Preparation of Triiodide Resin Using Potassium Iodide and Peracetic Acid: Application to Wastewater Treatment

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This manuscript presents a novel and practical method for preparing triiodide resin (TR) by chemically reacting potassium iodide (KI) with peracetic acid (PAA), without the use of crystalline iodine (I₂). The prepared TR was applied to the sterilization of anaerobically treated livestock wastewater. While the experimental design is logical and the results are clearly presented, several important revisions are necessary before the manuscript can be considered for publication. These revisions pertain to the quantitative presentation of iodine species, clarification of wastewater pre-treatment procedures, and more intuitive expression of experimental outcomes such as yields and bacterial reduction.

1. The manuscript presents the concentration of iodine compounds based solely on absorbance values. Please convert the absorbance into actual molar concentrations or % values where applicable to enhance interpretability.

2. The manuscript lacks detail regarding the pre-treatment of anaerobically treated livestock wastewater before TR application.

3. It is recommended to provide a more detailed description of the procedure used for measuring CFU.

4. It would be advisable to include statistical annotations in all figures where statistical analysis is applicable.

Author Response

Reviewer 1

This manuscript presents a novel and practical method for preparing triiodide resin (TR) by chemically reacting potassium iodide (KI) with peracetic acid (PAA), without the use of crystalline iodine (I₂). The prepared TR was applied to the sterilization of anaerobically treated livestock wastewater. While the experimental design is logical and the results are clearly presented, several important revisions are necessary before the manuscript can be considered for publication. These revisions pertain to the quantitative presentation of iodine species, clarification of wastewater pre-treatment procedures, and more intuitive expression of experimental outcomes such as yields and bacterial reduction.

1. The manuscript presents the concentration of iodine compounds based solely on absorbance values. Please convert the absorbance into actual molar concentrations or % values where applicable to enhance interpretability.

Sol) Absorbance values at wavelengths of 226 nm (I⁻), 460 nm (I₂), 290, and 350 nm (I₃⁻), which reflect the volumetric iodine spectrum. The concentration of each iodine compound was calculated using molar absorptivity values (12,600 L·mol^‑1·cm^-1 at 226 nm for I^-, 728 L·mol^-1·cm^-1 at 460 nm for I₂; 25,000 L·mol^-1·cm^-1 at 350 nm for I₃^- and 26,000 L·mol^-1·cm^-1 at 290 nm for I₃^-). The concentrations of each iodine compound, initially represented by absorbance values, were converted to millimolar (mM) units using their respective molar absorptivity coefficients (ε), and the all-corresponding figures have been revised to reflect these quantitative changes. The absorbance-based values of the iodine compounds presented in the main text were appropriately converted to millimolar (mM) concentrations.

The revised parts are highlighted in red color in the text of this manuscript (Line 69 – Line 72 on Page 2).

 

2. The manuscript lacks detail regarding the pre-treatment of anaerobically treated livestock wastewater before TR application.

Sol) The anaerobically treated livestock wastewater was filtered using fabric, and the upper layer of the sample was used to verify the disinfection effect by TR prepared by chemical reaction of a KI solution with PAA.

The revised parts are highlighted in red color in the text of this manuscript (Line 99 – Line 101 on Page 3).

 

3. It is recommended to provide a more detailed description of the procedure used for measuring CFU.

Sol) After the contaminated water was treated with TR in cycles one, two, and three times, each sample for the CFU test was plated onto potato dextrose agar and incubated at 25 °C for 48 hours. After incubation, the number of bacterial colonies per sample was counted.

We added additional information related to CFU test in the main text of this manuscript.

The revised parts are highlighted in red color in the text of this manuscript (Line 104 – Line 106 on Page 3).

 

4. It would be advisable to include statistical annotations in all figures where statistical analysis is applicable.

Sol) Thank you for the suggestion. We added statistical indications to Figures 2, 3, 4, 5, and 6 using SAS ver. 9.4 (SAS Institute Inc., Cary, NC, USA) to enhance the reliability and interpretation of the data. Data were analyzed using one-way ANOVA followed by Duncan’s test (p <0.05).

