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.

The controlling hydrogeochemical processes of an intermontane aquifer in central Mexico were identified through multivariate statistical analysis. Hierarchical cluster (HCA) and k-means clustering analyses were applied to Na⁺, K⁺, Ca²⁺, Mg²⁺, F⁻, Cl⁻, SO₄²⁻, NO₃⁻, HCO₃⁻, As, pH and electrical conductivity in 40 groundwater samples collected from shallow and deep wells, where As and F⁻ are contaminants of concern. The effectiveness of each hierarchical and k-means clustering method in explaining solute concentrations within the aquifer and the co-occurrence of arsenic and fluoride was tested by comparing two datasets containing samples from 40 and 36 wells, the former including ionic balance outliers (>10%). When tested without outliers, cluster quality improved by about 5.4% for k-means and 7.3% for HCA, suggesting that HCA is more sensitive to ionic balance outliers. Both algorithms yielded similar clustering solutions in the outlier-free dataset, aligning with the k-means solution for all 40 samples, indicating that k-means was the more robust of the two methods. k-means clustering resolved fluoride and arsenic concentrations into four clusters (K1 to K4) based on variations in Na⁺, Ca²⁺, As, and F⁻. Cluster K2 was a Na-HCO₃ water type with high concentrations of As and F. Clusters K1, K3, and K4 exhibited a Ca-HCO₃, Na-Ca-HCO₃, and Ca-Na-HCO₃ water types, respectively, with decreasing As and F concentrations following the order K2 > K3 > K1 > K4. The weathering of evaporites and silicates and Na-Ca ion exchange with clays were the main processes controlling groundwater geochemistry. The dissolution of felsic rocks present in the aquifer fill is a likely source of As and F⁻, with evaporation acting as an important concentration factor.

Domestic and industrial wastewaters are complex matrices that contain a large variety of pollutants. Consequently, the conventional processes at wastewater treatment plants (WWTPs) cannot remove these. These pollutants remain in the effluent and are discharged into different environmental compartments worldwide, generating a range of negative impacts on the environment and human health. In this chapter, general features and the application of the most common advanced oxidation processes (AOPs) for the treatment of domestic and industrial wastewater are described. Also, the feasibility of scaling up advanced oxidation processes for pollutants removal (emerging and conventional) and the advantages and complications of each type of advanced oxidation process when applied to wastewater treatment (domestic and industrial) are shown.

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.