Recent Advances in Nanomaterials: Classification, Synthesis and Environmental Remediation

Nanomaterials have attracted considerable interest because their nanoscale dimensions and tunable surfaces can produce physicochemical properties that differ from those of bulk materials. This review examines advances in nanomaterial classification, synthesis, physicochemical characteristics and environmental remediation. It considers dimensional classifications from zero- to three-dimensional structures, together with distinctions based on composition, origin, morphology, porosity and electrical properties. Top-down, bottom-up, hybrid and green synthesis routes are discussed in relation to particle size, morphology, surface chemistry and functional performance. Particular attention is given to metal-based and magnetic nanoparticles, graphene and other carbon-based materials, photocatalytic oxides, metal–organic frameworks and covalent organic frameworks. Their reported environmental applications include the adsorption of inorganic and organic pollutants, redox transformation, photocatalytic degradation, antimicrobial treatment, selective contaminant capture and magnetic recovery. The review also examines nanocomposites and surface-functionalised systems that combine complementary properties for pollutant removal and material separation. Although laboratory studies indicate considerable potential, practical implementation remains constrained by particle aggregation, metal-ion leaching, limited regeneration, uncertain long-term stability, possible ecotoxicity and difficulties in reproducible scale-up. Environmental factors, including competing ions, natural organic matter and varying pH, may further influence remediation performance. The review consequently identifies the importance of standardised evaluation, recoverable material designs, sustainable synthesis, field-relevant testing and life-cycle assessment. Balancing treatment performance with environmental safety and material reusability remains central to the responsible development of nanomaterial-based remediation technologies.