KR20220155806A - Sulfonated reed biochar for the removal of ammonium from water and method of mamufacturing, and absorbent composition for removing ammonium including the same - Google Patents

Abstract

The present invention relates to sulfonated reed biochar for effective removal of ammonium from water, a manufacturing method thereof, and an ammonium adsorbent composition comprising the same. Since the sulfonated reed biochar manufactured by the method of the present invention has ammonium adsorption ability that can remove ammonium very effectively from water, the biochar can be usefully used as an ammonium adsorbent for removing ammonium from water.

Description

Sulfonated reed biochar capable of effectively removing ammonium from water, manufacturing method thereof, and ammonium adsorbent composition containing the same {Sulfonated reed biochar for the removal of ammonium from water and method of mamufacturing, and absorbent composition for removing ammonium including the same}

The present invention relates to sulfonated reed biochar capable of effectively removing ammonium from water, a method for preparing the same, and an ammonium adsorbent composition comprising the same.

As artificial ammonium, which has increased excessively due to agricultural revolution and industrialization, is excessively contained in water such as seas and rivers, many technologies are being developed to remove it.

On the other hand, biochar, also called biochar, is a solid material with a high carbon content produced when various biomass is thermally decomposed in an oxygen-free environment. It has recently been attracting great attention for its important functions such as productivity improvement and environmental restoration.

In recent years, researchers have focused on the application of adsorbents such as clay minerals, volcanic materials, zeolites, polymer exchangers, and biochar to remove ammonium from wastewater. Biochar, a carbon-rich solid residue produced by thermal treatment of biomass waste, has received much attention as a low-cost adsorbent. A high cation exchange capacity (CEC) and an abundance of oxygen-containing functional groups are known to promote ammonium uptake. Previous studies have shown that the ammonium adsorption capacity of biochar varies greatly depending on the type of feedstock and pyrolysis conditions, some of which release ammonium when applied to water treatment.

Various modifications have been attempted based on two main strategies to further enhance the ability of biochar for ammonium adsorption and removal. Increasing the cation exchange capacity (CEC) of biochar can provide more exchangeable cations to ammonium. In addition, since biochar with a high O/C molar ratio showed higher ammonium adsorption capacity, introduction of a functional group containing oxygen (O) on the surface of biochar could further promote chemical bonding or electrostatic interaction with ammonium. have.

Under this background, the present inventors, while researching to develop a new adsorbent capable of effectively removing ammonium from water, can improve the ammonium adsorption effect through sulfonation in reed biochar, and ammonium in the production of biochar The present invention was completed by identifying the optimal temperature conditions that can further enhance the adsorption performance.

Republic of Korea Patent Publication No. 10-2020-0106583 Republic of Korea Patent Publication No. 10-2019-0102927

Accordingly, an object of the present invention is to provide a method for producing sulfonated reed biochar capable of effectively removing ammonium from water.

Another object of the present invention is to provide a sulfonated reed biochar capable of effectively removing ammonium from water produced by the above production method.

Another object of the present invention is to provide an ammonium adsorbent composition capable of effectively removing ammonium from water, containing the sulfonated reed biochar as an active ingredient.

In order to achieve the object of the present invention as described above, the present invention comprises the steps of a) preparing reed biochar by pyrolysis of reeds; and b) introducing a sulfone group into the reed biochar.

In one embodiment of the present invention, the reeds in step a) may be powdered by washing and drying the reed stems and then pulverizing them.

In one embodiment of the present invention, the thermal decomposition of step a) may be performed at a temperature of 300 ° C to 700 ° C.

In one embodiment of the present invention, the thermal decomposition of step a) may be performed at 300 ° C.

In one embodiment of the present invention, in step b), a sulfuric acid solution is mixed with reed biochar, reacted at 150 ° C to 180 ° C for 10 to 15 hours, and then washed and dried to introduce a sulfone group into reed biochar. may be a step.

In addition, the present invention provides a sulfonated reed biochar for removing ammonium in water prepared by the above method.

In addition, the present invention provides an ammonium adsorbent composition comprising the sulfonated reed biochar as an active ingredient.

In one embodiment of the present invention, the ammonium adsorbent composition can remove ammonium in water.

Since the sulfonated reed biochar prepared by the method of the present invention has an ammonium adsorption ability that can remove ammonium from water very effectively, it can be usefully used as an ammonium adsorbent for removing ammonium from water.

