Photoinactivation of sulfate-reducing bacteria using 1,9-dimethyl-methylene blue - DMMB and laser light.

Annually, the oil and gas industry faces equipment losses and product quality degradation due to the presence of sulfate-reducing bacteria (SRB). Given the negative impact of SRB, this study evaluates the use of photoinactivation (PI) with zinc chloride double salt of 1,9-Dimethyl-Methylene Blue (DMMB) as a photosensitizer (PS) in varying concentrations and combined with Laser light at different exposures in an SRB consortium. For culture growth, a modified Postgate C medium (without ferrous sulfate) was used, and cell quantification was performed on 100 µL aliquots of the consortium, read on a spectrophotometer (λ600 nm) in an oxygen- and light-free environment at room temperature. Statistical analyses included two-way ANOVA and ANOVA with interaction to separately and jointly evaluate the effects of PS and light in PI. Results indicated microbial activity in all groups, with an antimicrobial inhibition rate exceeding 50 % (p < 0.05) for concentrations above 1.5 µg/mL of DMMB. PI efficacy significantly depended on DMMB concentration and light density, achieving a 70.58 % (55.73-70.58, with a mean of 66.71 %) reduction (p < 0.05) with 1.5 µg/mL of DMMB and a 70.15 % (65-70.15, with a mean of 68.21 %) reduction with 2.0 µg/mL at an intensity of 21.6 J/cm2. In conclusion, PI presents a promising alternative to biocides in the oil and gas industry, offering easy application, avoiding bacterial resistance, being environmentally safe, and compatible with other SRB population control techniques.

In vitro evaluation of antimicrobial photodynamic therapy with photosensitizers and calcium hydroxide on bond strength, chemical composition, and sealing of glass-fiber posts to root dentin.

Investigate the impact of antimicrobial photodynamic therapy (aPDT) using different photosensitizers (PSs) such as indocyanine green (IG), curcumin (CC), and methylene blue (MB), with or without intracanal application of calcium hydroxide (CH), on the push-out bond strength of glass-fiber posts (GFPs) to intraradicular dentin, the chemical composition of the root substrate, and the sealing of the adhesive interface across different thirds of intraradicular dentin. A total of 112 bovine teeth underwent biomechanical preparation and were divided into eight experimental groups (n = 14 each): Negative control with deionized water; positive control with deionized water + CH; IG group with indocyanine green and infrared laser; IG + CH group; CC group with curcumin and blue LED; CC + CH group; MB group with methylene blue and red laser; and MB + CH group. The push-out bond strength was measured using a universal testing machine (n = 8), and scanning electron microscopy characterized the fracture patterns. Energy dispersive spectroscopy (n = 3) analyzed the chemical composition of the dentin substrate, while fluorescence confocal microscopy (n = 3) assessed the adhesive interface sealing between the resin cement and root dentin. Data were analyzed using two-way repeated measures ANOVA and the Tukey test for push-out bond strength and chemical composition comparison, with the Kruskal-Wallis and Dunn's tests (α = 0.05) for adhesive interface sealing. Significant bond strength differences were noted across root thirds and experimental groups (P < .05), with the IG + CH group showing the highest cervical bond strength and the IG group the lowest. Apical bond strength was highest in the CC group but lower in the NC and PC groups. Mixed failures predominated, except in the MB + CH group, where adhesive failures prevailed. Elemental composition varied among groups treated with different PSs and CH (P < .05), but interface quality, tag formation, and penetration depth showed no significant differences (P > .05). Laser-activated 500 mg/L CC combined with CH emerged as a clinically relevant option for root canal decontamination before GFPs luting. aPDT with different PSs and root canal depth influenced the push-out bond strength of GFPs and the chemical composition of root dentin. Curcumin-mediated aPDT at 500 mg/L proved effective, enhancing bond strength and sealing while maintaining consistent dentin composition across depths.

Potentiation of antimicrobial photodynamic therapy with potassium iodide and methylene blue: targeting oral biofilm viability.

