Construction of phase-separated Co/MnO synergistic catalysts and integration onto sponge for rapid removal of multiple contaminants.

Wastewater treatment recycling is critical to ensure safe water supply or to overcome water shortage. Herein, we developed metallic Co integration onto MnO nanorods (MON) resulting in a phase-separated synergetic catalyst by creating more Mn(III) via the Jahn-Teller effect and oxygen vacancies and improving the redox capability of Co nanoparticles mediated by a thin carbon layer. Additionally, the N-doped surface carbon network on MON contributes to polar sites, facilitating the enrichment of contaminants around reactive sites, thereby shortening the migration of reactive oxidative species (ROS) toward contaminants. The optimized MnO@Co/C-600 exhibits superior PMS activation efficiency for bisphenol A degradation (0.463 min-1), displaying nearly a 20-fold enhancement in the rate constant compared to Mn3O4/C-600. Subsequent experiments involving variable modulation and extension were conducted to further elucidate the multiple synergistic effects. The mechanism study further confirms the synergy of ˙SO4-, ˙OH, ˙O2-, and 1O2, along with additional electron transfer pathways. The intermediates generated during degradation pathways and their toxicity to aquatic organisms were identified. Notably, a monolith integrated catalyst was explored by anchoring MnO@Co/C-600 onto a tailored melamine sponge based on Ca ion triggered crosslink tactic for the photothermal degradation of bisphenol A, tetracycline and norfloxacin, endowed with easy recovery and good stability. Furthermore, we demonstrated that the total organic carbon removal of multiple contaminants surpassed that of sole contaminants.

Monolith floatable dual-function solar photothermal evaporator: efficient clean water regeneration synergizing with pollutant degradation.

Meeting the growing demands of attaining clean water regeneration from wastewater and simultaneous pollutant degradation has been highly sought after. In this study, nanometric CuFe2O4 and plasmonic Cu were in situ confined into graphitic porous carbon nanofibers (CNF) through electrospinning and controlled graphitization, which were integrated onto a melamine sponge (S-FeCu/CNF) as a monolithic evaporator via a calcium ion-triggered network crosslinking method using sodium alginate (SA). This monolithic evaporator serves a dual purpose: harnessing solar-driven photothermal energy for water regeneration and facilitating synchronous contaminant mineralization through advanced oxidation processes (AOPs). The metal-modified FeCu/CNF graphitic porous carbon exhibited an enhanced light absorption property (≥95%) and was further securely anchored on the sponge by a calcium ion-triggered SA crosslinking technique, thereby efficiently restraining salt deposition. The FeCu/CNF evaporator demonstrated a solar-vapor conversion efficiency of 105.85% with an evaporation rate of 1.61 kg m-2 h-1 under one sun irradiation. The evaporation rate of the monolithic S-FeCu/CNF evaporator is close to 1.76 kg m-2 h-1, and an evaporation rate of 1.54 kg m-2 h-1 can be achieved even in 20% NaCl solution, with resistance to salt deposition and cycling stability. Synchronously, the monolithic D-S-FeCu/CNF evaporator also acts as a heterogeneous catalyst to activate peroxymonosulfate (PMS) and trigger rapid pollutant degradation, which also shows excellent catalytic cycling stability, producing clean water that satisfies the World Health Organization (WHO) standards. This work provides a potentially valuable solution for addressing desalination and wastewater treatment.

Functional study of the novel multidrug efflux pump KexD from Klebsiella pneumoniae.

We cloned a gene, kexD, that provides a multidrug-resistant phenotype from multidrug-resistant Klebsiella pneumoniae MGH78578. The deduced amino acid sequence of KexD is similar to that of the inner membrane protein, RND-type multidrug efflux pump. Introduction of the kexD gene into Escherichia coli KAM32 resulted in a MIC that was higher for erythromycin, novobiocin, rhodamine 6G, tetraphenylphosphonium chloride, and ethidium bromide than that of the control. Intracellular ethidium bromide levels in E. coli cells carrying the kexD gene were lower than that in the control cells under energized conditions, suggesting that KexD is a component of an energy-dependent efflux pump. RND-type pumps typically consist of three components: an inner membrane protein, a periplasmic protein, and an outer membrane protein. We discovered that KexD functions with a periplasmic protein, AcrA, from E. coli and K. pneumoniae, but not with the periplasmic proteins KexA and KexG from K. pneumoniae. KexD was able to utilize either TolC of E. coli or KocC of K. pneumoniae as an outer membrane component. kexD mRNA was not detected in K. pneumoniae MGH78578 or ATCC10031. We isolated erythromycin-resistant mutants from K. pneumoniae ATCC10031, and some showed a multidrug-resistant phenotype similar to the drug resistance pattern of KexD. Two strains of multidrug-resistant mutants were investigated for kexD expression; kexD mRNA levels were increased in these strains. We conclude that changing kexD expression can contribute to the occurrence of multidrug-resistant K. pneumoniae.