Hybrid Chitosan–Silver Nanoparticles Enzymatically Embedded on Cork Filter Material for Water Disinfection

Abstract

Microbial contamination remains a major challenge in drinking water supplies in developing regions, despite the continuous advances being made in water purification processes. The spread and transmission of pathogens due to consuming unsafe water culminate in waterborne diseases and increased number of deaths worldwide. Recently, the application of nanotechnology for water purification, and in particular the use of antibacterial nanoparticles (NPs) to control microbial contaminations, has received considerable interest. In this study, antibacterial chitosan−silver nanoparticles (CS/AgNPs) were enzymatically grafted on cork matrixes to design a water purification point-of-use device. The antibacterial efficiency of the constructed filtering system was further evaluated against water severely contaminated with Escherichia coli (∼10 7 CFU/mL). The system was tested in two operating filtration modes with varied water residence times. The antibacterial nanocomposite decreased the water bacterial contamination by 4 and 5 log CFU/mL when performing a series of continuous short disinfection cycles of 15 min residence time (experiment I). Nevertheless, complete bacteria removal was achieved only after increasing the water residence time in the filters up to 8 h (experiment II). Durability of the system was demonstrated via performing five disinfection cycles after which the hybrid CS/AgNPs remained on the cork surface. Importantly, the antibacterial nanocomposite prevented bacteria attachment and proliferation during all cycles of the disinfection process.

Biofunctionalization of Cork with Moringa oleifera Seeds and Use of PMA Staining and qPCR to Detect Viability of Escherichia coli

“…The filter cartridges were organized in a system of four filters (Figure 1), replicates of cork functionalized with MoSe and granulated cork not functionalized with MoSe as control. To determine the efficiency of E. coli cell death, the influent flow was equally divided between the cartridges at a constant flow of 3 mL/min [35].…”

Laccase‐Mediated Grafting on Biopolymers and Synthetic Polymers: A Critical Review

“…Although substantial grafting can be expected, washing after modification was performed with water, which might not have removed all adsorbed insoluble NPs. To test the antibacterial efficiency during use, water filtration cartridges were filled with the cork–AgNP–CS composite material . All bacteria could be removed from the effluent at 8 h residence time.…”

“…To test the antibacterial efficiency duringu se, water filtrationc artridges were filled with the cork-AgNP-CS composite material. [59] All bacteria could be removed from the effluent at 8hresidence time. However,a pproximately 25 %o ft he total silver contentl eachedo ut after five disinfection cycles.…”

Effects of Chloride Concentration on the Water Disinfection Performance of Silver Containing Nanocellulose-based Composites

“…Point-of-use (POU) water treatment is often used when drinking water is retrieved from untreated natural sources 2 where centralized water treatment facilities are not available 3 . Chlorine treatment is a generic method for household water disinfection, but the formation of toxic byproducts makes it problematic 4 , resulting in a need for alternative methods. Nanotechnology and especially nanoparticles have been studied as a possible solution to challenges related to water disinfection 5,6 .…”

“…Unfortunately, the antibacterial tests of silver-releasing materials in laboratory conditions are often conducted in solutions with [Cl − ] irrelevant to freshwaters in rural areas. The tests are often performed in very low [Cl − ], such as highly diluted buffer solution or deionized water 4,32 , or very high [Cl − ] such as undiluted PBS buffer where [Cl − ] is typically around 5000 ppm 33 . When silver concentration is high, charged silver polychloride complexes are formed, which can contribute to the antibacterial activity 34 .…”