The intensifying global challenges of environmental degradation, escalating energy demands, and unsustainable waste accumulation necessitate the exploration of alternative, high-value biomass resources. Algal biomass has emerged as a uniquely versatile and sustainable candidate, offering transformative potential across a broad range of industrial and environmental sectors. This review comprehensively evaluates the recent advancements and multidisciplinary applications of algae, with a strong emphasis on their distinctive chemical composition, bioactive compounds, and environmental adaptability. The novelty of this review lies in its integrative scope, which spans from algae cultivation, production, and trade to cutting-edge extraction technologies for bioactive constituents. Furthermore, the review presents a detailed exploration of algae’s functionality as a feedstock for biofuels, pharmaceuticals, sustainable agriculture, bioplastics, green chemistry, and water treatment, positioning it as a cornerstone in the development of the blue economy. By critically analyzing both conventional and innovative applications, this work contributes to a deeper understanding of algae’s strategic role in shaping a sustainable and resilient bioeconomy.

Magnetic polymer nanocomposites (MPNCs) have attracted considerable attention as advanced multifunctional materials for water purification due to their high adsorption capacity, magnetic recoverability, and excellent reusability. This review presents a comprehensive overview of recent developments in the synthesis, characterization, and environmental applications of MPNCs for wastewater treatment. Particular emphasis is placed on the principal synthesis strategies, including in situ and ex situ approaches, and their influence on nanoparticle dispersion, interfacial interactions, and the physicochemical properties of the resulting nanocomposites. The review covers the most widely investigated magnetic nanomaterials, such as Fe₃O₄, γ-Fe₂O₃, CoFe₂O₄, ZnFe₂O₄, and other ferrites, incorporated into natural and synthetic polymer matrices including chitosan, cellulose, alginate, polyaniline, polypyrrole, poly(vinyl alcohol), and polystyrene. Advanced characterization techniques, including X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM/TEM), Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), vibrating sample magnetometry (VSM), and superconducting quantum interference device (SQUID) measurements, are discussed to evaluate the structural, chemical, thermal, and magnetic properties of these hybrid materials. The adsorption performance and underlying mechanisms of MPNCs for the removal of heavy metals, dyes, pharmaceutical compounds, organic pollutants, and oil contaminants are critically analyzed, highlighting the roles of polymer functionalization, nanocomposite architecture, and magnetic separation in enhancing treatment efficiency and reusability. In addition, the contribution of density functional theory (DFT) to understanding adsorption mechanisms and guiding the rational design of high-performance adsorbents is reviewed. Finally, current challenges and future perspectives, including green synthesis, multifunctional and stimuli-responsive materials, scalable manufacturing, and industrial implementation, are discussed. This review provides a comprehensive framework for the design and development of next-generation magnetic polymer nanocomposites for sustainable water remediation applications.