Fluoride Concentration Research Articles

Geoecological Assessment of Fluorine Contamination of Environmental Components in the Zone of Influence of an Abandoned Rare-metal Mine in the Murmansk Region

A geoecological assessment of fluorine contamination of environmental components in the zone of influence of an abandoned rare-metal mine in the Murmansk region was carried out. Samples were taken of loparite ore enrichment tailings, soils around the tailings pond and the Loparitovy, Alluaiv, Azimut creeks and the watercourse flowing through the mine after the mining impact. The content of water-soluble fluorine in the collected samples was determined. No exceedance of maximum permissible concentration (MPC) of fluorides in soil was found. Increased content of fluoride ions (up to 15 MPC) in water samples from the watercourse was recorded. It is concluded that the production facility closed more than 15 years ago has a negative impact on ecosystems.

Fluoride Ingestion Induces Formation of Unusual Macromolecular Complexes in Gut Lumen Which Retard Absorption of Essential Minerals and Trace Elements by Chelation.

This study investigates the impact of chronic fluoride exposure on the absorption of essential minerals in the gut and explores the mechanisms underlying mineral deficiencies due to fluoride ingestion. Male Wistar rats were randomly assigned to three groups: group 1 (G-1) served as the control (non-fluoride exposed), while group 2 (G-2) and group 3 (G-3) received human equivalent doses (HED) of fluoride (50 and 100ppm ad libitum, corresponding to 5 and 10ppm in humans, respectively) for 75days. Serum fluoride concentrations were measured, and the levels of essential minerals and trace elements in blood and stool were analyzed using ICP-MS. X-ray diffraction (XRD) analysis was performed on stool samples to identify chemical compounds. The chemical compounds and macromolecular complexes containing fluoride and essential minerals were identified and quantified using Match3 software. Results indicated that the blood concentrations of essential minerals were significantly lower (p ≤ 0.05) in the fluoride-exposed groups compared to the control, while excretion of essential elements in stool was significantly higher (p ≤ 0.05) in the fluoride-administered groups. XRD analysis revealed the formation of unusual macromolecular chemical complexes in the stool of fluoride-treated groups, with the types and concentrations of these compounds increasing with higher fluoride doses. The study concludes that fluoride in the stomach chelates minerals, reducing their absorption, and induces the formation of unusual high molecular weight macromolecular chelation complexes, which alter the chemical species in the gut and further impair the absorption of essential minerals.

Access to dental services and use of toothpaste with optimal fluoride content in Peruvian children

BackgroundLeading international health organizations advise using toothpaste that contains at least 1,000 parts per million of fluoride, emphasizing that this practice should begin with the eruption of the first primary tooth.AimTo determine the association between access to dental services and the use of toothpaste with 1,000 ppm fluoride or more in Peruvian children under twelve years of age.Materials and methodsA cross-sectional analysis was conducted using data from the 2021 Demographic and Family Health Survey. The main variable studied was the use of toothpaste containing a fluoride concentration of 1,000 ppm or more. Additionally, the access to dental care, the time elapsed since the last dental visit, and the type of healthcare facility were analyzed. Multilevel regression was applied to examine the relationship between variables and the dependent variable, with Peru's 24 regions serving as the analytical level.ResultsAccording to the bivariate analysis, the natural region, area of residence, place of residence, wealth index, and age were associated with the use of fluoride toothpaste with 1,000 ppm or more. In the multilevel analysis, the access to dental services was not associated with the use of fluoride toothpaste with 1,000 ppm or more (p = 0.454); similarly, the time elapsed since the last dental visit also showed no association (p = 0.676), as did the type of healthcare facility (p = 0.752, p = 0.896, p = 0.983).ConclusionAccessing dental services, the time elapsed since the last dentist visit, and the location where that care was received were not associated with the use of toothpaste containing 1,000 ppm or more of fluoride among Peruvian children during the year 2021.

Characterization of hydrogeochemical elements in determining the ground water quality for irrigation potential and its correlation with climatological parameters of chennai basin aquifer system, southern india.