The study aimed to assess the impact of combining potassium iodide (KI) with methylene blue (MB) in antimicrobial photodynamic therapy (aPDT) within an oral biofilm formed in situ. A single-phase, 14 days in situ study involved 21 volunteers, who wore a palatal appliance with 8 bovine dentin slabs. These slabs were exposed to a 20% sucrose solution 8 times a day, simulating a high cariogenic challenge. Following the intraoral phase, the biofilms formed on the slabs were randomly assigned to the treatments: C (0.9% NaCl); CHX (0.2% chlorhexidine); KI (75 mM KI); MBKI (0.005% MB + 75 mM KI); L (0.9% NaCl + red laser 660 nm, 18 J, 180 s); LMB (0.005% MB + laser); LKI (75 mM KI + laser); LMBKI (0.005% MB + 75 mM KI + laser). The treated biofilms were collected, diluted, and incubated to assess cell viability (CFU/mL) for total microorganisms, total lactobacilli, total streptococci, and mutans streptococci. Data were subjected to analysis using the Friedman test, followed by the Dunn test (α = 0.05). LMBKI group exhibited a noteworthy decrease in the viability of all microorganisms in comparison to groups C, KI, MBKI, MB, L, LMB, and LKI (p < 0.0001), and demonstrated a comparable reduction to the CHX group (p > 0.99). The combination of KI with MB in aPDT may be advocated as a non-invasive technique for diminishing the viability of polymicrobial oral biofilms, thereby aiding in the management of dental diseases.

Antimicrobial photodynamic therapy effects mediated by methylene blue in surfactant medium as an adjuvant treatment of teeth with apical periodontitis and presence of fistula-Protocol for randomized, controlled, double-blind clinical trial.

OBJECTIVE: This study aims to evaluate the efficacy of photodynamic therapy as an adjunct to conventional endodontic treatment in patients with apical periodontitis and fistulas. In this study, a fistula is characterized as a pathological conduit originating from the infected region at the root apex of the tooth, traversing the oral mucosa, and extending to the external surface of the gingiva. This pathological condition frequently complicates the management of endodontic infections, thereby necessitating the evaluation of supplementary therapeutic interventions. The standard treatment for endodontic infections involves thorough disinfection of the root canal system to remove microbial contamination from the canal and surrounding tissues. To potentially augment the efficacy of conventional treatment, aPDT is proposed as a supplementary, non-invasive technique. This innovative technique uses a photosensitizer, which is a light-sensitive dye, in combination with a light source to produce reactive oxygen species. Reactive oxygen species can effectively target and eliminate bacteria in the root canal system, potentially enhancing treatment outcomes. METHODS: The study will involve 140 teeth with apical periodontitis and fistulas. The teeth will be randomly assigned to one of two treatment groups. Group I will receive only the conventional endodontic treatment, which includes root canal cleaning, shaping, and obturation. Group II will undergo the same conventional endodontic treatment, but with an additional step of aPDT. The aPDT procedure involves applying a photosensitizer to the root canal and irradiating it with light to produce reactive oxygen species. Each group will consist of 70 teeth to ensure adequate statistical power. The primary outcome is fistula resolution, assessed clinically at 15 and 30 days post-treatment. The secondary outcome is the comparison of apical radiolucency from periapical radiographs to evaluate healing and reduction of periapical pathology. CONCLUSIONS: The study aims to determine if adding aPDT significantly improves the management of apical periodontitis and overall success rates of endodontic treatment. The results will provide insights into the effectiveness of aPDT as an adjunctive treatment and its potential benefits in clinical practice.

Light-driven Lytic Polysaccharide Monooxygenase Catalysis Mediated by Type I Photosensitizers.

The use of light as abundant, renewable, and clean energy source to boost lytic polysaccharide monooxygenase (LPMO) reactions represents an exciting and yet under-explored opportunity. Herein we demonstrated that photosensitizers, commonly used in photodynamic therapy, which act through the photocatalytic Type I mechanism can drive the oxidation of PASC by LPMOs, whereas Type II photosensitizers are not capable of promoting the LPMO activity. We analyzed Type I and Type II photosensitizers (methylene blue and tetraiodide salt of meso-tetrakis-(4-N-methylpyridyl) porphyrin, respectively) and demonstrated that, even without an addition of external reductant, Type I was capable of boosting Thermothelomyces thermophila MtLPMO9A activity in the presence of light. We also evaluated the photobiosystem in the presence and/or absence of molecular oxygen (O2) and hydrogen peroxide (H2O2), and investigated the role of superoxide radical in the methylene blue fueled reactions. Furthermore, we demonstrated that sodium bisulfite (NaHSO3), a chemical scavenger of H2O2, acts by safeguarding the enzyme from oxidative damage caused by accumulation of H2O2 early in photosensitizer-driven LPMO reactions. Finally, the results of the present work demonstrated that light-driven LPMO reactions mediated photodynamic therapy (PDT) Type I photosensitizers, which also includes molecules such as curcumin and riboflavin, is a general phenomenon.

