Alginate/geopolymer hybrid beads as an innovative adsorbent applied to the removal of 5-fluorouracil from contaminated environmental water

Biopolymer-based beads for the adsorptive removal of organic pollutants from wastewater: Current state and future perspectives

Among biopolymer-based adsorbents, composites in the form of beads have shown promising results in terms of high adsorption capacity and ease of separation from the effluents. This review addresses the potential of biopolymer-based beads to remediate wastewaters polluted with emerging organic contaminants, for instance dyes, active pharmaceutical ingredients, pesticides, phenols, oils, polyaromatic hydrocarbons, and polychlorinated biphenyls. High adsorption capacities up to 2541.76 mg g-1 for dyes, 392 mg g-1 for pesticides and phenols, 1890.3 mg g-1 for pharmaceuticals, and 537 g g-1 for oils and organic solvents have been reported. The review also attempted to convey to its readers the significance of wastewater treatment through adsorption by providing an overview on decontamination technologies of organic water contaminants. Various preparation methods of biopolymer-based gel beads and adsorption mechanisms involved in the process of decontamination have been summarized and analyzed. Therefore, we believe there is an urge to discuss the current state of the application of biopolymer-based gel beads for the adsorption of organic pollutants from wastewater and future perspectives in this regard since it is imperative to treat wastewater before releasing into freshwater bodies.

A critical review of sodium alginate-based composites in water treatment

The global freshwater crisis is a pressing issue, especially in areas with little rainfall and inner continental regions. The growing attention to water scarcity has induced increased interest in research on advanced water treatment technologies. As an abundant bioactive material in nature, sodium alginate (SA) has been widely used in water management due to its outstanding water absorption and holding ability, reversible swelling property, and pollutant adsorption performance. Building on this, progress made in using various modified forms of SA to access clean water is addressed in this review. Covering studies concern the adsorption and separation of pollutants in wastewater by SA-based absorbents and freshwater harvesting by SA-based collectors. This review explores SA-based composites' composition-structure-construction designs and emphasizes the impact of materials like inorganic materials, functional polymers, and porous matrices and how they can be exploited for water treatment. It also highlights the mechanisms of contaminants adsorption and freshwater desorption of SA-based composites. Finally, the shortcomings and future orientation of SA-based composites are proposed, including performance optimization, structural modification, application expansion, and mechanism in-depth investigation. This review aims to offer a theoretical basis and technical guidance for the use of natural materials to respond to the shortage of freshwater resources.

Fluorescent composite beads: An advanced tool for environmental monitoring and harmful pollutants removal from water

The quality and safety of water sources have been significantly impacted by various pollutants, including trace elements. To address this concern, this study utilized composite beads made of alginate and carbon quantum dots (CDs) for detecting and removing As(III) and Se(IV) ions in tap water. Fluorescent CDs were hydrothermally synthesized and incorporated into an alginate-Ca2+ matrix through a straightforward procedure. Characterization analyses revealed distinct properties of the composite beads, containing varying amounts of CDs, compared to the pristine beads. Optimal adsorption parameters (30 mg of adsorbent, 10 mg/L of initial pollutant concentration, 35 °C, and 180 min of contact time) for the beads containing 30 w/w-% of CDs (Alg@CDs30) were determined through a fractional factorial design. These composite beads exhibited the highest adsorption capacity for both metals, achieving a removal rate of 94.5% for As(III) and 98.0% for Se(IV) in tap water. Kinetic and isothermal analyses indicated that the adsorption of both metals on Alg@CDs30 involves a combination of chemisorption and diffusion processes. Recycling experiments demonstrated that the composite beads could be reused up to 20 times without a noticeable loss of adsorption efficiency. Regarding the sensing property, our experiments revealed a significant reduction in the fluorescence emission intensity of Alg@CDs30 upon interaction with As(III) and Se(IV), confirming its ability to detect both ions in tap water, with limits of detection (LOD) of 2.6 ± 0.5 μg/L for As(III) and 1.1 ± 0.2 μg/L for Se(IV). The alginate-Ca2+ matrix s contributed to the stability of the CDs' fluorescence. These results confirm the potential of Alg@CDs beads as effective tools for the simultaneous monitoring and removal of hazardous metal ions from real water samples.