Removal of Fluorides from Aqueous Solutions Using Exhausted Coffee Grounds and Iron Sludge

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.

Evaluation of a Smectite Adsorption-Based Electrostatic System to Decontaminate F− Rich Thermal Waters

Several studies have shown the presence of fluoride levels much higher than the 1.5 mg/L threshold concentration recommended by WHO in the spring waters and wells of the Ethiopian Rift Valley. Available defluoridation techniques can be costly, present complicated technical aspects, and show limited effectiveness. Therefore, it is necessary to devise innovative, sustainable, and effective solutions. This study proposes an alternative method of intervention to the known techniques for removing fluoride from water, particularly suitable for smaller rural communities. In particular, in this work, the possibility to use electromagnetic fields as a physical method for removing the excess fluoride was investigated. The study was carried out by developing a multiphysics model used for studying and envisaging the design of a device. In this framework, the combination of this approach with the use of highly reactive smectite clay was numerically studied. The results obtained, although preliminary, indicate that the proposed system could significantly impoverish the waters of the Rift Valley from fluoride, with the consequence of obtaining a resource suitable for human consumption, in particular for rural communities. However, further theoretical investigations and experimental phases will be necessary to achieve the desired results.

Bioaccumulation of Fluoride in Plants and Its Microbially Assisted Remediation: A Review of Biological Processes and Technological Performance

Fluoride is widely found in soil–water systems due to anthropogenic and geogenic activities that affect millions worldwide. Fluoride ingestion results in chronic and acute toxicity, including skeletal and dental fluorosis, neurological damage, and bone softening in humans. Therefore, this review paper summarizes biological processes for fluoride remediation, i.e., bioaccumulation in plants and microbially assisted systems. Bioremediation approaches for fluoride removal have recently gained prominence in removing fluoride ions. Plants are vulnerable to fluoride accumulation in soil, and their growth and development can be negatively affected, even with low fluoride content in the soil. The microbial bioremediation processes involve bioaccumulation, biotransformation, and biosorption. Bacterial, fungal, and algal biomass are ecologically efficient bioremediators. Most bioremediation techniques are laboratory-scale based on contaminated solutions; however, treatment of fluoride-contaminated wastewater at an industrial scale is yet to be investigated. Therefore, this review recommends the practical applicability and sustainability of microbial bioremediation of fluoride in different environments.

Comparison of Water Defluoridation Using Different Techniques

Fluoride pollution in subsurface water is a significant problem for different nations across the world because of the intake of excessive fluoride caused by the drinking of the contaminated subsurface. Water pollution by flouride can be attributed to the natural and human-made agents. Increased levels of fluoride in drinking water may result in the irretrievable demineralization of bone and tooth tissues, a situation called fluorosis, and other disorders. There has long been a need for fluoride removal from drinking water to make it safe for human use. Among the various fluoride removal methods, adsorption is the method most popularly used due to its cheap cost, ease of utilization, and being a scalable and simple physical technique. According to the findings of this study, the highest concentration of fluoride (0.1–15.0 mg/L) was found in Sweden and the lowest (0.03–1.14 mg/L) in Italy. We collected the values of adsorption capacities and fluoride removal efficiencies of various types of adsorbents from valuable released data accessible in the literature and exhibited tables. There is still a need to find the actual possibility of using biosorbents and adsorbents on a commercial scale and to define the reusability of adsorbents to decrease price and the waste generated from the adsorption method. This article reviews the currently available methods and approaches to fluoride removal of water.