Thiosulfate Solution Research Articles

Piezo-Photocatalytic Reduction of Au(I) by Defect-Rich MoS2 Nanoflowers for Efficient Gold Recovery from a Thiosulfate Solution

To achieve a more efficient gold recovery from a thiosulfate solution, piezo-photocatalytic reduction of Au(I) with defect-rich MoS2 nanoflowers (DR-MoS2 NFs) as a catalyst was proposed in this wor...

Determination of the butanone in urine by gas chromatography with precolumn derivation

Objective: To establish a method for determination of the butanone in urine by gas chromatography (GC) with pre-column derivation. Methods: For detecting of butanone in urine, potassium iodide and potassium dichromate were added into urine under acidic condition, sample derivatization was undertaken in 50 ℃ water bath for 60 min and the iodine butanone was extracted with n-hexane. After the sodium thiosulfate solution was used to remove excess iodine, urine samples were centrifuged at 10000 r/min for 5 min, then the supernatant was analyzed using temperature rising programming with the Agilent Hp-5 column (30 m×0.32 mm, 0.25 μm) and electron capture detector (ECD) as the detector. The detector temperature was 300 ℃, the inlet temperature was 200 ℃, and the carrier gas was nitrogen. Results: For detecting of butanone in urine, potassium iodide and potassium dichromate were added for derivatization under the acidic condition. After extraction and centrifugation, the supernatant directly put through column and detected by ECD. In present study, the sample pretreatment condition was optimized, the relative standard deviations of intra-day and inner-day, the spiked samples and its recovery were evaluated for analyzing the accuracy of the proposed method. Conclusion: This method has proved to be simple, efficient and highly sensitivity, it can be utilized for butanone detection in occupational population.

Electrodeposition of AuxAg1-X Alloys from Thiosulfate Solutions

Silver (Ag) and gold (Au) are noble metals of particular interest for future plasmonic, and (bio)sensing applications due to their unique coupling with light in the visible range.[1,2] Recent studies suggest that AuxAg1-x alloy nanostructures of different geometry, composition and size can exhibit interesting new optical phenomena.[3,4,5] Therefore developing new environmentally-friendly (cyanide-free) electrodeposition route to fabricate AuxAg1-x alloys is desirable.[6] Thiosulphate-based solutions are less toxic, and this solution was previously studied for pure Au,[7] pure Ag [8] and recently for AuxAg1-x alloys.[6]In this work, we will present a systematic study of electrodeposition of AuxAg1-x alloys from thiosulphate solutions on Au and indium-tin-oxide (ITO) substrates. Thin-film alloys (20 nm-100 nm thickness on Au on ITO) of different compositions were electrodeposited by variation of Ag+: Au+ ion concentrations in the solution. The structure of the deposited alloys was explored as a function of the electrodeposition potential and film thicknesses by Atomic Force Microscopy (AFM), and Scanning Electron Microscopy (SEM). Chemical composition of the electrodeposited alloys was determined using X-Ray Photoemission Spectroscopy (XPS).The electrodeposition on the two substrates showed higher Ag content in the films than expected from the solution composition ratios. Comparison of the linear sweep voltammetry for deposition of alloys on Au and ITO show that the potential at which alloys start depositing for ITO is more negative than on Au. Stoichiometry of films varied between Au20Ag80 to Au50Ag50. Diffusion-limited deposition of alloys at lower overpotentials produced smooth, homogenous films on Au substrates; at potentials higher than 1 V vs MSE, hydrogen-evolution reaction assisted non-uniform growth and formation of instabilities at the surface in both substrates. The electrodeposited alloys were characterised by surface composition and structure sensitive UPD processes such as Pb UPD and Cu UPD. The results showed a correlation between the UPD peaks potential shifts and the UPD charge with alloy compositions.

The effect of heat treatment on environment assisted cracking susceptibility of 9% Ni steel

ABSTRACT The influence of temper temperature on the environment assisted cracking of seamless 9% Ni steel tubes were investigated using scanning electron microscope (SEM), electron backscatter diffraction (EBSD), X-ray diffraction (XRD), slow strain rate tensile (SSRT) tests, hydrogen permeation tests and electrochemical measurements. Mechanical and electrochemical tests were conducted in sodium thiosulphate (Na2S2O3 10−3 mol L−1) solution at open circuit potential (OCP) and at cathodic potential. Results showed that 9% Ni steel had a higher ductility loss at OCP when compared with the results obtained under cathodic potential. The lower ductility loss at cathodic potential was attributed to the inhibition of the anodic dissolution. After the tests, the specimens were examined using scanning electron microscopy to characterise the fracture morphology. The fracture surface exhibited mixed morphology, with a ductile morphology in the centre and a brittle morphology near the edges.

