Junkang Guo,Yanping Li,Xinhao Ren,Huihui Xu,Ting Wei,Honglei Jia,Li Hua,Yi Zhang,Yongtao Li
A hydrophobic functional ionic liquid (IL) [N4444]AOT based on bis(2-ethylhexyl)sulfosuccinate anions was designed and synthesized for cadmium extraction. To study the characteristics of [N4444]AOT, Fourier transform infrared (FTIR) spectroscopy, hydrogen nuclear magnetic resonance spectroscopy (1H NMR), and thermogravimetric analysis were used. The extraction ability of [N4444]AOT towards Cd under ultrasonic conditions was also investigated. The results showed that more than 95.08% of Cd in a water solution could be extracted with [N4444]AOT under ultrasonic conditions. The results of FTIR and 1H NMR analyses showed that Cd mainly coordinated with the S–O bond provided by [N4444]AOT during extraction. The extraction of Cd from soil with [N4444]AOT was high and reached the value of 62.57%. Furthermore, [N4444]AOT could extract some stable and bound Cd species from the soil, which existed in a weakly acidic, reducible or oxidizable state. The application of [N4444]AOT significantly decreased the bioavailability of Cd in the soil. [N4444]AOT can be a good agent for Cd-contaminated soil remediation without changing the soil properties.
Four plant growth-promoting bacteria (PGPB) were used as study materials, among them two heavy metal-tolerant rhizosphere strains SrN1 (Arthrobacter sp.) and SrN9 (Bacillus altitudinis) were isolated from rhizosphere soil, while two endophytic strains SaN1 (Bacillus megaterium) and SaMR12 (Sphingomonas) were identified from roots of the cadmium (Cd)/zinc (Zn) hyperaccumulator Sedum alfredii Hance. A pot experiment was carried out to investigate the effects of these PGPB on plant growth and Cd accumulation of oilseed rape (Brassica napus) plants grown on aged Cd-spiked soil. The results showed that the four PGPB significantly boosted oilseed rape shoot biomass production, improved soil and plant analyzer development (SPAD) value, enhanced Cd uptake of plant and Cd translocation to the leaves. By fluorescent in situ hybridization (FISH) and green fluorescent protein (GFP), we demonstrated the studied S. alfredii endophytic bacterium SaMR12 were able to colonize successfully in the B. napus roots. However, all four PGPB could increase seed Cd accumulation. Due to its potential to enhance Cd uptake by the plant and to restrict Cd accumulation in the seeds, SaMR12 was selected as the most promising microbial partner of B. napus when setting up a plant–microbe fortified remediation system.