Per- and polyfluoroalkyl substances (PFASs) are commonly used in many consumer and industrial products. However, their resulting widespread release into aqueous environments and their potential toxicities to organisms have raised significant environmental concern. Among the various approaches to the removal of PFAS contaminants, adsorption has proven to be highly effective, especially when carbonaceous nanomaterials (CNMs) are used as the adsorbent. Nonetheless, the interfacial adsorption of PFASs on CNMs is affected by many factors. In this work, the adsorption behaviors of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS), two highly representative PFASs, on different CNMs are reviewed. We also examine the mechanisms of PFOA and PFOS adsorption on CNMs, including electrostatic and hydrophobic interactions, ligand exchange and hydrogen bonding. Due to the significant influence of hydrophobic interactions on adsorption, CNMs rich in oxygen-containing functional groups will result in weaker PFAS adsorption than achieved using pristine materials. The important contribution of nanobubbles to hydrophobic interactions is considered herein. Overall, this work contributes to a better understanding of the adsorption affinity of PFASs on CNMs in water environments. Moreover, it provides the systematic theoretical support that is needed for the more effective use of CNMs in the removal of PFASs from aqueous systems.

Graphene-based composite aerogel doped with other low-cost materials can reduce the cost and promote the use in water treatment. This work prepared ball-milled biochar/reduced graphene oxide aerogel (BC/rGA) using GO and low-cost ball-milled biochar (BC) in a certain proportion with the freeze-thawing technique and sol–gel method, and applied BC/rGA on the Cr(VI) removal from aquatic environments. The characterization results showed that aerogel had a honeycomb briquette three-dimension (3D) and mesoporous structure with interconnected pores, and proved the preparation progress of aerogel in principle. Compared with GO, rGA and BC/rGA had better adsorption performance with 3D structure and well-developed pores, and BC/rGA with the mixture ratio of BC and GO of 1:4 was more appropriate. The adsorption kinetics data of rGA and BC/rGA_(1:4) were fitting well with the pseudo-second-order model (R² > 0.951), and the isotherm adsorption results were fitting the Langmuir model well (R² > 0.974). The results demonstrated that the adsorption process was monolayer and endothermic adsorption involving chemisorption. Additionally, the adsorption capacities of rGA and BC/rGA_(1:4) at solution pH 2 were 3.71 and 3.89 times greater than those at solution pH 8, respectively. High background ion strength and low temperature slightly inhibited the adsorption of Cr(VI) by both rGA and BC/rGA_(1:4). The adsorption mechanisms of Cr(VI) on rGA and BC/rGA_(1:4) were electrostatic interaction, reduction and ion exchange. The use of BC/rGA could reduce the cost and promote the green reuse of agricultural waste. Overall, BC/rGA could be used as a promising green adsorbent alternative for the feasible treatment of heavy metal contaminated water. Graphical Abstract

Perfluorooctanoic acid (PFOA) persists in the environment for a long time due to its stable physical and chemical properties, and it is harmful to the environment and biological system. In order to effectively remove PFOA from aqueous solution, Cu nanoparticles and fluorine-modified graphene aerogel (Cu/F-rGA) were fabricated by the microbubble template method. Compared with unmodified aerogels (rGA), the adsorption rate of PFOA on Cu/F-rGA was enhanced 2.68-fold. These significant improvements were assumed to benefit from the ligand exchange reaction and hydrophobic and F–F interactions. The regeneration of Cu/F-rGA maintained 73.26% with ethanol as the desorption solvent after 10 times adsorption–desorption. The fitting results of the statistical physics model showed that PFOA tended to be parallel to the adsorption site at low temperature and perpendicular at high temperature. The number of PFOA molecules connected to each adsorption site was 0.53 to 1.41, and the number of adsorption layers of PFOA on the Cu/F-rGA was between 1.63 and 2.51. Compared with the response surface methodology and artificial neural network, an adaptive neuro-fuzzy inference system had more accurate analysis and prediction results. These results provide an effective and alternative strategy to remove PFOA from aqueous solution with environment-friendly consumption.