Nanoscale Zero Valent Iron Supported by Biomass-Activated Carbon for Highly Efficient Total Chromium Removal from Electroplating Wastewater
Round 1
Reviewer 1 Report
Water
TITLE: Nano zero valent iron (nZVI) supported by biomass activated carbon for highly efficient Chromium (Cr) removal from electroplating wastewater
The authors investigated removal efficiency of total Cr from real wastewater ad different experimental condition. Since Authors explore real wastewater problem this manuscript is valuable for scientific population. Also, the Authors should give more effort into this manuscript (Experimental, Results and Discussion) for possible publication in this Journal.
My comments follow:
GENERAL RECOMMENDATION
There are a lot of typographical errors.
E.g.
Some sentences are missing the point (line 16, 135).
Equalize mL or ml; L or l.
On some places in the manuscript, you write the numerical percentage amount together with the number, and somewhere not. Equalize.
On many places in the manuscript, you write the number together with the measurement unit! 298.15K, 30g/l, 2-4mm, 200 gBC, 180min,…..Please correct in all manuscript!
Use the symbol (-) for the range and not symbol for approximately (line 37, 67, 99).
Generally, Figure resolution from 2 to 8 is poor! The symbols are indistinguishable! Please correct.
SPECIFIC RECOMMENDATION
TITLE
If possible, do not use abbreviations in the title.
Emphasize that Cr is total chromium in title and in all text and Figures.
ABSTRACT
For the same thing, you use different synonyms, uniform names (nano, nanoscale, nanoparticle). In title you used name nano zero valent iron while in line 10 and 20, 21 you not.
INTRODUCTION
Introduction is well written.
Line 40 and 55: in Introduction is first time mentioned nZVI and BC, please add full name
Describe where you sampled the wastewater, the location and country, unless it is a secret.
Be sure to describe what method of electroplating wastewater treatment is currently used and what the efficiency is. This will give us an answer on the contribution of your wastewater treatment method.
MATERIALS AND METHODS
Line 62: 2.1.Mate… space.
Line 66: „in detail in Ref. [26].“ not in ref., change in “Name of Authors”.
Section 2.4. Mention the sampling location.
Section 2.4.1.
Completely reorganize!
Please explain each experiment in detail you performed with experimental condition. Please not put experimental condition in figure caption.
Line 101-102: in three copies change in three replicates.
Line 105-106: Symbol C must be in italic like in Eqs. 2 and 3.
RESULTS AND DISCUSSIONS
3.1 Synthesis and Characterization of materials
Part described in lines 115-119: better explain.
Why you are shooting SEM images with different magnifications for BC, nZVI and BC-nZVI sample when you comparing them? Explain morphological differences between BC-nZVI in relation to BC. Enlarge SEM images ijn Fig 2 - I cannot see clearly SEM images.
Did you have XPS analysis for BC sample? Give comparison of XPS for BC and BC-nZVI.
3.2 Degradation mechanism 134
Experimental condition given in capture of Figure 4 transfer to the experimental section.
Line 153: “…BC-nZVI after different standby time.” - you did not explain this procedure in section 2.2.
Line 154: “The removal efficiencies decrease from 94.88% to 72.45% and 33.42%......“
air” - I disagree with what was written. Removal efficiency for 3 different standby time increase in time, but different rem. eff. is achieved.
Line 156-157: “Therefore, the removal efficiencies of Cr in wastewater by nZVI particles can
be effectively improved by supporting on BC, but the retention of its activity was not obvious.” - This assertion indicates that they should have results of chromium sorption on the BC sample. Give the results of chromium sorption to BC in the manuscript and explain the justification of preparation of the BC-NZVI sample based on that results.
Line 160: “ … Fe0 was mainly distributed in the outer layer of BC-nZVI in this study.” How did you conclude this? You should have a mapping analysis on the surface of the BC-nZVI sample before and after the sorption of chromium in crushed and uncrushed sample.
Please describe in detail SEM images in Fig 6. Also, capture of Fig 6 is unclear, meaning of a, b, c, d…
3.3 Kinetic of Cr removal by BC-nZVI
Line 188: Fig 7 instead Fig 8.
