The Effect of Temperature on the Biosorption of Dyes from Aqueous Solutions

Round 1

Reviewer 1 Report

The topic of dye biosorption is not new, however, good summarisation of one effect on the process could bring some value in the study. However, the article is written in a poor way and the focus on the temperature is lost. It describes various parameters, not explaining which dyes are just commented. The way how the abstract and the article is written is very strange – it states how many articles were included in the review, how many authors had similar views, I think other parameters are more important in a good review. It is quite unusual to start with the number of papers involved in the review especially without explanation if just 36 articles were already published, without that 36 articles is quite low number of articles to be included in the review.  The abstract, conclusion and even the text should contain the summarization of obtained results not summarization of how many authors had found the results.

Using shortcuts of normal words such as temperature or biosorption in the text is quite unusual and remining more students notes. For all just one example “Generally, in seven cases, the authors stated Pos T effect on the Bios, twice Neg effect and three times Pos and then Neg effect along with further increase of T parameter.“ Line 178 I would suggest authors not to use shortcuts in the text it significantly decrease the value of the article.

In Introduction incorrect statement is suggested without any explanation: „Also, with respect to biosorption of pollution in the natural environment, the term phytoremediation [2] appears “. However, biosorption and phytoremediation are two different processes without a link between them. Then Fig. 1 has no meaning in the text describing biosorption.

Biosorption definition is incorrectly stating adsorption and absorption by living and non-living biomass as one process. In general, biosorption is used for the process of pollutant sequestration by non-living biomass and bioaccumulation for removal of pollutants by living cells.

In general, very poor explanation of biosorption phenomena is provided in the Introduction, the chaotic mixture of information is provided. Own unpublished results using living Lemna minor freshwater aquatic plant are described in the Introduction mixing terms biosorption and bioaccumulation.

The reasons why to study the effect of temperature on dye biosorption are explained in a limited way. The temperature of dyeing process itself has very little effect on waste treatment – if necessary, the waste flow can get colder before processing. In the previous studies it was found that the temperature in range of 20 – 35°C (usual ambient temperature) has negligible effect on biosorption process so statement: “In general, if the sorption is chemical, then the influence of T is positive; however, if the sorption involves physical process, then the influence of T is mostly negative. Therefore, the conclusion about the influence of T on the biosorption used in the treatment plants seems to be questionable and hence there was a genesis to develop the presented here review.“ gives  incorrect information. From scientific view, biosorption as a process (based on main mechanisms) can be influenced by temperature, however, it is not clear why the effect of temperature on biosorption as a technology in treatment plant should be questionable.

It is not clear why information that every published article contains a SEM photography is important for the article.

Presenting that comprehensive database of dye biosorption have been made is quite overestimated.

Naming microscopic fungi mushrooms (Table 1) suggest not good knowledge of the authors in the field. Mixing the way of preparation (e.g. drying) with belonging to fungi group (basidiomycetes) in a bracket does not help the Table. Listing remarks after the name of dye is very confusing.

Aspergillus niger not Aspergillus Niger, Streptomyces not streptomyces

English needs correction sometimes the sentences are not correct, e.g. “the biomass was dried and prepared in the laboratory by means of a dead biosorbent”. Line 120

The aim of article was to summarise the effect of temperature on dye biosorption, but it is describing various parameters and summarising in general the articles dealing with dye biosorption, presenting very chaotic mixture of information, difficult to read and understand what authors wanted to show with the article.

I do not recommend the article for publication.

Author Response

Reviewer # 1:

1. In the revised manuscript, we have now significantly improved and expanded this work. The improvement among others included changes in Abstract, and Conclusions sections, assignment of various parameters to specific dyes and many other corrections marked with the red font in the revised manuscript. Especially, the comment about the number of articles was taken into consideration. However, we cannot fully agree with the Referee that focusing strictly on the temperature effects is a disadvantage of our article; on the contrary, we find it to be an asset. Nevertheless, other parameters on biosorption were also discussed, including the concentration of dye solutions, biosorbent doses, biosorbent-biosorbate contact time, pH of the system, etc.
2. According to the Reviewer’s suggestion, the abbreviations of ordinary words have been reduced. However, abbreviation of temperature as "T" has been left in most of the text.
3. As suggested by this Reviewer, all contents regarding phytoremediation were removed, including Fig. 1, corresponding text in the manuscript and references.
4. The definition and explanation of biosorption phenomenon have been adjusted to the Reviewer's requirements (see page 2 of the revised manuscript).
5. In the revised manuscript, a short explanation has now been added regarding the influence of hot textile wastewaters on biosorption.
6. Although SEM micrograph (Figure 2) is just a small addition to the review, it gives a quite good insight to the biosorption process.
7. The database of dye biosorption has been enriched with eight additional papers; also the word "comprehensive" has been removed.
8. In the revised manuscript, the content of Table 1 has been changed into a more readable form.
9. The names of microorganisms have been corrected.
10. We have now somewhat improved English of the revised manuscript.
11. In our opinion, a comparison of various parameters influencing the biosorption gives us an overall background view, necessary to fully assess the influence of temperature on the biosorption.