1 is a scanning microscope photograph showing the morphological changes of reed biochar (RBC) and sulfonated reed biochar (SRBC) according to the thermal decomposition temperature of the present invention (A: RBC300, B: SRBC300, C: RBC500, D: SRBC500 , E: RBC700, F: SRBC700).
Figure 2 is a graph showing the adsorption kinetics of reed biochar (RBC) and sulfonated reed biochar (SRBC) of the present invention (Q _t = amount of adsorbed ammonium). The solid line fits a pseudo-first-order kinetic model, and the dotted line fits a pseudo-second-order kinetic model.
Figure 3 shows the adsorption isotherm of ammonium by reed biochar (RBC) and sulfonated reed biochar (SRBC) of the present invention (Q _e = Qe is the amount of ammonium adsorbed at equilibrium concentration; Ce = equilibrium concentration ). The solid line is a curve fitted to the Langmuir adsorption model.
Figure 4 shows the adsorption and desorption isotherms of ammonium by the sulfonated reed biochar (SRBC300) of the present invention. Desorption was performed after adsorption by replacing 15 mL equilibrium adsorption solution with 15 mL water, and the sample was resealed and stirred for an additional 24 hours. The _Qe of the desorption isotherm was calculated by mass balance.
5 shows the spectrum results of FTIR analysis of the reed biochar (RBC300) and the sulfonated reed biochar (SRBC300) of the present invention, and the difference spectrum of the sulfonated reed biochar (SRBC300) before and after the ammonium reaction. it is shown
6 is an FTIR analysis result showing the aliphatic quartet of the IR band of the reed biochar (RBC300) and the sulfonated reed biochar (SRBC300) of the present invention. The spectrum shows a decrease in the aliphatic peak after sulfonation.
Figure 7a shows the low-resolution XPS spectra of reed biochar (RBC300) and sulfonated reed biochar (SRBC300) of the present invention.
Figure 7b shows high-resolution XPS spectra of S2p for reed biochar (RBC300) and sulfonated reed biochar (SRBC300) of the present invention.
Figure 7c shows high-resolution XPS spectra of C1s for reed biochar (RBC300) and sulfonated reed biochar (SRBC300) of the present invention.
Figure 7d shows high-resolution XPS spectra of O1s for reed biochar (RBC300) and sulfonated reed biochar (SRBC300) of the present invention.

The present invention is characterized by providing a method for producing sulfonated reed biochar capable of effectively adsorbing and removing ammonium in water.

Specifically, the method for producing sulfonated reed biochar for removing ammonium in water according to the present invention includes the steps of a) thermally decomposing reed to produce reed biochar; and b) introducing sulfonic groups into the reed biochar.

Biochar, a carbon-based adsorbent, has attracted attention due to its advantages such as low cost, availability of biomass obtained from nature, abundant carbon content, and applicability to various environmental fields. Biochar can be used to remove various pollutants such as organic pollutants and heavy metals due to its unique properties such as large surface area, high porosity, and various mineral components.

The biomass used in the present invention is also referred to as reed for short, and is referred to as no (蘆) or stomach (葦) in Chinese characters. It grows in wetlands, seashores, and sandy areas around lakes. This plant is distributed throughout the world from cool to warm temperate zones, including Korea, and is often used in wetlands constructed for water and wastewater treatment because of its rapid growth, resistance to drought and flooding, and high yield. In addition, since the proper treatment of huge reed wastes harvested from wetlands constructed in autumn/winter is an urgent problem, it is advantageous for industry if the difficult reed wastes can be recycled.

In the present invention, biochar was prepared from reed waste, and a method for using it as a raw material for preparing an adsorbent for removing ammonium in water is devised, thereby providing a new recycling method for reed waste.

The process of the method for manufacturing sulfonated reed biochar for removing ammonium in water according to the present invention is described in detail as follows.

First, in the manufacturing method of the present invention, step a) is a step of producing reed biochar by pyrolysis _of reeds. Alternatively, it is a step of performing thermal decomposition in a nitrogen (N ₂ ) gas atmosphere.

In step a) of the present invention, the thermal decomposition may be performed at a maximum temperature of 300 °C to 700 °C at a heating rate of 5 °C/min, preferably at 300 °C.

If the heating rate and temperature are performed within the above ranges, thermal decomposition may be insufficient and the effect of manufacturing biochar may be insufficient. There is a risk of being thrown away. Therefore, it is preferable to perform thermal decomposition under the above conditions.

