Applications of biomass-based materials to remove fluoride from wastewater: A review

Amino-functionalized novel biosorbent for effective removal of fluoride from water: process optimization using artificial neural network and mechanistic insights

Aqueous fluoride (F - ) pollution is a global threat to potable water security. The present research envisions the development of novel adsorbents from indigenous Limonia acidissima L. (fruit pericarp) for effective aqueous defluoridation. The adsorbents were characterized using instrumental analysis, e.g., TGA-DTA, ATR-FTIR, SEM-EDS, and XRD. The batch-mode study was performed to investigate the influence of experimental variables. The artificial neural network (ANN) model was employed to validate the adsorption. The dataset was fed to a backpropagation learning algorithm of the ANN (BPNN) architecture. The four-ten-one neural network model was considered to be functioning correctly with an absolute-relative-percentage error of 0.633 throughout the learning period. The results easily fit the linearly transformed Langmuir isotherm model with a correlation coefficient( R 2 ) > 0.997. The maximumF - removal efficiency was found to be 80.8 mg/g at the optimum experimental condition of pH 7 and a dosage of 6 g/L at 30 min. The ANN model and experimental data provided a high degree of correlation (R 2 = 0.9964), signifying the accuracy of the model in validating the adsorption experiments. The effects of interfering ions were studied with realF - water. The pseudo-second-order kinetic model showed a good fit to the equilibrium dataset. The performance of the adsorbent was also found satisfactory with field samples and can be considered a potential adsorbent for aqueous defluoridation.

Fixed-bed column adsorption modeling using Zr biocomposites for fluoride removal

This research involved conducting continuous adsorption experiments to assess fluoride elimination from drinking water achieved by utilizing biocomposites created from the peels of oranges and apples, which were impregnated with zirconium (Zr), to form BOP-Zr and BAP-Zr, respectively. The findings from the experimental data indicate that BOP-Zr and BAP-Zr are effective biosorbents with a solid ability to remove fluoride selectively. Additionally, these biosorbents were found to be stable, as they do not release Zr into the treated water. Notably, these environmentally friendly biosorbents are derived from renewable sources and enhance the value of waste materials. The study employed various empirical models, including Bohart-Adamas, Thomas, Yoon-Nelson, BDST, Clark, Yan, and Woolborska, to elucidate the mechanisms and crucial parameters involved in fluoride adsorption within packed bed columns. The Yan model demonstrated the highest correlation among these models, indicating a chemical adsorption process with kinetics following a pseudo-second-order pattern. BOP-Zr and BAP-Zr exhibited a maximum adsorption capacity of 59.3 and 47.5 mg/g, respectively, under a flow rate of 4 mL/min and an inlet fluoride concentration of 25 mg/L. The analysis of mass transfer coefficients revealed that the primary step governing the adsorption procedure was diffusion through pores. Consequently, the study conclusively establishes that BOP-Zr and BAP-Zr biocomposites, originating from lignocellulosic biomass remains, present a practical and competitive choice for eliminating fluoride from water. These materials surpass waste materials in performance and rival more expensive options in efficiency and performance.

Photothermal Conversion of Hydrogel-Based Biomaterial

Traditional energy from fossil fuels like petroleum and coal is limited and contributes to global environmental pollution and climate change. Developing sustainable and eco-friendly energy is crucial for addressing significant challenges such as climate change, energy dilemma and achieving the long-term development of human society. Biomass hydrogels, which are easily synthesized and modified, have diverse sources and can be designed for different applications. They are being extensively researched for their applications in artificial intelligence, flexible sensing, biomedicine, and food packaging. The article summarizes recent advances in the preparation and applications of biomass-based photothermal conversion hydrogels, discussing the light source, photothermal agents, matrix, and preparation methods in detail. It also explores the use of these hydrogels in seawater desalination, photothermal therapy, antibacterial agents, and light-activated materials, offering new ideas for developing sustainable, efficient, and advanced photothermal conversion biomass hydrogel materials. The article concludes with suggestions for future research, highlighting the challenges and prospects in this field and paving the way for developing of long-lasting, efficient energy materials.