Construction and demolition waste as a low-cost adsorbent for water treatment: kinetics, isotherm, thermodynamics, and Fenton regeneration.

The present study proposes to investigate the feasibility of using construction and demolition waste (CDW) as an aqueous remediation agent through adsorption. The CDW, with and without chemical and thermal pre-activation, was evaluated to remove the methylene blue (MB) dye from the water solution. Variables interfering with adsorption processes, such as adsorbent dosage, solution pH, and particle size, were evaluated. The material was characterized by pHZPC, FTIR, XRD, SEM, EDS, and TG. The kinetic and equilibrium data better fitted the Elovich and Sips models, respectively. A maximum adsorption capacity of 18.62 mg g-1 at 60 °C was observed. Thermodynamic data indicated that adsorption occurred through a spontaneous and favorable process governed mainly by physical processes. The regeneration studies were carried out using processes based on the Fenton reaction, where the catalytic action of the iron naturally present in the CDW was evaluated. The results showed that the desorption balance was the main limiting factor for the effective regeneration of the saturated material. Adding Fe2+ to the system made this process suitable for the regeneration of the CDW and degradation of the pollutant in the aqueous phase. A regeneration efficiency of 65%, maintained practically constant during five adsorption-regeneration cycles, was observed. These results highlight the high potential of using CDWs as an adsorbent material.

Adjuvant antimicrobial photodynamic therapy improves periodontal health and reduces inflammatory cytokines in patients with type 1 diabetes mellitus.

BACKGROUND: Antimicrobial photodynamic therapy (aPDT) is an adjuvant treatment to scaling and root planing (SRP) which improves periodontal health. It may be beneficial to patients with systemic diseases, such as type 1 diabetes mellitus. OBJECTIVE: This randomized clinical trial evaluated the adjunctive effect of aPDT on the periodontal treatment of patients with type 1 diabetes (T1D). METHODOLOGY: 38 patients were included in the study and divided into four groups: DSRP - T1D patients treated with SRP; CSRP - normoglycemic patients treated with SRP; DPDT - T1D patients treated with SRP + aPDT (methylene blue and red laser); CPDT - normoglycemic patients treated with SRP + aPDT. , Periodontal clinical parameters and inflammatory cytokines in crevicular fluid were recorded at baseline and then after 1, 3 and 6 months. The clinical endpoint for treatment was evaluated after 6 months. RESULTS: Adjuvant aPDT treatment resulted in reduction of probing depth after 3 months (0.38 mm - p<0.05) on T1D patients and in control group after 6 months (0.66 mm - p<0.05). Reduction of clinical attachment levels was similar for both treatments in control patients (p>0.05). There was a significant reduction of TNF-α in crevicular fluid in both groups treated with aPDT (p<0.05). The T1D (65%) and normoglycemic (72%) groups achieved the clinical endpoint after both treatments (p>0.05). CONCLUSIONS: Adjuvant aPDT provided additional benefits in improving periodontal clinical parameters and reducing inflammatory cytokines in both T1D and normoglycemic patients. However, normoglycemic patients showed greater clinical improvements compared to T1D patients following adjuvant aPDT treatment.

Methylene Blue and Blood Transfusion in Hemorrhagic Shock Resuscitation: An Experimental Porcine Study.

INTRODUCTION: Hemorrhagic shock requires immediate treatment to prevent mortality and organ dysfunction. This study evaluates the efficacy of methylene blue (MB) with blood transfusion (BT) as a potential rescue therapy in acute severe bleeding in pigs. METHODS: Thirty animals were randomly assigned to one of six groups following the induction of fixed-pressure hemorrhagic shock, after reaching a mean arterial pressure (MAP) of 55 mmHg - Group 1 (60 BT: BT after 60 minutes), Group 2 (60 MB: MB infusion after 60 minutes), Group 3 (60 MB + BT: MB and BT after 60 minutes), Group 4 (15 MB + BT: MB and BT after 15 minutes), Group 5 (15 BT + 60 MB: BT after 15 minutes and MB infusion after 60 minutes), and Group 6 (15 MB + 60 BT: MB infusion after 15 minutes and BT after 60 minutes). Hemodynamic and blood gas parameters were meticulously recorded, reversal of the shock was considered when MAP reached 90% of the baseline MAP. RESULTS: Except for Group 2, all groups reverted from the shock. However, groups that received MB in combination with BT, specifically Groups 3 and 4, exhibited statistically significant higher ratios of maximum MAP to baseline MAP. CONCLUSION: Using MB concomitant with BT allowed the reversal of hemorrhagic shock with higher median arterial pressure levels compared to BT alone or applying MB separately from BT. This suggests that simultaneous application of MB and BT could be a more effective strategy for reversing the effects of severe acute bleeding.

