by K₂CO₃, no specific peaks corresponding to K₂CO₃ were seen on KC-2, supporting the previous claim that K₂CO₃ no longer exists after heat treatment. No obvious crystalline diffraction for KNO₂ or KNO₃ was present on KC-2 after NO adsorption probably because of the highly amorphous feature of AC.

Figure 4 Dynamic NO and NO₂ flow test results:(inset: Normalized NO adsorption capacity after each cycle)

                   (10)

                (11)

                (12)

Figure 5(b) shows the FTIR spectra of AC and KC-2 before and after NO adsorption. The weak band at 3440 cm^–1 for the unimpregnated AC and KC-2 was due to the stretching vibration of water. The other band at 1560 cm^–1 for KC-2 can be assigned to the bending mode of water. The adsorption bands corresponding to K₂CO₃ (at 865,1450 and 3220 cm^–1 [44]) were not observed. After NO adsorption, KC-2 exhibits the typical bands for KNO₃ and KNO₂ at 1380 cm^–1 and 1260 cm^–1, which were related to the stretching vibrations of NO₃^– and NO₂^– respectively [44]. The bands at 3440 cm^–1 and 1560 cm^–1 for water can still be observed.

Figure 5 Powder XRD patterns (a) and FTIR spectra (b) of KC-2 before and after NO adsorption

The temperature programmed desorption (TPD) of KC-2 after NO adsorption was performed in helium atmosphere and the NO/NO₂ evolution in the effluent stream monitored by mass spectrometry is shown in Figure 6. Figure 6(a) involves NO desorption at temperatures below 600 °C. The presence of two peaks at 130 and 310 °C agreed with Lee’s TPD results on KOH ACs after the adsorption of NO₂/NO (482/18×10^–6) [41]. The weak peak at 130 °C was attributed to the physical adsorption of NO while the strong peak at 310 °C mainly derived from the decomposition of KNO₂ as described by Eq. (13). Figure 6(b) illustrates the desorption isotherm of NO₂ till 800°C and two main concentration peaks were observed. The small peak at 210 °C corresponds to the physically adsorbed NO₂. Compared to the physical desorption of NO at 130 °C, NO₂ can be more tightly bound onto the carbon surface. The very broad peak in the range of 420–470 °C was due to the decomposition of KNO₃, as depicted by Eq. (14). The full decomposition of KNO₃ was not completed at 800 °C. According to Eq. (14), the decomposition of KNO₃ emitted the same amount of NO and NO₂. Consistently, the NO concentration at 400 °C was ~70×10^–6 in Figure 6(a), comparable to the concentration of NO₂ (~60×10^–6) in Figure 6(b). Note that the desorbed NO was at least two orders of magnitude higher than NO₂ (8000×10^–6 NO vs 60×10^–6 NO₂ at the highest concentration), indicating that the NO chemisorption on K₂CO₃ ACs was dominated by the formation of KNO₂.

               (13)

         (14)

In order to investigate the regeneration ability of K₂CO₃ ACs, the cyclic NO adsorption on KC-2 was performed by activating the sample at 700 °C after saturated adsorption of NO. K₂O will start to react with carbon to form metallic potassium again at above 700 °C as discussed previously in Eq. (5). Therefore, the regeneration temperature was set at 700 °C in order to stabilize the dispersion of K₂O. Figure 4(d) shows four NO adsorption cycles on KC-2. For each cycle, KC-2 lost part of the NO adsorption capacity compared to the previous one. After the fourth cycle, the amount of NO absorbed by KC-2 decreased to 73 mg/g, which is 76% of the original capacity (see the inset of Figure 4(d)). Two possible reasons may lead to the reduction of NO adsorption capacity on K₂CO₃ ACs: NO adsorbed onto the surface of ACs was not removed completely during the regeneration, or the pore structure of ACs was damaged after regeneration, which further affected the dispersion of potassium.

Figure 6 Temperature programmed desorption of NO_x on KC-2:

4 Conclusions

K₂CO₃ ACs were prepared from the impregnation of AC in K₂CO₃ solutions followed by temperature programmed heat treatment at 800 °C in helium atmosphere. The K₂CO₃ modification drastically decreased the specific surface areas and total pore volumes of ACs due to the reaction between carbon and K₂CO₃. On the other hand, potassium vapor penetrated and settled among carbon layers. The importance of potassium settling in AC was reflected by the improved NO dynamic adsorption on K₂CO₃ ACs at room temperature.

K₂CO₃ ACs exhibited much higher NO adsorption than the unimpregnated AC. Among all the measured samples, KC-2 with potassium loading of 19.5 wt% showed the highest adsorption capacity (96 mg/g). FTIR and powder XRD patterns demonstrated that the mechanism of NO adsorption on K₂CO₃ ACs mainly concerned the formation of KNO₂ and a limit amount of KNO₃, which decomposed at high temperatures as indicated by the TPD measurements. The adsorption capacity of K₂CO₃ ACs decreased to 76% after four regeneration cycles. Overloaded potassium (>19.5 wt%) significantly reduced NO uptake on K₂CO₃ ACs.

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(Edited by HE Yun-bin)

中文导读

K₂CO₃ 改性活性炭上NO的吸附和程序升温脱附

摘要：燃料电池易受到空气中的NO_x的影响，因此有必要净化进入燃料电池汽车的空气。本文研究了通过K₂CO₃ 增强商用活性炭吸附NO的性能。K₂CO₃改性活性炭（K₂CO₃ ACs）是通过超声波环境下的溶液浸渍活性炭，然后在800 ℃高温下热处理得到的。NO流量曲线表明，当K₂CO₃ 溶液的浓度达到19.5 wt%时，NO在室温下的吸附容量最高，可达96 mg/g，这相当于1196.1 m²/g的比表面积和0.70 cm³/g的总孔容。与未经改性的活性炭相比，K₂CO₃ ACs的吸附能力提升了十倍；这主要应归因于亚硝酸钾的生成，这也经FTIR和程序升温脱附实验结果得以证明。此外，该样品还表现出一定的可再生性，经四次NO吸附和脱附实验室，它还能保持76%的初始吸附容量。

关键词：活性炭；碳酸钾；改性；NO吸附；程序升温脱附

Foundation item: Project(2018YFB0105303) supported by the Ministry of Science and Technology of China; Project(17DZ1200702) supported by the Shanghai Science and Technology Committee, China

Received date: 2017-06-17; Accepted date: 2018-02-26

Corresponding author: LV Hong, PhD, Associate Professor; Tel: +86–21–69583850; E-mail: lvhong@tongji.edu.cn; ORCID: 0000- 0003-4899-1088