The model and mechanism of adsorptive technologies for wastewater containing fluoride: A review

With the continuous development of society, industrialization, and human activities have been producing more and more pollutants. Fluoride discharge is one of the main causes of water pollution. This review summarizes various commonly used and effective fluoride removal technologies, including ion exchange technology, electrochemical technology, coagulation technology, membrane treatment, and adsorption technology, and points out the outstanding advantages of adsorption technology. Various commonly used fluoride removal techniques as well as typical adsorbent materials have been discussed in published papers, however, the relationship between different adsorbent materials and adsorption models has rarely been explored, therefore, this paper categorizes and summarizes the various models involved in static adsorption, dynamic adsorption, and electrosorption fluoride removal processes, such as pseudo-first-order and pseudo-second-order kinetic models, Langmuir and Freundlich isotherm models, Thomas and Clark dynamic adsorption models, including the mathematical equations of the corresponding models and the significance of the models are also comprehensively summarized. Furthermore, this comprehensive discussion delves into the fundamental adsorption mechanisms, quantification of maximum adsorption capacity, evaluation of resistance to anion interference, and assessment of adsorption regeneration performance exhibited by diverse adsorption materials. The selection of the best adsorption model not only predicts the adsorption performance of the adsorbent but also provides a better description and understanding of the details of each part of the adsorption process, which facilitates the adjustment of experimental conditions to optimize the adsorption process. This review may provide some guidance for the development of more cost-effective adsorbent materials and adsorption processes in the future.

KOH-modified bamboo charcoal loaded with α-FeOOH for efficient adsorption of copper and fluoride ions from aqueous solution

In this work, bamboo charcoal (BC) is prepared by pyrolysis of bamboo. Then, KOH modification and surface deposition of Goethite (α-FeOOH) are performed to obtain a new KOH-modified BC loaded with α-FeOOH (FKBC) adsorbent for copper (Cu2+) and fluoride (F-) ion adsorption from aqueous solution. Surface morphology and physiochemical properties of the prepared adsorbent are characterized by scanning electron microscopy-energy dispersive spectrometer, X-ray diffraction, and N2 adsorption-desorption. The effect of pH, contact time, adsorbent dosage, and initial concentration on Cu2+ and F- adsorption is also investigated. In addition, adsorption kinetics and isotherms are fitted to pseudo-second-order kinetics and Langmuir model, respectively. Thermodynamic parameters suggest that the adsorption process is spontaneous and endothermic. The adsorption mechanism is further characterized by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The Cu2+ absorption mainly occurs through ion exchange, coordination reactions, and surface precipitation, while the F- adsorption mainly occurs via ion exchange and hydrogen bonding. The selective adsorption experiments reveal that FKBC has good selectivity for Cu2+ and F-. The adsorption-desorption experimental results indicate that FKBC can be reused for Cu2+ and F- adsorption after regeneration. Results indicate that FKBC can be a promising adsorbent for Cu2+ and F- removal from aqueous solutions.

Remediation of water tainted with noxious aspirin and fluoride ion using UiO-66-NH2 loaded peanut shell

One green adsorbent, UiO-66-NH2 modified peanut shell (c-PS-MOF), was prepared in a green synthetic route for improving the capture level of aspirin (ASP) and fluoride ion (F-). The adsorption properties of c-PS-MOF were evaluated by batch experiments and its physicochemical properties were explored by various characterization methods. The results showed that c-PS-MOF exhibited a wide range of pH applications (ASP: 2-10; F-: 3-12) and high salt resistance in the capturing processes of ASP and F-. The unit adsorption capacity of c-PS-MOF was as high as 84.7 mg·g-1 for ASP as pH = 3 and 11.2 mg·g-1 for F- under pH = 6 at 303 K from Langmuir model, respectively. When the solid-liquid ratio was 2 g·L-1, the content of ASP (C0 = 100 mg·L-1) and F- (C0 = 20 mg·L-1) in solution can be reduced to 0.48 mg·L-1 and 1.05 mg·L-1 separately. The recycling of c-PS-MOF can be realized with 5 mmol·L-1 NaOH as eluent. Analysis of simulated water samples showed that c-PS-MOF could be used to remove ASP and F- from actual water. The c-PS-MOF is promising to bind ASP and F- from rivers, lakes, etc.

