Bisphenol A and 17α-Ethinylestradiol Removal from Water by Hydrophobic Modified Acicular Mullite

Round 1

Reviewer 1 Report

Comments for author File: Comments.pdf

Author Response

Reviewer #1:

Specific Comments:

1)Abstract-The full names of BPA and EE2 must be stated before using their abbreviations.

Author reply: thank you very much. The full names of bisphenol A (BPA) and 17α-ethinylestradiol (EE2) have been added.

 “To effectively remove BPA and EE2 from water, here the CTMAB was used to modified acicular mullite to increase the hydrophobicity of the mullite.”

2) So many grammatical errors are found in the whole manuscript. Many sentences require restructuring/rephrasing for clarity.

Author reply: thank you for pointing out this. We have revised and polished the full text language to correct any language errors.

3) Page 1 (Introduction) – first sentence. Rephrase this sentence. Last sentence – what do the authors mean by traditional water treatment technology? Give examples.

Author reply: Thanks for your comments. The first sentence of the introduction part has been rephrased. “Endocrine disrupting chemicals (EDCs) have the capacity to cause reproductive disorders and damages to the nervous system and other metabolic systems of both humans and animals, especially during pregnancy and adolescence. EDCs attract more and more attention from researchers all over the world.”

The last sentence “Therefore, it is necessary to improve the removal efficiency of BPA and EE2 by traditional water treatment technology.” – the authors mean that the ubiquitous occurrences of a variety of EDCs challenge  the treatment and remediation processes. Existing technologies in water plants cannot effectively remove EDCs from raw water, and emerging technologies have problems of high cost and complicated operation. Therefore, it is necessary to improve the removal efficiency of EDCs from raw water in drinking water treatment plants through technological innovation. For example, by modifying the filter material, the removal effect of the filter tank on EDCs can be improved. Upgrading the existing treatment process for drinking water treatment plants could improve the remove efficiency of EDCs and control the cost at the same time. It is more in line with the national conditions of developing countries.

4) Page2 (2^nd paragraph)-Provide a citation for this sentence “Wang et al. modified graphite with CTMAB to remove BPA from water”. Rephrase this sentence “Under the synergistic effect of the electrostatic interaction and the hydrophobic interaction, with CTMAB modification sample increased the adsorption capacity of graphite on BPA, and its equilibrium adsorption capacity reached to 125.01mg/g.”

Author reply: The reference has been added to the sentence of “Wang et al. modified graphite with CTMAB to remove BPA from water[13].”. The sentence of “Under the synergistic effect of the electrostatic interaction and the hydrophobic interaction, with CTMAB modification sample increased the adsorption capacity of graphite on BPA, and its equilibrium adsorption capacity reached to 125.01mg/g.” has been change to “The equilibrium adsorption capacity of BPA by CTMAB modified graphite was 125.01mg/g. The adsorption mechanism could be explained with electrostatic interaction and hydrophobic interaction”.

Section 2.2-It is suggested to write the chemical formulas of compounds (instead of naming them). Examples: HCl, CH₃OH, N₂, etc.

Author reply: thank you for your suggestion, all the chemical names were rewritten to use their chemical formulas. “BPA and EE2 in water samples were enriched by solid phase extraction (SPE, Oasis HLB, 3cc/60mg, Water, USA), with the following steps: 10 mL of CH₃OH and 10 mL of HCl solution (pH = 3.0 ± 0.5) flowed through the SPE column to activate the columns. Then 80 mL water sample with a drop of the HCl solution (the volume ratio of HCl: H₂O = 1:3) was pass through the SPE column. The extraction rate was 1~2 mL/min. After extraction, 10 mL HCl solution (pH = 3.0 ± 0.5) was passed through the SPE column to remove the impurities. Finally, 10 mL of CH₃OH was used to eluted the BPA or EE2 molecules. The samples were gently blew dry with N₂. The samples were dissolved with1 mL of CH₃OH and filtrated with a 0.22 μm membrane. The concentrations of BPA and EE2 in the samples were detected by a high performance liquid chromatography (HPLC, 1260 Infinity HPLC System, Agilent Technologies). The operating conditions were as follows: the injection volume was 10 μL, 100% CH₃OH was used as the mobile phase with the flow rate of 1 mL/min at the column temperature of 30 °C, the UV detector wavelength was 230 nm, each sample was measured twice. The standard samples and blanks were used for quality control. The recovery for BPA was 92.56%~100.06% and the recovery for EE2 was 93.50%~107.37%. ”.

What are the detection and quantification limits (LOD and LOQ) of HPLC?

EE2 and BPA were quantified according to a calibration curve (the coefficient of determination is greater than 0.999), which was performed well within the range of experimental concentrations in this study.

5) Section 2.3.2 – The purpose of conducting zeta potential must be clarified. Section 3.1.3, however, stated the pH of zero-point charge. Usually, the pH_zpc analysis can be done without using the zeta potentiometer, although both techniques are used to determine the net charge of the adsorbent.

