Activation of H2O2/PDS/PMS by Iron-Based Biochar Derived from Fenton Sludge for Oxidative Removal of 2,4-DCP and As(III)
Round 1
Reviewer 1 Report
Comments and Suggestions for Authors
1. In the abstract, line 12, authors are suggested to define "2,4-DCP" as this abbreviation has not been introduced earlier, which may cause difficulty for readers in understanding its meaning.
2. Kindly check for minor grammatical errors, typos, and spacing issues in the paper, particularly in line 100, line 179, and line 263.
3. In Section 2, "Materials and Methods," the authors discuss pyrolysis but do not mention the medium or gas used in the preparation of biochar. This should be clarified.
4. The authors should include an analysis of SEM-EDX to determine the concentration of Fe in the prepared catalyst. Additionally, they should investigate the effect of Fe concentration on the oxidative removal of 2,4-DCP and As(III).
5. In Section 3.2, "Degradation of 2,4-DCP in Different Systems," the authors should study the adsorption behavior of the prepared catalysts.
6. The roles of adsorption and the specific surface area of the catalyst on the oxidative removal of 2,4-DCP and As(III) have not been clarified. It is suggested that the authors discuss these factors in more detail.
7. The authors should explain the degradation mechanism by which the prepared catalyst facilitates the oxidative removal of 2,4-DCP and As(III).
8. A separate comparative study should be included to demonstrate how the prepared catalyst performs relative to available catalysts of its kind.
9. The conclusion should be improved to better represent the overall findings of the paper, and should also include numerical results for other activation methods, such as PDS and H2O2.
Comments on the Quality of English LanguageShould improve
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsIn their paper the authors describe the utilisation of calcined Fenton sludge as photocatalyst for oxidative wastewater treatment with peroxides.
The experiments are well described and the subject definitely justifies publication.
Some minor issues should be addressed:
* Section 2: Is the reaction temperature controlled during the experiment? Is it constant or affected by the UV source? How sensitive are results towards changes in temperature?
* Did the authors perform a control experiment with a soluble Fe-precursor (to exclude that soluble Fe-ions are the actual catalyst?
* Section 3: What is the mass loss of the sludge after 300, 500, 700°C calcination? When comparing the activity of 300°C, 500°C and 700°C calcined sludge: How was the catalyst amount normalized? Based on total mass or based on iron content? I would expect the higher calcined samples loose more organic and therefore will contain more iron?
* Maybe table S3 should be included in the text? The accessible surface area is a critical parameter for a heterogeneous catalytic reaction and the authors should discuss the huge increase in surface area when increasing the calcination temperature from 500 to 700°C. Would it make sense to run a TGA or DSC analysis on the sludge to identify the temperature at which a phase transition or activation of organic material occurs? This could help to find an optimal calcination temperature.
* Figure 2: This Figure is very hard to read. Although the spider plot looks fancy, wouldn't a simple bar chart like Figure S2b (x-axis = pH or ion, groups of bars by oxidant) transport the information more efficiently?
* Throughout the text, conversions are reported with two decimal digits. What is the error bar of the measurement (e.g. to be determined by repeating the experiment several times)? Does it justify to report two digits?
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
