Synergistic effect of microwave assisted devulcanization of waste NBR rubber and using superhydrophobic/superoleophilic silica nanoparticles on oil-water separation

Abstract

In this work, waste nitrile rubber (NBR) was radio-chemo-mechanically devulcanized and used as oil/seawater separator. Pure and surface modified silica nanoparticles were applied to the new and recycled NBR compounds at different contents (i.e. 1, 2, 3, 5 and 10 wt%). The surface modification of nanoparticles was performed using triethoxyvinylsilane (TEVS) at different concentrations (i.e. 1, 5 and 10X). The rheological/mechanical properties and water/oil contact angles (WCA/OCA) of the new and recycled NBR based nanocomposites were evaluated. The results showed that using modified silica nanoparticles (at 5 wt% loading content) caused increment in the WCA from 89.89 and 95.3° to 151.56 and 153.3° and decrease in the OCA from 73.39 and 71.3° to 14.1 and 11.1° for new and recycled NBRs, respectively. It was also found that durability of sorbent against oil absorption–desorption cycles declined using the recycled rubber instead of new NBR compound (i.e. from 1000 to 700 cycles), but the oil absorption capacity enhanced (i.e. from 2.2 to 2.4 g/g). The oil separation efficiencies (OSE) of the modified nanocomposites were more than 99%. It was shown that using modified nanoparticles in RNBR caused 50% decrement in the Payne effect and 33% enhancement in the chemical/physical bonds, respectively.