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The suitability and efficacy of three-dimensional (3D) graphene, including its derivatives, have garnered widespread attention towards the development of novel, sustainable materials with ecological amenability. This is especially relevant towards its utilization as adsorbents of wastewater contaminants, such as heavy metals, dyes, and oil, which could be majorly attributed to its noteworthy physicochemical features, particularly elevated chemical and mechanical robustness, advanced permeability, as well as large specific surface area. In this review, we emphasize on the adsorptive elimination of oil particles from contaminated water. Specifically, we assess and collate recent literature on the conceptualization and designing stages of 3D graphene-based adsorbents (3DGBAs) towards oil adsorption, including their applications in either batch or continuous modes. In addition, we analytically evaluate the adsorption mechanism, including sorption sites, physical properties, surface chemistry of 3DGBA and interactions between the adsorbent and adsorbate involving the adsorptive removal of oil, as well as numerous effects of adsorption conditions on the adsorption performance, i.e. pH, temperature, initial concentration of oil contaminants and adsorbent dosage. Furthermore, we focus on the equilibrium isotherms and kinetic studies, in order to comprehend the oil elimination procedures. Lastly, we designate encouraging avenues and recommendations for a perpetual research thrust, and outline the associated future prospects and perspectives.

Dye effluents released from numerous dye-utilizing industries are harmful towards the environment and living things. Consequently, existence of dye effluent in environmental water bodies is becoming a growing concern to environmentalists and civilians. A long term sustainable and efficient dye effluent treatment method should be established to eliminate this issue. Dye wastewater should be treated first before release to minimize its negative impacts towards the environment and living things. However, due to lack of information on efficient dye removal methods, it is difficult to decide on a single technique that resolves the prevailing dye effluent issue. Therefore, this paper reviews existing research papers on various biological, chemical and physical dye removal methods to find its efficiency through percentage of dye removal. Although there are numerous existing tried and tested methods to accomplish dye removal, most of them have a common disadvantage which is the generation of secondary pollution to the environment. This paper highlights enzyme degradation (biological) and adsorption (physical) dye removal as these are known as one of the most efficient dye removal techniques these days. This paper also suggests the usage of a combined adsorbent as it is envisioned that this technique has better efficiency and is able to remove dyes at a faster rate.

The introduction of aptameric ligands onto disk-monolithic adsorbent, representing a unique strategy for convective isolation of target molecules with high specificity and selectivity, is investigated for the first time. Experimental results showed that the disk monolith possessed a good permeability of 1.67 ± 0.05 × 10–14 m2 (RSD = 3.2%). The aptameric ligand density for the aptamer-modified disk monolith was 480 pmol/uL. Chromatographic analysis of the aptamer disk-monolith efficiency showed an optimum linear velocity of 126 cm/min (≈0.25 mL/min) at room temperatures 25 ± 2°C. The theoretical number of plates corresponding to the optimum linear velocity was 128.2 with an height equivalent to the theoretical plate of 0.022 mm. The disk aptamer-immobilised monolithic system demonstrated good selectivity and isolation of thrombin from non-targets.

The large capacity of wastewater production due to rapid growth of industries has resulted in limited water resources. The need to protect and conserved water resources have enforced researchers worldwide to focus on the development of an effective, economical and environmentally friendly novel materials. In this study, green synthesis of zinc oxide nanoparticles (ZnONPs) using T. diversifolia leaf extract by hydrothermal method was loaded on the surface of flamboyant pods (Delonix regia) activated carbon (FPAC). The developed ZnONPs loaded on the surface flamboyant pods activated carbon (ZnONPs-FPAC) was used successfully to remove of methylene blue (MB) from aqueous solution. The developed FPAC, ZnONPs and ZnONPs-FPAC were characterized UV–Vis spectroscopy, Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDX), Transmission electron microscope (TEM) and Brunauer-Emmett-Teller (BET) techniques. The antibacterial activity of the synthesized FPAC, ZnONPs and ZnONPs-FPAC were screened and the results revealed that ZnONPs has an excellent antibacterial activity when compared. Batch adsorption studies were conducted to investigate the influence of process parameters such as initial concentration, contact time, pH, adsorbent dosage and temperature on MB uptake. The high BET surface area of 794.48 m2/g and mesoporous ZnONPS-FPAC developed gave good adsorption capacity of 186 mg/g. Equilibrium adsorption data of MB were modelled using Langmuir, Freundlich, Temkin and Dubinin–Radushkevich (D–R) isotherm model. The adsorption of MB onto ZnONPs-FPAC was best described by Freundlich model indicating surface heterogeneity, and pseudo-second-order kinetics according to % Δ q e (normalized standard deviation), SSE (sum of square error), and R2 (coefficient of determination) values. The results of the thermodynamic suggest that the adsorption process of MB onto ZnONPs-FPAC is endotherm, favourable, spontaneous, and physical. In nature. The reusability of ZnONPs-FPAC was examined upto five cycles with no significant loss in removal efficiency. The mean free energy (E), and Enthalpy ( Δ H ) values calculated, suggested that the adsorption mechanism of MB on ZnONPs-FPAC is dominated by physical adsorption.

The pollution of water resources caused by heavy metal ions has become one of the most critical environmental issues nowadays. Recently, carbon nanomaterials have attracted immense attention as superior adsorbents for removal of heavy metal from waste effluents due to their unique structural properties and outstanding performances. Nevertheless, there are some drawbacks which hampered the use of pristine carbon nanomaterials in many applications, particularly their low solubility and dispersability. Numerous researchers have developed various surface modifications of carbon nanomaterial techniques in order to enhance its solubility, stabilities, and efficiencies. In this chapter, a comprehensive review of functionalized carbon nanomaterials, mainly carbon nanotubes and graphene-based materials, for the removal of heavy metal ions from wastewater are addressed. Lastly, challenges and future opportunities of functionalized carbon nanomaterials for the wastewater treatment applications are also included.

Enzymes are known to catalyze reactions at high efficiency, operate at milder conditions and are biodegradable. Due to enzyme limitations such as sensitivity to environmental conditions, enzyme immobilization is often used. The commonly employed immobilization methods include adsorption, entrapment, covalent attachment and cross-linking. Many research works have now focused on the immobilization of enzymes on nanoscale support due to the higher surface area to volume ratio, effective enzyme loading, significantly enhanced mass transfer efficiency and minimization of diffusional problems. The application of enzyme incorporated nanotechnology in the treatment of dye wastewater is thus, of high interest. Therefore, this paper has critically reviewed (1) the current technologies available for dye wastewater treatment; (2) different methods utilized for enzyme immobilization; and (3) the application and performance of enzyme incorporated nanotechnology for dye wastewater treatment. We identified that there is high potential for enzyme incorporated nanotechnology to be implemented in dye wastewater treatment due to the high decolorization performance (e.g. laccase immobilized on Fe3O4/SiO2 nanoparticles achieved 99% decolorization of Procion Red MX-5B in 20 min). We have also identified the key challenges faced by enzyme incorporated nanotechnology in dye wastewater treatment that includes: (i) realization of lab scale experiments to industrial applications; (ii) lack of understanding of enzymes incorporated nanotechnology; (iii) recovery of immobilized enzyme; (iv) synthesis of hybrid nanoflowers; and (v) sustainability of the nanomaterials used.