Haofeng Wu,Yanhong Chao,*,Yan Jin,Duanjian Tao,Xiaowei Li,Jing Luo,Guohua Xia,Linhua Zhu,Wenshuai Zhu,*

1 School of Pharmacy,Jiangsu University,Zhenjiang 212013,China

2 College of Chemistry and Chemical Engineering,Jiangxi Normal University,Nanchang 330022,China

3 School of Chemistry and Chemical Engineering,Jiangsu University,Zhenjiang 212013,China

4 Key Laboratory of Tropical Medicinal Plant Chemistry of Education,Hainan Normal University,Haikou 571158,China

Keywords:Boron nitride Ball mill Exfoliation Adsorption Water treatment

ABSTRACT The method of fabricating low-cost adsorbents with high activity and durability via a convenient and ecofriendly procedure is of great importance to wastewater treatment.Herein,a high-efficient mechanical exfoliation strategy was proposed to facilely prepare few-layered graphene-analogue boron nitride(BN)via a one-step non-organic solvent assisted wet ball mill procedure.Ball-milling treatment increased the specific surface area of BN 3.5-fold by reducing the thickness to～3 layers with 45 min.The exfoliated BN exhibited strikingly improved sorption performance to organic contaminants with around 124% and 116%increased removal efficiency respectively for oxytetracycline(OTC)and Rhodamine B(RhB)as compared to the bulk BN.Batches sorption experiments showed that the sorption processes were thermodynamic endothermic,and well fitted to pseudo-second-order kinetic model and Freundlich isotherm equation.The π-π stacking interaction,hydrophobic effect and electrostatic interaction were proposed as the dominated sorption mechanism.In addition,no significant decline in adsorptive removal ability for the sorbent after 5 times recycling.The results indicate that the ball-milling exfoliation is a fast,green,sustainable and promising strategy for synthesis of highly potent BN based two-dimensional layered adsorbents.

1.Introduction

Water pollution has become more and more serious with the development of industrialization,which seriously affects the sustainable development of society and human health [1,2].It is of great urgency to develop practical ways to treat the contaminants efficiently before discharging them into the environment.Various techniques for wastewater treatment have been reported in recent years,such as electro-Fenton method [3],photocatalytic degradation [4,5],biodegradation [6],membrane separation [7] and adsorption [8,9],etc.The adsorption method has drawn considerable attention with respect to the advantages of simple operation,low cost,wide availability and no risk of high toxic by-products.

Over the past few years,numerous adsorbents including active carbons [10],carbon nanotubes [11],biochar [12],metal-organic frameworks [13],silica [14],chitosan [15],resin [16] and layered two-dimension (2D) nanomaterials [8] have been applied to remove organic pollutants from contaminated water.Among these adsorbents,hexagonal boron nitride (h-BN) is of great concern because of its thermal stability,chemical inertness,environmental friendliness and cost effectiveness.One of the most effective way to improve the sorption performance of h-BN is to increase the specific surface area and the surface active-sitesviavarious physical or chemical means.Changet al.[8] synthesized few-layer graphene-like BNviahigh-temperature pyrolysis method and g-BN showed excellent adsorption ability to methylene blue (MB)and rhodamine B (RhB).Up to now,to synthesize few-layered graphene-analogue h-BN,hydrothermal method [17],chemical vapor deposition(CVD)[18],ultrasound-assisted liquid exfoliation,template method [19],high-temperature pyrolysis [20] and gas exfoliation method,etc.[21]have been developed.However,there are always more or less limitations using these technologies,such as complex processes,time-consuming procedures,expensive/toxic reagents or harsh experimental conditions.Hence,it is of great significance to develop a facile,faster and more eco-friendly method to prepare few-layered BN.

As a simple,effective and green technology,mechanical ball milling method has attracted tremendous interest in the preparation of alloys,composites and ultra-fine powders [22-24].Recently,planetary ball-milling technology has been proposed as an extensible top-down method to shear two-dimensional bulk materials to the thin layers [25,26].Not only that,the ball milling technology plays an important role in improving the porosity,specific surface area,surface functional group contents and creating new defects on the surface of materials[27].For instance,Xianget al.[28] reported that ball milled biochar significantly enhanced the adsorption ability of volatile organic compounds(VOCs),which may be attributed to the increase of the specific surface area,hydrophilicity and polarity.Huanget al.[29]employed ball milling to modify biochar and showed that,compared with the pristine biochar,the specific surface area and surface functional groups of ball-milled biochar increased and the removal efficiency of sulfamethoxazole (SMX) increased from 33.4% to 83.3% and sulphapyridine (SPY) increased from 39.8% to 89.6%.However,there is rarely research on the adsorption of organic pollutants onto ball milled BN.

