Intake of fluoride and other Hofmeister ions from black tea consumption in CKDu prevalent areas, Sri Lanka

Dietary exposure of selected Hofmeister ions-fluoride, chloride, sulfate, phosphate, sodium, potassium, magnesium, and calcium from black tea consumption in chronic kidney disease of unknown etiology (CKDu) prevalent areas in Sri Lanka-were assessed in order to understand exposure and risk. Black tea samples (n = 25) were collected from CKDu prevalent areas and control areas (n = 15). Total fluoride content in alkali fused digested black tea samples was determined. The available Hofmeister ions in tea infusions prepared using deionized water and the groundwater collected by CKDu endemic areas were compared. Dietary exposure was calculated by chronic daily intake data. Total fluoride concentrations ranged from 80 to 269 mg/kg in tea collected from the CKDu endemic regions and 62.5-123.5 mg/kg in non-endemic regions. The fluoride content in infusions ranged from 1.45 to 2.04 mg/L in CKDu endemic areas and 1.11-1.38 mg/L in control samples. The infusions prepared with local groundwater from the CKDu endemic areas showed an elevated level of fluoride 95% than that of the infusion prepared using same tea with deionized water. Aggregated chronic daily intake value from tea and groundwater exceeds the estimated adequate daily intake value of fluoride. The hazard quotient (HQ) values of fluoride in 5 min and 120 min tea infusions were 1.60 and 2.20, respectively, and indicate an adverse health risk. Potassium content in tea infusions collected from CKDu endemic areas is higher than in the control. Even though these values are less than the adequate intake, it may pose an impairment on a weak kidney. Chronic daily intake of Hofmeister ions, i.e., fluoride and potassium from black tea consumed in CKDu endemic areas may induce a risk for CKDu.

Synthesis of stable flowerlike MgAl-LDH@MIL-88A and its adsorption performance for fluoride

MgAl-LDH@MIL-88A as an effective adsorbent was successfully prepared by a simple stirring method in water bath through loading MIL-88A onto the surface of flowerlike MgAl-LDH, which was synthesized via solvothermal method. Interestingly, the results of characterizations showed that the MIL-88A could still grow, but extrude the brucite-like layers of MgAl-LDH. The influences of initial solution pH, contact time, temperature, and co-existing ions on the adsorption performance of MgAl-LDH@MIL-88A were studied systematically by batch static adsorption experiments. It was found that MgAl-LDH@MIL-88A represented the highest adsorption loading of fluoride (14.00 mg g−1) at initial pH 7.0 in 420 min. The uptake process was described appropriately by the pseudo-second-order, the Temkin and the Freundlich isotherm models. The thermodynamic parameters confirmed the endothermic and spontaneous nature of adsorption. MgAl-LDH@MIL-88A was the green adsorbent as the residual mental contents ([Mg2+] = 1.095 mg L−1, [Fe3+] = 0.007 mg L−1, [Al3+] = 0.076 mg L−1) after adsorption met the Chinese sanitary standard for drinking water (GB 5749-2006). The mechanism of fluoride removal by MgAl-LDH@MIL-88A involved the electrostatic interactions between Fe3+ of MIL-88A and fluoride, and ligand exchange among hydroxyl groups of MgAl-LDH, carboxylate groups of the C4H4O4 and fluoride.

Adsorption of paratoluic acid on MIL-53 (Al) metal-organic framework, and response surface methodology optimization

In this study, an organic metal framework adsorbent was used to remove paratoluic acid from aqueous solutions. The effect of various parameters such as pH, initial concentration of paravoluic acid, contact time, and amount of adsorbent was investigated by experimental design method. Central composite design (CCD) was used to optimize paratoluic acid uptake. Initially, MIL-53 (Al) was synthesized, and characterized by X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FTIR), spectroscopy, and thermogravimetry (TGA). The results of central composite design showed that pH is the most essential factor in the removal of paratoluic acid with MIL-53 (Al). The maximum removal efficiency of paratoluic acid by MIL-53 (Al) adsorbent is 93.67%, the optimal amount of adsorbent is 0.396 g, the optimal time is 35.67 min, the initial concentration is 11.12 mg L−1. The pH is 6.6 with the desired amount 1 is. Isothermal, and kinetic models have also examined. The maximum adsorption capacity was 132.05 (mg g−1), and the adsorption data of MIL-53 (Al) were well consistent with the quasi-second order, and Langmuir isotherm models.