In the present invention, the reed biochar prepared through step a) is briefly abbreviated as RBC, and the reed biochar pyrolyzed at three temperature conditions (300 ° C, 500 ° C, 700 ° C) is called 'RBC300' and 'RBC500', respectively. ', 'RBC700'.

Step b) of the present invention is a step of introducing a sulfone group into the reed biochar. This step introduces sulfonic groups into reed biochar through washing and drying processes.

In the present invention, the sulfonated reed biochar prepared in step b) is briefly abbreviated as SRBC, and the final sulfonated reed biochar derived from RBC300, RBC500, and RBC700 is 'SRBC300', 'SRBC500', respectively. It was named 'SRBC700'.

In addition, the present invention provides a sulfonated reed biochar for removing ammonium in water prepared by the above method.

Since the sulfonated reed biochar of the present invention prepared by the above method can effectively remove ammonium in water, it can be usefully used as a biochar having an application for removing ammonium in water.

In addition, the present invention provides an ammonium adsorbent composition comprising sulfonated reed biochar as an active ingredient.

As the ammonium adsorbent composition of the present invention includes sulfonated reed biochar as an active ingredient, it can effectively remove ammonium in water.

Hereinafter, the present invention will be described in more detail through examples. These examples are intended to explain the present invention in more detail, and the scope of the present invention is not limited to these examples.

<Example>

Preparation of sulfonated biochar of the present invention

1. Experiment method

<1-1> Production of reed biochar of the present invention

Giant reed stems ( Arundo donax L. ) were collected from a wetland in Zhejiang Province, China, washed with tap water to remove particles and impurities, and then dried in an oven at 60 °C for 24 hours. The dried reed stems were pulverized using a tissue grinder and sieved to obtain a fine powder (<100 mesh), which was then heated at a heating rate of 5 °C/min in a continuous N2 atmosphere at maximum temperatures of 300 °C, 500 °C, and 700 °C. It was pyrolyzed in a custom quartz vessel using a muffle furnace (Nabertherm B180) at °C. Samples were stored at maximum temperature for 1 hour and then cooled to room temperature for later use. In the present invention, the reed biochar produced through the above process is abbreviated as 'RBC', and the reed biochar thermally decomposed under the above three temperature conditions is named 'RBC300', 'RBC500', and 'RBC700', respectively.

<1-2> Preparation of sulfonated reed biochar of the present invention

The sulfonation of reed biochar was carried out through a thermal reaction with concentrated sulfuric acid. In detail, the reed biochar (RBC300, RBC500, RBC700) of the present invention prepared through <1-1> was mixed with 98% H at a solid to liquid ratio of 1:15 (g:mL) at 150 ° C in a glass reactor. After separately mixing with ₂ SO ₄ , the mixture was magnetically stirred for 12 hours. The solid residue was repeatedly washed with hot water until the washing solution reached a neutral pH, and then dried in an oven at 60° C. for 48 hours to finally prepare the sulfonated reed biochar of the present invention. In the present invention, the sulfonated reed biochar prepared through the above process is abbreviated as 'SRBC', and the final sulfonated reed biochar derived from RBC300, RBC500, and RBC700 is referred to as 'SRBC300', 'SRBC500', and 'SRBC700', respectively. named.

<1-3> Adsorption experiment

Ammonium chloride (NH ₄ Cl, Sinopharm Chemical Reagent Co.) was used to prepare an ammonium solution for adsorption experiments. NH ₄ Cl was dissolved in distilled water at a concentration of 100 mg N/L. Different concentrations of ammonium used in adsorption experiments were diluted in stock solutions. The solution chemistry beyond this was not further calibrated. The final concentration of ammonium in all samples, including the control group, was measured using salicylic acid spectrophotometry, a national standard method in China (Ministry of Environmental Protection, Water quality. Determination of ammonia nitrogen. Salicylic acid spectrophotometry, China Environmental Science Press, Beijing , 2009).

(A) Adsorption kinetics

Adsorption kinetics were performed using batch experiments. Each sample contained 20 mL ammonium solution at a concentration of 5 mg N/L with 0.05 g RBC or 0.02 g SRBC, and was sealed with a Teflon sealing cap in a 22 mL glass tube. Two samples were prepared at each time interval (0, 0.25, 0.5, 0.75, 1.0, 2.0, 4.0, 6.0, 8.0, 12.0, 16.0, 24.0 hours), each with two controls without RBC or SRBC. Samples were stirred at 150 rpm with a shaker at a temperature of 25±0.5° C., collected at hourly intervals, and filtered through a 0.22 μm hydrophilic syringe filter prior to NH4+ analysis. The amount of NH4+ adsorbed by biochar at each time interval was calculated based on the following equation.

where Q _t is the amount of NH4+ (mg N/g) adsorbed at time t and C ₀ and C _t are the initial and residual solution phase NH4+ concentrations (mg N/L) at time t, respectively. V and m are the solution amount (L) and mass (g) of biochar in each sample, respectively.

