Calcium and zirconium modified acid activated alumina for adsorptive removal of fluoride: Performance evaluation, kinetics, isotherm, characterization and industrial wastewater treatment

Enhancing fluoride ion removal from aqueous solutions and glass manufacturing wastewater using modified orange peel biochar magnetic composite with MIL-53

In this study, we developed new adsorbents derived from orange peel biochar (BCOP) and enhanced them with CoFe2O4 magnetic nanoparticles (BCOP/CoFe2O4) and MIL-53(Al) (BCOP/CoFe2O4/MIL-53(Al)). These adsorbents were utilized to remove fluoride (FL) ions from aqueous solutions. We analyzed the properties of these adsorbents using a range of techniques, including FTIR, XRD, SEM, EDX-Map, VSM, Raman spectroscopy, and BET. Our findings indicate that the components interact effectively with one another. Specifically, the BCOP/CoFe2O4/MIL-53(Al) sample exhibited a specific surface area of 196.430 m2/g and a magnetic saturation value of 9.704 emu/g. The maximum FL ion adsorption capacities for BCOP, BCOP/CoFe2O4, and BCOP/CoFe2O4/MIL-53(Al) were 7.618, 16.330, and 37.320 mg/g, respectively, indicating that the modifications significantly enhanced the adsorption capacity. The optimum fluoride ion removal rates using BCOP, BCOP/CoFe2O4, and BCOP/CoFe2O4/MIL-53(Al) were 97.88%, 98.23%, and 99.06%, respectively, at adsorbent doses of 2.5, 1.5, and 0.8 g/L, contact times of 90, 70, and 50 minutes, pH 4, temperature 50°C, and a FL concentration of 10 mg/L. Thermodynamic studies revealed that the adsorption process was spontaneous and endothermic, with increased randomness between the adsorbent and fluoride ions. Kinetic analyses showed that fluoride ion adsorption by BCOP/CoFe2O4/MIL-53(Al) followed a pseudo-second-order (PSO) model, while BCOP and BCOP/CoFe2O4 followed a pseudo-first-order (PFO) model. Additionally, the equilibrium data for fluoride ion adsorption on BCOP/CoFe2O4/MIL-53(Al) adhered to the Freundlich model, whereas the other samples conformed to the Langmuir model. The study evaluates the effectiveness of BCOP, BCOP/CoFe2O4, and BCOP/CoFe2O4/MIL-53(Al) in removing FL ions from glass manufacturing wastewater, highlighting the superior performance of the magnetic composite due to its enhanced surface area and functional groups. Notably, the adsorbents demonstrated good regenerative capabilities, maintaining high performance over multiple adsorption cycles.

Recent advances in chitosan-based nanocomposites for adsorption and removal of heavy metal ions

Due to the high concentration of various toxic and dangerous pollutants, industrial effluents have imposed increasing threats. Among the various processes for wastewater treatment, adsorption is widely used due to its simplicity, good treatment efficiency, availability of a wide range of adsorbents, and cost-effectiveness. Chitosan (CS) has received great attention as a pollutant adsorbent due to its low cost and many -OH and -NH2 functional groups that can bind heavy metal ions. However, weaknesses such as sensitivity to pH, low thermal stability and low mechanical strength, limit the application of CS in wastewater treatment. The modification of these functional groups can improve its performance via cross-linking and grafting agents. The porosity and specific surface area of CS in powder form are not ideal, so physical modification of CS via integration with other materials (e.g., metal oxide, zeolite, clay, etc.) leads to the creation of composite materials with improved absorption performance. This review provides reports on the application of CS and its nanocomposites (NCs) for the removal of various heavy metal ions. Synthesis strategy, adsorption mechanism and influencing factors on sorbents for heavy metals are discussed in detail.