In Table 1: k1 instead K2.
Beside to the reaction kinetic models, you must conduct the fitting of the experimental results with the diffusion kinetic models - this is biochar and the diffusion of chromium in the biochar particle or BC-nZVI. Consider if the chemical reaction alone is limiting step. What is the purpose of using kinetic models?
3.4 Effect of operated factors on total Cr removal
For experiment given in Fig 8a) did you use modal chromium solution?
Line 223-228: Experimental details transfer in section 2! Effect of dosage ????? which type of sample…
From Fig 8a it is clear that the best sorption achieved with co=400 and 600 mg/L, I can say same removal efficiency is achieved. Why did you use for other experiments initial conc. of total Cr of 400 mg/L?
What is the maximum permitted concentration of chromium by law for the discharge of treated wastewater? Have you reached these conditions?
Author Response
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Author Response File: 
Author Response.docx
Reviewer 2 Report
The manuscript deals with the application of nanoscale zero valent iron supported by biomass activated carbon for removal of chromium from electroplating wastewater. Introduction sufficiently shows background of this topic and the aim of this study is clearly defined. Paper is interesting, but main disadvantage is description of methods, which is incomplete and not allow another researcher to reproduce this experiments. In results and discussion is some of results, which are not supported by methodology. Authors should intimately improve sections “Materials and methods” and “Results and discussion” before publication. See specific comments below:
Line 30: Please improve symbol of anion. In present form, the chromium has oxidation state (– III), not (VI)…
Line 94: Please define “certain amount”. This expression is not concrete and it should not be in scientific reports.
Line 95: Each sample was prepared with 150 ml untreated wastewater? See comment for lines 98-100.
Lines 98-100: Description of methods is incomplete. lack of details, which are significant for reproduction of this experiment. First of all, you gave information only about ranges of five parameters. You should define how many samples were prepared, because range of Cr initial concentration 20-300 mg/L can be obtained through analysis of two as well twenty samples…
You did not precise, whether reaction temperature, pH and interaction time were changed for single sample or for each combinations of five factors were prepared new samples?
You wrote, that Cr initial concentration was from 20 to 300 mg/L… Concentration of Cr in untreated wastewater was 292.25 mg/L, so in 150 ml of wastewater is 43.84 mg Cr. If you filled up conical flask to 250 ml, concentration of chromium was 175.35 mg/L and it is the lowest concentration, which you can obtain in 250 ml conical flask. This is about 9 times higher than the lowest initial concentration. In which way did you prepare concentrations lower than 175 mg/L?
Line 100: Please define “specified time”. This is ambiguous expression…
Lines 116-117: The same information is in lines 64 and 67.
Lines 131-133: This part should be moved to section “Materials and methods”.
Figure 4: As you mentioned in “Materials and methods” interaction time was 60-180 min, but on the figure time is 0-180 min. Please explain this difference.
Figure 4b: How did you obtain these results? In “Materials and methods” you did not write about experiment with different standby time…
Line 188: It should be “Figure 7” not “Figure 8”.
Figure 8: Why did you present results without values of removal efficiencies for 180 min?
In all manuscript: Please improve editing of text, because is a lot of unnecessary spaces, missing dots and the like. Please, separate the numbers by their units of measure.
Author Response
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Author Response File: Author Response.docx
Reviewer 3 Report
The paper presents characterisation of nano zero valent iron nanoparticles bounded to biomass activated carbon and its application for Cr remowal from wastewaters. Overall the manuscript is well prepared and has potential to be frequently cited, however English should be improved. Authors constantly use “shown” in grammar form. Please ask native speaker or commercial translator to improve the language. From analytical point of view I will suggest to add some information about ICP-OES measurements. Was any external standard used to correct matrix effect? It will be worth to study removals of other metals that probably exist in electroplating wastewater. The quality of most of Figures is poor and can be also improved.I also suggest to change the title of subchapter 3.2 because it presents rather mechanism for the reduction-adsorption of Cr on BC-nZVI.