An attempt has been made to comprehend the ground water quality and climate impacts of the Chennai River basin, which is aimed at its main socio-economic growth of the state of Tamil Nadu. The ground water samples collected from the study area were analyzed for its hydrogeochemical elements. The ground water quality and irrigation suitability were determined using several water quality assessment metrics. Ground water is extensively utilized for irrigation in the entire basin area for the past two decades, especially in the 38 over-exploited Firkas out of the 109 Firkas of the basin. It is inferred that the phreatic aquifer ground water quality is fresh in about 20%, as indicated by the EC value (< 750µs/cm) at 25°C. In about 63% of the ground water indicating the moderately fresh showing the EC varies between 751 and 2250µs/cm at 25°C, 11% of ground water exerted an EC ranging between 2251 and 3000µs/cm at 25°C indicating that the ground water is slightly mineralized, and in about 6% of groundwater, the EC is > 3000µs/cm at 25°C indicating that the ground water is highly mineralized. There were no water samples that exceeded the permissible limit of chloride either in phreatic aquifer or in fracture aquifer. The changes in rainfall frequency and atmospheric temperature affect the ground water movement and storage directly and indirectly. Similarly, the temperature data shows a positive relationship with the concentration of fluoride and nitrate ions in the water.

Effect of Co-exposure to Additional Substances on the Bioconcentration of Per(poly)fluoroalkyl Substances: A Meta-Analysis Based on Hydroponic Experimental Evidence.

A consensus has yet to emerge regarding the bioconcentration responses of per(poly)fluoroalkyl substances under co-exposure with other additional substances in aqueous environments. This study employed a meta-analysis to systematically investigate the aforementioned issues on the basis of 1,085 published datasets of indoor hydroponic simulation experiments. A hierarchical meta-analysis model with an embedded variance covariance matrix was constructed to eliminate the non-independence and shared controls of the data. Overall, the co-exposure resulted in a notable reduction in PFAS bioaccumulation (cumulative effect size, CES = - 0.4287, p < 0.05) and bioconcentration factor (R2 = 0.9507, k < 1, b < 0) in hydroponics. In particular, the inhibition of PFAS bioconcentration induced by dissolved organic matter (percentage form of the effect size, ESP = - 48.98%) was more pronounced than that induced by metal ions (ESP = - 35.54%), particulate matter (ESP = - 24.70%) and persistent organic pollutants (ESP = - 18.66%). A lower AS concentration and a lower concentration ratio of ASs to PFASs significantly promote PFAS bioaccumulation (p < 0.05). The bioaccumulation of PFASs with long chains or high fluoride contents tended to be exacerbated in the presence of ASs. Furthermore, the effect on PFAS bioaccumulation was also significantly dependent on the duration of co-exposure (p < 0.05). The findings of this study provide novel insights into the fate and bioconcentration of PFAS in aquatic environments under co-exposure conditions.

Spatial and temporal variations of dug well water quality in Korba basin, Chhattisgarh, India: Insights into hydrogeological characteristics

Comprehensive assessment of groundwater quality in mining-affected regions is crucial to sustainably manage water resources and protect public health and ecosystems. This study investigated the hydrogeochemical characteristics and water quality of 18 dug wells in the Korba basin, Chhattisgarh, India, an area heavily impacted by coal mining activities. Water samples were collected over three seasons (pre-monsoon, monsoon, and post-monsoon) and analyzed to determine physicochemical parameters, major ions, trace elements, and carbon content. Results revealed very high total dissolved solids concentrations ranging from 315 to 19,738 mg L−1. Nitrate levels surpassed the Bureau of Indian Standard (BIS) limit of 45 mg L−1 in over 50% of samples, reaching a maximum of 200 mg L−1. Fluoride concentrations in all samples exceeded the BIS limit (1.5 mg L−1), ranging from 1.5 to 15.2 mg L−1. The predominant water type was Ca-Mg-HCO₃, primarily influenced by rock-water interactions. Factor analysis indicated that both geogenic and anthropogenic processes influence pollution levels. Pollutant concentrations exhibited seasonal variations, generally peaking during the monsoon period. Temporal analysis from over six years revealed increasing trends for most parameters, indicating deteriorating water quality. Based on Water Quality Index values, all samples were classified as unsuitable for drinking, while assessments of irrigation water quality using various indices indicated that 61.11% of samples were suitable for agricultural use. The findings provide data to inform decision-making and public health protection in this heavily industrialized region and emphasize the urgent need for sustainable water resource management and pollution prevention strategies in the Korba basin to align with UN Sustainable Development Goals 3 (good health and well-being) and 6 (clean water and sanitation).