Herein,we applied the ball milling procedure to be as a powerful green strategy to prepare few-layered BN for organic dyes and antibiotics removal.The synthesis method was simple,fast,lowcost and required no organic solvents.The principle was that grinding by ball milling can reduce the particle size and enhance the specific surface area,and thus,improve its adsorption ability.After ball milling,the specific surface area of BM-BN was increased to 3.5 times than that of commercial BN with significantly enlarged pore volume.It is noteworthy that the thickness of BM-BN was successfully stripped to about 1.2 nm after ball milling for 45 min,and the removal efficiencies of oxytetracycline (OTC) and Rhodamine B (RhB) were both increased by approximately 120%.

2.Materials and Methods

2.1.Materials

Boron nitride (BN),oxytetracycline hydrochloride (OTC) and levofloxacin hydrochloride (LOF) were obtained from Sigma-Aldrich.Rhodamine B(RhB),methylene blue(MB),NaOH,HCl,NaCl and CaCl2were obtained from Sinopharm Chemical Reagent Co.

2.2.Preparation of graphene-analogue few-layered BN

The preparation of graphene-analogue few-layered BN was performed in a PM-100 ball miller.The specific experimental steps were as follows:commercial BN and the zirconia balls were placed in the stainless-steel ball milling tank at a mass ratio of 1:200,and 0.5 m H2O was added.The samples were milled for 45 min at a speed of 400 r·min-1,and then dried at 80℃.The final samples were used to study the adsorption ability.And the milling parameters were optimized by varying milling speed,powder-to-ball mass ratio,milling time and solid-to-liquid mass ratio (the mass ratio of commercial BN to water).The graphene-analogue fewlayered BN prepared by ball milling was marked as BM-BN.

2.3.Characterization

The morphologies of adsorbents were detected by scanning electron microscopy (SEM,JSM-7800F,Japan).Crystal structure of adsorbent was determined by X-ray diffractometer (XRD-6100,Shimadzu,Japan).The nitrogen adsorption-desorption isotherms were testedviaa Micromeritics 2020 HD88 surface area and porosity analyzer.FT-IR spectra was detected on a Nexus 470 spectrometer.The surface structure of adsorbent was analyzed by atomic force microscope (AFM,Asylum MFP-3D,Asylum Research Company,USA).

2.4.Adsorption experiments

In a typical experiment,10 mg of BM-BN was placed in 10 ml of OTC or RhB solution with certain initial concentrations.Then the mixture was shaken at 130 r·min-1in a thermostatic water bath.The sorption behaviors of OTC and RhB on the BM-BN were investigated in terms of adsorption kinetics,isotherms,and thermodynamic as well as pH and ionic strength.All samples were filtered with 0.22 μm filters.Then the absorbance data of the samples were detected by a UV-Vis spectrophotometer.The calculation formulas of the removal efficiency and the adsorption capacity (qe/mg·g-1)are as following:

whereC0is the pollutant concentration in the initial liquid(mg·L-1).CtandCeare the residual pollutant concentrations at timetand equilibrium time,respectively(mg·L-1).Vis the volume of the solution (ml) andmrefers to and the mass of adsorbent (mg).

3.Results and Discussion

3.1.Characterization of BM-BN

The morphologies of commercial BN and BM-BN were studied by SEM,and the results are displayed in Fig.1(a)and(b).The commercial bulk BN was comprised of smaller flakes,and the thickness was obviously reduced after ball milling.To further study the thickness of BM-BN,AFM was employed.It was illustrated in Fig.1(c)and(d)that the thickness of BM-BN was～1.2 nm(～3 layers) [30].However,the thickness of commercial BN was found to be 25-42 nm in the previous work [31].This kind of thickness change is due to that the mechanical shear force can easily peel off BN sheets from the parent material [32].Therefore,it clearly indicated that the commercial bulk BN was successfully exfoliated into graphene-analogue few-layered BN after ball milling.