Removal of Fluoride from Aqueous Solution Using Shrimp Shell Residue as a Biosorbent after Astaxanthin Recovery

Natural astaxanthin has been widely used in the food, cosmetic, and medicine industries due to its exceptional biological activity. Shrimp shell is one of the primary natural biological sources of astaxanthin. However, after astaxanthin recovery, there is still a lot of chitin contained in the residues. In this study, the residue from shrimp (Penaeus vannamei) shells after astaxanthin extraction using ionic liquid (IL) 1-ethyl-3-methyl-imidazolium acetate ([Emim]Ac) was used as a bioadsorbent to remove fluoride from the aqueous solution. The results show the IL extraction conditions, including the solid/liquid ratio, temperature, time, and particle size, all played important roles in the removal of fluoride by the shrimp shell residue. The shrimp shells treated using [Emim]Ac at 100 °C for 2 h exhibited an obvious porous structure, and the porosity showed a positive linear correlation with defluorination (DF, %). Moreover, the adsorption process of fluoride was nonspontaneous and endothermic, which fits well with both the pseudo-second-order and Langmuir models. The maximum adsorption capacity calculated according to the Langmuir model is 3.29 mg/g, which is better than most bioadsorbents. This study provides a low-cost and efficient method for the preparation of adsorbents from shrimp processing waste to remove fluoride from wastewater.

Dihydrophenazine-derived oligomers from industrial waste as sustainable superior cathode materials for rechargeable lithium-ion batteries

Organic materials with the 5,10-dihydrophenazine motif are superior cathode materials for lithium-ion batteries. However, the difficult accessibility and low capacity of such cathodes materials are obstacles to their practical applications. Herein, two novel oligomers, termed poly(5-methyl-10-(2-methacryloxypropyl)-5,10-dihydrophenazine) (PMPPZ) and poly(5-methyl-10-(2-methacryloxyethyl)-5,10-dihydrophenazine) (PMEPZ), were effectively synthesized from an industrial waste phenazine. Both oligomers were exploited successfully as excellent cathode materials for sustainable lithium-ion batteries. PMPPZ and PMEPZ exhibited good electrochemical stability and high initial discharge specific capacities of 88 mA h g^-1 and 152 mA h g^-1, respectively. Furthermore, upon in situ composition with MWCNTs, a composite material, named PMEPZ-MWCNTs, was achieved with enhanced stability and superior specific discharge capacity with the active-site utilization rate of up to 99%. PMEPZ-MWCNTs delivers high initial discharge capacity of up to 303 mA h g^-1 and even 252 mA h g^-1 after 300 cycles. Both oligomers exhibit double-electron transfer mechanisms. This work affords an alternative approach to utilizing phenazine as a useful material, circumventing the emission of vast environment harmful gases.

Adsorption of Fluoride onto Acid-Modified Low-Cost Pyrolusite Ore: Adsorption Characteristics and Efficiencies

Fluoride concentrations in the groundwater continue to be a major cause for concern in Thailand, particularly in the country's north and west. The process of removing fluoride through adsorption has captured the attention of the abundance of ore in the mining industry. For the purpose of this investigation, the utilization of the adsorbent pyrolusite, which is a manganese mineral largely composed of MnO₂, was a major component. Lab-scale experiments were conducted to investigate the efficacy of original pyrolusite ore (PA-1) and acid-modification PA (PA-2) created as low-cost adsorption materials for fluoride removal. The results of the adsorption rate in both PAs showed a fast rate of adsorption within 60 min of reaching equilibrium. According to the results of the adsorption capacity (q_e) tests, PA that had been treated with an acid solution (PA-2) had the capacity to contain more fluoride (q_e = 0.58 mg/g) than the PA that had been used initially (PA-1) (q_e = 0.11 mg/g). According to the findings of an isotherm, primary adsorption behavior is determined by the effect that surface components and chemical composition have on porous materials. This is the first current study that provides a comparison between pyrolusite from Thailand's mining industry and basic modified pyrolusite regarding their ability to remove a fluoride contaminant in synthetic groundwater by an adsorption process. Such an approach will be able to be used in the future to protect the community from excessive fluoride concentrations in household and drinking water treatment technology.