Author reply: To draw the zeta potential of CTMAB modified acicular mullite in water with different pH values, the zeta potential was measured. The pH_pzc (the pH value at which the zeta potential is zero) could be obtained from the Potential distribution diagram. When the pH value of the solution less than the pH_pzc, the surface of the adsorbent is usually positively charged, it is easier for the adsorbent to adsorb anionic contaminants. Otherwise the surface of the adsorbent is negatively charged and the adsorbent can easily adsorb cationic pollutants. So the pH_pzc is important to understand the effect of solution pH value to the adsorption.

Usually, N2 gas is used in the TGA analysis, not air.

Author reply: When perform TGA analysis, different atmospheric conditions need to be selected according to the purpose of the experiment. For example, when analyzing the catalytic combustion temperature of soot particles, it needs to be carried out in air atmosphere. When analyzing the biomass pyrolysis process, it is usually carried out in N₂ atmosphere. CTMAB will decompose in the air atmosphere. Here, in order to estimate the loading of CTMAB on acicular mullite, TGA analysis was performed in air.

 

6) Section 2.4.2 – What is the volume of BPA and EE2? At what pH were the experiments done?

Author reply: unless otherwise specified, the volume of BPA or EE2 solution in this study was 100 mL and the pH value of the BPA or EE2 solution was 6.5 ± 0.2. The paragraph has been changed to “A series of 100 mL BPA and EE2 aqueous solutions (pH = 6.5 ± 0.2) at different con-centration (0 ~ 8 mg/L) were prepared. After adding 1 g CTMAB-M, the samples were stirred at 120 r/min for 24 h at 288, 298 and 308 K. After filtering through 0.45 μm mem-brane, 80 mL filtrate was collected to determine the concentration of BPA and EE2 in the samples.”

The same comments applied to section 2.4.3.

Author reply: the section 2.4.3 was changed to “1 g CTMAB-M was added into 100 mL BPA or EE2 aqueous solution (pH = 6.5 ± 0.2) with the concentration of 1 mg/L. Sampled at a series of time points (5 to 1500 min) and determined the concentration of BPA and EE2 in the filtrate.”

7) Section 2.4.4 – What acid and base were used to adjust the pH of the solution?

 Author reply: thank you very much for your reminding. 0.1 M HCl and 0.1 M NaOH were used to adjust the pH value. Section 2.2.4 has been changed to “Effect of ionic strength on the adsorption of BPA and EE2 over the CTMAB-M was conducted by adding different concentrations of NaCl (0.01, 0.1, 0.3 and 0.5 mol/L) during adsorption experiment. Effect of solution pH value on the adsorption of BPA and EE2 by CTMAB-M was operated by preparing 100 mL of BPA and EE2 aqueous solution (1 mg/L) with a series (3.0~11.0) pH value (0.1 M HCl and 0.1 M NaOH were used to adjust the pH value).”

8) Figure 3. Spelling error ‘Schemat’

Author reply: thank you for your reminding. The title of figure 3 has been changed to “Figure 3. (a) The zeta potential of acicular mullite and CTMAB-M, (b) Schema diagram of CTMAB loaded acicular mullite.”

9) Figure 4. Replace the time symbol (T) with ‘t’ (not to confuse it with temperature).

Author reply: thank you for your reminding. The symbol “T” has been replaced by “t”.

 

Figure 4. (a) Kinetic study of BPA and EE2 adsorption on CTMAB-M, (b) the relationship between q_t and t^1/2 of intraparticle diffusion model.

10) Page 7. All the kinetic and isotherm equations must be stated in the text. Did the authors use linear or non-linear equations? Do not start a sentence with ‘And’. The types of chemical bonding involved in BPA and EE2 adsorption should not rely only on the kinetic equation. Most organic compounds are adsorbed by weak physical interactions, not chemical adsorption. Last sentence of 3.2 – What did the authors mean with ‘other adsorption forces’? Please give examples.

 Author reply: thank you for your reminding. All the kinetic and isotherm equations have been added to the section of 2.5 Data analysis.

 “Adsorption isotherms were conducted to study the adsorption behavior of BPA and EE2 on CTMAB-M. The experimental equilibrium data were fitted by Freundlich (Eq. (1)), Langmuir (Eq. (2)), and Langmuir-Freundlich model (Eq. (3)).

The Freundlich model:

                                         (1)

Where q_e is the equilibrium adsorption capacity (mg/g), C_e is the concentration in solution at equilibrium moment (mg/L),  is the Freundlich constant related to the sorption affinity, 1/n is the Freundlich exponential coefficient.

The Langmuir model:

                                          (2)

Where  is the maximum adsorption capacity (mg/g),  is the Langmuir constant refer to the adsorption affinity (L/mg).

The Langmuir-Freundlich model:

                                       (3)

Where  is the maximum adsorption capacity (mg/g),  is the Langmuir-Freundlich constant related to the adsorption affinity, n is the relating to the heterogeneity of adsorbent surface.

Adsorption kinetics

Kinetic models (pseudo-first-order model (Eq. (4)), pseudo-second-order (Eq. (5)) intra-particle diffusion model(Eq. (6)) were applied to describe different steps involved in the adsorption process.