Investigation of the influence of fluorine on metal elution from cathodic active material liberated from spent lithium-ion batteries with a focus on the underwater electrical pulse method

Abstract As a promising candidate to separate the cathode materials and aluminum foils, the underwater electrical pulse method is an environmentally friendly method that can effectively liberate cathodic active material in a very short time. However, performing the electric pulse separation in aqueous media may cause the release of fluoridated elements, which may come from fluoridated components formed during battery cycles or due to the remaining electrolyte within the cathode particles. Thus, the purpose of this work is to study the solution obtained after pulse discharge in terms of fluoridated entities, to understand their effect on the elution of active cathodic materials. Herein, to investigate the potential source of F and its possible effects on metal extraction, leaching experiments were conducted in the presence of different fluoride concentrations with a solid/liquid ratio of 0.5g/L under circumneutral pH conditions (pH range: 5.7-7.5) using a spent nickel-cobalt-manganese lithium battery sample liberated by N-Methyl pyrrolidone. The results show that the amounts of F ions in solution increased with leaching time, with a maximum value close to 2.34 ppm F obtained after 2 h. It is worth noting that the presence of fluoride-ion can promote the elution of aluminum, as a maximum concentration of 1.85 ppm Al was observed at 2 h in the presence of 40 ppm F, whereas only about 0.32 ppm Al was detected in the case of fluoride-free solutions. Consequently, our results demonstrated that the amounts of transition metals (Ni, Mn, and Co) released towards liquid changed very little irrespective of the concentrations of dissolved fluoride, suggesting that the released F ions do not affect metals elution.

Effect of clayey sediment compression on fluoride enrichment in the Quaternary groundwater system of Cangzhou Plain, China

The effect of clay layer compression on the enrichment of groundwater fluoride remains unknown. Quaternary groundwater with high fluoride levels at the Cangzhou Plain, which has a long history of land subsidence caused by clay layer compression, poses a potential health risk. The spatial distribution and enrichment mechanisms of groundwater fluoride are identified by sample collection, hydrochemical analysis, and geochemical inverse modeling. The results revealed that fluoride concentrations in 82 % of the 122 groundwater samples above the limit in drinking water as 1.0 mg/L in China. Fluoride in shallow groundwater (depth <20 m, ∼average = 2.08 mg/L) was mainly originated from fluorite dissolution and influenced by groundwater HCO3−, pH, and cation exchange levels. Below ∼200 m, the main source of groundwater fluoride (∼average = 3.12 mg/L) was the compression−release of clay pore water with high F− concentration, which was generated by complex water-rock interaction. Based on hydrochemical inverse simulation and end-member mixing models, the pore water released from clayey sediments supplied 53 %−56 % of deep groundwater (>200 m) and contributed 2.07 −2.87 mg/L to F− concentration. The findings of this study provide a theoretical basis for future research on prevention of high fluoride groundwater induced by clayey sediment compression.

Organic manures reduce the bioavailability of fluoride in soil via different mechanisms

Fluoride (F) pollution in soils, which can be caused by long-term application of phosphate fertilizers, has serious socio-economic and ecological impacts. Therefore, it is important to find economically viable and environmentally friendly remediation technologies that mitigating the potential hazards of F-contaminated soil while maintaining crop yields. In this study, a soil incubation experiment was carried out to investigate the effects of two different organic manures at various amounts on soil F content and soil properties. We demonstrated that organic manure application at a rate of 5% was optimal to control the content of available fluoride (AE-F) in soil. Organic manure decreased the AE-F content and increased the residual or organically bound content. Furthermore, organic manure application also increased the contents of carbohydrates, proteins, and amides, which can anchor AE-F to the dissolved organic matter (DOM) in soil through physicochemical reactions, thereby reducing the migration of F. Moreover, after organic manure application, complex humus compounds were formed through microbial action, thus reducing the bioavailability of soil F. In summary, the application of organic manures can reduce the accumulation of soil AE-F, thereby reducing the absorption of F by crops in F-contaminated soil and alleviating the potential risk of F contamination.

