ABSTRACT
A large amount of metal tailings causes many environmental issues. Thus, the techniques for their ecological restoration have garnered extensive attention. However, they are still in the exploratory stage. Biological soil crusts (BSCs) are a coherent layer comprising photoautotrophic organisms, heterotrophic organisms and soil particles. They are crucial in global terrestrial ecosystems and play an equal importance in metal tailings. We summarized the existing knowledge on BSCs growing on metal tailings. The main photosynthetic organisms (cyanobacteria, eukaryotic algae, lichens, and mosses) of BSCs exhibit a high heavy metal(loid) (HM) tolerance. BSCs also have a strong adaptability to other adverse conditions in tailings, such as poor structure, acidification, and infertility. The literature about tailing BSCs has been rapidly increasing, particularly after 2022. The extensive literature confirms that the BSCs distributed on metal tailings, including all major types of metal tailings in different climatic regisions, are common. BSCs perform various ecological functions in tailings, including HM stress reduction, soil structure improvement, soil nutrient increase, biogeochemical cycle enhancement, and microbial community restoration. They interact and accelerate revegetation of tailings (at least in the temperate zone) and soil formation. Restoring tailings by accelerating/inducing BSC formation (e.g., resource augmentation and inoculation) has also attracted attention and achieved small-scale on-site application. However, some knowledge gaps still exist. The potential areas for further research include the relation between BSCs and HMs, large-scale quantification of tailing BSCs, application of emerging biological techniques, controlled laboratory experiments, and other restoration applications.
Subject(s)
Environmental Restoration and Remediation , Soil Microbiology , Soil Pollutants , Soil , Soil/chemistry , Soil Pollutants/analysis , Environmental Restoration and Remediation/methods , Metals, Heavy/analysis , Ecosystem , Metals/analysis , MiningABSTRACT
It is still very challenging to obtain colorful and long-afterglow room-temperature phosphorescent (RTP) materials from pure organic polymers. Herein, it is found that chitosan (CS), a natural polymer, not only has its own RTP, but also reacts with different phosphorescent molecules to obtain a multicolor, long-afterglow RTP material. CS can emit RTP with a lifetime of 48 ms. In addition, CS is rich in amino groups, and grafting different phosphorescent molecules onto CS by an amidation reaction can modulate it to emit different colors of phosphorescence and obtain a series of colorful CS derivatives. The obtained polymer films also have ultra-long RTP due to the good film-forming ability. In addition, one of the CS derivatives selected with α-cyclodextrin is used to construct RTP materials with lifetimes of up to seconds. The host-guest interactions are used to suppress nonradiative relaxation and build crystalline domains, thus synergistically enhancing the RTP. Interestingly, the RTP properties of the CS derivative films are extremely sensitive to water and heat stimuli, because water broke the hydrogen bonds between adjacent CS molecules and thus altered the rigid environment in the material. Finally, they can be used as a stimuli-responsive ink and for monitoring environmental humidity.
ABSTRACT
Hydrogels constructed by traditional polymer networks usually have poor mechanical properties limiting their applications. Here, we proposed a new strategy for ionic interaction modulation of crystalline micro-nanoparticles (CMNPs) to enhance the mechanical properties of polyacrylamide hydrogels. CMNPs were formed via confinement assembly under an aggregated state based on host-guest interactions between chitosan-grafted polyethylene glycol (CS-PEG) and γ-cyclodextrin (γ-CD). Furthermore, the aggregation behavior of the CMNPs was achieved based on the ionic interaction of CS with citrate (Cit3-). These Cit3--regulated CMNPs were introduced into PAM hydrogels. The modulus (618.44 kPa, 67.6 times), fracture stress (1054.59 kPa, 25.3 times), and toughness (6.23 MJ m-3, 41.7 times) of the composite hydrogels were greatly improved without affecting the tensile properties (fracture strain, ~1000 %). Finally, we further designed a strain sensor that could monitor human motion, and we verified its potential application in the field of wearable flexible electronics.