The Antiproteinopathy, Antioxidant, and Antiapoptotic Effects of Methylene Blue and 4-Phenylbutyric Acid Alone, and in Combination on Familial Alzheimer's Disease PSEN1 I416T Cholinergic-Like Neurons.

Familial Alzheimer's disease (FAD) is a chronic neurological condition that progresses over time. Currently, lacking a viable treatment, the use of multitarget medication combinations has generated interest as a potential FAD therapy approach. In this study, we examined the effects of 4-phenylbutyric acid (4-PBA) and methylene blue (MB) either separately or in combination on PSEN1 I416T cholinergic-like neuron cells (ChLNs), which serve as a model for FAD. We found that MB was significantly efficient at reducing the accumulation of intracellular Aß, phosphorylation of TAU Ser202/Thr205, and increasing Δψm, whereas 4-PBA was significantly efficient at diminishing oxidation of DJ-1Cys106-SH, expression of TP53, and increasing ACh-induced Ca2+ influx. Both agents were equally effective at blunting phosphorylated c-JUN at Ser63/Ser73 and activating caspase 3 (CASP3) into cleaved caspase 3 (CC3) on mutant cells. Combination of MB and 4-PBA at middle (0.1, 1) concentration significantly reduced iAß, p-TAU, and oxDJ-1 and augmented the ACh-induced Ca2+ influx compared to combined agents at low (0.05, 0.5) or high (0.5, 5) concentration. However, combined MB and 4-PBA were efficient only at dropping DJ-1Cys106-SO3 and increasing ACh-induced Ca2+ inward in mutant ChLNs. Our data show that the reagents MB and 4-PBA alone possess more than one action (e.g., antiamyloid, antioxidant, anti-TAU, antiapoptotic, and ACh-induced Ca2+ influx enhancers), that in combination might cancel or diminish each other. Together, these results strongly argue that MB and 4-PBA might protect PSEN1 I416T ChLNs from Aß-induced toxicity by working intracellularly as anti-Aß and anti-Tau agents, improving Δψm and cell survival, and extracellularly, by increasing ACh-induced Ca2+ ion influx. MB and 4-PBA are promising drugs with potential for repurposing in familial AD.

Sodium lignosulfonate as an extracting agent of methylene blue dye using a polymer-enhanced ultrafiltration technique.

The purpose of this research was to evaluate the efficacy of sodium lignosulfonate (LS) as a dye adsorbent in the removal of methylene blue (MB) from water by polymer-enhanced ultrafiltration. Various parameters were evaluated, such as membrane molecular weight cut-off, pH, LS dose, MB concentration, applied pressure, and the effect of interfering ions. The results showed that the use of LS generated a significant increase in MB removal, reaching an elimination of up to 98.0 % with 50.0 mg LS and 100 mg L-1 MB. The maximum MB removal capacity was 21 g g-1 using the enrichment method. In addition, LS was reusable for up to four consecutive cycles of dye removal-elution. The removal test in a simulated liquid industrial waste from the textile industry was also effective, with a MB removal of 97.2 %. These findings indicate that LS is highly effective in removing high concentrations of MB dye, suggesting new prospects for its application in water treatment processes.

Coconut shell-based biochars produced by an innovative thermochemical process for obtaining improved lignocellulose-based adsorbents.