Increase in gold dissolution in copper ammonia thiosulfate solution via cobalt surface modification

When gold was leached using copper ammonia thiosulfate solution, the dissolution rate of gold decreased as the leaching time increased. The dissolution of gold powder with 44 and 77 μm particles was studied，and the results indicated that the dissolution rate was not decreased by surface passivation or the decrease in copper concentration but by the changes of the electronic structure of the gold surface caused by the change in the exposed crystal surface. The transmission electron microscopy images of the gold powder revealed that the high-index (220) and (311) crystal surfaces almost disappeared during leaching. Furthermore, the surface of gold consisted mainly of the low-index (111) crystal surface during the later stages of leaching. Owing to the changes in crystal surface, the work function of the gold surface increased from 6.56 to 6.95 eV, and the increase in work function hindered the loss of electrons from the gold surface. When cobalt was used to modify the gold surface, the work function decreased from 6.56 to 5.99 eV. The leaching results indicated that the cobalt modification increased gold dissolution, and the gold leaching percentage was increased by 40% within 8 h. the tendency of gold to dissolve more easily after it underwent surface modification was confirmed by the apparent activation energy of the surface-modified being lower than that of the fresh gold powder, the formation of intermediate products of Co3O4 with high oxidation ability and the galvanic interaction between cobalt and gold electrodes. Dry-grind was applied for gold concentrate calcine and different contents of cobalt powder to study the possibility of industrial application of this effect. The results showed that only adding 50 mg cobalt to 100 g gold ores was beneficial to gold leaching

Staphylococcus spp Resistance to Chlorhexidine: Is There Any Impact Related to the Routine Use for Hand Hygiene?

Background: Although guidelines recommend the use of chlorhexidine gluconate (CHG) for hand hygiene (HH), the impact of its routine use on antimicrobial resistance is not clear. Objective: To analyze the impact on the CHG susceptibility among isolates obtained from hands of HCW during its routine use for HH. Methods: We conducted a crossover study at 4 medical-surgical wards of a tertiary-care hospital in São Paulo, Brazil. In 2 units (intervention group), we established routine use of CHG for HH. For the other 2 units (control group), regular soap was provided. The availability of alcohol formulation for HH was not changed during the study. Every 4 months we swapped the units, ie, those using CHG changed for regular soap and vice versa. At baseline, we cultured the hands of HCWs. Only nursing staff hands were investigated. For hand culturing, HCWs placed their hands inside a sterile bag containing a solution of phosphate-buffered saline, Tween 80, and sodium thiosulfate. After the solution incubated overnight, it was inoculated onto brain-heart infusion. Next, it was plated on McConkey and Mannitol agar. MALDI-TOF was used for identification. Agar dilution was performed for Staphylococcus spp. We selected all Staphylococcus spp with MIC ≥ 8 and performed inhibition of efflux pump test. For isolates that showed a decrease of 2 dilutions, we searched the gene qacA/B by polymerase chain reaction. Results: We obtained 262 samples from HCW hands yielding 428 isolates. The most frequent genera were Staphylococcus spp (58%), Acinetobacter spp (8%), Enterobacter spp (8%), Stenotrophomonas spp (5%), Klebsiella spp (4%), Pseudomonas spp (3%), and others (14%). Staphylococcus spp were less frequent in the intervention compared to control group (43% vs 61%; OR, 0.48; 95% CI, 0.29–0.69; P = .005). Among all Staphylococcus spp, the proportion of chlorhexidine resistance (RCHG; MIC ≥ 8) was 12%. All resistant isolates recovered susceptibility after inoculation with pump-efflux inhibitor. For pump-inhibited isolates, 53% had the gene qacA/B amplified by PCR. We did not investigate RCHG among gram-negative isolates. There was a nonsignificant increase in Staphylococcus spp RCHG in the intervention group (4% to 6%; P = .90). Healthcare-acquired infection rates did not change significantly during the intervention. The consumption of CHG increased from 7.3 to 13.9 mL per patient day. Conclusions: We did not detect a significant difference in RCHG during the routine use of CHG for HH, although we observed increasing resistance. Further investigation is needed to clarify other reasons for increasing MIC to CHG.Funding: NoneDisclosures: None