                                   (4)

                                         (5)

                                        (6)

Where q_e and q_t are the adsorption capacity (mg/g) at equilibrium moment and time t (min),  and  are the rate constant of the pseudo-first-order (1/min) and pseudo-second-order model (g/(mg min)) [1].  (mg/(g min^1/2) is the rate constant of intraparticle diffusion, and c is associated with the thickness of the boundary layer at each adsorption stage.

Adsorption thermodynamic

The thermodynamic parameters such as free energy change (∆G⁰) and enthalpy change (∆H⁰) and entropy change (∆S⁰) for the adsorption reaction are estimated using the following equations:

                                               (7)

                                             (8)

                                    (9)

                                           (10)

                                               (11)

where R is the gas constant=8.314 J/(mol·K); T is the absolute temperature (K); K_c is the equilibrium constant, the equations (9)~ (11) is the unit conversion formula of K_c ; M_W is the molecule weight of BPA or EE2 (g), 55.5 is the moles of per liter of pure water (1000 g/L divided by 18 g/mol), ρ is the density of water (g/cm³), , K_L and  are the parameters of isothermal adsorption models.”

The sentence “And the equilibrium adsorption capacity (q_e,exp) is closer to the fitting data by the pseudo-second-order model (q_e,calculated).” has been changed to “The equilibrium adsorption capacity (q_e,exp) is closer to the data calculated by the pseudo-second-order model (q_e,calculated).”

Adsorption kinetic studies can replay the dynamic process of adsorption，which could benefit to understand the adsorption process and possible interactions between the adsorbent and the adsorbate. In addition, through the kinetic study the equilibrium time could be calculated. The pseudo-first-order kinetic and the pseudo-second-order kinetic models were most commonly used to determine the rate constant and to analyze the mechanism of the adsorption process. There are a lot of literatures to study the type of adsorption reaction based on adsorption kinetic data. For example Zhou et al. studied the adsorption kinetics of MB onto HPAM/CNC, results showed that the MB adsorption in HPAM/CNC nanocomposite hydrogels can be described very well by the pseudo-second-order kinetic model. According to this the authors claimed that the adsorption of MB onto HPAM/CNC hydrogels was mostly controlled by the chemisorption behavior likely attributed to exchange or sharing of electrons between cation groups of dye and anion groups (mainly sulfate ester groups of CNCs and carboxyl from HPAM) of HPAM/CNC nanocomposites[2].

In this study the authors just roughly determined the type of adsorption reaction based on the results of kinetic data. The adsorption mechanisms of BPA and EE2 on CTMAB-M were further studied by adsorption thermodynamics and site energy distribution model.

“Other adsorption forces” in the last sentence of 3.2 refers to the hydrophobic interaction and the electrostatic attraction.

11) Table 1. The unit ‘µg/g’ does not seem to be correct. Should it be ‘mg/g’. The value 8.69E-04 should be properly written in scientific notation.

Author reply: thank you for your reminding. All the unit “µg/g” in Table 1 and Figure 4 has converted into “mg/g”. The values in the tables are written in a standardized manner.

 

Figure 4. (a) Kinetic study of BPA and EE2 adsorption on CTMAB-M, (b) the relationship between q_t and t^1/2of intraparticle diffusion model.

Table 1. Kinetic models parameters for the adsorption of BPA and EE2 on CTMAB-M
adsorbates	qe ,exp mg/g		Pseudo-first-order model			Pseudo-second-order model			intra-particle diffusion model
			K1 min-1	qe mg/g	R2	K2/ g/(mg·min)1/2	qe mg/g	R2	kpi mg/(g ∙min1/2)	c	R2
BPA	0.052	0.030		0.047	0.91	0.869	0.050	0.97	0.91	23.76	0.68
EE2	0.055	0.021		0.047	0.84	0.581	0.051	0.94	1.06	20.13	0.77

12) Table 2 - the maximum adsorption capacities are lower than those reported in the kinetic analysis. This is incorrect. The data (kinetics or isotherm) must be rechecked and recalculated. The unit here is ‘mg/g’, but in Table 1, it is written ‘µg/g’. This is quite confusing.

 Author reply: thank you for your suggestion. The units in the manuscript have been unified. All the “µg/g” in this manuscript has converted into “mg/g”.

The maximum adsorption capacities calculated by Langmuir model are higher than the value of q_e reported in the kinetic analysis. This is because the initial concentration of BPA and EE2 in kinetics studies was 1 mg/L. The q_e is the equilibrium adsorption capacity with the initial concentration of 1 mg/L. While the q_m is the maximum adsorption capacity calculated from Langmuir model with the initial concentrations of BPA and EE2 in isotherm adsorption experiment were 0~8 mg/L. The q_e,exp of BPA and EE2 adsorbed by CTMAB-M were 0.052 mg/g and 0.055 mg/g in kinetic studies. The q_m of BPA and EE2 adsorbed by CTMAB-M calculated by Langmuir model were 0.483 mg/g and 0.212 mg/g.

