Effect of nanoparticles on desulfurization/regeneration performance of deep eutectic solvent based nanofluid system

•DES based nanofluid systems with different viscosities were used for H2S adsorption.•With the increase of particles, the viscosity increased firstly and then decreased.•The performances of DES were improved greatly after the addition of nanoparticles.•The moisture plays a crucial role in the regeneration process.•Plenty liquid substances were found gather on the surface of nanoparticles. Using choline chloride as hydrogen bond acceptor and urea as hydrogen bond donor, the deep eutectic solvent (DES) was prepared, and different alkaline substances were added to obtain two alkaline DES systems with different viscosities. SiO2 nanoparticles were introduced into the above two systems to construct different DES-based nanofluid systems: ethanolamine-deep eutectic solvent (E-DES-NF) system and polyethyleneimine-deep eutectic solvent (P-DES-NF) system. The viscosity of the nanofluid system was measured, and it was found that with the increase of the proportion of nanoparticles, the viscosity of both nanofluids increased firstly and then decreased. The hydrogen sulfide absorption experiment was carried out to explore the effect of nanoparticles on the desulfurization and regeneration performance of different nanofluid systems. The experimental results showed that the DES system synthesized in this study can maintain 100% removal rate for at least 40 min. The desulfurization and regeneration performances were improved simultaneously after the addition of moderate nanoparticle. In the E-DES system, when the mass fraction of SiO2 nanoparticles was 0.1%, the highest desulfurization performance was conducted. Besides, the addition of an appropriate amount of water was found to be beneficial to the regeneration of exhausted desulfurizer of E-DES-NF system. In the P-DES-NF system, the optimal mass fraction of SiO2 nanoparticles was confirmed as 0.01%. Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy and X-ray diffraction were used for the characterization of the nanofluid systems as well as SiO2 nanoparticles before and after absorption as well as after multiple absorption–regeneration cycles. The morphology of SiO2 nanoparticles itself had little changes. A large amount of liquid substances were found gather on the surface of nanoparticles, and with the increase of the number of absorption–regeneration cycles, the surface attachment gradually decreased.