Adsorption of Heavy Metals and Biocides from Building Runoff onto Granular Activated Carbon—The Influence of Different Fractions of Dissolved Organic Matter

Round 1

Reviewer 1 Report

Concerning our main remarks, corrections and suggestions about your work are:

1/ The novelty of this study should be clear in the introduction?

2/ Why is decentralized on-site runoff treatment using granular activated carbon (GAC) a promising option for mitigating building runoff pollution?

3/ How do biocides leach from building façades, and what are the potential consequences of their presence in runoff?

4/ How does the concentration of biocides change over time in façade runoff?

5/ What are the reasons for the author's decision not to employ multiple techniques like SEM, TEM, FTIR, and XPS to analyze the properties of granular activated carbon?

6/ How does the presence of heavy metals and dissolved organic matter (DOM) influence the adsorption of biocides onto granular activated carbon (GAC), as described?

 

7/ Given the topic and scope of the paper, some important references about sustainable water should be highlighted to broaden the readership such as https://doi.org/10.1016/j.colsurfa.2023.131509 and https://doi.org/10.1016/j.mtcomm.2023.105915.

Author Response

see attached document

 

Author Response File: Author Response.pdf

Reviewer 2 Report

General comments：

This article explores the potential use of Granular Activated Carbon (GAC) for adsorbing heavy metals and biocides in building runoff. The study examines the influence of different fractions of Dissolved Organic Matter (DOM) on the adsorption process. The Langmuir and Freundlich models are also applied to analyze the adsorption process. The findings suggest that >50% of DOM is adsorbed at low concentrations, and DOM at a small molecular size exhibits improved adsorption. The adsorption capacity for Cu2+ and Zn2+ is 157 and 85.7 μmol/g, respectively, and the presence of DOM improves the adsorption of Cu2+. The study also found that GAC is an ideal adsorbent material for retaining building runoff pollutants. The experimental design is logical and appropriate, but there are still the following problems：

1)        Introduction and Statement of Purpose: In the introduction, provide a more detailed overview of the pollution of heavy metals and biocides in building runoff and their impact on water quality, in order to better situate the research within the background. Additionally, in the statement of purpose, explicitly state the research objectives and their significance.

2)        Method Description: Provide more details about the experimental design and methods, such as specific locations and frequencies of sample collection, methods for DOM isolation and concentration, contact time and concentration of GAC and heavy metals/biocides. This will help readers better understand the experimental process and the reliability of the results.

3)        Results and Discussion: In the results section, provide more detailed information on experimental data, such as adsorption percentages of different DOM fractions at various concentrations, adsorption of Cu2+ and Zn2+, etc. Furthermore, in the discussion section, conduct a more in-depth analysis and interpretation of the results, exploring the relationship between DOM fractions and the adsorption of heavy metals/biocides, and comparing them with previous studies.

4)        Applicability of the Model: When conducting adsorption analysis using Langmuir and Freundlich models, discuss the applicability and limitations of the models. For example, discuss whether there are other models that could better describe the adsorption process and assess the fit of the models under the current experimental conditions.

5)        Conclusion: In the conclusion, summarize the main findings and contributions of the study, emphasizing the potential of GAC as an adsorbent material for pollutants in building runoff. Additionally, propose future research directions, such as further investigating the influence of DOM fractions on the adsorption of different types of pollutants, optimizing the conditions for GAC utilization, etc.

Moderate editing of English language required

Author Response

see attached document

Author Response File: Author Response.pdf

Reviewer 3 Report

The authors studied the adsorption of heavy metals and biocides using GAC. Overall, the manuscript is of sufficient quality, however some parts should be improved and some results should be added.

1) Please shorten the Introduction as it is too long 

2) Did you also study the kinetics of the adsorption. It would improve the quality of the manuscript if you included some kinetic results (i.e. peseudo-first ori pseudo-second order kinetic models), which can also be used for the characterization of the adsorption as physisoprtion or chmisoprtion.

3) Did you study the effect of temperature as it can greatly influence the efficacy of the adsorption? 

4) Did you conduct experiments regarding the regeneration of the adsorbents?

5) Please explain why both Langmuir and Freundlich models are a good fit for the adsorption data.

English language is of high quality

Author Response

see attached document

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

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