Optimized removal of hexavalent chromium from water using spent tea leaves treated with ascorbic acid

Spent tea leaves were functionalized with ascorbic acid to obtain treated tea waste (t-TW) to encourage the adsorption of hexavalent chromium from water. The adsorption removal of Cr(VI) was systematically investigated as a function of four experimental factors: pH (2–12), initial Cr(VI) concentration (1–100 mg L⁻¹), t-TW dosage (0–4 g L⁻¹), and temperature (10–50 °C) by following a statistical experimental design. A central composite rotatable experimental design based on a response surface methodology was used to establish an empirical model that assessed the individual and combined effects of factors on adsorptive removal of Cr(VI). The model was experimentally verified and statistically validated then used to predict optimal adsorption removal of Cr(VI) from water. At optimized conditions, ≥ 99% of 1 mg L⁻¹ Cr(VI) can be removed by 4 g L⁻¹ t-TW at a pH of 9. The adsorptive mechanism was assessed by conducting kinetics and equilibrium studies. The adsorption of Cr(VI) by t-TW followed a pseudo-second-order kinetics model (k₂ = 0.001 g mg⁻¹ h⁻¹) and could be described by Langmuir and Temkin isotherms, indicating monolayer adsorption and predominantly adsorbate-adsorbent interactions. The t-TW exhibited a competitive Cr(VI) adsorption capacity of 232.2 mg g⁻¹ compared with the other low-cost adsorbents. These results support the utilization of tea waste for the removal of hazardous metal contaminants from aqueous systems.

Valorization of agro-industrial biowaste to green nanomaterials for wastewater treatment: Approaching green chemistry and circular economy principles

Water pollution is one of the most critical issues worldwide and is a priority in all scientific agendas. Green nanotechnology presents a plethora of promising avenues for wastewater treatment. This review discusses the current trends in the valorization of zero-cost, biodegradable, and readily available agro-industrial biowaste to produce green bio-nanocatalysts and bio-nanosorbents for wastewater treatment. The promising roles of green bio-nanocatalysts and bio-nanosorbents in removing organic and inorganic water contaminants are discussed. The potent antimicrobial activity of bio-derived nanodisinfectants against water-borne pathogenic microbes is reviewed. The bioactive molecules involved in the chelation and tailoring of green synthesized nanomaterials are highlighted along with the mechanisms involved. Furthermore, this review emphasizes how the valorization of agro-industrial biowaste to green nanomaterials for wastewater treatment adheres to the fundamental principles of green chemistry, circular economy, nexus thinking, and zero-waste manufacturing. The potential economic, environmental, and health impacts of valorizing agro-industrial biowaste to green nanomaterials are highlighted. The challenges and future outlooks for the management of agro-industrial biowaste and safe application of green nanomaterials for wastewater treatment are summarized.

Effects of brewing conditions on infusible fluoride levels in tea and herbal products and probabilistic health risk assessment

Excessive ingestion of fluorides might adversely affect the health of humans. Hence, this study aimed to investigate the concentrations of infusible fluoride in five different types of tea and herbal products; additionally, the probabilistic health risks associated with the ingestion of fluoride in drinking tea and herbal products were estimated. The highest and lowest concentrations of infusible fluoride were detected in black and white tea, respectively. On average, the highest amount of infusible fluoride was extracted following a short brewing time of 5 min in the case of black tea (2.54 mg/L), herbal tea (0.40 mg/L), and white tea (0.21 mg/L). The level of infusible fluoride during brewing was inversely associated with the leaf size of the tea and herbal products. Furthermore, the type of water used influenced the release of infusible fluoride; purified water yielded lower amounts of infused fluoride. The findings of the probabilistic health risk assessment indicated that the consumption of black tea can increase the fluoride intake leading to chronic exposure. Thus, the health risk posed by fluoride intake from drinking tea needs to be evaluated in more details in the future. Appropriate measures for health risk mitigation need to be implemented to minimize the total body burden of fluorides in humans.

Pb2+ and Cd2+ recovery from water using residual tea waste and SiO2@TW nanocomposites

This work reports the fabrication of SiO₂@TW nanocomposites and their application for Pb²⁺ and Cd²⁺ ions sequestration from simulated water. Residual tea waste has also been used for metal ions sequestration to compare the potential of SiO₂@TW nanocomposites. The SEM, TEM, BET, FTIR and EDX techniques were employed for the characterization of SiO₂@TW nanocomposites and residual tea waste. Particle sizes of SiO₂@TW nanocomposites was in the range of 6.8-12 nm. The experiments were carried out in batch mode to explore the effect of various operating parameters on the sequestration of Pb²⁺ and Cd²⁺ ions from water. The experimental data was subjected to various thermodynamic, kinetic and isothermic models. According to Langmuir model, the maximum adsorption efficiency of the SiO₂@TW nanocomposites was 153 mg/g for Pb²⁺ and 222 mg/g for Cd²⁺ but maximum adsorption efficiency of residual tea waste for Pb²⁺ was 125 mg/g and for Cd²⁺ was 142.9 mg/g. This study suggested that due to the presence of active sites SiO₂@TW nanocomposites has greater potential for metal sequestration than residual tea waste.