Author Response
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Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
Water
TITLE: Nanoscale zero valent iron supported by biomass activated carbon for highly efficient total Chromium removal from electroplating wastewater
The corrected manuscript has been much improved, but in my opinion there are some other modifications to be made.
My comments follow:
There are still some typographical errors.
On some places in the manuscript, you write the numerical percentage amount together with the number, and somewhere not. Equalize. Line 80, 90, 113 On some places in the manuscript, you write the number together with the measurement unit! Please correct in all. Line 109, 117, 154, 165PLEASE CHECK CAREFULLY!
INTRODUCTION
Line 40-49: Is this general or is it related to the plant where you sampled the waste water? I would say that in general, you can write that way, in general, I agree, but with corrections.
“…three-stage treatment methods, i.e. the initial treatment, advanced treatment and membrane treatment “ – What is the difference between advanced treatment and membrane treatment? I think that membrane technique is advanced. Maybe I am wrong.
“…by chemical precipitation and activated carbon adsorption.” - Explain separately what is achieved with each method
“…treatment by adding the flocculant and adsorption materials” Floculation and adsorption together?
MATERIALS AND METHODS
Section 2.4.1.
My previous comment:
Completely reorganize!
Please explain each experiment in detail you performed with experimental condition. Please not put experimental condition in figure caption.
EXPLAIN IN DETAIL EACH EXPERIMENT AS DESCRIBED IN THE RESULTS AND DISCUSSIONS!
RESULTS AND DISCUSSIONS
3.1 Synthesis and Characterization of materials
Part described in lines 115-119: better explain.
Explain morphological differences between BC-nZVI in relation to BC.
Give comparison of XPS for BC and BC-nZVI. Describe differences!
3.2 Degradation mechanism
My first comment: Experimental condition given in capture of Figure 4 transfer to the experimental section. Move the text in line 158-160 to the Materials and Methods section.
Give the results of chromium sorption to BC in the manuscript and explain the justification of preparation of the BC-NZVI sample based on those results. I think this is important results.
3.3 Kinetic of Cr removal by BC-nZVI
My first comment:
Beside to the reaction kinetic models, you must conduct the fitting of the experimental results with the diffusion kinetic models - this is biochar and the diffusion of chromium in the biochar particle or BC-nZVI. Consider if the chemical reaction alone is limiting step. What is the purpose of using kinetic models?
Your answer is not satisfactory. What if diffusion is a limiting step?
3.4 Effect of operated factors on total Cr removal
For experiment given in Fig 8a) did you use modal chromium solution?
My first comment:
Line 223-228: Experimental details transfer in section 2! You did not do that!
What is the maximum permitted concentration of chromium by law for the discharge of treated wastewater? – You answered in the introductory part. HAVE YOU REACHED THESE CONDITIONS? – Please, give me the answer and empower the manuscript with that answer.
Author Response
请参阅附件
Author Response File: Author Response.docx
Reviewer 2 Report
The authors have addressed each of the reviewer's comments and the manuscript has been improved. I recommend accepting the paper.
Author Response
Thank you!!
Round 3
Reviewer 1 Report
The authors improved the manuscript, but some of my questions were not answered.
My comments are as follows:
In lines 175 and 177: aBsorption change in aDsorption
The scetion “2.4.1 Batch experiments” has been improved, but my suggestion is that the description of the experiments should be in the same order as in the Results and Discussion section.
The order should be: Kinetic, dosage, initial concentration, pH and temperature.
There is no explanation of kinetic experiments.
My previous comment:
Explain morphological differences between BC-nZVI in relation to BC. – There is no new enhanced explanation
My previous comment:
Beside to the reaction kinetic models, you must conduct the fitting of the experimental results with the diffusion kinetic - the answer is to cite 3 references.
Just comment on author answer:
“Membrane treatment is more advanced than advanced treatment, and can get lower Cr content, but the cost of membrane treatment is higher than that of advanced treatment. Therefore, we often use the cheap method to reduce Cr as far as possible before the membrane treatment.”- Membrane treatment is advanced treatment!
Author Response
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Author Response File: Author Response.doc
This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.