FT-IR spectroscopy was used to investigate the surface functional groups and bonding nature in BM-BN and the commercial BN.In the Fig.2(a),the two characteristic peaks around 1378 and 806 cm-1corresponded to B-N in-plane stretching vibration and B-N-B out-of-plane bending vibration,respectively.The peak around 806 cm-1of BM-BN was significantly enhanced compared to the pristine commercial BN,this change could be attributed to the smaller thickness of the BM-BN after they were peeled from the BN powder [32-34].In addition,BM-BN exhibited O-H stretching at around 3391 cm-1,it was suggested that these functional groups were formedviacleavage of B-N bond by moisture[35],which showed that ball milling enhanced the functional groups of BM-BN.

The specific surface area and pore volume of BM-BN and commercial BN were evaluated by nitrogen adsorption-desorption analysis,and the results can be observed in Fig.2(b) and Table S1 (in Supplementary Material).The commercial BN and BM-BN showed a type II curve and the hysteresis loop at a relative pressureP/P0of 0.6-1.0 were H3-type,indicating a slit-shaped porous channel[36].The measurements showed that the specific surface area of BM-BN was 80 m2·g-1,which was 3.5 times than that of commercial BN.Meanwhile,the total pore volume of BM-BN increased to 0.335 cm3·g-1[37].The high surface area and large pore volume are beneficial to enhance the adsorption ability of the adsorbent.

Fig.1.SEM images of (a) commercial BN and (b) BM-BN;(c) AFM image and (d) the height profiles of BM-BN.(Ball milling parameters:milling time=45 min,milling speed=600 r·min-1,powder-to-ball mass ratio=1:250,solid-to-liquid mass ratio=1:0.0075).

The normalized X-ray diffraction(XRD)patterns of the samples are displayed in Fig.2(c).Compared to commercial BN,BM-BN showed similar but intensity decreased characteristic diffraction peaks at 26.6°,41.5°,54.9° and 75.9° arising from the (002),(100),(004),(100) plane [32].Notably,the (002) peak of BM-BN decreased significantly,indicating that the numbers of layers of the commercial BN reduced.And the two-theta peak slightly downshifted from 26.60 to 26.45° (Fig.2(d)),indicating that the distance between the planes increased [30].

3.2.Optimization of ball milling parameters

The efficiency of ball milling is closely related to the milling parameters,such as milling speed,milling time,powder-to-ball mass ratio and solid-to-liquid mass ratio.By altering the type of ball milling agent and ball milling parameters,the yield and size of h-BNNS can be regulated [38].The optimization results of various milling parameters are presented in Fig.3.As shown in Fig.3(a),when increasing the ball milling speed from 100 to 600 r·min-1,the removal efficiency of OTC increased from 31% to 84%.As milling speed increased,shear force and impact force enhanced and more adsorption sites of BM-BN were generated[39].The optimum milling speed was 600 r·min-1.It can be seen from Fig.3(b),with the increase of the ball milling time,the removal efficiency of OTC increased firstly and then tended to equilibrium.Considering ball milling efficiency and energy saving,it was believed that 45 min was the best ball milling time.Fig.3(c)revealed that the removal efficiency of BM-BN was increased from 43% to 88% when the powder-to-ball mass ratio increased from 1:50 to 1:250.However,with the further increase,the removal efficiency only increased by 1%.So,1:250 was the best powder-to-ball mass ratio.Fig.3(d) showed that the removal efficiency reached 92% when the solid-to-liquid mass ratio was 1:0.0075.When the solid-to-liquid mass ratio reached 1:0.01,the adsorption performance decreased.Consequently,the ball milling parameters were optimized as following:the ball milling time was 45 min;the ball milling speed was 600 r·min-1;the powder-to-ball mass ratio was 1:250 and the solid-to-liquid mass ratio was 1:0.0075.In the present work,water as a colorless,nontoxic,and good fluidity substance was used for BN ball milling,the obtained BM-BN was no need to be further purified,which effectively regulates the cost,reduces the emission of toxic substances,and facilitates the safety factor in the synthesis [38].

3.3.Adsorption performance of BM-BN

The adsorption performance of BM-BN to OTC and RhB was investigated.As shown in Fig.S1,the removal efficiencies of OTC and RhB by BM-BN were both enhanced significantly.For OTC,the removal efficiency increased from 41% to 92%.For RhB,the removal efficiency was also increased from 37% to 80% after ball milling.Combined with the characterization results,it was concluded that the significantly improved adsorption efficiency of BM-BN could be resulted from the increase of specific surface area and pore volume.

