RESUMEN
Synthetic organic dyes constitute a major pollutant in wastewater. Here, we describe the synthesis and characterization of N-halamine nanoparticles (NPs) for decomposition of organic dyes from contaminated wastewater. Cross-linked poly(methacrylamide) (PMAA) NPs of hydrodynamic diameters ranging from 11 ± 1 to 161 ± 31 nm were synthesized at room temperature by redox surfactant-free dispersion copolymerization of methacrylamide and the cross-linking monomer N,N'-methylenebis(acrylamide) in an aqueous continuous phase. The effect of various polymerization parameters on the diameter and size distribution of the formed NPs was studied. Additionally, thin coatings composed of cross-linked PMAA NPs were grafted onto oxidized corona-treated polypropylene (PP) films by redox graft polymerization of the monomers in the presence of oxidized PP films. The free and grafted NPs were converted to N-halamine species by chlorination with sodium hypochlorite. The decomposition kinetics of two model organic dyes, methylene blue (MB) and crystal violet (CV), was evaluated for both free and grafted PMAA-Cl NPs. Free cross-linked PMAA-Cl NPs at room temperature, with concentrations of 5 and 0.5 mg/mL, illustrated full decomposition of CV and approximately 90% decomposition of MB after 42 and 97 h. In order to enhance the dye decomposition, the mixtures were heated to 70 °C. Complete decomposition of CV and MB at PMAA-Cl NP concentrations of 5 and 0.5 mg/mL required 60 and 240 min for CV, respectively, and 180 and 420 min for MB, respectively. Similarly, the PP/PMAA-Cl films also demonstrated a high reduction in the MB concentration after 150 min. Due to the highly efficient dye decomposition, these free and immobilized chlorinated NPs may be utilized as new reagents for decomposition of organic materials from contaminated wastewater.
RESUMEN
Harmful cyanobacterial blooms (HCBs) are becoming a major challenge for the management of both natural and man-made freshwater lakes and reservoirs. Phytoplankton communities are an essential component of aquatic ecosystems, providing the basis for natural food webs as well as important environmental services. HCBs, driven by a combination of environmental pollution and rising global temperatures, destabilize phytoplankton communities with major impacts on aquatic ecology and trophic interactions. Application of currently available algaecides generally results in unselective elimination of phytoplankton species, disrupting water ecology and environmental services provided by beneficial algae. There is thus a need for selective cyanocidal compounds that can eliminate cyanobacteria while preserving algal members of the phytoplankton community. Here, we demonstrate the efficacy of N-halamine derivatized nanoparticles (Cl NPs) in selectively eliminating cyanobacteria, including the universal bloom-forming species Microcystis aeruginosa, while having minimal effect on co-occurring algal species. We further support these results with the use a simple microfluidic platform in combination with advanced live-imaging microscopy to study the effects of Cl NPs on both laboratory cultures and natural populations of cyanobacteria and algae at single cell resolutions. We note that the Cl NPs used in this work were made of polymethacrylamide, a nonbiodegradable polymer that may be unsuitable for use as a cyanocide in open aquatic environments. Nevertheless, the demonstrated selective action of these Cl NPs suggests a potential for developing alternative, biodegradable carriers with similar properties as future cyanocidal agents that will enable selective elimination of HCBs.
Asunto(s)
Cianobacterias , Nanopartículas , Ecosistema , Eutrofización , Floraciones de Algas Nocivas , Lagos , FitoplanctonRESUMEN
BACKGROUND: Isothiouronium salts are well known in their variety of antimicrobials activities. The use of polymeric biocides, polymers with antimicrobial activities, is expected to enhance the efficacy of some existing antimicrobial agents, thus minimizing the environmental problems accompanying conventional antimicrobials. METHODS: The current manuscript describes the synthesis and characterization of crosslinked polyisothiouronium methylstyrene (PITMS) nanoparticles (NPs) of narrow size distribution by dispersion co-polymerization of the monomer isothiouronium methylstyrene with the crosslinking monomer ethylene glycol dimetacrylate. RESULTS AND DISCUSSION: The effect of total monomer, crosslinker and initiator concentrations on the size and size distribution of the formed NPs was also elucidated. The bactericidal activity of PITMS NPs of 67 ± 8 nm diameter was illustrated for 4 bacterial pathogens: Listeria innocua, Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus. In order to demonstrate the potential of these PITMS NPs as inhibitor of biofilm formation, polyethylene terephthalate (PET) films were thin-coated with the PITMS NPs. The formed PET/PITMS films reduced the viability of the biofilm of Listeria by 2 orders of magnitude, making the coatings excellent candidates for further development of non-fouling surfaces. In addition, PITMS NP coatings were found to be non-toxic in HaCaT cells. CONCLUSIONS: The high antibacterial activity and effective inhibition of bacterial adsorption indicate the potential of these nanoparticles for development of new types of antibacterial and antibiofilm additives.