A pseudo first-order kinetic model (Eq.2) was first proposed by Lagergren to explain the liquid-solid adsorption rate, and a pseudo-second-order kinetic model (Eq.3) was proposed by Ho when chemisorption occurred. has been suggested Both are often applied as potential predictive models to fit adsorption kinetic data, and both were used in this study to fit the determined kinetic data.

where k ₁ and k ₂ are first-order and second-order rate constants, respectively, and Q _e1 and Q _e2 are the maximum adsorption amounts estimated by pseudo-first-order and pseudo-second-order kinetic models, respectively.

(B) Adsorption isotherm

Adsorption isotherms were investigated through batch adsorption experiments. Biochar (0.1 g for RBC, 0.02 g for SRBC) was mixed with 20.0 mL ammonium solution (1–15 mg N/L) of various N concentrations at 25 ± 0.5 °C in a 22 mL glass tube with a Teflon sealed cap. After stirring at 150 rpm for 24 hours, all samples were filtered using a 0.22 μm hydrophilic syringe filter prior to ammonium analysis of the solution. All samples were prepared in duplicate and a control without biochar was included. The classical Langmoor adsorption model (Eq.4), which describes monolayer adsorption behavior and adsorption maxima, is used in this study to fit the nonlinear adsorption.

where Q _e is the amount of ammonium (mg N/g) adsorbed by the biochars at the equilibrium concentration C _e (mg N/L), K _L is the Langmoor adsorption constant, and Q _m (mg N/g) is the biomass is the estimated adsorption capacity of the car.

(C) Characteristics of reed biochar and sulfonated reed biochar of the present invention

The morphology of RBC and SRBC was observed with a field emission scanning microscope (FE-SEM, Hitachi SU-8010) by coating the sample with Pt, and all FE-SEM images were recorded at 10.0 kV.

The surface area of biochar was analyzed using a surface area analyzer using the N2 adsorption-desorption method (Micromeritics' Gemini VII, USA). All samples were degassed at 90 °C and 200 °C before measurement. Surface area was determined using N2 adsorption-desorption data and Brunauer-Emmett's multi-point analysis. The Teller (BET) surface area was recorded. For quality control, standard specimens with known surface area were analyzed along with RBC and SRBC samples. The elemental composition (C, S, O, H, N) of biochar was measured using an elemental analyzer (Vario EL Cube, UK).

Fourier-transform infrared spectroscopy (FTIR) data were collected in the Wavenumber Range of 4,000–400 cm ⁻¹ using a Thermo Fisher NicoletiS 5 spectrometer and a DTGS detector with 4 cm ⁻¹ resolution. A transport assay was performed on KBr pellets to characterize the functional groups of the biochar samples. X-ray photoelectron spectroscopy (XPS) analyzed the chemical state of selected elemental constituents using a thermal science K-alpha+ spectrometer.

2. Experimental results

<2-1> Forms of reed biochar and sulfonated reed biochar

The morphology of RBC and SRBC was observed by scanning electron microscopy (SEM).

As a result, as shown in FIG. 1, there was no clear difference in morphology between RBC and SRBC prepared by varying the thermal decomposition temperature conditions. When the pyrolysis temperature increased from 300 °C to 700 °C, no visible pore structure was formed on the surface of biochar. Many studies have reported that the surface area (SA) of biochar increases as the pyrolysis temperature increases due to the decomposition of organic components of biomass, but the surface area (SA) of the RBC of the present invention does not appear to correlate with the pyrolysis temperature. .

In this experiment, the RBCs pyrolyzed at 300 °C to 700 °C had a very low surface area ranging from 2.63 to 39.51 m ² /g, and a pore volume ranging from 0.005 to 0.016 cm ³ /g. On the other hand, the surface morphology of SRBC (Fig. 1D, E, F) also showed no significant difference from RBC at the same pyrolysis temperature, indicating that sulfonation did not change the physical morphology of biochar. On the other hand, as evidenced by the similarly low surface area (4.17–13.31 m ² /g) and low pore volume (0.010–0.022 cm ³ /g) of SRBC and RBC, the sulfonation process etched the biochar surface or created new pore structures. appeared not to have been created. These results imply that any difference in ammonium adsorption between RBC and SRBC cannot be attributed to surface area differences.