The urgent need for a simple and cost-effective thermochemical process to produce biochar has prompted this study. The aim was to develop a straightforward thermochemical process under O2-limited conditions for the production of coconut-based biochar (CBB) and to assess its ability to remove methylene blue (MB) through adsorption, comparing it with CBB produced by slow pyrolysis. CBBs were obtained under different atmospheric conditions (O2-limited, muffle furnace biochar (MFB); and inert, pyrolytic reactor biochar (PRB)), at 350, 500, and 700 °C, and for 30 and 90'. MFB and PRB were characterized using FTIR, RAMAN, SEM, EDS, and XRD analyses. Adsorption tests were conducted using 1.0 g L-1 of MFB and PRB, 10 mg L-1 of MB at 25 °C for 48 h. Characterization revealed that atmospheric conditions significantly influenced the yield and structural features of the materials. PRB exhibited higher yields and larger cavities than MFB, but quite similar spectral features. Adsorption tests indicated that MFB and PRB had qt values of 33.1 and 9.2 mg g-1, respectively, which were obtained at 700 °C and 90', and 700 °C and 30', respectively. This alternative method produced an innovative and promising lignocellulose-based material with great potential to be used as a biosorbent.

Development of a sustainability-oriented university laboratory: Insight into adsorption kinetics models for the removal of pollutants from aqueous solution.

The aim of the present research is to show the development of a sustainability-oriented lab that teaches adsorption concepts in a virtual environment based on the premise "learning-through-play". Kinetic results in the virtual environment are contrasted to those obtained experimentally when diverse adsorbents prepared from Agave Bagasse (Raw Fibers, Hydrothermal Fibers, and Activated Fibers) were synthesized. Comparison between virtual and real-life experiments involving removal of methylene blue in solution showed that a pseudo-first-order model could describe adsorption kinetics satisfactorily. The study is complemented with a characterization of the adsorbents through SEM, nitrogen adsorption isotherms, FTIR and Raman. In addition, the environmental impact of the synthesis of adsorbents was evaluated through well-known methodologies (GAPI, NEMI, and Eco-Scale), which agree that raw fibers are the most eco-friendly material. This research provides an exciting opportunity to advance our knowledge on developing new technologies for teaching in engineering and to compliment real-life practices that consider environmental impacts with virtual experiments.

Effect of teak wood lignocellulose pretreatment on the performance of cellulose-graft-(net-poly(acrylamide-co-acrylic acid)) for water absorption and dye removal.

Cellulose modified hydrogels can be produced directly from raw biopolymers in novel cellulose solvents such as NaOH/urea aqueous solution. The effect of cellulose characteristics on the synthesis of a cellulose-graft-(net-poly(acrylamide-co-acrylic acid)) and its performance as water absorbent/methylene blue dye removal material is analyzed. Three cellulose samples, one analytical grade and two obtained from teak wood sawdust with different pretreatments (one alkaline and the other, a novel one known as (gas phase) acid pretreatment) were compared. The starting raw celluloses were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray diffraction (XRD) and viscosity in cupri ethylenediamine hydroxide (CED) solution, whereas the chemically modified materials were characterized by SEM, FTIR, and TGA. The pretreatment used influences composition, crystallinity index and degree of polymerization (DP) of the cellulose obtained. The modified material produced with cellulose from alkaline pretreatment showed the highest swelling ratio in water absorption tests at room temperature (12,714 %); in contrast, the one with cellulose from acid pretreatment showed the lowest swelling ratio (7,470 %). However, this difference is not so significative in dye removal tests, where absorption capacity is 139 and 140 mg/g, respectively. The results indicate that cellulose composition, particularly structures with significant hemicellulose and lignin remaining content, has a major effect on the performance of modified materials for water absorption, and degree of polymerization has a major effect on adsorption capacity of methylene blue.

The feedstock anatomical properties determine biochar adsorption capacities: A study using woody bamboos (Bambuseae) and methylene blue as a model molecule.

Feedstock characteristics impact biochar physicochemical properties, and reproducible biochar properties are essential for any potential application. However, in most articles, feedstock aspects (i.e., taxonomic name of the species, part of the plant, and phenological phase) are scarcely reported. This research aimed at studying the effect of species and phenological stage of the feedstock on the properties of the derived biochars and, thus, adsorption capacities in water treatment. In this study, we analysed the anatomical characteristics of three different woody bamboo species [Guadua chacoensis (GC), Phyllostachys aurea (PA), and Bambusa tuldoides (BT)] in culms harvested at two different phenological phases (young and mature), and statistically correlated them with the characteristics of the six derived biochars, including their adsorption performance in aqueous media. Sclerenchyma fibres and parenchyma cells diameter and cell-wall width significantly differed among species. Additionally, sclerenchyma fibres and parenchyma cell-wall width as well as sclerenchyma fibre cell diameters are dependent on the phenological phase of the culms. Consequently, differences in biochar characteristics (i.e., yield and average pore diameter) were also observed, leading to differential methylene blue (MB) adsorption capacities between individuals at different phenological phases. MB adsorption capacities were higher for biochar produced from young culms compared to those obtained from matures ones (i.e., GC: 628.66 vs. 507.79; BT: 537.45 vs. 477.53; PA: 477.52 vs. 462.82 mg/g), which had smaller cell wall widths leading to a lower percentage of biochar yield. The feedstock anatomical properties determined biochar characteristics which modulated adsorption capacities.

