Carboxylated carbon nanotubes-graphene oxide aerogels as ultralight and renewable high performance adsorbents for efficient adsorption of glyphosate

Environmental context Glyphosate is a highly effective and widely used organophosphorus pesticide, but its residues can harm the environment and human health. We report a carboxylated carbon nanotubes-graphene oxide aerogel that can efficiently remove glyphosate from water. This technology has great application prospects in dealing with water contaminated with glyphosate. Abstract Glyphosate, an organophosphorus pesticide, has received considerable attention in recent years owing to its carcinogenic potency. The technologies that remove glyphosate in the environment, especially in water, are important. In this work, we prepare a carboxylated carbon nanotubes-graphene oxide aerogel (cCNTs-GA) by the freeze-drying method for the adsorption of glyphosate. The prepared aerogel exhibits an ultra-low density (7.30 mg cm−3), good morphology and strong mechanical strength. Meanwhile, a NaOH solution (0.5 mol L−1) is selected as an eluent and the adsorption parameters for the adsorption of glyphosate are optimised. The properties of the adsorbents after multiple repetitions and the adsorption mechanism of the cCNTs-GA are also studied. The results show that the adsorbent can be recycled more than 20 times and maintains a good adsorption performance. The maximum adsorption capacity of glyphosate at pH 3 is calculated from the Langmuir isotherm model (546 mg g−1 at the temperature of 298 K), and the cCNTs-GA exhibits a high adsorption affinity and adsorption capacity for glyphosate, as determined by the partition coefficient (PC). The pseudo-second-order kinetic model fits well to the dynamic behaviour. The equilibrium adsorption process follows the Langmuir isotherm model and the adsorption process is mainly controlled by the intraparticle diffusion model. Furthermore, thermodynamic analysis indicates that the adsorption of glyphosate on the cCNTs-GA is exothermic and spontaneous. The adsorbent is used to remove glyphosate from waste water and the adsorption capacity of the cCNTs-GA for glyphosate is higher than other adsorbents, which indicates that the developed adsorbent has a great potential application in environmental pollution treatment.