An electrochemical method to investigate the effects of compound composition on gold dissolution in thiosulfate solution

AbstractThe electrochemical behavior of gold dissolution in the Cu2+–NH3–S2O32−–EDTA solution has been investigated in detail by deriving and analyzing the Tafel polarization curve, as this method is currently widely implemented for the electrode corrosion analysis. The dissolution rate of gold in Cu2+–NH3–S2O32−–EDTA solution was determined based on the Tafel polarization curves, and the effects of various compound compositions in a Cu2+–NH3–S2O32−–EDTA mixture on the corrosion potential and corrosion current density were analyzed. The results showed that the corrosion potential and polarization resistance decreased, whereas the corrosion current density increased for certain concentrations of S2O32−–NH3–Cu2+and EDTA, indicating that the dissolution rate of gold had changed. The reason for promoting the dissolution of gold is also discussed.

Increased Recovery of Gold Thiosulfate Alkaline Solutions by Adding Thiol Groups in the Porous Structure of Activated Carbon.

Thiosulfate leaching combined with ion-exchange resins is an innovative alternative for gold recovery. According to the properties of activated carbon, it could replace resins in the gold recovery process, improve efficiency, and reduce operating cost. In this research, the adsorption process of gold thiosulfate complex on thiol-modified activated carbon was studied. Thioglycolic acid (ATG) was impregnated in activated carbon, and its adsorption ability was tested with synthetic solutions of gold and sodium thiosulfate (Au 10 mg·L−1, Na2S2O3 0.1 mol·L−1, pH = 10.0). Carbon was characterized by infrared spectroscopy, SEM-EDS, PZC titration, hardness number measures, and proximal analysis. Synthetic solutions were also characterized by UV-vis spectroscopy and cyclic voltammetry. The percentage of volatile material increased from 10.0 to 13.9% due to the impregnation process of ATG. Infrared spectra show characteristic bands of C-H, S-H, and C-S bonds. In the adsorption tests, the ATG-impregnated carbon achieved 91% of gold recovery, while the same amount of ATG in the liquid phase stirred with unmodified activated carbon reached 90% of gold recovery. The 44.9% of gold recovered with activated carbon impregnated with ATG was eluted with sodium cyanide ([NaCN] = 0.2 mol·L−1; [NaOH] = 0.25 mol·L−1; [CH3CH2OH] = 30% V/V; pH = 12.0; t = 24 h). These results suggest the gold transferred from the thiosulfate complex to a new gold thiolate complex.

Low Potential Pitting Corrosion of Ni-Cr-Fe Alloys in Chloride Plus Thiosulfate Solutions: Determination of Potential and Concentration Boundaries

Low potential pitting corrosion (LPPC) of Alloys 690 and 800 (UNS N06690 and N08800) was studied in neutral solutions, containing chloride ions from 0.1 M to 1 M and thiosulfate ions from 5 × 10−5 M to 10−3 M. LPPC occurred close to the corrosion potential (–0.25 VAg/AgCl) by a synergic effect of the chloride and thiosulfate ions. The threshold concentrations of aggressive species for LPPC occurrence were identified by potentiostatic tests with mechanical scratching of the surface, which yielded more conservative estimations compared to other electrochemical tests. The ranges of potential and concentration of chloride and thiosulfate where LPPC occurred and where it merged with the conventional chloride pitting were determined. The lowest threshold concentrations were measured in Alloy 800, with a lower Cr content than Alloy 690. Thermally-aged Alloys 800 and 690 had lower resistance to LPPC than the corresponding solution-annealed material. In 1 M chloride-based solutions, for aged Alloy 800, LPPC occurred at a thiosulfate concentration as low as 5 × 10−5 M; in 10−3 M thiosulfate-based solutions, the chloride threshold was 0.1 M. For thermally-aged alloys, pits propagated intergranulary in some experiments. In solutions with chloride and thiosulfate concentrations close to the threshold required for pitting, repassivation of LPPC was observed after a sustained period of pit growth, originally initiated by scratching the surface. Such a repassivation has not been reported before in the literature in chloride and thiosulfate solutions. Two possible explanations were presented for this phenomenon.