Rapid removal of lead(II) ions from water using iron oxide-tea waste nanocomposite - a kinetic study

Lead (Pb) ions are a major concern to the environment and human health as they are contemplated cumulative poisons. In this study, facile synthesis of magnetic iron oxide-tea waste nanocomposite is reported for adsorptive removal of lead ions from aqueous solutions and easy magnetic separation of the adsorbent afterwards. The samples were characterised by scanning electron microscopy, Fourier transform-infrared spectroscopy, X-ray diffraction, and Braunner-Emmet-Teller nitrogen adsorption study. Adsorptive removal of Pb(II) ions from aqueous solution was followed by ultraviolet-visible (UV-Vis) spectrophotometry. About 95% Pb(II) ion removal is achieved with the magnetic tea waste within 10 min. A coefficient of regression R² ≃ 0.99 and adsorption density of 18.83 mg g^-1 was found when Pb(II) ions were removed from aqueous solution using magnetic tea waste. The removal of Pb(II) ions follows the pseudo-second-order rate kinetics. External mass transfer principally regulates the rate-limiting phenomena of adsorption of Pb(II) ions on iron oxide-tea waste surface. The results strongly imply that magnetic tea waste has promising potential as an economic and excellent adsorbent for the removal of Pb(II) from water.

Biomaterial functionalized cerium nanocomposite for removal of fluoride using central composite design optimization study

Excess fluoride concentration in drinking water is a global issue, as this has an adverse effect on human health. Several adsorbents have been synthesized from natural raw material to remove fluoride from water. Reported adsorbents have some problems with the leaching of metal ions, fewer adsorption sites, and low adsorption capacity. Therefore, to address this, an effective biomaterial derived from the Luffa cylindrica (LC), containing many active sites, was integrated with a nano form of cerium oxide to form a robust, biocompatible, highly porous, and reusable LC-Ce adsorbent. This synthesized biosorbent offers better interaction between the active sites of LC-Ce and fluoride, resulting in higher adsorption capacity. Several factors, influence the adsorption process, were studied by a central composite design (CCD) model of statistical analysis. Langmuir's and Freundlich's models well describe the adsorption and kinetics governed by the pseudo-second-order model. The maximum monolayer adsorption capacity was found to be 212 and 52.63 mg/g for LC-Ce and LC, respectively determined by the Langmuir model. Detailed XPS and FTIR analyses revealed the underlying mechanism of fluoride adsorption via ion-exchange, electrostatic interaction, H-bonding, and ion-pair formation. All the results indicate that LC-Ce could serve as a suitable adsorbent for efficient fluoride removal (80-85%).

Highly selective defluoridation of brick tea infusion by tea waste supported aluminum oxides

BACKGROUND

Brick tea usually contains very high fluoride, which may affect human health. Biosorbents have received much attention for selective removal of fluoride because of low cost, environmental friendliness, and relative safeness.

RESULTS

In the present study, a highly selective fluoride tea waste based biosorbent, namely, aluminum (Al) oxide decorated tea waste (Tea-Al), was successfully prepared. The Tea-Al biosorbent was characterized by energy-dispersive spectrometry, Fourier transform infrared spectroscopy, powder X-ray diffraction and X-ray photoelectron spectroscopic analysis. The Tea-Al sample exhibited remarkably selective adsorption for fluoride (52.90%), but a weaker adsorption for other major constituents of brick tea infusion, such as catechins, polyphenols and caffeine, under the same conditions. Fluoride adsorption by Tea-Al for different times obeyed the surface reaction and adsorption isotherms fit the Freundlich model. In addition, the fluoride adsorption mechanism appeared to be an ion exchange between hydroxyl and fluoride ions.

CONCLUSION

Results from this study demonstrated that Tea-Al is a promising biosorbent useful for the removal of fluoride in brick tea infusion. © 2016 Society of Chemical Industry.

Adsorption behavior of carboxymethyl konjac glucomannan microspheres for fluoride from aqueous solution

The CMKGM–La–Al is characterized by SEM, EDX, and XPS. We find that adsorption mechanism of the adsorbent involved coordination reaction and electrostatic interaction. The schematic diagram of preparation of CMKGM–La–Al is shown as above.

Efficient fluoride adsorption by mesoporous hierarchical alumina microspheres

Mesoporous Hierarchical Alumina Microspheres (HAM) with high efficiency for fluoride removal have been synthesized and characterized.

Enhanced fluoride removal by loading Al/Zr onto carboxymethyl starch sodium: synergistic interactions between Al and Zr

In this paper, a novel type of adsorbent was prepared by loading Al/Zr onto carboxymethyl starch sodium to generate CMS–Al, CMS–Zr or CMS–Al–Zr.