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

Alginate-based materials as adsorbent for sustainable water treatment

With the encroaching issue of water pollution, the use of involved chemicals to remove pollutants from water is not only a risk of chemical contamination, a potential hazard to the environment and human health but also requires significant investment in managing and improving the chemicals. Therefore, alginate as one of the nanomaterial-adorned polysaccharides-based entity that usually extract from brown algae has been used as novel and more efficient catalysts in the removal of a variety of aqueous pollutants from wastewater, including ionic metals and organic/inorganic pollutants by using the adsorption techniques. Adsorption is a technique used in water treatment where non-polar or particles less soluble in water are stuck to the surface of the adsorbent and therefore purifying it. An example of pollutant typically removed via this method is an organic dye. Alginate-based composites due to their ability to bind to metals like Cd, Au, Cu, Fe, Ni, Pb, and Zn, are a common low-cost and highly effective adsorbents used to remove heavy metals, industrial paints, pesticides, and antibiotics. This review focusses on augmenting the recent status, challenges, and further prospects in alginate-based materials for their potential role exclusively in wastewater treatment, including their modification as adsorbents and their adsorption behaviors. Various applications of alginate-based adsorbent are showcased and tabulated their role in treatment of diverse range of pollutants. It can be concluded that the role of alginate in wastewater treatment is indispensable in the future with its biodegradability, low cost, stability, and high-water permeability properties. However, some challenges need to be identified and overcome to ensure the application of alginate in wastewater treatment can be widely used throughout the world, especially in Malaysia, a country with an abundance of water.

Enhanced Pollutant Removal and Antifouling in an Aerobic Ceramic Membrane Bioreactor with Bentonite for Pharmaceutical Wastewater Treatment

This study examined the impact of adding bentonite clay (concentration of 1.5 to 10 g/L) to a pilot-scale aerobic ceramic membrane bioreactor (AeCMBR) for treating pharmaceutical wastewater (PhWW). The hydraulic retention time (HRT) was maintained at 24 h; the dissolved oxygen was between 2 mg/L (on) and 4 mg/L (off) throughout operation. Organic and nitrogen pollution removal rates and heavy metal (Cu, Ni, Pb, Zn) reduction rates were assessed. The chemical oxygen demand (COD) removal efficiency exceeded 82%. Adsorption improved ammonia (NH4+) removal to 78%; the addition of 5 g of bentonite resulted in a 38% improvement compared with the process without bentonite. The average nitrate concentration decreased from 169.69 mg/L to 43.72 mg/L. The average removal efficiencies for Cu, Ni, Pb and Zn were 86%, 68.52%, 46.90% and 56.76%, respectively. Bentonite at 5 g/L significantly reduced membrane fouling. The cost-benefit analysis enabled us to predict that the process will meet the multiple objectives of durability, treatment performance and economic viability. The combination of an AeCMBR and bentonite adsorption has proven to be a valuable solution for treating highly polluted wastewater.

Biocomposite Material Based on Lactococcus lactis sp. Immobilized in Natural Polymer Matrix for Pharmaceutical Removal from Aqueous Media

Ecosystems are negatively impacted by pharmaceutical-contaminated water in different ways. In this work, a new biosorbent obtained by immobilizing Lactococcus lactis in a calcium alginate matrix was developed for the removal of pharmaceuticals from aqueous solutions. Ethacridine lactate (EL) was selected as the target drug. Lactococcus Lactis biomass was chosen for the biosorbent synthesis for two reasons: (i) the microbial biomass used in the food industry allows the development of a low-cost biosorbent from available and renewable materials, and (ii) there is no literature mentioning the use of Lactococcus Lactis biomass immobilized in natural polymers as a biosorbent for the removal of pharmaceuticals. The characterization of the synthesized biosorbent named 5% LLA was performed by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) analysis. Additionally, particle size and the point of zero charge were established. Batch biosorption investigations showed that using 5% LLA at an initial pH of 3.0 and a biosorbent dose of 2 g/L resulted in up to 80% EL removal efficiency for all EL initial concentrations (20-60 mg/L). Four equilibrium isotherms, given in the order of Redlich-Peterson > Freundlich > Hill > Temkin, are particularly relevant for describing the experimental data for EL biosorption on the 5% LLA biosorbent using correlation coefficient values. Kinetic parameters were determined using kinetic models such as pseudo-first-order, pseudo-second-order, Elovich, Avrami and Weber-Morris. The pseudo-second-order kinetics model provides the greatest fit among the evaluated equations, with correlation coefficients greater than 0.99. According to the study's findings, the developed biocomposite is a potentially useful material for the removal of pharmaceuticals from aqueous matrices.

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.