Effective strategy for alleviation of oil contamination in marine via the superhydrophobic biochar: Performances, mechanisms and environmental recalcitrance

Abstract

The performance of layered double hydroxides (LDH)-biochar composite on alleviating oil spill pollution is poorly understood. A superhydrophobic biochar (NCY) was synthesized from the pristine wood chips biochar (WCB) after the surface deposition of NiCo-LDH (NCB) and hydrophobic modification with stearate. The oil removal potential of the designed biochars was investigated via the diesel oil/crude oil adsorption experiments and the environmental recalcitrance evaluation. The compared characterization results revealed that NiCo-LDH was successfully deposited onto biochar matrix via the electrostatic attraction and pore filling effect, which facilitated a special flower-like hierarchical architecture rough surface for biochar and hinder the multi-layer stacking of LDH. Benefit from the constructed hierarchical architecture, the occupancy of oxygen-containing functional groups and hydrophobic modification of stearate, the water contact angle of NCY (156°) was remarkably larger than NCB (117°) and WCB (50.1°), which exhibit a superhydrophobic. The maximum diesel oil sorption capacities of biochars increased from 3.28 g/g in WCB to 5.64 g/g in NCB and 11.6 g/g in NCY, as well as the maximum crude oil sorption capacities of biochars showed a similar trend (WCB: 4.64 g/g, NCB: 8.74 g/g, NCY: 18.6 g/g). Accordingly, NCY showed higher oil adsorption capacity than NCB and WCB mainly due to the enhanced hydrophobic forces and the π-π electron donor-acceptor interaction resulted from lower amount of O-containing functional groups and superhydrophobic surface wettability. Furthermore, the application of LDH remarkably improved the environmental recalcitrance of biochar (resist to the chemical oxidation and thermal decomposition in marine) due to the coating of NiCo-LDH could enhance the bulk stability of biochar and increase the liable carbon content in biochar. This study proved that the application of NiCo-LDH and stearate could be an effective approach for improve the oil pollution remediation capacity and the environmental recalcitrance of biochar.