Tantalum in hydrothermal fluids

Understanding the behaviour of tantalum (Ta) in hydrothermal systems is pivotal for understanding its geochemical enrichment processes and economic extraction via hydrometallurgy. Yet, its behaviour in hydrothermal systems remains poorly characterised. This study investigates the coordination chemistry, speciation, and solubility of pentavalent Ta(V) in fluoride (F) − and chloride (Cl) −rich hydrothermal solutions up to 413 °C and 800 bar, utilising in-situ High Energy Resolution Fluorescence Detected X-ray Absorption Spectroscopy (HERFD-XAS). The results reveal the stability of high order fluoridotantalate complexes in fluoride-rich fluids solutions up to the highest investigated temperature, highlighting fluoride’s paramount role in enhancing Ta solubility through the formation of stable complexes in aqueous solutions. A transition from nonafluoridotantalate tetraanion (TaF94−) to heptafluoridotantalate dianion (TaF72−) complexes was observed as a function of temperature in solutions containing ≥1 m fluoride. Conversely, our findings indicate a negligible role for chloride in Ta complexation even in high Cl (∼6 m) aqueous solutions, suggesting that Ta chloride complexes do not contribute significantly to Ta transport in hydrothermal systems. Existing solubility data were reinterpreted based on an updated speciation model that integrates the in-situ XAS results. This confirms that Ta(OH)5(aq) predominates in solutions containing <0.02 m fluoride; oxyfluoridotantalate anions such as [TaF3(OH)3−] dominate in solutions containing intermediate fluoride concentrations (0.02–1 m), and the fluoridotantalate anions [TaF94− to TaF72−] occur in more concentrated fluoride solutions (>1 m) at hydrothermal conditions (∼100–400 °C). Derived thermodynamic data for these species enable better understanding and geochemical modelling of Ta transport in hydrothermal fluids, highlighting the potential of F-rich fluids to transport significant amounts of Ta.

Association of fluoride exposure with disease burden and neurodevelopment outcomes in children in South Korea.

Community water fluoridation is an effective public health strategy for preventing dental caries, yet. Concerns exist about potential health problems. This study explores associations between tap water fluoride levels and pediatric disease burden, as well as neurodevelopmental outcomes at 6years of age. This nationwide population-based cohort study included children born in Korean cities with and without tap water fluoridation projects, between 2006 and 2012, aiming for a fluoride concentration of 0.8 ± 0.2mg/L in treated tap water. Data from the National Health Insurance Service were used, spanning from birth to 2018. The relationship between exposure to fluoridated tap water and incidence of 16 childhood diseases that were previously identified as potentially linked to fluoride exposure were examined. Additionally, we evaluated the neurodevelopmental outcomes across various domains, including gross motor, fine motor, cognition, language, social skills, and self-help functions. These assessments were performed using data from a comprehensive national health screening program for children aged six years. A fluoride-unexposed group included 22,881 children, whereas a fluoride-exposed group comprised 29,991 children (52% males). Children in the fluoride-exposed group had a decreased risk of dental caries and bone fractures [hazard ratio (95% confidence interval, CI), 0.76 (0.63-0.93) and 0.89 (0.82-0.93), respectively] and increased risk of hepatic failures [1.85, (1.14-2.98)] compared to those in the unexposed group. Additionally, the risk ratio of abnormal neurodevelopmental screening outcomes increased by 9%, but this was statistically uncertain (95% CI, 0.95-1.26). Fluoridated tap water was associated with an increased risk of hepatic failure but a decreased risk of bone fractures in children. The association between fluoridated tap water and neurodevelopmental screening outcomes at 6years remains unclear, highlighting the need for further studies to clarify this association.

Health Risk Assessment of Nitrate, Nitrite, and Fluoride Ions in Water Reservoirs of Mehriz, Iran in 2023

Introduction: High concentrations of nitrate, nitrite, and fluoride in drinking water can cause adverse health effects. This study aims to investigate concentration and health risks assessment of nitrate, nitrite, and fluoride ions in water reservoirs of Mehriz city and Bahadoran district. Materials and Methods: Monthly sampling was done from water reservoirs of Mehriz city and Bahadoran district for 6 months. Nitrate, nitrite, and fluoride concentrations were measured in the samples using a spectrophotometer. Then, health risk assessment and sensitivity analysis were performed on the obtained data using Crystal Ball software and Monte Carlo simulation method. Results: Nitrate, nitrite, and fluoride concentrations were lower than the standard limitation in all of the studied areas. Risk assessment findings indicated that hazard quotient (HQ) values of nitrite in Miankoh-Movahedin, Bidok and Bahadoran water reservoirs were less than 1 for all age groups. HQ values of nitrate were also below 1 for all age groups except children. HQ values of fluoride in Bahadoran water reservoir were below 1 for all age groups except children. Conclusion: Health risk of consuming water containing nitrates and fluorides is high for children. Based on sensitivity analysis, the concentration of nitrate and fluoride in drinking water is the key factor in raising health risks. Reducing nitrate and fluoride concentrations in drinking water can reduce health risks in the population.