<2-2> Adsorption kinetics

The kinetics of ammonium adsorption by RBC and SRBC were investigated at different time intervals with an ammonium concentration of 5 mg N/L, and the adsorption rate and equilibration time of each isotherm were investigated.

As a result, as shown in FIG. 2, in the case of all RBCs and SRBCs, a rapid increase in Q _t was observed at the beginning of adsorption, especially during the first 2 hours, and the possibility of initial adsorption was higher due to the maximum concentration difference between the adsorbent and the solution. After that, the curve gradually reached a plateau, and it was found that adsorption was approaching equilibrium. Both the pseudo-first-order and pseudo-second-order kinetic models fit the decision data well, but the pseudo-second-order kinetic models performed much better with R2 values higher than 0.94 (see Table 1). This indicates that ammonium adsorption by RBC and SRBC may be through chemisorption. In particular, it was confirmed that SRBC reached equilibrium faster than RBC. As shown in Figure 2, the equilibration time of RBC was about 8 hours, whereas the equilibration time of SRBC was about 2 hours. In addition, the reaction rate constants k ₁ and k ₂ values of SRBC were much higher than those of RBC, indicating that the ammonium adsorption rate of SRBC was significantly faster than that of RBC (see Table 1). In detail, the k ₁ values of RBC ranged from 0.61 to 0.98 h ^-1 , whereas the values of k 1 from SRBC ranged from 2.09 to 5.34 h ^-1 . The same trend was also shown for k ₂ . In a previous study, it was reported that the equilibrium time of ammonium adsorption by MgCl ₂ modified reed biochar produced at 600 ° C was about 10 hours, and the kinetic curve fit well with a pseudo second-order kinetic model. Therefore, it can be inferred that chemisorption including reaction with polar functional groups on the surface of biochar and cation exchange is the main mechanism of ammonium adsorption. Similarly, previous studies have reported that ammonium adsorption by pine sawdust and wheat straw biochar (300 °C and 500 °C) reaches equilibrium in 12 h. Compared with these results, the SRBC of the present invention showed a much faster adsorption rate compared to the prior art, suggesting that the SRBC of the present invention is suitable for water or wastewater treatment. In addition, as shown in FIG. 2, it can be confirmed that the equilibrium adsorption amount of SRBC is significantly higher than that of RBC with the same initial ammonium concentration. On the other hand, RBC and SRBC pyrolyzed at 300 °C showed a higher adsorption capacity for ammonium than those pyrolyzed at 500 °C and 700 °C.

Ammonium adsorption kinetic parameters for biochar in pseudo-first and pseudo-second-order kinetic models biochar Pseudo-first-order kinetics model Pseudo-second-order kinetics model k ₁ , h ^-1 Q _e1 , mg N/g ^R2 k ₂ , g·mg-1·h- ¹ Q _e2 , mg N/g ^R2 RBC300 0.98 0.54 0.9497 2.22 0.59 0.9884 RBC500 0.61 0.19 0.8869 3.81 0.21 0.9468 RBC700 0.62 0.17 0.887 4.15 0.19 0.9457 SRBC300 5.34 2.27 0.9763 5.58 2.32 0.9857 SRBC500 4.89 2.18 0.9097 3.91 2.27 0.9589 SRBC700 2.09 2.02 0.9088 2.24 2.07 0.9552 Q _t = amount of ammonium adsorption at equilibrium
k ₁ = first order rate constant
k ₂ = second order rate constant

<2-3> Adsorption isotherm

Ammonium adsorption was performed at initial ammonium concentrations of 0 to 15 mg N/L for both RBC and SRBC, and the results are detailed in FIG. 3 . Isothermal curves are generally non-linear and represent surface-based adsorption patterns instead of partitioning the biochar matrix into matrices. At low concentrations of ammonium, the adsorption site of biochar was abundant, and the amount of adsorbed ammonium increased rapidly. As the ammonium concentration in the aqueous phase was further increased, fewer adsorption sites became available, and the isothermal curves tended to bend and level. Afterwards, the adsorption site on the surface of biochar became saturated and reached the maximum adsorption. As a result, the isotherm curve was fitted using the Langmoor model based on monolayer adsorption, and the maximum adsorption capacity (Q _m ) of each biochar was estimated. The estimated adsorption model parameters are detailed in Table 2. The correlation coefficients (R ² ) of the models for the determined adsorption data were all higher than 0.94, indicating that the Langmoor model could effectively explain the adsorption behavior of ammonium on RBC and SRBC.