Fig.2.(a) FT-IR spectra,(b) N2 adsorption-desorption isotherm,(c,d) XRD patterns of commercial BN and BM-BN.

3.4.Adsorption kinetics,isotherms and thermodynamics of OTC and RhB

The removal efficiencies of OTC and RhB at different time were explored.It could be observed from Fig.4a and b,when the commercial bulk BN was used as adsorbent,the removal efficiencies were both low for OTC and RhB.However,the few-layered BMBN showed significantly higher removal efficiencies.The removal efficiencies of OTC and RhB by BM-BN increased rapidly at the initial stage,and then raised slowly until equilibrium was reached.This may be ascribed to the abundant active adsorption sites on the BM-BN surface at the initial stage.Subsequently,the removal efficiency tended to increase slowly as a result of the decrease of the sorption sites.The adsorption process reached equilibrium at 6 and 36 h for the removal of RhB and OTC,respectively.

The adsorption kinetics of OTC and RhB onto BM-BN were studied by the pseudo-first-order and pseudo-second-order kinetic models.The expressions of the two kinetic models are as follows:

Pseudo-first-order model

Pseudo-second-order model

whereqtandqerefer to the adsorption capacity at timetand equilibrium(mg·g-1),respectively.K1is adsorption rate constant of the pseudo-first-order model (h-1) andK2is that of pseudo-secondorder model (g·mg-1·h-1).

The corresponding kinetic parameters of the two fitting kinetic models are summarized in Table 1.The correlation coefficients(R2)of pseudo-second-order kinetic model are closer to 1,indicating the experimental values of OTC and RhB could be fitted well by pseudo-second-order model.Moreover,the equilibrium adsorption capacity (qe,cal) calculated by pseudo-second-order model was extremely close to that of the experimental value (qe,exp),which also verified the adsorption behavior can be well described by this model.These results indicated that the adsorption behavior was much affected by chemisorption [40,41].

To further analyze the adsorption process,intra-particle diffusion model (Eq.(5)) and liquid-film diffusion model (Eq.(6)) were studied.

whereKdis the rate constant of intra-particle diffusion model(mg·g-1·min-1/2) andKfis that of liquid-film diffusion model(h-1).Irefers to the parameter related to the boundary layer thickness.Arepresents the liquid-film diffusion constant.

The fitting results and parameters of intra-particle diffusion and liquid-film diffusion models are presented in Fig.S2 and summarized in Table 2,respectively.Fig.S2 (c,d) shows that the adsorption process can be divided into two different segments.The first segment was attributed to the rapid diffusion of OTC and RhB to the external surface of BM-BN.The second segment was the gradual pore diffusion of OTC and RhB to the adsorption site.The high correlation coefficients (R2) indicated that the adsorption process was related to intra-particle diffusion.Moreover,the curves of two segments were not through the origin,which indicated that the intra-particle diffusion was not the only limiting-step to control the adsorption rate [42,43].The fitting results of the liquidfilm diffusion model are shown in Fig.S2 (a,b),it was observed that theR2were all above 0.9722,certifying that liquid-film diffusion was involved in the adsorption process [44].

Fig.3.Effect of different ball milling parameters for OTC adsorption onto BM-BN (Experimental conditions: C0=50 mg·L-1,dosage=1 g·L-1, T=298 K).

Adsorption mechanism can be analyzed by adsorption isotherm.Langmuir and Freundlich isotherm models were applied to fit the adsorption data at 293,303 and 313 K,respectively.The linear mathematical expressions of Langmuir and Freundlich isotherm models are presented as follows:

whereqmrefers to the maximum adsorption capacity(mg·g-1).Ceis the residual pollutant concentration in solution at adsorption equilibrium (mg·L-1).KLis the adsorption constant of Langmuir isotherm model (L·mg-1) andKFis that of Freundlich isotherm model ((mg·g-1) (L·mg-1)1/n).nis a nonlinear factor,which is related to adsorption properties.

Fig.4(c),(d) and Table 3 show the equilibrium adsorption isotherm of OTC and the fitting curves by Langmuir and Freundlich models,and the corresponding calculated isothermal parameters,respectively.For OTC and RhB,the experiment values were both well fitted with Freundlich isotherm model due to the higherR2values and lower APE (%) than that of Langmuir isotherm model.So,the adsorption of OTC and RhB onto BM-BN can be described as multilayer adsorption on the heterogeneous surfaces [45].Moreover,the parameters of 1/nless than 1 indicated that BM-BN had favorable adsorption behavior and great affinity toward OTC and RhB [46].