13) Section 3.4 – Check the unit for y-axis. Is it supposed to be ‘mg/g’?

 Author reply: thank you for your suggestion. The unit for y-axis in Figure 6 has been changed to “mg/g”.

 

Figure 6. Effects of solution pH value on BPA and EE2 adsorption by CTMAB-M

14) Page 10. Is the adsorption reaction exothermic or endothermic? The authors mentioned both (exothermic and endothermic) in this paragraph.

 Author reply: according to the results of thermodynamic study, the adsorption of BPA and EE2 by CTMAB-M was exothermic. To avoid confusion, the first paragraph was changed to “The adsorption isothermals of EE2 and BPA at 288, 298 and 308 K were shown in Figure 8, and it can be seen that the adsorption amount of EE2 and BPA on CTMAB-M showed a strong correlation with temperature. The adsorption amount of EE2 and BPA both decreased with increasing temperature, indicating that the low temperature favors the adsorption of EE2 and BPA, which was consistent with the results reported in the literature.”

15) Page 12. The authors wrote, “The acicular mullite had open-pore structure extending in all directions, with a multi-level distribution of super-large pores, macropores, mesopores, and micropores”. Where are the data that support that acicular mullite has these types of pores?

 Author reply: The crystal structure, micromorphology and pore structure of acicular mullite have been reported in detail in our previous studies[3, 4]. The related references have been added after the sentence of “The acicular mullite had open-pore structure extending in all directions, with a multi-level distribution of super-large pores, macropores, mesopores, and micropores”. The following picture shows the pore distribution and microstructure of acicular mullite.

The porosity of acicular mullite in this study is 63.7 ± 2.7 %. The aspect ratio is an important index for evaluating mechanical strength and porosity. The average aspect ratio of mullite made from the sintering reaction was as high as 9.13, with a grain length of 3.48 μm and needle diameter of 383.33 nm. The specific surface area of acicular mullite was 1.96 m²/g. The pore size of mullite distributed in multi-levels with most ranged 0.26 ~ 5.84 μm, which can provide plenty of specific surface area. Besides, pore sizes of mullite were widely distributed at 11.15 ~ 13.54 µm, 14.87 ~ 17.54 µm, 18.68 ~ 22.50 µm and 29.36 ~ 35.95 µm, not only bringing considerate specific surface area but also making mullite less possible to be blocked by the diesel soot. However, in the cordierite substrate, only narrow band (3 ~ 7 µm) distribution was observed, implying evenly porous structure. This could be explained by pores in mullite was formed naturally due to the acicular structure of mullite, while pores in cordierite was produced by adding pore forming materials. The non-overlapped mercury intrusion and extrusion curves of both porous ceramic indicated that some mercury remained in the pores. Generally, complex network of pores could be responsible for such entrapment.

 

Pore size distribution of acicular mullite gauged by mercury intrusion data and the microstructure (SEM) of acicular mullite

16) Reference list - Please ensure all journal names are written in abbreviated form.

 Author reply: done. All the references have been checked and all journal names are written in abbreviated form.

 

1. J, Z.; R, S., Slow adsorption reaction between arsenic species and goethite (a-FeOOH): diffusion or heterogeneous surface reaction control. Langmuir 2005, 21, (7), 2895-2901.
2. Zhou, C.; Wu, Q.; Lei, T.; Negulescu, I. I., Adsorption kinetic and equilibrium studies for methylene blue dye by partially hydrolyzed polyacrylamide/cellulose nanocrystal nanocomposite hydrogels. Chem Eng J 2014, 251, 17-24.
3. Wan, Y.; Xu, C.; Zhou, Q.; Chen, H.; Xu, Q. In Synthesis of nanoporous acicular-mullite ceramic and electroless platinum coating for particulate matter entrapment and catalytic combustion, IOP Conference Series: Earth and Environmental Science, 2022; IOP Publishing: 2022; p 012107.
4. Zhou, Q.; Long, T.; He, J.; Guo, J.; Gao, J., Cadmium removal from water by enhanced adsorption on iron-embedded granular acicular mullite ceramic network. J Taiwan Inst Chem E 2020, 106, 92-98.

 

 

Author Response File: Author Response.pdf

Reviewer 2 Report

This paper reports on the Bisphenol A and 17α-ethinylestradiol Removal from Water by Hydrophobic Modified Acicular Mullite. The English language needs to be thoroughly reviewed throughout the paper. The article is incomplete in parts, with some explanations and clarifications needed for better understanding. I do recommend that this article be published in Journal of Sustainability after Major revision.

 

1)      The English writing in the paper also needs to be improved as there are many grammatical errors and incomplete sentences throughout the paper that made it difficult to read.

2)      In the abstract section, the main findings of the research should be written numerically and quantitatively.

3)      At the end of the abstract, write a general conclusion.

4)      In the introduction and discussion sections, use the content of the following articles to promote the Bisphenol A section and refer to them in the references section: 10.1016/j.jece.2021.106072; 10.5004/dwt.2018.21736

5)      In the introduction section, refer to the standard of phenolic compounds (Bisphenol A) in water and wastewater, how they are discharged into the environment, and the methods of removing Bisphenol A. For this purpose, use the articles mentioned in comment 4 and refer to them in the references section.