 

 

 

 

 

 

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

This manuscript describes the development of a novel method for preparing triiodide resin (TR) using potassium iodide (KI) and peracetic acid (PAA), eliminating the need for crystalline iodine (I2). The authors demonstrate that the chemical radical reaction between KI and PAA produces I2 and triiodide ions (I3-), which can be combined with a strong basic anion exchange resin to form TR. The authors validate the sterilization efficacy of their prepared TR by treating anaerobically digested livestock wastewater and assessing bacterial inactivation. The experimental approach is generally sound, with appropriate controls and analytical methods. The spectrophotometric monitoring of various iodine species (I-, I2, I3-) provides convincing evidence for the formation of triiodide ions via the proposed mechanism. However, the study would benefit from more detailed characterization of the prepared TR: What is the loading capacity of I3- on the resin? Is there any leaching of iodine species during water treatment? What is the stability of the prepared TR over time?

Author Response

Reviewer 2

This manuscript describes the development of a novel method for preparing triiodide resin (TR) using potassium iodide (KI) and peracetic acid (PAA), eliminating the need for crystalline iodine (I2). The authors demonstrate that the chemical radical reaction between KI and PAA produces I2 and triiodide ions (I3-), which can be combined with a strong basic anion exchange resin to form TR. The authors validate the sterilization efficacy of their prepared TR by treating anaerobically digested livestock wastewater and assessing bacterial inactivation. The experimental approach is generally sound, with appropriate controls and analytical methods. The spectrophotometric monitoring of various iodine species (I-, I2, I3-) provides convincing evidence for the formation of triiodide ions via the proposed mechanism. However, the study would benefit from more detailed characterization of the prepared TR: What is the loading capacity of I3- on the resin? Is there any leaching of iodine species during water treatment? What is the stability of the prepared TR over time?

Sol) Thank you for your interest in my research and for your valuable feedback. TRILITE® MA-12 is a strong base Type I gel-type anion exchange resin, featuring trimethylammonium (-N⁺(CH₃)₃) functional groups on a styrene-divinylbenzene (Styrene-DVB) matrix. The resin has a total exchange capacity of at least 1.3 equivalents per liter (eq/L). Therefore, up to 1.3 moles of monovalent anions (e.g., Cl⁻, OH⁻, I₃⁻) can theoretically be exchanged using 1 liter of the resin employed in this experiment. Using 20 g of resin and taking into account an apparent density of 670 g/L, the theoretical maximum loading capacity of I₃⁻ ions is calculated to be 39 mM. When reacting with a 100 mM KI solution, the resin was able to accommodate up to 84.6% of its theoretical maximum exchange capacity. To evaluate the potential leaching of iodine species during water treatment, 1 L of deionized water was passed through a TR column (23 mm in diameter, 80 mm in height). The effluent was analyzed using UV-Vis spectrophotometry, with absorbance measurements recorded at 226 nm, 290 nm, 350 nm, and 460 nm.

Sample Name	460.0 nm (I2)	350.0 nm (I3-)	290.0 nm (I3-)	226.0 nm (I-)
DW (Blank)	0.000	0.000	0.000	0.000
1st 1L effluent	0.000	-0.006	-0.006	0.001
2nd 1L effluent	0.000	-0.005	-0.006	-0.001
3rd 1L effluent	0.000	-0.004	-0.006	0.000

 

As a result, no significant leaching of iodine species was observed during the treatment of up to 3 L of water. The mechanism of sterilization by TR is inactivation of the cell membrane via electrostatic interaction, and the killed bacteria do not remain attached to the resin but will readily pass on through a bed of the resin. Therefore, disregarding the potential loss of I₃⁻ ions upon contact between bacteria and TR, and the possible physicochemical reactions during water treatment, TR is expected to retain its sterilizing efficacy over a prolonged period.

The revised parts are highlighted in red color in the text of this manuscript (Line 205 – Line 212 on Page 7).

 

 

 

Author Response File: Author Response.pdf