Abstract
MnO2 and MnO2 blended with 1 and 2 weight percent of activated carbon (AC), MnO2/AC1 and MnO2/AC2 were synthesized through the sol–gel method. The pure chitosan (CS) films were cast in the form of films. Similarly, 5 weight% of each MnO2, AC, MnO2/AC1 and MnO2/AC2 was intermingled with the CS to produce different films, such as CS-AC, CS-MnO2, CS-MnO2/AC1 and CS-MnO2/AC2. Zero-valent Co NPs were then supported on these films through the chemical reduction method and expressed as CS@Co, CS-AC@Co, CS-MnO2@Co, CS-MnO2/AC1@Co and CS-MnO2/AC2@Co NPs. All the catalysts were characterized by field emission scanning electron microscopy (FESEM), energy-dispersive spectroscopy (EDS) and X-ray diffraction (XRD) techniques. The synthesized catalysts were used as a dip catalyst against the hydrogenation of 4-nitrophenol (4NP), and for the degradation of methyl orange (MO) and Congo red (CR) dyes. The kapp and R2 values were deduced from pseudo-first-order kinetics for 4NP and MO and zero-order kinetics for CR dye. The kapp values of CS-AC@Co and CS-MnO2/AC1@Co NPs for 4NP hydrogenation were higher than those for any other member of the series, at 1.14 × 10−1 and 1.56 × 10−1 min−1 respectively. Similarly, the rate of CR degradation was highest with CS-AC@Co. The R2 values for 4NP, MO and CR dyes were above 0.9, which indicated that the application of pseudo-first- and zero-order models were appropriate for this study. Furthermore, the antibacterial activity of all the catalysts was evaluated against Pseudomonas aeruginosa and Escherichia coli. The CS-AC@Co NPs exhibited the highest zone of inhibition compared to other catalysts against P. aeruginosa, while all the catalysts were inactive against E. coli. This study reveals that the catalyst can be used for the degradation of other pollutants and for microbial inhibition.
Highlights
A dramatic increase in the anthropogenic activities, such as industrialization, modernization and urbanization, has contaminated water bodies to a serious extent
Synthesis of MnO2 For the synthesis of MnO2 NPs, 1 M MnCl2 solution was prepared in 200 mL distilled water and basified with NaOH solution till pH 11, which was monitored on a pH meter
0.2 mM 4NP solution was prepared in 100 mL of distilled water and 2.5 mL of it was placed in a cuvette and the absorption noted
Summary
A dramatic increase in the anthropogenic activities, such as industrialization, modernization and urbanization, has contaminated water bodies to a serious extent. The catalytic potential of ZVM and various metal oxide nanoparticles is attributed to their remarkably high surface to volume ratio, large surface energy and tiny quantum size effect, diversity, versatility and ease of application over a broad spectral regime of pollutants in water [23,24]. The above-mentioned composites were templates in the form of films and were employed as a solid supportive matrix for Co NPs’ stabilization; they were evaluated in terms of the inhibition of pathogenic bacteria These stabilized Co NPs were utilized to address the degradation/reduction of target contaminants such as 4NP and different dyes to evaluate the comparative role of the matrix.
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