Innovations and challenges in adsorption-based wastewater remediation: A comprehensive review

Water contamination is an escalating emergency confronting communities worldwide. While traditional adsorbents have laid the groundwork for effective water purification, their selectivity, capacity, and sustainability limitations have driven the search for more advanced solutions. Despite many technological advancements, economic, environmental, and regulatory hurdles challenge the practical application of advanced adsorption techniques in large-scale water treatment. Integrating nanotechnology, advanced material fabrication techniques, and data-driven design enabled by artificial intelligence (AI) and machine learning (ML) have led to a new generation of optimized, high-performance adsorbents. These advanced materials leverage properties like high surface area, tailored pore structures, and functionalized surfaces to capture diverse water contaminants efficiently. With a focus on sustainability and effectiveness, this review highlights the transformative potential of these advanced materials in setting new benchmarks for water purification technologies. This article delivers an in-depth exploration of the current landscape and future directions of adsorbent technology for water remediation, advocating for a multidisciplinary approach to overcome existing barriers in large-scale water treatment applications.

Reutilization of carbon of waste filter cartridge after its surface modification for the fluoride removal from water by continuous flow process

In the present study, the waste carbon cartridge of the water filter was modified and reutilized for defluoridation of water. The modified carbon was characterized by particle size analysis (PSA), Fourier transformed infrared spectroscopy (FTIR), zeta potential, pHzpc, energy-dispersive X-ray (EDS), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and X-ray crystallography (XRD). The adsorptive nature of modified carbon was investigated with pH (4-10), dose (1-5 g/L), contact time (0-180 min), temperature (25-55 °C), fluoride concentration (5-20 mg/L), and the effect of the competitive ions. Adsorption isotherm, kinetics, thermodynamics, and breakthrough studies were evaluated for fluoride uptake on surface-modified carbon (SM*C). Fluoride adsorption on the carbon accepted Langmuir model (R2 = 0.983) and pseudo-second-order kinetic (R2 = 0.956). The presence of HCO3- in the solution reduced the elimination of fluoride. The carbon was regenerated and reused four times; the removal percentage was decreased from 92 to 31.7%. This adsorption phenomenon showed exothermic behavior. The maximum fluoride uptake capacity of SM*C achieved 2.97 mg/g at 20 mg/L of initial concentration. The modified carbon cartridge of the water filter was successfully employed for fluoride removal from water.

A novel tri-metal adsorbent used for defluoridation technique from groundwater: performance and mechanism

In this research article, a novel adsorbent (Zn-Fe-Al) was synthesized successfully by a simple chemical route where three oxides combined to enhance affinity towards fluoride. The physicochemical properties of the adsorbent were used to characterize and assess its effectiveness in defluoridation with both synthetic and groundwater. The TEM results demonstrated the overlapping of metals, and EDX shows the metals present in the adsorbent. The maximum defluoridation efficiency (97%) of Zn-Fe-Al was obtained at an optimized initial pH 7 and adsorbent dose 0.08 g L-1. The fluoride adsorption on Zn-Fe-Al followed the D-R isotherm and intraparticle diffusion. The maximum adsorption capacity of Zn-Fe-Al was found to be 187 mg g-1. The adsorption of fluoride on Zn-Fe-Al was found to be endothermic and spontaneous. The Zn-Fe-Al adsorbent exhibited satisfactory defluoridation performance on real groundwater. The co-existing ions were also investigated. The adsorption mechanisms for fluoride were electrostatic interaction and ion exchange. These results demonstrated that Zn-Fe-Al adsorbent was considered high potential for effective defluoridation of groundwater.