As shown in Figure 3, in the case of RBC, the isothermal curves of RBC300 greatly exceeded those of RBC500 and RBC700, and the isothermal curves of RBC500 were slightly higher than those of RBC700 in the test concentration range. Therefore, the order of apparent adsorption capacity is RBC300 > RBC500 > RBC700. The estimated maximum adsorption capacity (Q _m ) based on the Langmoor model of RBC300 was 1.92 mg N/g, which was higher than that of RBC500 (1.09 mg N/g) and RBC700 (1.30 mg N/g).

_The Q _m value of SRBC was significantly higher than that of RBC, confirming that ammonium adsorption of biochar could be greatly improved through the sulfonation process. Specifically, the Q _m of SRBC300 was 5.19mg N/g, which was more than 2.7 times higher than the 1.92mg N/g of RBC300. Similarly, the Q _m values of _SRBC500 and SRBC700 were found to be 3.85 and 3.65 times higher than those of RBC500 and RBC700, respectively. In addition, since the difference in Q _m between _SRBCs was not as great as that between RBCs, it was found that the sulfonation process could be a controlling factor contributing to the improvement of ammonium adsorption capacity of SRBCs. Through this experiment, it was objectively demonstrated that the sulfonation process can be usefully used to improve ammonium removal in surface modification of biochar and can greatly improve the binding ability of ammonium and biochar.

Desorption of ammonium after adsorption on SRBC300 was also investigated. The results are shown in detail in FIG. 4 . It can be seen from Fig. 4 that almost no decomposition was desorbed from SRBC300, indicating that ammonium was tightly bound to the surface of SRBC300. It is believed that strong interactions between oxygen (O)-containing functional groups on SRBC300 contributed to this effect.

Estimated Langmoor isotherm model parameters for ammonium adsorption on RBC and SRBC biochar k _L , L/mg Q _m , mg/g ^R2 RBC300 0.28 1.92 0.9891 RBC500 0.12 1.09 0.9484 RBC700 0.07 1.3 0.9691 SRBC300 0.69 5.19 0.9858 SRBC500 0.67 4.2 0.9649 SRBC700 0.66 4.74 0.9836 K _L = Langmoor adsorption constant
Q _m = adsorption capacity of biochar

<2-4> Ammonium adsorption enhancement mechanism by SRBC

To elucidate the mechanism of how sulfonation enhances ammonium adsorption, a detailed comparison between SRBC300 and RBC300 with the best performance for ammonium adsorption was performed. In this experiment, we hypothesized that the sulfonation process might have introduced oxygen (O)-containing functional groups on the biochar surface, leading to stronger interactions and consequently enhancing the adsorption and removal of ammonium from water. As a result, various approaches including FTIR, elemental analysis, XPS, etc. have been adopted to characterize the surface properties of biochar before and after sulfonation.

(a) FTIR

Surface functional groups, especially oxygen (O) containing functional groups, are believed to play an important role in controlling the adsorption of ammonium on carbon surfaces. 5 shows FTIR spectra of RBC300, SRBC300 and ammonium-bound SRBC300.

As shown in FIG. 5, biochar produced at 300 ° C. compared to high temperature has more oxygen-containing functional groups and less prominent aromatic carbon peaks. The largest difference between the FTIR spectra of RBC and SRBC is the band at 1174 cm ^-1 . In previous studies, it has been reported that the FTIR bands of 1172 and 1031 cm ^-1 of sulfurized biochar can be considered as S=O expansion modes of -SO ₃ H, which is in the bands of 1174 cm ^-1 and 1037 cm ^-1 for SRBC300 Corresponds (see Fig. 5). These IR bands indicate that -SO ₃ H was successfully incorporated into the SRBC300 surface. In addition, the band at 1712 cm ⁻¹ indicates that O other than -SO 3 H was additionally introduced to the surface of SRBC300 after sulfonation, since C=O expanded in carboxyl. There are bands of about 1600 cm ^-1 and 1400 cm ^-1 in the RBC300 and SRBC300 spectra, which correspond to the asymmetric (ν _as ) and symmetric (ν _as ) extended vibrations of the carboxyl group. In addition, in the case of sulfonation, it was found that the band of 2924 cm ⁻¹ significantly decreased (see FIG. 6). This band is part of a quartet of peaks due to symmetrical and asymmetrical vibrations of CH2 and CH3 of the aliphatic chain. Other signs of a reduced Aliph population can be seen at 1455, 887, and 796 cm ^-1 . Since the pyrolysis temperature of RBC300 was 300 °C, a significant portion of non-carbon biomass residues containing aliphatic rings remained. After sulfonation, the dehydration and carbonation effects of concentrated sulfuric acid reduced the presence or absence of CH bonds in the aliphatic ring, significantly lowering the strength of the band corresponding to the aliphatic group.