In-situ reduction of gold thiosulfate complex on molybdenum disulfide nanosheets for a highly-efficient recovery of gold from thiosulfate solutions

Thiosulfate leaching is widely considered an alternative and nontoxic technique for cyanidation in gold hydrometallurgy; however, the main problem with this technique is the difficulty in recovering gold from pregnant solutions. Here, we report that a simple and accessible material, molybdenum disulfide nanosheets, can effectively in-situ reduce and recover gold from pregnant solution based on its semiconducting properties. The results of the in-situ reduction showed that the gold-thiosulfate complex([Au(S2O3)2]3−) can be reduced to elemental gold particles with a particle size of 130–320 nm. The origin of the in-situ reduction of gold might be derived from the photo generated electrons released by molybdenum disulfide. The 1866.762 mg∙g−1 recovery capacity of gold on molybdenum disulfide from a 100 mg∙L−1 initial gold solution, which is 1000 times the recovery capacity of modified activated carbon, further demonstrates that molybdenum disulfide is a superior gold recovery material. Moreover, the removal of ~99% gold from gold-loaded MoS2 indicates the recyclability of MoS2 in gold recovery. Based on these results, it is obvious that molybdenum disulfide nanosheets is an excellent material to recover gold from gold-thiosulfate complexes. Besides, the application of molybdenum disulfide to gold recovery can simplify the traditional thiosulfate leaching process.

A review of gold extraction using noncyanide lixiviants: Fundamentals, advancements, and challenges toward alkaline sulfur-containing leaching agents

Alkaline sulfur-containing lixiviants, including thiosulfate, polysulfides, and alkaline sulfide solutions, stand out as a promising class of alternatives to cyanide because of their low toxicity, high efficiency, and strong adaptability. In this paper, we summarized the research progress and remaining challenges in gold extraction using these noncyanide reagents. After a brief introduction to the preparation method, the transformation process of various sulfur-containing species in alkaline solutions was discussed. Thereafter, some insights into the mechanism of gold leaching in alkaline sulfur-containing solutions were presented from different aspects, including thermodynamics analysis, electrochemical dissolution, and leaching kinetics. Moreover, recent progress in in-situ generation of sulfur-containing anions from gold-bearing sulfide minerals was outlined as well. Gold passivation caused by sulfur species was discussed in particular because it is considered the greatest challenge facing sulfur-containing leaching systems. Alkaline sulfur-containing lixiviants are expected to serve as alternatives in industrial applications of gold extraction, particularly for refractory gold ores containing copper and carbonaceous matter.

Interfacial properties of mercaptopropyl-functionalised silica gel and its adsorption performance in the recovery of gold(I) thiosulfate complex

Abstract Silica gel (SG) was modified using 3-mercaptopropyl trimethoxysilane (MPTMS) and used as an adsorbent for the recovery of gold(I) from a thiosulfate solution, based on the hard and soft acids and bases theory. The interfacial properties of the mercaptopropyl-functionalised silica gel (MP–SG) and its performance for the adsorption of gold(I) from a thiosulfate solution were examined. An optimized modification procedure was determined to produce a MP–SG mercapto group content of 1.1 mmol·g−1. Characterisation of the prepared samples revealed the immobilisation of the MPTMS on the SG surface through chemical adsorption, and that the modification process was accompanied by the release of methanol. The ratio of methanol to the mercapto groups was determined to be 2.06, indicating the formation of 1, 2, or 3 bonds between the SG and MPTMS. The effects of the solution pH, adsorption temperature, thiosulfate concentration and gold concentration on the adsorption of gold(I) onto MP–SG, were also evaluated. The adsorption of gold onto the MP–SG surface was determined to involve ion-interchange between the mercapto groups and Au(S2O3)23−. Numerical investigation of the gold adsorption mechanism, revealed that the charge of gold(I) decreased through charge transfer from the ligand to gold(I). The Au–MP–SG could be eluted using mixture of 1% thiourea and 2 mol·L−1 HCl. The findings of this study demonstrate the potential of SG for practical application to gold recovery from a thiosulfate solution.