Antimicrobial photodynamic therapy with methylene blue and its derivatives in animal studies: Systematic review.

BACKGROUND: Infections are complications in the wound healing process, and their treatment can lead to antibiotic overuse and bacterial resistance. Antimicrobial photodynamic therapy (aPDT) is used to treat infectious diseases caused by fungi, viruses, or bacteria. Methylene blue (MB) and its derivatives are commonly used dyes in antimicrobial photodynamic therapy (aPDT-MB). METHODS: This study is a PRISMA systematic review of animal models used to discuss the usefulness and therapeutic parameters of aPDT-MB or its derivatives for treating infected skin wounds. RESULTS: After an extensive literature review, 13 controlled trials totaling 261 animals were selected to evaluate skin infection by leishmaniasis and cutaneous bacterial and fungal infections. All studies found results favoring the use of aPDT-MB. Great variability in parameters was found for radiant exposure from 12 to 360 J/cm2, MB diluted in saline solution or distilled water, irradiation time from 40 to 3600 s, irradiance most commonly at a maximum of 100 mW/cm2, and wavelength used mainly in the 630-670 nm range. CONCLUSION: MB is a safe and promising agent used as a photosensitizer in aPDT for skin-infected lesions. There is great variability in the parameters found. Comparisons concerning concentration, irradiation time, and light intensity need to be performed.

Response surface and DFT protocols for improvement of the adsorption process of lignocellulosic-based biomass for the removal of basic dyes.

Jatobá-do-cerrado fruit shells, archetypical of lignocellulosic-based biomass, were used as an adsorbent to remove crystal violet (CV) and methylene blue (MB) from water. The adsorbent was characterized using various techniques, and kinetic studies showed dye adsorption followed second-order kinetics. An experimental design investigated the effects of pH and temperature on removal efficiency, with a quadratic model fitting the data best. The results suggest pH influences MB's adsorption capacity more than temperature and at 25 °C and pH 8, MB had a desirability value of 0.89, with 95 % removal efficiency. For CV, temperature had a greater influence, with a desirability value of 0.874 at 25 °C and pH 10, and 95 % removal efficiency. Adsorption isotherm studies revealed maximum adsorption capacities of 123.0 mg·g-1 and 113.0 mg·g-1 for CV and MB, respectively. Experimental thermodynamic parameters indicated an endothermic and spontaneous process which it was supported by quantum chemistry calculations. The protocols developed confirmed the potential for adsorbing CV and MB dyes in water, achieving over 73.1 and 74.4 mg g-1 dyes removal.

Monitoring Photo-Fenton and Photo-Electro-Fenton process of contaminants emerging concern by a gas diffusion electrode using Ca10-xFex-yWy(PO4)6(OH)2 nanoparticles as heterogeneous catalyst.

The catalytic performance of modified hydroxyapatite nanoparticles, Ca10-xFex-yWy(PO4)6(OH)2, was applied for the degradation of methylene blue (MB), fast green FCF (FG) and norfloxacin (NOR). XPS analysis pointed to the successful partial replacement of Ca by Fe. Under photo-electro-Fenton process, the catalyst Ca4FeII1·92W0·08FeIII4(PO4)6(OH)2 was combined with UVC radiation and electrogenerated H2O2 in a Printex L6 carbon-based gas diffusion electrode. The application of only 10 mA cm-2 resulted in 100% discoloration of MB and FG dyes in 50 min of treatment at pH 2.5, 7.0 and 9.0. The proposed treatment mechanism yielded maximum TOC removal of ∼80% and high mineralization current efficiency of ∼64%. Complete degradation of NOR was obtained in 40 min, and high mineralization of ∼86% was recorded after 240 min of treatment. Responses obtained from LC-ESI-MS/MS are in line with the theoretical Fukui indices and the ECOSAR data. The study enabled us to predict the main degradation route and the acute and chronic toxicity of the by-products formed during the contaminants degradation.

