Although tremendous works have been done on metal adsorption via biochar, mechanisms responsible for metal adsorption remain uncertain. This is the first work that provides direct evidence on the identification of Ni(II), Zn(II), and Cu(II) adsorption mechanisms on pineapple leaf biochar (PLB) using surface characteristics analyses, including X-ray photoelectron spectroscope (XPS), Fourier transform infrared spectroscope (FTIR), and scanning electron microscope with energy-dispersive X-ray spectroscope (SEM-EDS). From Langmuir isotherm fitting, the maximum adsorption capacity of PLB for Ni(II), Zn(II), and Cu(II) are 44.88, 46.00, and 53.14 mg g-1, respectively, surpassing all biochars reported in the literature. Findings of surface characterization techniques coupled with cation released during adsorption, cation exchange, and surface complexation mechanisms were proposed. PLB is reusable and remains sufficient adsorption capacity even six consecutive cycles via pressure cooker regeneration. With high regenerability and ultrahigh adsorption capacity, PLB defines itself as a promising adsorbent for future applications in metal-laden wastewater.
Saltwater intrusion (SWI) into coastal agricultural lands represents a growing threat to agricultural productivity, ecosystem stability, and local economies. This phenomenon, affecting coastal surface and ground waters, is driven by intensified natural processes and anthropogenic factors under a changing climate. Here, we provide a comprehensive review of the drivers and trends of SWI and their impacts on the transition of coastal agricultural systems. We emphasize the importance of developing salt-tolerant crop varieties and implementing controlled environment agriculture to maintain agricultural productivity in affected coastal regions. Additionally, we discuss the role of marsh migration (i.e., allowing marshes to migrate into agricultural lands) in enhancing biodiversity and ecological resilience, and protecting remaining farmlands from SWI. This review highlights the urgent need for multidisciplinary research, strategic policy frameworks, and community engagement to ensure the sustainability of future coastal agriculture in the face of increasing SWI challenges.
Four types of pathogens, namely, Staphylococcus aureus (S. aureus, gram-positive bacteria), Escherichia coli (E. coli, gram-negative bacteria), Mycobacterium avium (M. avium, mycobacteria), and Candida albicans (C. albicans, fungi), are common microorganisms that cause serious human health issues. However, searching for an efficient material for inactivating pathogens via visible light driven photocatalysts remains a challenge. An attempt was made to compare the photocatalytic performance using nano-sized nitrogen-doped titanium oxide (N-TiO2) and tourmaline-nitrogen-co-doped titanium oxide (T-N-TiO2) for inactivation of pathogens under visible light irradiation. S. aureus was used to compare the photocatalytic inactivation performance of N-TiO2 and T-N-TiO2. The findings showed that photocatalyst dosage, initial microbial concentration, and visible light intensity are the key factors affecting photocatalytic inactivation process for both photocatalysts. A 2-log-inactivation of S. aureus under 7.25 mW/cm2 visible light irradiation via T-N-TiO2 was achieved within 3 h, which is shorter than the inactivation via N-TiO2 (4 h). TEM observations had proved that both visible-light-induced photocatalysis could cause severe damage to the cell membrane. The results of electron paramagnetic resonance also indicated that more hydroxyl radicals generated in the T-N-TiO2 photo-inactivation system allowed a better inactivation performance of the visible-light-induced T-N-TiO2. This is the first work exploring that Light-responsive Modified Hom's model (LHM) is able to simulate photocatalytic inactivation of S. aureus. T-N-TiO2 composite was firstly evaluated for its efficacy of photocatalytic inaction of S. aureus, E. coli, and M. avium, and an increasing order of time was required for complete inactivation as follows: S. aureus < E. coli < M. avium < C. albicans. We have found that the inactivation efficiency of tested pathogens using T-N-TiO2 is the highest as compared with literature works. Overall, T-N-TiO2 exhibits a better inactivation efficiency than that of N-TiO2 in all the tested pathogens.
Photocatalysis is an efficient process for degrading organic pollutants and inactivating pathogenic microorganisms. However, this process constantly suffers from turbidity shading and particle aggregation in a catalyst suspension system, thereby reducing its photocatalytic activity. Immobilizing the photocatalyst on the light-transmissible surface is a viable solution to the obstacles. So far, the photo-inactivation efficacy between the immobilized photocatalyst and suspension systems has yet to be compared and investigated. In this study, N-TiO2 (NT) immobilized on poly-methyl-methacrylate (PMMA) was fabricated via a dip-coating method, which has a high transmittance rate of 92 % - better than all of the previous works (50 %). By immobilizing N-TiO2 on PMMA, up to 60 % and 19 % improvements in inactivation efficiencies against Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Escherichia coli (E. coli) are achieved, respectively, relative to a photocatalyst suspension. Notably, reactive oxygen species (ROSs) detection results indicate that 5 g/L NT coated PMMA ((NT-PMMA)5) has higher intensities of singlet oxygen (1O2), hydroxyl radicals (HO•), and higher concentration of hydrogen peroxide (H2O2) than the NT suspension. The as-made NT-PMMA sustains a 99.99 % inactivation efficiency (5-log-inactivation) against S. aureus through five consecutive photocatalysis cycles of reuse. The inactivation kinetics of S. aureus and E. coli fit well with the modified Hom model. Atomic force microscopy observations indicate that the NT-PMMA inactivation causes more severe damage to S. aureus's cell wall than E. coli due to the different susceptibility of cell wall structure to ROSs. This study paves a substantial way for scaling up the immobilizing catalyst on PMMA for the effective photocatalytic inactivation of pathogens under visible light.
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