Electrochemical performance of graphene oxide synthesized from graphitic spent potlining for energy storage application

The hazardous nature of spent pot lining (SPL) generated from aluminum smelters poses environmental challenges due to its high fluoride and cyanide content. However, techniques and recent studies have shown that SPL can be converted into valuable carbon-based materials through innovative recycling with potential applications in energy storage devices. This work presents an electrochemical performance evaluation of graphene oxide (GO) electrodes derived from acid-treated SPL for supercapacitor applications. The SPL-derived graphene oxide (SPL-GO) was synthesized via a facile and scalable improved Tour method. SPL-GO electrodes were fabricated by drip-coating SPL-GO/PVDF/DMF suspension on nickel foams. The morphology, structure, and chemical composition of the SPL-GO were characterized using advanced techniques such as energy dispersive X-ray (EDX) spectroscopy, scanning electron microscopy (SEM), Fourier transforms infrared (FTIR) spectroscopy, Raman spectroscopy, and X-ray diffraction (XRD). The electrochemical properties of the SPL-GO in 3 M KOH were characterized with a three-electrode system using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) measurements. The results demonstrate that SPL-GO exhibits a relatively high specific capacitance of 762.90 F/g at 1 A/g with corresponding power and energy densities of 502 W/kg and 106.60 Wh/kg, respectively. Additionally, excellent cycling stability of 85.4 % was achieved after 10,000 cycles with a coulombic efficiency of 95.23 %. These results suggest a superior rate capability of SPL-GO, rendering it a viable candidate for supercapacitor applications. Furthermore, this work sets the foundation for the sustainable use of industrial waste in energy storage devices, suggesting a novel, eco-friendly material for practical supercapacitor applications.

Tap water filtration and purification usage and their impact on the concentrations of fluoride and other minerals – A community-based study

ObjectiveThis study investigated the prevalence of water filtration and purification system (WFPS) use among residents of central Indiana (USA) and determined the effects of WFPS on the concentrations of fluoride, calcium, magnesium, potassium, and sodium in tap water. MethodsA census-based questionnaire collected data on demographics, water use, and water sources. Participants were also asked to provide water samples from their tap water or the WFPS they used. Water samples were analyzed using ion-specific electrodes (fluoride) and atomic absorption spectrometry (metals). Mineral concentration comparisons between water sources used nonparametric tests; questionnaire associations were testing using correlations, chi-square tests, and nonparametric tests. ResultsOne hundred and one participants completed the study, of which 71 % used some type of WFPS. Blacks were less likely to use WFPS than Asian or White participants (p = 0.045). Those with bachelor's degrees or higher were more likely to use WFPS (p = 0.003). The most used WFPS were pitcher filters (31 %), water softeners (21 %), reverse osmosis systems (11 %), faucet-mounted filters (4 %), and whole-house carbon filters (1 %). Reverse osmosis systems resulted in the lowest mineral concentrations (median, ppm; F-0.08, Ca-2.30, Mg-0.46, Na-4.60, P-0.35). Pitcher filters were largely comparable to unfiltered tap water. Water softeners resulted in the highest sodium concentrations (78.40 ppm). ConclusionA large proportion of study participants use WFPS, with pitcher filters being the most common. Reverse osmosis systems had the most significant impact on reducing mineral levels in tap water, while pitcher filters do not adversely affect mineral concentrations. Clinical SignificanceUnderstanding how different WFPS affect the various minerals in tap water is essential for helping consumers in choosing the right system and for oral care providers to guide patients on water consumption and the need for fluoride supplementation, especially for those at high risk of dental caries.