Author Response File: Author Response.docx

Reviewer 2 Report

Processes (MDPI)

Authors: Smoczyńsky et al.

Title: The effect of temperature on the biosorption of dyes from aqueous solutions

(review)

The influence of temperature is one of the key parameters for sorption efficiency. Thus, I think that the idea of the paper is relevant. It is necessary to summarize the results of temperature effect with the goal to understand sorption mechanisms and relationships between sorbate and sorbent. This work is focused on biosorption. I suppose there are several issues which must be corrected or deeply examined and clearly explained (see my comments). The basic structure of the review is good (the biosorbents were divided to the 3 types displayed in 3 tables – fungal, microbiological and let’s say plant biomass), however, text elaboration is poor (I will explain it later) and must be improved (section 2).

ABSTRACT

Line 1: rewrite or remove the sentence “Determination of the temperature is important…” everything is important …

Line 12-14: “Also, the dyeing process is usually carried-out at high temperatures, which leads to the formation of hot textile sewage” – remove it or explain it. How it correlates with biosorption. Do you mean that after dying procedure at high temperatures, the sorption process will be applied immediately? 

1. INTRODUCTION

Line 25: “make a key element” – better one of the key …

Please clearly explain some sentences and add my remarks to the text:

The question: Biosorption = phytoremediation? Line 49 was taken from [4]? Line 53-55 unpublished results, OK you can use it, but add some facts, e.g. your maximum sorption capacity of your biosorbent, type of biosorbent, conditions etc.  Compare it with literature Qm of concrete AC or commercial sorbent... or remove it. Line 64: hot textile sewage – explain it why is important... as I wrote previously.

Very important are the statements in the line 66-67 about chemical and physical sorption vs. T. Is it possible to connect these statements with the well-known isotherm models (e.g. Langmuir, Dubinin-Radushkevich and Freudlich)? Or PSO and PFO kinetic models? It is well-known that Langmur model is applied during monolayer sorption, which primarily signifies chemisorption. How correlates the results from temperature experiments with results taken from kinetic studies or isotherm experiments? The similar problem is kinetic models: second-order kinetics model implies for chemisorption … You have to make a review for these basic models and connect it with your topic of the paper (temperature effect).

In general, the paper presents results from sorption of carbon-based biosorbents Table 1-3. However, Figure 1 presents the inorganic crab carapace.  Just to be clear: Is your paper centred on biosorption to carbon (organic) biomaterials? Can you include to a group of biosorbent also inorganic materials such as zeolites, minerals (e.g. olivine, eggshells), sediments, humic acids etc.? If yes, there are many studies about the adsorption of dyes to the inorganic adsorbents. Please clearly define it or include the data from an inorganic family of sorbents.   

Line 89: Q_ph and Q_ch – it means physical and chemical?

When the favourable effect of temperature was recorded, which chemical bonds are generally presented during temperature increase? In the case of physical adsorption - physical interactions, concretely?

2. Temperature effect on dyes biosorption from aqueous solutions and/or wastewater.

I think you have to rewrite this section. It is not well structured. There is no connection between the effect of temperature and other parameters (influence of pH, initial concentration, time etc.) E.g.  lines 127-177; as well as 199-241 or 265-335. In these paragraphs, you wrote about the influence of other parameters excepting of T but how it is related to temperature? There is no connection in your text. You wrote about PSO, isotherm models, initial concentration but without any connection to your topic.     

How the charge influences the sorption mechanism from the viewpoint of temperature. Could you add to the tables 1-3 a short annotation to individual dyes?  E.g. charge of the dyes. Whether they are ionic (anionic or cationic) or non-ionic dyes. Can you perform some classification and discuss it?

Line 125-126: I do not understand: The article [9] refers to two types of biosorbents - fungi and algae; hence, the indices „m” and „a” are shown in green colour.