6)      In the introduction section, a number of similar studies should be mentioned.

7)      Add error bars for figures 1 and 3-8.

8)      Write the LOD and LOQ of the devices used to measure pharmaceuticals compounds.

9)      In the method section, the specifications of all chemicals and equipment used in the present study should be written with the brand (Sigma or Merck, etc.) and the country of manufacture, etc.

10)  The authors should include a comparative table to include operation conditions and cost. 

11)  A table should be included about removal efficiency and cost for removal of same or similar wastewater based on the current method and other methods.

12)  In the Methods, the type of study to be written.

13)  In the methods section, the number of samples studied in this study should be written. Explain how to determine the samples in full.

14)  In the introduction and discussion sections, use the content of the following article to improve the explanations related to the absorption process and refer to it in the references section: 10.1007/s13399-021-01601-y

15)  The discussion section of the article is poorly written. Must be upgraded with new articles.

16)  The strengths and weaknesses of this study compared to other studies should be written.

Author Response

Reviewer #2:

Comments and Suggestions for Authors

This paper reports on the Bisphenol A and 17α-ethinylestradiol Removal from Water by Hydrophobic Modified Acicular Mullite. The English language needs to be thoroughly reviewed throughout the paper. The article is incomplete in parts, with some explanations and clarifications needed for better understanding. I do recommend that this article be published in Journal of Sustainability after Major revision.

Author reply: Thank you for your comments. The language of the manuscript has been thoroughly revised. Besides, the manuscript has been polished by an English expert.

Comments:

1. The English writing in the paper also needs to be improved as there are many grammatical errors and incomplete sentences throughout the paper that made it difficult to read.

Author reply: Thank you very much for your suggestion. We have strived to eliminate the grammatical errors of the manuscript. Please refer to the revised manuscript for more details, and the revisions are marked in red.

2. In the abstract section, the main findings of the research should be written numerically and quantitatively.

Author reply: thank you very much for the comments. We have added the key data from the results to the abstract of the revised manuscript. The revised abstract was “The hydrophilicity and hydrophobicity of adsorbent has an important influence on organic pollutants adsorption. To effectively remove bisphenol A (BPA) and 17-acetylene estradiol (EE2) from water, here acicular mullite was modified by cetyl trimethyl ammonium bromide (CTMAB) to increase the hydrophobicity of the mullite. The adsorption process and mechanism of BPA and EE2 by modified acicular mullite were studied in detail. Results indicated that the concentration of CTMAB solution was related to the contact angle of CTMAB modified mullite (CTMAB-M). The optimal concentration of CTMAB was 4 mmol/L. The CTMAB-M could adsorb more hydrophobic organic pollutants than virgin acicular mullite. Due to the electrostatic attraction and hydrophobic partitioning, the adsorption amount of BPA and EE2 on CTMAB-M increased with increasing pH. The adsorption amounts of BPA and EE2 on CTMAB-M increase with increasing ionic strength. The adsorption kinetics of BPA and EE2 adsorption on CTMAB-M could be best described by the pseudo second-order kinetics model. Thermodynamic analysis showed that the low temperature favored the adsorption of BPA and EE2 on CTMAB-M, and the adsorption was driven by entropy increase. Site energy studies indicated that BPA and EE2 firstly occupy high energy adsorption sites and then switch to low energy sites during the adsorption process. The average adsorption site energy μ(E*) of EE2 on CTMAB-M is smaller than BPA. CTMAB modification can significantly improve the removal efficiency of ceramsite on EDCs.”

3. At the end of the abstract, write a general conclusion.

Author reply: Thank you very much for your suggestion. The sentence “CTMAB modification can significantly improve the removal efficiency of ceramsite on EDCs” has been added to the end of the abstract.

4. In the introduction and discussion sections, use the content of the following articles to promote the Bisphenol A section and refer to them in the references section: 10.1016/j.jece.2021.106072; 10.5004/dwt.2018.21736

Author reply: Thank you very much for your suggestion. After reading these references “10.1016/j.jece.2021.106072 and 10.5004/dwt.2018.21736”, we found that the two articles are very interesting. The two articles have been cited in the Introduction of the revised manuscript.

“6. Shokoohi, R.; Gillani, R. A.; Mahmoudi, M. M.; Dargahi, A., Investigation of the efficiency of heterogeneous Fenton-like process using modified magnetic nanoparticles with sodium alginate in removing Bisphenol A from aquatic environments: kinetic studies. Desalin Water Treat 2018, 101, 185-192.

9. Samarghandi, M. R.; Ansari, A.; Dargahi, A.; Shabanloo, A.; Nematollahi, D.; Khazaei, M.; Nasab, H. Z.; Vaziri, Y., Enhanced electrocatalytic degradation of bisphenol A by graphite/β-PbO2 anode in a three-dimensional electrochemical reactor. Journal of Environmental Chemical Engineering 2021, 9, (5), 106072.”
10. In the introduction section, refer to the standard of phenolic compounds (Bisphenol A) in water and wastewater, how they are discharged into the environment, and the methods of removing Bisphenol A. For this purpose, use the articles mentioned in comment 4 and refer to them in the references section.