The introduction of oxygen (O)-containing functional groups such as -SO ₃ H, -OH, and -COOH was also reflected in the element composition of RBC300 and SRBC300 (see Table 3). The weight ratio of oxygen (O) increased from 18.35% in RBC300 to 33.44% in SRBC300, and the weight ratio of sulfur (S) increased from 0.35% in RBC300 to 2.73% in SRBC300. The O/C molar ratio of RBC300 was 0.21 and 0.52 for SRBC300, and Q _m of RBC300 was 1.92 mg N/g and 5.19 mg N/g for SRBC300, respectively. As the O/C molar ratio increased after sulfonation, the ammonium adsorption capacity was greater in SRBC than in RBC. In addition, the fraction of H decreased from 3.25% in RBC300 to 2.39% in SRBC300, which supports the FTIR analysis and suggests that the loss of H occurred because the sulfonates disrupted the CH bond of the aliphatic ring of RBC.

Elemental analysis of RBC300 and SRBC300 Sample The weight fraction of elements, % O/C Mole ratio C H O N S Ash RBC300 66.21 3.25 18.35 1.18 0.35 10.66 0.21 SRBC300 48.5 2.39 33.44 0.98 2.73 11.96 0.52

(B) XPS

The XPS spectra of RBC300 and SRBC300 were scanned to observe the difference in biochar before and after sulfonation, and the results are shown in detail in FIG. 7 . Low-resolution XPS spectra for RBC300 and SRBC300 showed changes in the elemental composition of biochar upon sulphination (see Fig. 7a). Thus, sulfuric acid modification introduced more oxygen-containing functional groups to the SRBC sample, and the oxygen to carbon (O/C) atomic ratio increased from 0.17 to 0.29 after treatment. The findings also suggest that the sulfur compound increased the atomic percent of sulfur to about 2 at.%. Nitrogen (N) was detected in all of the biochar samples, but at minor levels (i.e., detected in 1-2%). Nitrogen could have been present in the form of N-C and N-H groups, but not oxygen-bonded N groups.

The high-resolution XPS data of S2p, C1s, and O1s separated the spectral peaks to study the bonding state between sulfur, carbon, and oxygen. Tougaard background correction was applied to these peaks to obtain quantification. As shown in Fig. 7b, analysis of the high-resolution S2p scan revealed two S species in the SRBC300 sample: C-S-C (sulfide) or C-S-H (thiol), S2p3/2 at the binding energy (BE) of another peak3/2. showed a peak. Most of S was present in sulfur compounds and/or sulfur compound functional groups (~92.%), and sulphides were present to a much smaller extent. These peaks are consistent with those reported in the literature on the S2p3/2 binding energy of organosulfur compounds. The high-resolution scan of S2p in RBC300 also showed a small peak at BE168-170 eV due to the S content of the precursor.

On the other hand, as shown in Fig. 7c, due to the close BE between the C1 peaks of graphitic carbon and aromatic carbon (sp3 and sp2C, respectively), these two carbon bonding states do not separate into two separate peaks, but form one main peak at 284.8 eV. shared This step is a normal calibration step for comparing XPS data and XPS data of RBC300 and SRBC300. Therefore, the C1s XPS spectrum was separated into 6 peaks. For RBC300, C-C/C-H=C was the major component (~71 at.%). The presence of aromatic carbons in the sample was also evidenced by the presence of π-π* satellite peaks at several eV beyond the BE of the main peak (~6 eV). Carbon could also be present in the form of carbonates, but only in small proportions (~2%). Alcohol and ether carbons (C-OH, C-O) were the second most widely used carbon bonding state, up to 17 at.%. Ketones and carboxylates were also present, but ~4 and 3, respectively, in small fractions. Sulfonation greatly reduced the fraction of C-C/C-H in SRBC300, remaining the aliphatic carbon major component but occupying only up to 60 at.%. In contrast, the atomic percentage of carbon bonded to oxygen increased to ~20 at.% for ethers, ~7 at.% for ketones, and ~7.7 at.% for carboxy functional groups. This increase is consistent with the FTIR results (Fig. 5), indicating a higher proportion of C=O functional groups in SRBC300 than in RBC300. The reduction of the main carbon peak of SRBC300 is also due to the sulfurization of aromatic carbon. Also, the decrease of C=C aromatic carbons is consistent with the decrease (stasis) of the π-π* satellite peaks in the C1s spectrum of SRBC300. Also, as shown in Fig. 7d, the O1s envelope of RBC300 was separated into four peaks attributed to C-type oxygen groups. O1 of SRBC300 was separated into five peaks to account for C-SO2-C (sulfone) and/or C-SO3H (sulfonic acid), which was consistent with the high-resolution scans of S2p and C1s.