To analyze the adsorption thermodynamic,the influence of temperature on OTC and RhB adsorption was further studied at three different temperatures.In Fig.S3,we observed that the adsorption capacity increased as the temperature increased from 298 to 318 K,implying that high temperature was more favorable to the adsorption.Due to the swelling effect of high temperature on the porosity of particle,OTC/RhB molecules were allowed to diffuse rapidly through the outer boundary layer and inner pores of BM-BN.The thermodynamic parameters are listed in Table S2.Both for RhB and OTC,the values of ΔHowere positive,illustrating the endothermic nature of the adsorption,which may be associated with the strong π-π stacking interaction between hexagonal honeycomb structure of BM-BN and aromatic rings structure of OTC/RhB [47,48].The value of ΔHofor OTC (53.44 kJ·mol-1) was between 40 and 84 kJ·mol-1indicating that physical adsorption and chemical adsorption existed simultaneously [43].While,the value of ΔHofor RhB(11.02 kJ·mol-1)was lower than 40 kJ·mol-1,which revealing that the adsorption mechanism of RhB on BM-BN was mainly physisorption.The negative ΔGovalues demonstrated that the adsorption of OTC and RhB onto BM-BN was a spontaneous process [49].The values of ΔGofor RhB were in the range of-20 to 0 kJ·mol-1,further confirming that the physical function played an important role in the process of the adsorption of RhB onto BM-BN.Moreover,with the temperature increasing,the ΔGovalues of OTC and RhB decreased from -1.62 to -5.31 kJ·mol-1and from-3.46 to-4.43 kJ·mol-1,respectively,further confirming that higher temperature was more favorable for adsorption,which was consistent with the result of the temperature effect study.Meanwhile,the positiveΔSovalues for OTC (184.97 J·mol-1·K-1)and RhB (7.75 J·mol-1·K-1) indicated that the randomness increased at the solid-liquid interface over the whole adsorption process,and the adsorbed molecules might adopt random orientation rather than orderly arrangement [50].

Table 3Isotherm parameters for the adsorption of OTC/RhB onto BM-BN under three different temperatures

Fig.4.Effect of time on the adsorption of (a) RhB and (b) OTC onto commercial BN and BM-BN (Experimental conditions: C0 (OTC)=50 mg·L-1, C0 (RhB)=100 mg·L-1,dosage=1 g·L-1);adsorption isotherms for (c) RhB and (d) OTC onto BM-BN (Experimental conditions: C0=50-300 mg·L-1,dosage=1 g·L-1, T=293,303,313 K).

Table 1Pseudo-first order kinetic and pseudo-second order kinetic parameters for the adsorption of OTC/RhB onto BM-BN

Table 2Intra-particle diffusion model and liquid-film diffusion model parameters for RhB/OTC adsorption onto BM-BN

3.5.The effect of ionic strength and pH

Some coexisting substances in wastewater may affect the adsorption ability.Therefore,different quantities of NaCl and CaCl2were added into the solution in this work to analyze the influence of ionic strength on OTC and RhB removal.As shown in Fig.5(a),with the concentration of NaCl increased to 1 mol·L-1,the removal efficiency of OTC improved obviously.This demonstrated that the existence of NaCl promoted the adsorption of OTC onto BM-BN.This phenomenon may arise from the salting out effect [51].As the amount of NaCl increased,the solubility of OTC in water was restricted gradually.As a result of salting out,the dissolution of OTC decreased and this promoted the spread of OTC to the surface of BM-BN,indicating that hydrophobic effect played a significant role in the adsorption process.It could be observed from Fig.5(b),the OTC adsorption decreased significantly with the increasing of CaCl2concentration,indicating that CaCl2could compete with OTC to adsorption sites on BM-BN surface,which would negatively affect the adsorption capacity of BM-BN [52].While for RhB,NaCl and CaCl2had little influence on the adsorption performance ofBM-BN.When the concentration of NaCl was under 1 mol·L-1,the adsorption capacity did not change significantly,and the adsorption capacity decreased slightly at the concentration of 0.5 mol·L-1[53].Meanwhile,the adsorption capacity of RhB adsorbed on BMBN increased slightly with the increasing of the amount of CaCl2(Fig.5(b)).