Evaluation of fluoride adsorption in solution by synthetic Al2 O3 /CeO2 : A fixed-bed column study

A highly efficient fluoride adsorbent Al₂ O₃ /CeO₂ was synthesized in this work and used it to fluoride removal in the fixed-bed adsorption through changing the different experimental conditions (influent F^- concentration, flow velocity, and bed heights). The adsorption capacity was 9.72 mg/g. In addition, the Adams-Bohart and Thomas models were used to fit and evaluate the column breakthrough curve of fluoride removal process by Al₂ O₃ /CeO₂ , and the correlation coefficients (R² ) of the Thomas model were close to 1 under all experimental conditions. The structure of Al₂ O₃ /CeO₂ and the adsorption mechanism were confirmed by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), N₂ adsorption and desorption isotherm, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). Moreover, the adsorption of fluoride (F^- ) was mainly through metal binding (MF) and hydroxyl binding (AlOH⋯F) on the surface of the Al₂ O₃ /CeO₂ . Furthermore, the regeneration and coexisting anions studies of Al₂ O₃ /CeO₂ were carried out, and the efficiency of adsorption was still above 70% after five cycles. PRACTITIONER POINTS: Removal of fluoride was studied by fixed-bed experiment, and the adsorption capacity of composite Al₂ O₃ /CeO₂ was 9.72 mg/g. The metal complex played important role in fluoride removal and reusability makes a long-term application for fluoride adsorption. Fluoride wastewater is pumped to the fixed-bed column, and fluoride ions are absorbed by Al₂ O₃ /CeO₂ through fluoride metal complex and aluminum hydrofluoride.

Emission-to-ash detoxification mechanisms of co-combustion of spent pot lining and pulverized coal

In response to the global initiative for greenhouse gas emission reduction, the co-combustion of coal and spent pot lining (SPL) may cost-effectively minimize waste streams and environmental risks. This study aimed to quantify the emission-to-ash detoxification mechanisms of the co-combustion of SPL and pulverized coal (PC) and their kinetics, gas emission, fluorine-leaching toxicity, mineral phases, and migrations. The main reaction covered the ranges of 335-540 °C and 540-870 °C while the interactions occurred at 360-780 °C. The apparent activation energy minimized (66.99 kJ/mol) with 90% PC addition. The rising PC fraction weakened the peak intensity of NaF and strengthened that of Ca₂F, NaAlSiO₄, and NaAlSi₂O₆. The addition of PC enhanced the combustion efficiency of SPL and raised the melting temperature by capturing Na. PC exhibited a positive effect on solidifying water-soluble fluorine and stabilizing alkali and alkaline earth metals. The leaching fluorine concentrations of the co-combustion ashes were lower than did SPL mono-combustion. The main gases emitted were HF, NH₃, NO_x, CO, and CO₂. HF was largely released at above 800 °C. Multivariate Gaussian process model-based optimization of the operational conditions also verified the gas emissions results. Our study synchronizes the utilization and detoxification of SPL though co-combustion and provides insights into an eco-friendlier life-cycle control on the waste-to-energy conversion.

Fabrication of Manganese-Supported Activated Alumina Adsorbent for Defluoridation of Water: A Kinetics and Thermodynamics Study

Fluoride pollution frequently occurs in many underground drinking water sources due to discrepancies in the geological environment. To address this problem, a manganese-supported activated alumina (MnOOH-supported AA) adsorbent was proposed in the present study. The adsorbent was prepared with an impregnation method, then the morphology and microstructure were systematically characterized. Further, the adsorption kinetics and thermodynamics were systematically explored through static experiments to confirm the adsorption mechanism. The results showed that MnOOH was successfully loaded on the activated alumina (AA), and irregular and convex spinous structures were formed on the surface of particles. Compared with the AA, MnOOH-supported AA exhibited a significantly higher defluoridation rate, which has been doubled. The kinetic behavior of fluoride adsorption on MnOOH-supported AA was governed by the quasi-second-order kinetics model with regression coefficients of 0.9862, 0.9978 and 0.9956, respectively. The adsorption rate was mainly ascribed to the intra-particle diffusion. Additionally, the Freundlich isotherm equation fitted the adsorption thermodynamic process reasonably well compared with the Langmuir adsorption model. Specifically, the correlation coefficients were 0.9614, 0.9383 and 0.9852 at 25 °C, 35 °C and 45 °C, respectively. The adsorption–desorption isotherm plot was similar to the Type V isotherm. The whole fluoride adsorption was a spontaneous endothermic reaction, and controlled by chemical adsorption. These results demonstrated that MnOOH-supported AA as an alternative to the conventional AA showed promising potential for defluoridation in drinking water treatment.