Modulating temperature for Cu2ZnSnS4 (CZTS) synthesis via hot injection method and studying the photocatalytic efficiencies for the degradation of rhodamine 6G and methylene blue pollutants.

Cu2ZnSnS4 (CZTS) was synthesized following hot injection method and the process was optimized by varying temperature conditions. Four samples at different temperatures viz., 200, 250, 300 and 350 °C were prepared and analyzed using different characterization techniques. Based on the correlation between XRD, Raman and XPS, we conclude that the formation of ZnS and SnS2 occurs at 350 °C but at 200 °C there is no breakdown of the complex as per XRD. According to Raman and XPS analysis, as the temperature rises, the bonds between the metals become weaker, which is visibly seen in Raman and XPS due to the minor peaks of copper sulfide. Scanning electron microscopic analysis confirmed nanometric particles which increase in size with temperature. The photocatalytic evaluation showed that CZTS synthesized at 200 °C performed efficiently in the removal of the two colorants, methylene blue and Rhodamine 6G, achieving 92.80% and 90.65%, respectively. The photocatalytic degradation efficiencies decreased at higher temperatures due to bigger sized CZTS particles as confirmed by SEM results. Computational simulations confirm that CZTS has a highly negative energy -25,764 Ry, confirming its structural stability and higher covalent than ionic character.

Application of chemically modified waste tucumã (Astrocaryum aculeatum) seeds in the biosorption of methylene blue: kinetic and thermodynamic parameters.

Dye effluents cause diverse environmental problems. Methylene blue (MB) dye stands out since it is widely used in the textile industry. To reduce the pollution caused by the MB, we developed biosorbents from tucumã seeds, where the in natura seeds were treated with NaOH (BT) and H3PO4 (AT) solutions and characterized by Boehm titration, point of zero charges, FTIR, TGA, BET, and SEM. It was observed that the acid groups predominate on the surface of the three biosorbents. The process was optimized for all biosorbents at pH = 8, 7.5 g/L, 240 min, C0 = 250 mg/L, and 45 ℃. BT was more efficient in removing MB (96.20%; QMax = 35.71 mg/g), while IT and AT removed around 60% in similar conditions. The adsorption process best fits Langmuir and Redlich-Peterson isotherms, indicating a hybrid adsorption process (monolayer and multilayer) and pseudo-second-order kinetics. Thermodynamic data confirmed an endothermic and spontaneous adsorption process, mainly for BT. MB was also recovered through a desorption process with ethanol, allowing the BT recycling and reapplication of the dye. Thus, an efficient and sustainable biosorbent was developed, contributing to reducing environmental impacts.

Reduction of microorganisms in carious dentin by photodynamic therapy mediated by potassium iodide added to methylene blue and red laser.

OBJECTIVE: To evaluate the effect of the association of potassium iodide to antimicrobial photodynamic therapy on human carious dentin produced with a microcosm biofilm model. METHODS: A microcosm biofilm model was used to generate a caries lesion on human dentin. Pooled human saliva diluted with glycerol was used as an inoculum on specimens immersed on McBain artificial saliva enriched with 1 % sucrose (24 h at 37 °C in 5 % CO2). After refreshing culture media for 7 days, the dentin specimens were divided in 5 groups (3 specimens per group, in triplicate; n = 9): C (NaCl 0.9 %), CX (2 % chlorhexidine), PKI (0.01 % methylene blue photosensitizer+50 mM KI), L (laser at 15 J, 180 s, 22.7 J/cm2), and PKIL (methylene blue + KI + Laser). After the treatments, dentin was collected, and a 10-fold serial dilution was performed. The number of total microorganisms, total lactobacilli, total streptococci, and Streptococcus mutans was analyzed by microbial counts (CFU/mL). After normality and homoscedasticity analysis, the Welch's ANOVA and Dunnett's tests were used for CFU. All tests used a 5 % significance level. RESULTS: CX and PKIL groups showed significant bacterial decontamination of dentin, compared to group C (p < 0.05) reaching reductions up to 3.8 log10 for CX for all microorganisms' groups and PKIL showed 0.93, 1.30, 1.45, and 1.22 log10 for total microorganisms, total lactobacilli, total streptococci, and S. mutans, respectively. CONCLUSION: aPDT mediated by the association of KI and methylene blue with red laser reduced the viability of microorganisms from carious dentin and could be a promising option for cavity decontamination.