Lignocellulosic Biomass as Sorbent for Fluoride Removal in Drinking Water

Water supply to millions of people worldwide is of alarmingly poor quality. Supply sources are depleting, whereas demand is increasing. Health problems associated with water consumption exceeding 1.5 mg/L of fluoride are a severe concern for the World Health Organization (WHO). Therefore, it is urgent to research and develop new technologies and innovative materials to achieve partial fluoride reduction in water intended for human consumption. The new alternative technologies must be environmentally friendly and be able to remove fluoride at the lowest possible costs. So, the use of waste from lignocellulosic biomasses provides a promising alternative to commercially inorganic-based adsorbents-published studies present bioadsorbent materials competing with conventional inorganic-based adsorbents satisfactorily. However, it is still necessary to improve the modification methods to enhance the adsorption capacity and selectivity, as well as the reuse cycles of these bioadsorbents.

A critical review on adsorption and recovery of fluoride from wastewater by metal-based adsorbents

Rapid industrialization is deteriorating water quality, and fluoride pollution in water is one of the most serious environmental pollution problems. Adsorption technology is an efficient and selective process for removing fluoride from aqueous solutions using adsorbents. Metal-based adsorbents synergize the advantages of fast adsorption, high adsorption capacity, and excellent selectivity to effectively remove fluoride from water bodies, promising to satisfy environmental sustainability requirements. This paper reviews the metal-based adsorbents: iron-based, aluminum-based, lanthanum-based, cerium-based, titanium-based, zirconium-based, and multi-metal composite adsorbents, primarily focusing on the adsorption conditions and fluoride removal capacities and discusses prospects and challenges in the synthesis and application of metal-based adsorbents. This paper aims to stimulate new thinking and innovation in developing the next generation of sustainable adsorbents.

Calcium hydroxide recycled from waste eggshell resources for the effective recovery of fluoride from wastewater

In the hunt of waste recovery pathways, eggshells emerged as a potential adsorbent for fluoride because they contain plenty of calcium. However, as the main component, calcite has weak interaction with fluoride. In this study, calcium hydroxide was derived from waste eggshells successfully by an aging treatment with moisture for fluoride recovery from water. The X-ray diffraction (XRD) and infrared spectroscopy (FT-IR) analyses indicate that CaO in calcined egg shells (AEG900) is completely converted to calcium hydroxide. The adsorption experiments showed that the adsorption capacity of AEG900 for fluoride was improved by nearly 29.21% compared with the calcined eggshells without the aging treatment. In the batch experiment, the temperature effect is the most significant for the adsorption process, and nearly a half increment of removal rate is achieved by increasing the temperature by 30 °C. Further research revealed that the adsorption process fitted well with the pseudo-second order model and the Langmuir–Freundlich isotherm model, with a maximum adsorption capacity of 370.15 mg g⁻¹. Moreover, precipitation was regarded as the main step for fluoride removal mechanism based on the calculated results of the surface complexation model. X-ray photoelectron spectroscopy (XPS) results showed that the stable fluorite formed in situ of AEG900 avoids calcium loss in water. Finally, AEG900 was applied in fluoride removal with real-life groundwater and industrial wastewater, and the results showed that the final fluoride concentration could meet the WHO requirement and industrial wastewater discharge standard.

Calcium hydroxide derived from eggshells can remove F⁻ efficiently in water with the adsorption capacity of 370.15 mg g⁻¹, and the final concentration can meet the guidelines of the WHO, which is below 1.5 mg L⁻¹.

Electrochemical Evaluation of Protective Coatings with Ti Additions on Mild Steel Substrate with Potential Application for PEM Fuel Cells

In this work, the corrosion behavior of NiCr(Ti) protective coatings deposited on mild steel substrates through laser cladding technology is studied as an alternative new material for metallic bipolar plates used in PEMFC applications. For electrochemical testing, a solution consisting of 0.5 M H₂SO₄ + 2 ppm F⁻ at room temperature is used as an electrolyte. The fluoride ions are added to simulate the conditions in the PEM fuel cell due to degradation of the proton exchange membrane and fluoride release. A saturated calomel electrode (SCE) is used as a reference electrode and a platinum mesh as the counter electrode. Scanning electron microscopy (SEM) and optical microscopy (OM) are used for studying the morphology of the protective coatings and the effect of Ti addition. The electrochemical evaluation consisted of measuring the open circuit potential (OCP), followed by electrochemical impedance spectroscopy measurements (EIS) and potentiodynamic polarization. It is found that the coatings with 5% Ti, 7% Ti and 10% Ti addition comply with the conditions of the US DOE regarding corrosion performance to be used as materials for the manufacture of the bipolar plates.