Effective adsorption of nitroaromatics at the low concentration by a newly synthesized hypercrosslinked resin

Recyclable nanographene-based micromachines for the on-the-fly capture of nitroaromatic explosives

It has been more than a decade since nano/micromachines (NMMs) have received the particular attention of scientists in different research fields. They are able to convert chemical energy into mechanical motion in their surrounding environment. Herein, a powerful, efficient and fast strategy of using nanosized reduced graphene oxide flake (n-rGO)-based self-propelled tubular micromachines for the removal of nitroaromatic compounds (NACs) is described. This method relies on the integration of the rGO as a well-known adsorbent of aromatic compounds with chemically powered engines for the removal of explosive compounds such as 2,4,6-trinitrotoluene (TNT), 2,4,6-trinitrophenol (TNP) and 2,4-dinitrotoluene (DNT). Nanographene oxide reduced electrochemically inside the pores of the polycarbonate membrane to form an outer layer (n-rGO, adsorbent layer) of the micromachines. Subsequent electrodeposition of nickel (Ni, magnetic layer) and platinum (Pt, catalytic layer) resulted in the formation of n-rGO/Ni/Pt micromachines. Notably, the bubble-propelled micromachines were able to remove nitroaromatic compounds with high efficiency (∼90-92%) compared to the efficiency of magnetic-guided (22-42%) and static (2.5-7%) micromachines. Most importantly, the micromachines were regenerated and reused several times. The regeneration is based on an electrochemical method in which electron injection into the machine causes the expulsion of contaminants from the outer layer of the micromachines within a few seconds. The integration of the powerful self-propulsion, high adsorbent capacity of rGO and the introduced ultrafast regeneration procedure are beneficial for the realization of an active platform for water remediation.

Preparation of hypercrosslinked amine modification resin and its adsorption properties for nitroaromatics

A nitrosation-reduction method had been applied for the modification of DCE-4 h. It was a kind of non-polar hypercrosslinked resin and synthesized by our group. The functional resin, NR-07, exhibited good adsorption performance for NACs (Nitroaromatics). The adsorption capacity of NR-07 for p-nitrobenzoic acid was almost 1.3 times as much as that of H-103 in 24 h. The adsorption rate of NR-07 calculated by the kinetic function was 1.6 times as much as that of DCE-4h. According to the EA analysis and IR spectrum, the amine and carbonyl group were introduced onto the polymer chains of NR-07. These hydrophilic chemical groups of NR-07 contributed to a higher liquid-film diffusion rate than that of DCE-4h. Besides, the pore volume within 0.46~4.3 nm increased after the modification process, which had a positive effect on the intra-particle diffusion process.

Mechanism of aniline adsorption on post-crosslinked resins: pore structure and oxygen content

A series of post-crosslinked resins were synthesized from macroporous chloromethylated styrene-divinylbenzene copolymer by controlling post-crosslinked reaction conditions. Adsorption study towards aniline showed that the three resins, ST-DVB-WH5, ST-DVB-WH6, and ST-DVB-WH7, prepared at different temperatures, and which had nearly identical static adsorption capacity, displayed great disparity in kinetic behavior. The rate constant of ST-DVB-WH7 by the pseudo-first-order model was 1.50 and 1.19 times higher than that of ST-DVB-WH5 and ST-DVB-ST-DVB-WH6. Further analysis of the diffusion model showed that the three resins exhibited different diffusion rates due to the difference in oxygen content and pore structure of each resin. The results showed that the adsorption capacity was mainly decided by the pore volume within 1.14 and 3.42 nm and the adsorption rate was mainly decided by the oxygen content of the resin. In addition, as the best synthetic resin for aniline adsorption, the equilibrium adsorption capacity of ST-DVB-WH7 was 1.57 times and 1.44 times higher than that of H-103 and NKA-II, respectively.