 DISCUSSION

• There is no discussion section
• From line 350 - this paragraph is discussion? You should make a new section: DISCUSSION

Please make the fruitful discussion between the temperature effect and other parameters (related to the type of dyes (after some classification), type of biosorbent, kinetic models, isotherm models) and mechanism of the sorption. For example, is it possible to predict sorption behaviour (of concrete dyes (either ionic or non-ionic) and concrete sorbent) at a different temperature? Write it to the conclusion section.

Author Response

Reviewer # 2:

1. As suggested by this Reviewer, the Abstract of the revised manuscript has been improved.
2. As suggested by Reviewer #1, all contents regarding phytoremediation were removed, including Fig. 1, corresponding text in the manuscript and references. Thus, the mentioned lines 49, 53-55 were also removed.
3. In the revised manuscript, a short explanation has now been added regarding the influence of hot textile wastewaters on the biosorption process.
4. According to the Reviewer's suggestions, issues regarding chemical and physical sorption vs. T have been expanded and discussed in the new "Summary" chapter.
5. The question of whether crab carapace is a biosorbent or a sorbent is debatable; hence, this article was not included in the group discussed in Tables 1-3. Monteneiro et al. (2016) in the introduction (and in keywords) use the “biosorption and biosorbents” terms, then in the "Materials and Methods" the authors switch to the “sorbents” term. In many publications, this type of material is mentioned in the group of biosorbents and the concept of our paper aimed at determining the effect of temperature on the complicated process occurring at the interface: <natural, waste material with a developed surface - aqueous dye solution>. Furthermore, according to other Reviewer's comments, we have added new content to the revised manuscript together with additional references.
6. The definitions of the Q_ph and Q_ch abbreviation have been added.
7. As mentioned above, a new chapter has been added, where the comment about "favourable effect of temperature…" is given.
8. According to the Reviewer's suggestion, the second chapter was reorganized, including the addition of eight referencef papers, simplification of Tables has been made (see all changes in the revised manuscript).
9. The issues regarding influence of molecule charge on the sorption have been expanded and discussed in the new "Summary" chapter.
10. Readability of lines 125-126 has been improved by removing the algae data.

Each time the results are reviewed, a "statistical" discussion section appears, followed by several "records", which is why "Review and discussion of literature data" has been added to the title of the chapter. Additionally, the new "Summary" chapter has been added.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The quality of article did not improve significantly. Just few new paragraphs were added. Still many shortcuts are used without reasons decreasing the readability of the article. Despite the title stating the study of temperature effect, various parameters are discussed. The strange way of summarizing number of articles dealing with the day biosorption is still there as well as majority of weaknesses I mentioned in my previous review. However, the summary added (although it is not clear why so long summary should be in the article) brings information in more proper way. So I would recommend the authors to build new article on the basis of the summary – delete the previous parts and add more information as well as figures to the summary, change title (as more factors than just temperature were discussed) and in that way interesting article could be prepared.

I do not recommend the article for publication in submitted form.

Reviewer 2 Report

Processes (MDPI)

Authors: Smoczyńsky et al.

Title: The effect of temperature on the biosorption of dyes from aqueous solutions

(review)

The manuscript was improved. I suppose that the Summary chapter will afford a valuable part of the paper.

Check next points:

• check the use of italic and roman fonts for symbols in scientific text and equations
• at the end of introduction write main goals of your review (why you select this topic, what you want to reach …)
• my previous note was not fully accepted “In general, the paper presents results from sorption of carbon-based biosorbents Table 1-3. However, Figure 1 presents the inorganic crab carapace. Just to be clear: Is your paper centered on biosorption to carbon (organic) biomaterials? Can you include the group of biosorbent also inorganic materials such as zeolites, minerals (e.g. olivine, eggshells), sediments, humic acids, etc? If yes, there are many studies about the adsorption of dyes to the inorganic adsorbents. Please clearly define it or include the data from the inorganic family of sorbents.”    

You are writing that “The question of whether crab carapace is a biosorbent or a sorbent is debatable”

I think you have to choose whether you want to write about organic (carbon) biosorbents or also inorganic biosorbents. When you are writing about carbon-based biomass than you should remove Figure 2 (crab and clamshell) and accompanying description. If you want to cover also this type of material, you have to add other inorganic biosorbents to your review such as eggshells, bones, sediments, silica-based biomaterials, etc. They were also studied as sorbents of dyes.