Accessibility to sufficient clean and fresh water for human consumption is one of the most important issues worldwide, and thus extensive research has been conducted to address this issue. Nowadays, nanotechnology has become a fast-growing technology due to the features of engineered nanomaterials (NMs). Recent advances in nanotechnology provide leapfrogging approaches for contaminant removal by overcoming the shortcomings of existing treatment technologies and offering cost-effective treatment methods with high capacity. The goal of this review is to provide an in-depth overview of some of the recent advances in the development of functional NMs used for the environmental remediation of a variety of pollutants. In this critical review, a new and different categorization of NMs including carbonaceous nanostructures, nanoparticles and nanocomposites is provided. The properties, removal mechanism of pollutants by different NMs, advantages and disadvantages of each group of NMs and their recent development in water, wastewater and groundwater treatment are reviewed and scrutinized. Results revealed that among the different NMs, graphene and its derivatives (e.g. graphene oxide, reduced graphene oxide, graphene-based metals and metal oxide) with excellent environmental compatibility and selectivity, large surface area and high purity, exhibit great absorption capacity because they trap electrons, preventing their recombination. Due to the abundance, unique electronic structure, high porosity, stability, efficient light absorption and suitable charge transfer properties of metal oxides, they are mainly used as catalysts in photocatalytic reactions. The discovery of oxy-acids is another important finding in recent years. In some cases, oxy-acids exhibit higher photoactivity and surface areas and cost less than metal oxides. Thus, to benefit from the advantages of different NMs, binary or ternary composites of metal, metal oxides, oxy-acids and others have been developed. This strategy has led to an increase in surface area and a decrease in band gap, which can enhance environmental contaminant cleanup. Moreover, numerous recent studies have extensively highlighted their results and key findings. Finally, this review will present new horizons for the purposeful application of NMs in remediation by considering the associated challenges, including risk, toxicity and their fate in the environment.

This study investigated the performance of UVC/H₂O₂ and UVC processes for the degradation and mineralization of ceftriaxone as an antibiotic. The highest ceftriaxone degradation was obtained at a solution pH of 5 and H₂O₂ concentration of 10 mg/L. The apparent rate constant of ceftriaxone degradation was found to be 0.0302, 0.0165, and 0.0065 min⁻¹ in the UVC/H₂O₂ process for the initial ceftriaxone concentrations of 5, 10, and 20 mg/L, respectively. Degradation and mineralization efficiencies of ceftriaxone was obtained to be 100% and 58%, respectively, in UVC/H₂O₂ process at reaction time of 120 min, whereas only 61% and 2.5% of ceftriaxone could be degraded and mineralized by UVC. The synergistic effect of UVC/H₂O₂ was found to be 35%. The presence of anionic species improved the photolysis efficiency which degraded ceftriaxone from 61 to 83%, while, in the UVC/H₂O₂ process, ability degradation declined from 100 to 70%. The efficiency of UVC/H₂O₂ and UVC process was not greatly affected in real tap water. Besides, the reduction patterns in the UVC/H₂O₂ and UVC processes were better described by pseudo-first- and second-order kinetics model with a reaction rate constant of 0.0165 and 0.0012 min⁻¹, respectively. The rate constant of ceftriaxone degradation in the UVC/H₂O₂ process and at the presence of radical scavenger was found to be around 3.3 times lower than the one in its absence.

Rapid population growth and widespread industrialization are the main contributing factors to the increasing contamination of the world’s diminishing freshwater resources. This work investigates Fe/TiO₂ as an efficient and sustainable photocatalyst for treating organic micropollutants in water. The photocatalysts prepared by these mechanochemical methods used a high-energy ball milling technique to manipulate Fe/TiO₂’s structural, optical, and catalytic properties for the photo-oxidation of 2,4-Dichlorophenol (2,4-DCP). Doping with iron effectively reduced the band gap of rutile TiO₂ from 3 to 2.22 eV. By reducing the ball/powder ratio from 34 to 7, the removal efficiency of 2,4-DCP increased from 65.2 to 84.7%. Measuring the TOC indicated 63.5 and 49.4% mineralization by Fe/TiO₂-7 and rutile TiO₂, respectively, after 24 h. The energy yields for the Fe/TiO₂ and rutile TiO₂ were 0.13 and 0.06 g 2,4-DCP/kW h, respectively.

The family of carbon nitrides (CNs), including compounds such as C2N, C3N, C3N2, C3N3, C3N4, C3N5, C3N6, C3N7, C4N, C4N3, C5N, C5N2, C6N7, C6N9H3, and C9N5H3, has garnered growing attention for their tunable optoelectronic properties and applications in photocatalysis. While g-C3N4 remains the most widely studied member, emerging CN phases offer distinct structural motifs, nitrogen configurations, and electronic band structures that may outperform conventional systems. This review provides a comprehensive analysis of photoactive CN materials, with a special emphasis on less-explored CxNy compounds. It highlights their synthesis routes, classification based on active sites and solid-state behavior, and structural characteristics such as pore topologies, surface terminations, and nitrogen doping patterns. Furthermore, the diverse roles of CNs in photocatalysis as electron donors, sensitizers, redox mediators, and co-catalyst supports are critically evaluated. By correlating structure–property–performance relationships, this review offers a framework to guide the rational design of advanced CN-based photocatalysts for solar-driven energy conversion.