Change in Iodine Contents during Ripening of two <i>Capsicum annuum L.</i> Cultivars Fruits at Brazzaville, CONGO

To identity iodine, assessits concentration and analyse the variation of this concentration following the ripeness stages, its titrating from Capsicum annuum L. dried fruit extract by sodium thiosulfate and starch solution test were achieved. Small and big Capsicum annuum cultivars were planted according to completely randomised design onto eight rows with eight seedlings whose four was useful. One-factor Anova incorporating the means comparison according to Student-Newman-Keuls’ test at 5% level was applied. Likewise, Pearson’s linear correlation at 1‰00 probability was used. Results shown that small and big Capsicum annuum L. cultivars contained iodine. People should consum Capsicum annuum L. fruits to avoid goiter. Other animal and plant foods also contain iodine. Iodine concentration discriminated the fruit ripeness stages in small Capsicum annuum L. cultivar. At the pre-ripeness stage (PMG), iodine concentration was higher than the ripe one (MG). Consequently, the consumption of its fruits is recommended at pre-ripeness stage to optimise the ingesting of iodine. In the same way, iodine concentration of small Capsicum annuum L. cultivar at pre-ripeness stage was significantly higher than the big one. At such phenological stage it will be advised people to eat small Capsicum annuum L. fruit than the big one when fruit changes. Duration of "sowing-flowering", "sowing-fruit set" and "sowing-fructification" in small Capsicum annuum L. cultivar was shorter than in the big one. Such shorter duration of small Capsicum annuum L. will allow the early obtention of its fruits than those from the big one and thus, their early selling. Â

In Situ Reduction of Au(I) for Efficient Recovery of Gold from Thiosulfate Solution by the 3D MoS2/Chitosan Aerogel

A three-dimensional porous MoS2/chitosan (MoS2/CS) aerogel with excellent mechanical strength and stability was constructed in this work through anchoring MoS2 to the surface of the CS aerogel. It ...

Modification of activated carbon by chemical vapour deposition through thermal decomposition of thiourea for enhanced adsorption of gold thiosulfate complex

Modified activated carbon (SCN-AC) was prepared by chemical vapour deposition through the thermal decomposition of thiourea. Compared with the AC-modified by impregnation, the benefits of SCN-AC were a simpler modification process and a shorter modification time. The Au(I) ion adsorption performance of SCN-AC in thiosulfate solution was systematically studied. The adsorbent was well characterised by scanning electron microscopy–energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The effects of contact time, pH, temperature, and gold concentration were investigated, and the gold adsorption performances in Cu2+-NH3-Na2S2O3 and Cu2+-en-Na2S2O3 systems were also evaluated. More than 85% of Au(I) could be recovered over a wide pH range, and the adsorption capacity increased with decreasing adsorption temperature, reaching a maximum of 11.86 kg/t-AC. The adsorption followed pseudo-second order kinetics and was well explained by the Freundlich model. Analysis of the thermodynamic parameters indicated that the adsorption of Au(I) on SCN-AC was exothermic and spontaneous. The adsorption of Au(I) on SCN-AC was attributed to the strong affinity between the soft acid and soft base, the formation of a π-π conjugated system, and the electrostatic interaction between the adsorbent and adsorbate. Additionally, SCN-AC showed good adsorption properties in the Cu2+-NH3-Na2S2O3 system and the Cu2+-en-Na2S2O3 system. This strategy could be used as a green and environmentally friendly method for gold recovery.

Effect of Intermetallic and Secondary Phases on Dry and Wet Sliding Wear Behavior of Super Duplex Stainless Steel

The purpose of this investigation was to quantify the effects of intermetallic and secondary phases on the sliding wear behavior of super duplex stainless steel 2507 against bearing steel type EN-31 under both dry and wet contact conditions. Phases were precipitated by suitable heat treatment in the range of 475–875 °C. A pin-on-disc technique was used to investigate the wear characteristics in the wet environment of 3.5% NaCl solution, 1 M HCl solution, 10−2 M sodium thiosulfate solution, and artificial ocean water. These media were chosen to closely match the actual service environment of super duplex stainless steel 2507. Pins were slid against a disc of EN-31 steel for distances of 1,000, 1,500, 2,000, 2,500, and 3,000 m. Results indicate that precipitation of the sigma phase gives the best wear resistivity, followed by precipitation of chi and R phases and then precipitation of the α′ phase. The experimental investigations reveal that hydrogen in acidic medium accelerates the reaction kinetic compared to the neutral medium because of the different cathodic reactions. Progressive wear was closely observed using the change in the sliding pin’s contact face profile and corresponding weight loss data. Scanning electron microscopy was used to study the wear mechanism.