Author reply: done. The first paragraph has been revised accordingly. The two articles have been cited in the Introduction of the revised manuscript.

“Endocrine disrupting chemicals (EDCs) have the capacity to cause reproductive disorders and damages to the nervous system and other metabolic systems of both hu-mans and animals, especially during pregnancy and adolescence. EDCs attract more and more attention from researchers all over the world.[1]. BPA and EE2 are two typical endocrine disruptors which have been widely detected in surface water[2], sediment[3], sewage plant effluent[4], and even waterworks effluent in recent years[5]. Contamination of water sources with BPA and EE2 is occurred through both untreated industrial wastewater and aquaculture wastewater[6]. The traditional water treatment process cannot effectively remove BPA and EE2 from water[6]. The emerging water treatment technologies, such as chemical precipitation, electrodialysis, ion exchange, membrane and advanced oxidation processes [7-9] have the disadvantages of high cost and hard application in industrial process. Therefore, it is necessary to improve the removal efficiency of BPA and EE2 by traditional water treatment technology. For example, by modifying the filter material, the removal effect of the filter tank on EDCs can be improved.”

6. In the introduction section, a number of similar studies should be mentioned.

Author reply: thank you for your suggestion. Some similar studies have been summarized in the introduction section.

“Cetaletyl trimethylated ammonium bromide (CTMAB) is a cationic surfactant, whose head is a positively charged quaternary ammonium group, and whose tail is a hydrophobic alkyl chain. Due to the unique structure and physicochemical properties, CTMAB is often used for adsorbent modification to increase the removal performance of adsorbents. Wang et al. modified graphite with CTMAB to remove BPA from water. The equilibrium adsorption capacity of BPA by CTMAB modified graphite was 125.01mg/g. The adsorption mechanism could be explained with electrostatic interaction and hydrophobic interaction. Evans Dovi et al synthesis CTMAB modified walnut to enhance the uptake for BPA and Congo red. The adsorption equilibrium results showed that CTMAB modified walnut exhibited huge potential to use in the treatment of waste water and its maximum adsorption quantity of BPA was 38.5 mg/g.”

7. Add error bars for figures 1 and 3-8.

Author reply: All solutions in this paper were prepared with pure water. So the interference of impurities was very small. The acicular mullite and CTMAB modified acicular mullite were all synthesized in our laboratory. The adsorbents were relatively uniform. After mixing with the aqueous solution of the target substance, the environment for the adsorption reaction remained the same. So there are few factors that can cause experimental errors. In this paper, quality control was mainly carried out by using standard samples and blanks, i.e., two standard samples and one blank sample were added to the measurement batch for every fourteen samples. The recovery rate of BPA and EE2 in the experiment were 92.56~100.06% and 93.50~107.37%, respectively. In addition, some previous studies on similar topics did not add error bars due to similar reasons as above mentioned, such as the following literature:

1. Tagliavini M, Engel F, Weidler P G, et al. Adsorption of steroid micropollutants on polymer-based spherical activated carbon (PBSAC)[J]. Journal of hazardous materials, 2017, 337: 126-137.
2. Luo J, Sun M, Ritt C L, et al. Tuning Pb (II) Adsorption from Aqueous Solutions on Ultrathin Iron Oxychloride (FeOCl) Nanosheets[J]. Environmental science & technology, 2019, 53(4): 2075-2085.
3. Cui W, Zhang X, Pearce C I, et al. Cr (III) adsorption by cluster formation on boehmite nanoplates in highly alkaline solution[J]. Environmental Science & Technology, 2019.
4. Han J, Qiu W, Cao Z, et al. Adsorption of ethinylestradiol (EE2) on polyamide 612: molecular modeling and effects of water chemistry[J]. Water research, 2013, 47(7): 2273-2284.

So the error bars were not added for figures 1 and 3-8.

8. Write the LOD and LOQ of the devices used to measure pharmaceuticals compounds.

Author reply: EE2 and BPA were quantified according to a calibration curve (the coefficient of determination is greater than 0.999), which was performed well within the range of experimental concentrations in this study.

9. In the method section, the specifications of all chemicals and equipment used in the present study should be written with the brand (Sigma or Merck, etc.) and the country of manufacture, etc.

Author reply: thank you for your reminding. The brand and country of the chemicals and the equipments used in this study were added.

“2.1. Materials and Reagents

Acicular mullite (M) ceramsite with the diameter of 0.8 ~ 1.2 mm was laboratory synthesized and the synthetic method was listed in supporting information. Unless otherwise specified, all chemical reagents were analytical and were purchased from Sinopharm Group Chemical Reagents Co., LTD. The standard substances of BPA (99%) and EE2 (99%) were purchased from Dr. Ehrenstorfer GmbH (Dr. E, Germany).