Effective removal of fluoride ions from contaminated water using electrochemical techniques: A critical review on recent developments and environmental perspective

Worldwide, water pollution poses significant threats to human health, with fluoride contamination emerging as a critical hazard. High fluoride concentrations in water cause severe health impacts, including dental and skeletal fluorosis, neurological damage, and harm to the parathyroid gland, cardiovascular, and reproductive systems. Electrochemical technique is one of the most widely used treatment technologies that has been extensively studied and provides a very effective, low-cost method of removing fluoride from contaminated water. The review reports the comprehensive electrochemical strategies for fluoride ions removal. The sources, toxicity, and impacts of fluoride pollution on health are discussed in this review. A comprehensive analysis of current electrochemical methods, including electrolysis, electrocoagulation, and the electro-fenton process, was provided in the context to facilitate the efficient removal of fluoride ions from wastewater. These methods exhibit high removal efficiencies, reaching up to 95 %, and offer scalability and operational flexibility, making them suitable for both centralized and decentralized water treatment systems. Furthermore, the recent advancements in the development of electrochemical technique for fluoride removal are critically reviewed. This study has prospected the recent developments, recommendations and future outlooks on electrochemical technique for fluoride removal.

Utilization of organic waste from Chinar leaves as sustainable and eco-friendly adsorbent for fluoride removal.

Due to concerns about high water fluoride concentrations and their detrimental consequences on health, particularly dental and skeletal fluorosis, dependable and cost-effective defluoridation techniques are needed. Chinar leaves (Platanus orientalis), a common waste, might be utilized for the production of activated carbon. For Chinar leaf activated carbon (CLAC) manufacturing, two pre-pyrolysis chemical modification procedures were used: acidic HCl (H-activation) and alkaline NaOH (OH-activation). The success of fluoride removal suggests further research and implementation in locations with fluoride-related water quality issues. This study examines how CLAC dosage, fluoride concentration, temperature, pH, and contact exposure effect defluoridation efficiency. The pseudo-second-order non-linear kinetic model and Freundlich non-linear isotherm model with R2 = 0.99 fit the data, resulting in a peak adsorption capacity of 30.3mg/g for 0.3g CLAC. In the present work, the adsorption mechanism was regulated by more than intraparticle diffusion. Adsorption occurred spontaneously as exothermic monolayer chemisorption, according to thermodynamic studies. Adsorbent activated with HCl (H-activated) showed promising results, with 73% F- removal efficiency for OH-activated and 91% for H-activated CLAC.

Simultaneous precipitation removal of fluoride ion and chloride ion from smelting waste acid using renewable remover

Purification and reuse is a potential method of smelting waste acid disposal. High concentrations of fluoride and chloride in waste acid are harmful impurity and must be removed. Previous studies have shown that fluoride removal with rare earth and chloride removal with bismuth have similar cyclic process of "precipitation removal-agent regeneration" and similar reaction conditions. In this paper, a method of simultaneous precipitation removal of F− and Cl− from waste acid using La(OH)3 and Bi2O3 as a mixed remover was proposed, and the mixed remover is regenerated by sodium hydroxide solution for the recycling of the remover. Thermodynamic analysis of La3+-Bi3+-F−-Cl−-H2O system verified the feasibility of simultaneous removal. The experimental results showed that under the optimum reaction conditions, the removal efficiencies of F− and Cl− were 93.67 % and 96.47 %, respectively, and the concentrations of F− and Cl− in the solution after removal were 66.70 mg/L and 71.10 mg/L, respectively. Under the optimum conditions, the regeneration efficiencies of La(OH)3 and Bi2O3 were 96.80 % and 96.95 %, respectively. The proposed process has the advantages of no waste output, short process, and low energy consumption and provides an environmentally friendly method of removing fluoride and chloride from waste acid.

Fluoride Removal in Water Using Kaolin and Eggshell Powder Blend Adsorbents

Fluoride contamination in water has emerged as a significant global concern due to its adverse health effects when consumed in excess. This study is focused on developing an eco-friendly, cost-effective adsorbent for fluoride removal using eggshells and kaolin. Adsorbent blends were prepared by mixing kaolin and eggshell powder in six different ratios, namely; 100:0, 80:20, 65:35, 50:50, 35:65, and 20:80. Cylindrical-shaped pellets were produced from each of the blends and subjected to the thermal treatment at 950 ◦C. Fluoride adsorption capacities of the pellets were investigated at different pH conditions (from pH 2 to pH 10) for a 5 mg/L fluoride solution with 1 g of adsorbent dosage and 60 min of contact time. Pellets with a 50:50 ratio (CKE3) were found to be the most effective adsorbent considering the adsorption capacity and stability at all the studied pH conditions. At pH 6, CKE3 showed an adsorption capacity of 0.06 mg/g compared to 0.02 mg/g of kaolin-only pellets. XRD, TGA-DSC, EDX and SEM analysis were used to characterize the adsorbent. XRD analysis showed that the raw adsorbent contained phases of CaCO3 and kaolinite, whereas the calcined material comprised Ca(OH)2 and metakaolinite. Batch experiments were carried out with CKE3 for adsorbent dosage, pH, contact time, and initial fluoride concentration. An adsorbent dosage of 4 g was capable of resulting in a 53% removal of fluoride for a 5 mg/L solution after 60 min of contact time. Pseudo-first-order and pseudo-second-order kinetic models were applied in the study, and pseudo-second-order exhibited the best fit. The isotherm data were studied for Langmuir and Freundlich models, and the results were satisfactorily fitted with Langmuir isotherm.