Fig.5.(a,b)The effect of ionic strength(Experimental conditions:C0(OTC)=80 mg·L-1,C0(RhB)=100 mg·L-1,dosage=1 g·L-1),and(c)the effect of pH for the adsorption of OTC/RhB onto BM-BN (Experimental conditions: C0=80 mg·L-1,dosage=1 g·L-1).

Fig.6.(a)The sorption performance of different organic pollutants adsorbed by BM-BN(Experimental conditions:C0=50 mg·L-1,dosage=1 g·L-1)and(b)the regeneration ability of BM-BN for adsorption OTC/RhB.(Experimental conditions: C0=20 mg·L-1,dosage=1 g·L-1).

It is generally believed that pH has a significant impact on adsorption by influencing surface charges of adsorbent and adsorbate.The effect of pH on the adsorption performance was explored in the range of solution pH value from 2 to 12 and the corresponding results are shown in Fig.5(c).The pHPZCvalue of BM-BN was identified by salt addition method.According to Fig.S4,the BMBN zeta potential had a positive surface charge in pH ＜2.22 solution.Oppositely,a negative surface charge appeared in pH ＞2.22 solution.It could be observed that the adsorption capacity of OTC increased as the pH increased from 2 to 4,and remained stable at 4-10.When the pH value was between 4 and 10,OTC was mainly in the form of zwitterions.Due to no electrostatic attraction or repulsion interactions,the adsorption process was mainly controlled by hydrophobic effect and π-π stacking interaction [49].The adsorption capacity of OTC descended again at pH 12.For RhB,the adsorption capacity decreased under the condition of extreme acidity (pH=2) and alkalinity (pH=10-12),and the adsorption capacity was higher in the range of pH 4-8.

In this study,the main mechanism can be responsible for interactions occurring between OTC and BM-BN.(i) When the pH locates in a range of 4.0-10.0,BM-BN demonstrates the high adsorption capacity on OTC,which may be due to the favorable electrostatic interaction between zwitterionic OTC and positively charged BM-BN[54].(ii)The enhanced BM-BN adsorption capacity is due to π-π stacking interactions between the aromatic ring of oxytetracycline and the B-N hexagonal rings [55].

3.6.Sorption of different organic pollutants and regenerability of BMBN

The adsorbent was further used to adsorb another two pollutants,including MB and LOF.The results (Fig.6(a)) illustrated that the removal efficiency was in the order of MB ＞RhB ≈OTC ＞LOF.BM-BN showed excellent removal performance on various aromatic pollutants.The different adsorption ability of BM-BN to the pollutants may be related to the different physicochemical properties of pollutants,such as molecular structure,molecular dimension and isoelectric point [56].

The regeneration ability is another important factor for assessing commercial applicability of BM-BN.The regeneration ability of adsorbent was investigated by studying the adsorption ability of regenerative BM-BN.The OTC/RhB-adsorbed BM-BN were eluted with ethanol for～3 times,then dried in an oven,and then reused to adsorb OTC and RhB.As shown in Fig.6(b),the removal efficiency could still remain above 85% after 5 regeneration cycles,proving that BM-BN could be a promising adsorbent to remove organic pollutants from wastewater [57].

4.Conclusions

In conclusion,the few-layered graphene-analogue BM-BN was successfully prepared by a facile,fast,low-cost and eco-friendly one-step ball milling procedure.Compared to the commercial bulk BN,the adsorption efficiency on BM-BN is significantly improved by～124% and～116% for OTC and RhB,respectively.The adsorption processes were well fitted to the pseudo-second-order kinetic model and Freundlich isotherm model.Both liquid-film diffusion and intra-particle diffusion made contributions to the rate limiting steps in the adsorption process.Besides,the adsorption of OTC and RhB on BM-BN was spontaneous.The excellent OTC and RhB adsorption property,the fast and green preparation method,and good regeneration performance entrusted BM-BN with good potential to remove organic pollutants from aqueous solutions.The adsorption mechanism for OTC was mainly physical adsorption,which was the result of the joint action of,electrostatic interaction,hydrophobic effect and π-π stacking interaction.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

This work was financially supported by the National Natural Science Foundation of China (21878133 and 21722604) and Advanced Talents of Jiangsu University (15JDG176).

Supplementary Material

Supplementary data to this article can be found online at https://doi.org/10.1016/j.cjche.2021.09.025.