2.2. BPA and EE2 analysis methods

BPA and EE2 in water samples were enriched by solid phase extraction (SPE, Oasis HLB, 3cc/60mg, Water, USA), with the following steps: 10 mL of CH₃OH and 10 mL of HCl solution (pH = 3.0 ± 0.5) flowed through the SPE column to activate the columns. Then 80 mL water sample with a drop of the HCl solution (the volume ratio of HCl: H₂O = 1:3) was pass through the SPE column. The extraction rate was 1~2 mL/min. After extraction, 10 mL HCl solution (pH = 3.0 ± 0.5) was passed through the SPE column to remove the impurities. Finally, 10 mL of CH₃OH was used to eluted the BPA or EE2 molecules. The samples were gently blew dry with N₂. The samples were dissolved with1 mL of CH₃OH and filtrated with a 0.22 μm membrane. The concentrations of BPA and EE2 in the samples were detected by a high performance liquid chromatography (HPLC, 1260 Infinity HPLC System, Agilent, USA). The operating conditions were as follows: the injection volume was 10 μL, 100% CH₃OH was used as the mobile phase with the flow rate of 1 mL/min at the column temperature of 30 °C, the UV detector wavelength was 230 nm, each sample was measured twice. The standard samples and blanks were used for quality control. The recovery for BPA was 92.56%~100.06% and the recovery for EE2 was 93.50%~107.37%. EE2 and BPA were quantified according to a calibration curve (the coefficient of determination greater than 0.999), which was performed within the range of experimental concentrations in this study.

2.3. Material Synthesis and Characterization

2.3.2. Characterizations

The Zeta potential was measured under different pH conditions by using a Zeta potential analyzer (Malvin, England). Thermal weight analysis was performed on a TGA / DSC1 (Mettler, Germany) in a range of 25 to 700 °C under air and a heating rate of 10 °C /min. The hydrophobicity was evaluated by a dynamic contact angle meter DSA100 (KRüSS, Germany) in pure water at 25 ℃ and measured at least ten points per sample.”

10. The authors should include a comparative table to include operation conditions and cost.

Author reply: thank you for your suggestion. The operation conditions have been detailed in the experiment section.

This paper mainly focuses on the removal efficiency and the relative mechanism of BPA and EE2 by modified ceramsite. The cost analysis will be carried out in our future study.

11. A table should be included about removal efficiency and cost for removal of same or similar wastewater based on the current method and other methods.

Author reply: thank you for you suggestion. The particle size of the adsorbent is directly related to the specific surface area of the adsorbent. Larger specific surface area favors for adsorption. However, fine particles are difficult to separate from solid and liquid, which is not conducive to the recovery of adsorbents. Adsorbent used in the literature are usually fine particles, some of them are nano particles. While the diameters of the ceramsite and modified ceramsite used in this study are 0.8~1.2mm, which was easy to be separated from water and could be used as filter materials in the drinking water plant. Consequently, the q_m of BPA and EE2 were lower than the values reported in the literature. Due to the marked differences in the particle size of the adsorbents, the comparison with these literatures is not meaningful. In this study, the virgin acicular mullite could hardly adsorbed BPA and EE2. The maximum adsorption capacity (q_m) at 298 K of the BPA and EE2 on the CTMAB-M were 0.483 mg/g and 1.428 mg/g, respectively. It is indicated that CTMAB modification could significantly improve the removal efficiency of acicular mullite for BPA and EE2.

As for the cost of the method in this study, we will carry out in the future study.

12. In the Methods, the type of study to be written.

Author reply: all the conclusions of this study are based on experimental results. So the type of this study belongs to experimental science.

13. In the methods section, the number of samples studied in this study should be written. Explain how to determine the samples in full.

Author reply: in this study, the adsorbent was firstly synthesized and characterized. Then the batch adsorption experiments (adsorption kinetics, isothermal adsorption, thermodynamics study and effects of solution environment) were conducted. The number of the samples corresponding to each part of the experiment can be seen in the pictures in the results and discussion sections, and each point refers to a sample.

BPA and EE2 in water samples were firstly enriched by solid phase extraction (SPE, Oasis HLB, 3cc/60mg, Water, USA), with the following steps: 10 mL of CH₃OH and 10 mL of HCl solution (pH = 3.0 ± 0.5) flowed through the SPE column to activate the columns. Then 80 mL water sample with a drop of the HCl solution (the volume ratio of HCl: H₂O = 1:3) was pass through the SPE column. The extraction rate was 1~2 mL/min. After extraction, 10 mL HCl solution (pH = 3.0 ± 0.5) was passed through the SPE column to remove the impurities. Finally, 10 mL of CH₃OH was used to eluted the BPA or EE2 molecules. The samples were gently blew dry with N₂. The samples were dissolved with1 mL of CH₃OH and filtrated with a 0.22 μm membrane. The concentrations of BPA and EE2 in the samples were detected by a high performance liquid chromatography (HPLC, 1260 Infinity HPLC System, Agilent, USA). The operating conditions were as follows: the injection volume was 10 μL, 100% CH₃OH was used as the mobile phase with the flow rate of 1 mL/min at the column temperature of 30 °C, the UV detector wavelength was 230 nm, each sample was measured twice. The standard samples and blanks were used for quality control. The recovery for BPA was 92.56%~100.06% and the recovery for EE2 was 93.50%~107.37%. EE2 and BPA were quantified according to a calibration curve (the coefficient of determination greater than 0.999), which was performed within the range of experimental concentrations in this study. For more details please see our previous studies[1,2].