Fluoride removal using a rotating anode electro-coagulation reactor: Parametric optimization using response surface methodology, isotherms and kinetic studies, economic analysis and sludge characterization

The presence of fluoride in drinking water can cause various diseases, such as dental fluorosis and skeletal fluorosis. The present study aims to intensify the fluoride removal using a rotating anode electro-coagulation (EC) reactor with providing the proper hydrodynamics conditions. This fluoride removal is modeled and optimized using Response Surface Methodology (RSM) and central composite design (CCD) with varying operational parameters (rotation speed: 20–80 RPM, current: 0.2–1.0 A, initial fluoride concentration: 8–40 mg/L and time: 15–75 min). The maximum fluoride removal is obtained as 96.87% (predicted) and 95.40% (experimental) for the optimized process parameters, initial concentration of 32 mg/L, 0.8 A current, 60 min, and 60 RPM of rotating speed. Kinetic analysis reveals that the removal process adheres to a second-order kinetic model, suggesting that the rate of fluoride removal is dependent on the concentration of fluoride ions present. Isothermal studies indicate that the effective sorption of fluoride onto the generated flocs follows a sips isotherm. The optimal cost analysis is carried out to determine the operational cost as 0.256 USD/m3 for F removal of 93.49% at initial concentration 24 mg/L, time 50 min, current 0.7 A, and rotation 70 rpm and presenting a cost-effective solution for fluoride mitigation. Further, characterizations of the resultant sludge through X-Ray Diffraction (XRD), Fourier-Transform Infrared Spectroscopy (FTIR), and the Toxicity Characteristic Leaching Procedure (TCLP) confirmed the safe disposal potential of the sludge. The findings show a promising approach for fluoride removal, combining high efficiency, economic viability, and environmental safety.

Comparative Evaluation of Antimicrobial Activity and Minimum Inhibitory Concentration of Commercially Available Pediatric Dentifrices: An In Vitro Study.

The aim of this study was to evaluate the antimicrobial efficacy and minimum inhibitory concentration (MIC) of commercially available pediatric dentifrices containing different compositions against Streptococcus mutans and Lactobacillus activity. Four different commercially available brands of pediatric dentifrices, designated as sample I-fluoride, sample II-herbal, sample III-xylitol with nanosilver particles, and sample IV-xylitol with fluoride, along with two control groups (a positive control-ciprofloxacin and a negative control-distilled water), were tested for their antibacterial activity by measuring the zone of inhibition, followed by MIC against two dental bacterial pathogens, S. mutans strain and Lactobacillus acidophilus (LB) strain, at five different twofold dilutions of 100, 50, 25%, 12.5, and 6.25% concentrations. All four dentifrices were found to have wide variations in their effectiveness against the two tested microorganisms at 100% (pure) and 50% concentrations, with sample I having the highest activity, followed by sample IV and sample II. At 25% concentration, only sample I and sample IV showed antibacterial activity, while at 12.5 and 6.25% concentrations, none of the tested toothpastes exhibited any antibacterial activity. Sample III failed to show antibacterial activity even in pure form against the two microorganisms. In our present study, the fluoride-containing pediatric dentifrice with a lower fluoride concentration (458 ppm) exhibited the highest zone of inhibition, followed by the xylitol with fluoride dentifrice and the herbal dentifrice. No zone of inhibition was observed in the nanosilver with xylitol dentifrice. Dureha R, Navit S, Khan SA, et al. Comparative Evaluation of Antimicrobial Activity and Minimum Inhibitory Concentration of Commercially Available Pediatric Dentifrices: An In Vitro Study. Int J Clin Pediatr Dent 2024;17(8):938-944.