To overcome the low removal efficiency of common flocculants for bacterial pollutants, herein, a series of quaternary phosphine groups (QPGs)–modified chitosan (CTS)-based flocculants (CTS-P) was proposed. The removal efficiency of CTS-P for Escherichia coli ( E. coli ) and other coexisted pollutants was evaluated. The binding mode and interaction mechanism between CTS-P and E. coli were elucidated using theoretical calculations. Results showed that flocculation performance of CTS-P was the most efficient in near-neutral water (pH = 6–8). The removal efficiencies of CTS-P (10 mg/L) for humic acid and E. coli is 71 % and 1.82 1og, respectively, and the removal process was dominated by charge neutralization and adsorption bridging effects. The QPGs increased the charge density of the coagulation system and promoted the formation of large particle flocs. During the collision and growth processes of flocs, E. coli was quickly flocculated onto their surface and encapsulated within them. The binding of the QPGs to the cell membrane leads to E. coli cell death and structural rupture. Theoretical calculations show that the interfacial interaction energy of CTS-P for capturing E. coli is dominated by intermolecular interaction energy and polar interaction energy. The CTS-P flocculant proposed in this study provides a new pharmaceutical product and a theoretical basis for removing bacterial pollutants from drinking water sources.
With the fast-growing accumulation of precious metals, especially gold ions, in wastewater and electronic waste, achieving rapid and selective gold ions capture from water while maintaining high adsorption capacity is of vital importance to the environment and economy. Herein, a self-standing, quaternary phosphonium functionalized chitosan-based electrode (MTP-CS-CC) is proposed and fabricated via coating functional materials on carbon cloth for the electrochemical capture of Au(III) ions. Abundant quaternary phosphonium sites as nanotraps in MTP-CS-CC under the action of electric field deliver a fast extraction rate with high Au(III) removal efficiency (>99.5 %), a competitive uptake capacity (2114 mg g −1 ), superior selectivity, and long-term recycling stability. In-depth exploration of relevant mechanism by multiple characterizations and density functional theory (DFT) calculations illustrates that the capture of Au(III) ions by MTP-CS-CC electrode involves the electrosorption and electroreduction processes. In addition, when used as electrodes to recover gold from real e-waste leaching solution, the purity of recovered gold from computer central processing unit (CPU) boards reaches up to 23.8 Karat (99.17 % pure). Our work puts forward a facile strategy for preparing chitosan-based electrodes that can be innovatively used for the precious metal recovery and circular economy for recycling resources.
危险品化学品经营许可证（带存储）