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Waste cooking oil (WCO) appears to be a potential carbonaceous source for synthesizing graphene sand composite (GSC) adsorbent in removing pollutants. This study presents a green synthesis method of GSC using WCO as a sustainable carbon source for the synthesis of GSC through the thermal graphitization method. Characterization analysis conducted on GSCWCO verified the successful coating of WCO onto the sand surface and conversion to graphene, which possessed distinct functional groups and features of graphene materials. GSCWCO adsorbent effectiveness in removing Congo Red dye through batch adsorption was studied under the influence of different initial concentrations (20 to 100 mg/L), and the optimum pH (pH 2 to 10), contact time (5 to 240 min), and temperature (25 to 45 °C) were investigated. The GSCWCO showed removal rates of 91.5% achieved at an initial dye concentration of 20 mg L−1, 1.0 g of adsorbent dosage, a temperature of 25 °C, and 150 min of contact time. The GSCWCO exhibited a maximum capacity of 5.52 mg g−1, was well-fitted to the Freundlich isotherm model with an R2 value of 0.989 and had an adsorption mechanism that followed the pseudo-second-order kinetic model. Negative values of enthalpy (ΔH) and Gibbs free energy (ΔG) revealed that CR adsorption onto GSCWCO was a spontaneous and exothermic process. The presence of functional groups on the surface of GSCWCO with such interactions (π–π attractive forces, hydrophobic forces, and hydrogen bonding) was responsible for the anionic dye removal. Regeneration of GSCWCO adsorbent declined after four cycles, possibly due to the chemisorption of dyes with GSC that resulted in inefficient adsorption. Being a waste-to-wealth product, GSCWCO possessed great potential to be used for water treatment and simultaneously benefited the environment through the effort to reduce the excessive discharge of WCO.

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Environmental pollution has threatened the life of all living organisms on earth. The removal of pollutants from wastewater and contaminated water is desired to prevent the pollution issues from becoming worse. In this context, polymer-based nanocomposites have been developed and emerged as one of the advanced materials that can be used to solve the environmental pollution challenges. This composite material is produced by combining nanomaterials with polymers and usually appears in the form of membranes, adsorbents, hydrogels, and aerogels. These polymer-based nanocomposites possess improved characteristics and properties compared to the original individual material. Subsequently, the pollutants removal capability of the polymer-based nanocomposites has been enhanced significantly, with some even attaining new functionalities such as antibacterial and photocatalytic. This chapter features the development and application of four major classes of polymer-based nanocomposites (membrane, adsorbent, hydrogel, and aerogel) for environmental remediation. Various examples and latest findings are discussed, which provides up-to-date information for readers interested in this topic.