1. He, J.; Guo, J.; Zhou, Q.; Yang, J.; Fang, F.; Huang, Y., Analysis of 17α-ethinylestradiol and bisphenol A adsorption on anthracite surfaces by site energy distribution. Chemosphere 2019, 216, 59-68.
2. He, J.; Zhou, Q.; Guo, J.; Fang, F., Characterization of potassium hydroxide modified anthracite particles and enhanced removal of 17α-ethinylestradiol and bisphenol A. Environ Sci Pollut R 2018, 25, (22), 22224-22235.
3. In the introduction and discussion sections, use the content of the following article to improve the explanations related to the absorption process and refer to it in the references section: 10.1007/s13399-021-01601-y

Author reply: thank you for your reminding. The discussion section has been improved. The reference has been cited in the discussion section.

“The maximum adsorption capacity (qm) at 298 K of the BPA and EE2 on the CTMAB-M were 0.483 mg/g and 1.428 mg/g, respectively (Table 2). The removal efficiency of BPA and EE2 were better than that of virgin acicular mullite. The qm of BPA and EE2 were lower than the values reported in the literature[29]. The main reason is because the diameter of the ceramsite used in this study is 0.8~1.2mm, while the adsorbent are usually fine particles in the literature[30]. As the temperature increases, the adsorption amount of BPA and EE2 on CTMAB-M decreases, indicating that the temperature increase is not conducive to the adsorption of BPA and EE2.”

“30. Dargahi, A.; Samarghandi, M. R.; Shabanloo, A.; Mahmoudi, M. M.; Nasab, H. Z., Statistical modeling of phenolic compounds adsorption onto low-cost adsorbent prepared from aloe vera leaves wastes using CCD-RSM optimization: effect of parameters, isotherm, and kinetic studies. Biomass Conversion and Biorefinery 2021, 1-15.”

15. The discussion section of the article is poorly written. Must be upgraded with new articles.

Author reply: the discussion section of the article has been revised and polished. Two new articles have been cited to improve the discussion.

30. Dargahi, A.; Samarghandi, M. R.; Shabanloo, A.; Mahmoudi, M. M.; Nasab, H. Z., Statistical modeling of phenolic compounds adsorption onto low-cost adsorbent prepared from aloe vera leaves wastes using CCD-RSM optimization: effect of parameters, isotherm, and kinetic studies. Biomass Conversion and Biorefinery 2021, 1-15.
31. Zhou, G.; Cao, Y.; Jin, Y.; Wang, C.; Wang, Y.; Hua, C.; Wu, S., Novel selective adsorption and photodegradation of BPA by molecularly imprinted sulfur doped nano-titanium dioxide. Journal of Cleaner Production 2020, 274, 122929.
32. The strengths and weaknesses of this study compared to other studies should be written.

Author reply: The adsorbent modification method in this study is very simple but efficient. Usually normal temperature and pressure are sufficient, and no additional reagents are required. The particle size of is CTMAB-M 0.8~1.2 mm, which is common size for a filter material used for water plants. Due to its large size, it is easy to be separated from water. The disadvantage is that although the adsorption capacity is greatly enhanced, it may not be high enough. In the future, we will focus on improving its adsorption capacity.

 

 

1. Belachew, N.; Hinsene, H., Preparation of cationic surfactant-modified kaolin for enhanced adsorption of hexavalent chromium from aqueous solution. Applied Water Science 2020, 10, (1), 1-8.
2. Wang, L.-C.; Ni, X.-j.; Cao, Y.-H.; Cao, G.-q., Adsorption behavior of bisphenol A on CTAB-modified graphite. Appl Surf Sci 2018, 428, 165-170.
3. Dovi, E.; Kani, A. N.; Aryee, A. A.; Jie, M.; Li, J.; Li, Z.; Qu, L.; Han, R., Decontamination of bisphenol A and Congo red dye from solution by using CTAB functionalised walnut shell. Environ Sci Pollut R 2021, 28, (22), 28732-28749.
4. He, J.; Guo, J.; Zhou, Q.; Yang, J.; Fang, F.; Huang, Y., Analysis of 17α-ethinylestradiol and bisphenol A adsorption on anthracite surfaces by site energy distribution. Chemosphere 2019, 216, 59-68.
5. He, J.; Zhou, Q.; Guo, J.; Fang, F., Characterization of potassium hydroxide modified anthracite particles and enhanced removal of 17α-ethinylestradiol and bisphenol A. Environ Sci Pollut R 2018, 25, (22), 22224-22235.

 

 

 

 

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The authors have made all the corrections as required in the previous comments

Reviewer 2 Report

Accepted.