Defluoridationof drinking water by metal impregnated multi-layer green graphene fabricated from trees pruning waste

A novel adsorbent with excellent adsorptive properties for fluoride was prepared through a green and cheap synthesis route. Populus caspica pruning wastes, a cheap agri-waste material, were reduced to multi-layer green graphene (MLG) and then post-modified to aluminum/iron modified multi-layer green graphene (AMLG and IMLG). Batch experiments revealed the effect of pH (3-11), contact time (0.5-12 h), and initial fluoride concentration (5-40 mg/L). The conversion of raw material to MLG increased the specific surface area about 120 times (from 4 to 475 m²/g). Furthermore, a significant improvement in zero points of charge (pHzpc) was attained for IMLG (7.1) and AMLG (8) compared with pristine MLG (4.3). Fluoride showed superior affinity to AMLG and IMLG compared with MLG. Fluoride removal increased gradually by pH from 3 to 8 and then decreased sharply up to pH 11. The study of process dynamics demonstrated the monolayer fluoride adsorption onto AMLG and IMLG controlled by the chemisorptions. The highest predicted adsorption capacities based on the Langmuir model were 31.52, 47.01, and 53.76 mg/g for MLG, IMLG, and AMLG, respectively. Considering economic and technical feasibility presents AMLG and IMLG as a promising candidate against water contamination by elevated fluoride. Graphical abstract.

A state-of-the-art review on wastewater treatment techniques: the effectiveness of adsorption method

The world's water supplies have been contaminated due to large effluents containing toxic pollutants such as dyes, heavy metals, surfactants, personal care products, pesticides, and pharmaceuticals from agricultural, industrial, and municipal resources into water streams. Water contamination and its treatment have emerged out as an escalating challenge globally. Extraordinary efforts have been made to overcome the challenges of wastewater treatment in recent years. Various techniques such as chemical methods like Fenton oxidation and electrochemical oxidation, physical procedures like adsorption and membrane filtration, and several biological techniques have been recognized for the treatment of wastewater. This review communicates insights into recent research developments in different treatment techniques and their applications to eradicate various water contaminants. Research gaps have also been identified regarding multiple strategies for understanding key aspects that are important to pilot-scale or large-scale systems. Based on this review, it can be determined that adsorption is a simple, sustainable, cost-effective, and environmental-friendly technique for wastewater treatment, among all other existing technologies. However, there is a need for further research and development, optimization, and practical implementation of the integrated process for a wide range of applications.

Nanoadsorbents for water and wastewater remediation

Water has a wide-ranging effect on all aspects of human life, such as health and food. However, the water has often become polluted by the waste of our industrial, agricultural, and day-to-day activities due to the impact of humans. Therefore, there is an urgent need for new technologies to remove the contaminants from water and wastewater. Thence, many ways and techniques have been developed for water and wastewater remediation. Among all the methods of water and wastewater remediation techniques, the adsorption process has gained tremendous importance as a suitable water and wastewater remediation. The application of nanoadsorbent materials is a growing solution to solving this environmental problem. The unique physical and chemical properties of nanoadsorbents enhance their application due to its higher in ranking, status, and quality and beneficial in different fields compared to traditional adsorbents. Recently, numerous studies reported that the nanosorbent materials have a great and quite promising effect on water and wastewater treatment such as carbon tube, polymeric, zeolites, metal and metal oxides nanosorbents. Thus, the aim of this review article is to provide new data on the study and the improvement in this specific field, and to provide a version of the uses, benefits and restrictions of nanosorbents in water and wastewater remediation.