Recent advances in nanocomposites and nano-adsorbents for heavy metal and dye removal from water

The escalating contamination of aquatic systems by heavy metals and synthetic dyes poses severe risks to ecosystems and human health due to their toxicity, persistence, and bioaccumulation. Conventional wastewater treatment technologies such as chemical precipitation, membrane filtration, ion exchange, and oxidation often suffer from high operational costs, incomplete removal, secondary pollution, and limited efficiency at low contaminant concentrations. In this context, adsorption has emerged as a cost-effective and versatile alternative, particularly with the advent of nanotechnology. This review critically examines recent advances in nanocomposites and nano-adsorbents developed for the removal of priority heavy metals (As, Cd, Cr, Cu, Hg, Pb) and dyes from aqueous media. Various classes of nanoadsorbents, including carbon-based materials (carbon nanotubes, graphene and its derivatives), silica-based nanomaterials, zeolites, polymer-based nanocomposites, metal–organic framework (MOF) composites, and molecularly imprinted polymers, are systematically discussed. The adsorption mechanisms governing contaminant uptake, such as electrostatic interactions, surface complexation, ion exchange, precipitation, physisorption, and chemisorption, are elucidated, along with the influence of operational parameters, including pH, contact time, temperature, and sorbent dosage. Adsorption performance is evaluated using widely applied isotherm models (Langmuir, Freundlich, Temkin, Dubinin–Radushkevich), kinetic models (pseudo-first-order, pseudo-second-order, intraparticle diffusion), and thermodynamic analyses. Reported results demonstrate that many nano-adsorbents achieve removal efficiencies exceeding 90%, exhibit high adsorption capacities, show favorable kinetics, and possess good regeneration potential. The review highlights current limitations and future research directions needed to translate nanoadsorbent technologies from laboratory studies to sustainable, large-scale water remediation applications. • Heavy metals and dyes pose persistent, toxic risks to water systems, demanding efficient remediation beyond conventional physicochemical methods. • Adsorption emerges as the most viable technique due to low cost, simplicity, and high removal efficiency for trace contaminants. • Nanoadsorbents and nanocomposites achieve >90% removal via tailored physisorption and chemisorption mechanisms. • Carbon-, silica-, polymer-, zeolite-, and MOF-based nanomaterials show high capacities, fast kinetics, and regenerability. • Sustainable design, stability, and scalability remain key challenges for real-world water treatment deployment.