(c) potential mechanism

FTIR spectra and elemental analysis showed that there were more oxygen (O)-containing functional groups including -SO ₃ H and -COOH in SRBC than in RBC, indicating that the sulfur compound successfully incorporated such functional groups. Therefore, chemical bonding or electrostatic interaction between oxygen (O)-containing functional groups and ammonium is likely to be the main mechanism that enhances the ammonium adsorption of sulfide biochar.

Seredych and Bandosz proposed that ammonia could act as a Brensted or Lewis acid to form amines or amides with O-containing functional groups, the latter acid being more likely to occur in dry environments. According to their research, in the receiving phase of natural water and wastewater, ammonium is the main form of ammonia and acts as a bronsted acid to react with carboxyl groups.

After sulfonation, new sulfonic groups and more carboxyl groups were formed on the surface of biochar, greatly improving ammonium water adsorption.

In conclusion, in this study, batch adsorption kinetics and isotherm investigations were performed for both reed biochar (RBC) and sulfonated reed biochar (SRBC) to evaluate their potential ammonium removal capabilities. As a result, it was found that biochar pyrolyzed at a relatively low temperature (300 ° C) had a much higher adsorption capacity than bio char pyrolyzed at higher temperatures (500 ° C and 700 ° C), indicating that oxygen (O)-containing functional groups because the spread was higher. The ammonium adsorption rate of SRBC was much higher and the maximum adsorption capacity was much larger than that of RBC, indicating that sulfur compounds can greatly improve the adsorption performance of biocar for ammonium removal. Through further characterization of RBC and SRBC, -SO ₃ H was successfully introduced into SRBC and oxygen (O)-containing functional groups including -SO ₃ - and -COO were increased after sulfidation. Ammonium in water can act as a bronsted acid and react with the carboxyl and sulfone groups in biochar. Therefore, it was confirmed that the sulfur compound can be usefully used to increase oxygen (O)-containing functional groups and, as a result, greatly improve ammonium removal in biochar.

So far, the present invention has been looked at with respect to its preferred embodiments. Those skilled in the art to which the present invention pertains will be able to understand that the present invention can be implemented in a modified form without departing from the essential characteristics of the present invention. Therefore, the disclosed embodiments should be considered from an illustrative rather than a limiting point of view. The scope of the present invention is shown in the claims rather than the foregoing description, and all differences within the equivalent scope will be construed as being included in the present invention.

Claims (8)

a) preparing reed biochar by pyrolysis of reeds; and
b) a method for producing sulfonated reed biochar for removing ammonium in water, comprising introducing a sulfone group into reed biochar. According to claim 1,
The method of producing sulfonated reed biochar for removing ammonium in water, characterized in that the reeds in step a) are powdered by washing and drying the reed stems. According to claim 1,
The thermal decomposition of step a) is characterized in that it is carried out at a temperature of 300 to 700 ℃, a method for producing sulfonated reed biochar for removing ammonium in water. According to claim 3,
The thermal decomposition of step a) is characterized in that carried out at 300 ℃, a method for producing sulfonated reed biochar for removing ammonium in water. According to claim 1,
In step b), a sulfuric acid solution is mixed with reed biochar and reacted at 150 to 180 ° C for 10 to 15 hours, followed by washing and drying to introduce a sulfone group into reed biochar. Manufacturing method of phononized reed biochar. A sulfonated reed biochar for removing ammonium in water prepared by the method of any one of claims 1 to 5. An ammonium adsorbent composition comprising the sulfonated reed biochar of claim 6 as an active ingredient. According to claim 7,
The ammonium adsorbent composition is characterized in that for removing ammonium in water, ammonium adsorbent composition.

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