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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. [ABSTRACT FROM AUTHOR]

Pepsin is a protease used in many different applications, and in many instances, it is utilized in an immobilized form to prevent contamination of the reaction product. This enzyme has two peculiarities that make its immobilization complex. The first one is related to the poor presence of primary amino groups on its surface (just one Lys and the terminal amino group). The second one is its poor stability at alkaline pH values. Both features make the immobilization of this enzyme to be considered a complicated goal, as most of the immobilization protocols utilize primary amino groups for immobilization. This review presents some of the attempts to get immobilized pepsin biocatalyst and their applications. The high density of anionic groups (Asp and Glu) make the anion exchange of the enzyme simpler, but this makes many of the strategies utilized to immobilize the enzyme (e.g., amino-glutaraldehyde supports) more related to a mixed ion exchange/hydrophobic adsorption than to real covalent immobilization. Finally, we propose some possibilities that can permit not only the covalent immobilization of this enzyme, but also their stabilization via multipoint covalent attachment. • Pepsin is an aspartyl protease with intense applications in different areas. • The enzyme has a low IP, and only one Lys group. • Papain is unstable at neutral-alkaline pH values. • This makes pepsin immobilization a very complex goal. • Enzyme immobilization trials and their use are reviewed. [ABSTRACT FROM AUTHOR]

The world is facing environmental pollution and is in an alarming situation due to industrialization and urbanization. Especially, industrial wastewater discharge is causing serious pollution in the environment (water, soil, and air) and has become a challenge for researchers and scientists. Wastewater contains heavy metals like Cu, Ni, Cr, Pb, and Ar and causes toxicity in living beings and the environment. In this review, the sources of heavy metals and their toxicological effects on the environment have been reviewed. Various remediation techniques such as reverse osmosis, chemical precipitation, and ultrafiltration are being used for the treatment of wastewater, but still are limited in their efficiencies, residues, cost, and versatility. In this study, the most promising wastewater treatment technique, the physic-chemical technique, has been reviewed along with its working mechanism and efficiency. Further, the pros and cons of this technique and sub-techniques have also been reviewed to provide a basic understanding to beginners and a pathway to experts in the selection of better techniques. [ABSTRACT FROM AUTHOR]

This article reviews the historical uses of and current research into ion exchange for the removal of cesium from defense-related nuclear waste streams. Emphasis is placed on key attributes of the two current leading ion exchangers for Cs removal: spherical resorcinol-formaldehyde, an elutable organic resin, and crystalline silicotitanate, a non-elutable crystalline solid. An understanding of the successes, issues, and limitations of past ion exchange experience may be helpful in better understanding current ion exchanger use. Emphasis is placed on Cs capacity, exchange kinetics, stability, and column hydrodynamics for processing alkaline wastes as well as the final waste forms of the ion exchangers. [ABSTRACT FROM AUTHOR]

The occurrence of pharmaceutical products (PPs) within environmental compartments challenges the scientific community and water treatment operators to find suitable and practicable removal solutions. Clay minerals are among the oldest and cheapest adsorbents used for the removal of organic and inorganic pollutants. However, despite their significant adsorption properties, little is known about their potential to remove organic contaminants such as pharmaceutical products from wastewater effluents. Hence, based on the latest published articles this review aims to standardize the adsorption properties of clay minerals for the removal of PPs. Specifically, the charge state of PPs appears to play a key role in their adsorption mechanism. In order to overcome the limitations of batch experiments (i.e. idealized solutions, static conditions) and design of a field solution, the impact of external parameters on the adsorption capacities of clay minerals is reviewed. The effect of thermal treatment and acid activation of clay minerals is also assessed in order to better understand the consequences of such modifications on the adsorption properties of clay-based adsorbents. Finally, even if most authors agree on the potential of clay-based adsorbents for the removal of PPs from wastewater, there remain significant gaps in the existing literature that need to be filled, with the aim of forecasting the real potential of clay-based treatment for the removal of pharmaceutical products at industrial scale. [ABSTRACT FROM AUTHOR]