Fluoride concentration in drinking water has become a global challenge due to its effects on the human body. While small level (1–1.5 mg·L⁻¹) strengthens enamel and bone formation, higher concentration (>1.5 mg·L⁻¹) leads to dental and skeletal fluorosis. Globally, over 200 million people drink fluorinated water and more than 70 million people suffer from fluoride related diseases. As such, treating fluorinated water through the adsorption method has been the most ideal method due to its low cost, availability of adsorbents, pollution-free treated water and environmental friendliness. This review article summarizes the use of alumina and aluminum-based composites for fluoride removal. These adsorbents have been classified into three categorize based on their modifications thus: raw alumina-based adsorbents/geomaterials, activated alumina and modified activated alumina and aluminum-based adsorbents. Minimal activation (300–400 °C) and modification improve their overall adsorption capacity by increasing their specific surface area (250–1000 m²·g⁻¹) which ultimately improves the pore size and volume. Also, some can remediate as high as 450 mg·g⁻¹ of fluoride at a wider pH range (3–12) with stable thermodynamic properties. This grants them the ability to easily form aluminumfluoro complexes (AlF_x) for enhanced adsorption at near-neutral pH (5.5–6.5) making them the most ideal adsorbents.

The studies on microplastics are significant in the world. According to the literature, microplastics have greatly specific surface areas, indicating high adsorption capacities for highly toxic pollutants in aquatic and soil environments, and these could be used as adsorbents. The influencing factors of microplastic adsorption, classification of microplastics, and adsorption mechanisms using microplastics for adsorbing organic, inorganic, and mixed pollutants are summarized in the paper. Furthermore, the influence of pH, temperature, functional groups, aging, and other factors related to the adsorption performances of plastics are discussed in detail. We found that microplastics have greater advantages in efficient adsorption performance and cost-effectiveness. In this paper, the adsorptions of pollutants by microplastics and their performance is proposed, which provides significant guidance for future research in this field.