Investigation of iodine removal efficiency in a venturi scrubber using mass transfer model for CFD

Filtered containment venting system (FCVS) is important for the ultimate safety of a nuclear power plant owing to its use in containment pressure reduction in case of severe accident. It vents a portion of containment air after removal of harmful radioactive products including iodine through venturi scrubber. The purpose of this research was to develop a mass transfer model for estimation of performance of a venturi scrubber for removal of elemental iodine using Computational Fluid Dynamics. A mathematical model for transfer of iodine from air to water was developed based on two film theory of mass transfer and experimentally validated. Simulations were performed for self-priming non-submerged circular venturi scrubber using Fluent and the results were compared with experimental ones. Experimental data was used for validation in which an aqueous solution of sodium hydroxide and sodium thiosulfate was used as scrubbing solution for removal of iodine. For simulation, only water was used instead of scrubbing solution for simplicity. Euler-Euler approach was used for two-phase modeling and realizable k-epsilon model was used for turbulence modeling. The results obtained from simulations had a good match with the experimental ones.

Research of combined reagent schemes of activation leaching of gold from oxidized ores of the Malmyzh field

The results of studies of the cyanide and an alternative methods for leaching gold and silver from oxidized ores of the Malmyzh field are presented. The possibility of recovering gold and silver from oxidized porphyry copper ores by thiosulfate solutions in agitation and percolation modes without intensifying the process – heating the solutions and adding copper ions – has been shown. Also, in a separate cycle – copper leaching with low-concentration sulfuric acid-sulfite solutions with additional opening of the silicate matrix with ammonium hydrofluoride – has been studied. The possibility of using ammonia-thiosulfate leaching in percolation mode has been investigated.

The effect of tetrathionate on the anodic process of gold thiosulfate leaching

AbstractThe mechanism that tetrathionates retarded gold dissolution during the anodic process of gold thiosulfate leaching was studied with the help of electrochemical and spectroscopic techniques. The results show that the reduction in gold dissolution did not originate from the increase of a passive layer on the surface. When the gold electrode was controlled at 0.25 V, the topography of the gold surface and element composition in the tetrathionate‐supplemented solution is not easily distinguishable from that in the thiosulfate solution. The addition of tetrathionate in the thiosulfate solution reduces gold dissolution. This phenomenon is caused by the decrease in thiosulfate concentration at the gold interface. And the gold interface composition was also changed due to the presence of tetrathionate.

The safety and efficacy of 2% vitamin C solution spray for relief of mucosal irritation caused by Lugol chromoendoscopy: a multicenter, randomized, double-blind, parallel trial

Lugol chromoendoscopy facilitates endoscopic visualization of esophageal dysplasia and carcinoma. Vitamin C solution (VCS) can theoretically neutralize free iodine, which causes mucosal irritation. The aim was to assess the safety and efficacy of VCS for relieving adverse symptoms caused by Lugol iodine staining. Two hundred forty eligible patients were randomized to receive 20 mL of normal saline solution (NS), 5% sodium thiosulfate solution (STS), or 2% VCS after spraying 10 mL of 2% Lugol iodine solution on the mid-distal esophagus. The primary endpoints were statistically significant reductions in acute and late adverse symptom severity scores. The secondary endpoint was the discoloration effect on esophageal brown iodine-stained mucosa. Spraying both VCS and STS similarly decreased the severity scores of acute (NS vs VCS= 2.58 vs 1.61, P= .040; VCS vs STS= 1.61 vs 1.89, P > .999) and late (NS vs VCS= 1.70 vs 0.91, P= .002; VCS vs STS= 0.91 vs 1.38; P= .212) adverse symptoms after Lugol chromoendoscopy compared with spraying NS. Compared with STS spray, VCS spray alleviated acute acid regurgitation or heartburn (33% vs 15%, P= .017) and late retrosternal discomfort or pain (21% vs 9%, P= .027). Moreover, compared with spraying NS, spraying VCS quickly discolored the iodine-stained mucosa, with a better decolorization score (2.26 vs 3.56, P= .000), and the effects of fading iodine dye were similar between VCS and STS (3.56 vs 3.59, P= .908). VCS can reduce mucosal irritation symptoms induced by Lugol chromoendoscopy and can be routinely recommended. (Chinese Clinical Trial Registry number: ChiCTR1900022000.).