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Fenton oxidation, an advanced oxidation process, is an efficient method for the treatment of recalcitrant wastewaters. Unfortunately, it utilizes H2O2 and iron-based homogeneous catalysts, which lead to the formation of high volumes of sludge and secondary pollutants. To overcome these problems, an alternate option is the usage of heterogeneous catalyst. In this study, a heterogeneous catalyst was developed to provide an alternative solution for homogeneous Fenton oxidation. Iron Zeolite Socony Mobile-5 (Fe-ZSM-5) was synthesized using a new two-step process. Next, the catalyst was characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, fourier transform infrared spectroscopy, and Brunauer-Emmett-Teller analysis and tested against a model wastewater containing the azo dye Acid Blue 113. Results showed that the loading of iron particles reduced the surface area of the catalyst from 293.59 to 243.93 m2/g; meanwhile, the average particle size of the loaded material was 12.29 nm. Furthermore, efficiency of the developed catalyst was evaluated by performing heterogeneous Fenton oxidation. Taguchi method was coupled with principal component analysis in order to assess and optimize mineralization efficiency. Experimental results showed that under optimized conditions, over 99.7% degradation and 77% mineralization was obtained, with a 90% reduction in the consumption of the developed catalyst. Furthermore, the developed catalyst was stable and reusable, with less than 2% leaching observed under optimized conditions. Thus, the present study proved that newly developed catalyst has enhanced the oxidation process and reduced the chemicals consumption.

We demonstrate a passively Q-switched erbium-doped fiber laser (EDFL) using a copper nanoparticle (CuNP) thin film as the saturable absorber in a ring cavity. A stable Q-switched pulse operation is observed as the CuNP saturable absorber (SA) is introduced in the cavity. The pulse repetition rate of the EDFL is observed to be proportional to the pump power, and is limited to 101.2 kHz by the maximum pump power of 113.7 mW. On the other hand, the pulse width reduces from 10.19 µs to 4.28 µs as the pump power is varied from 26.1 mW to 113.7 mW. The findings suggest that CuNP SA could be useful as a potential saturable absorber for the development of the robust, compact, efficient and low cost Q-switched fiber laser operating at 1.5-µm region.

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We demonstrate passive Q-switching in an erbium-doped fiber laser (EDFL) cavity using gold nanoparticles as a saturable absorber (SA) for the first time. By using a thermal deposition method, gold with nanosized particles was plated onto polyvinyl alcohol film to form the SA. The SA was incorporated into a laser cavity, sandwiched between two fiber ferrules. The EDFL generates a Q-switching pulse in the 1560 nm region with a tunable repetition rate from 24.34 kHz to 88.11 kHz. The pulse tuned to a maximum input pump power of 179.5 mW produced a pulse width and pulse energy of 4.25 µs and 32.91 nJ, respectively.

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Abstract-We demonstrate an ultrafast TDFL Q-switched pulse in 2 µm wavelength using multi-walled carbon nanotubes (MWCNTs) as passive saturable absorber (SA). MWCNTs film is sandwiched between two fibre connectors or patch cords after deposited with index matching gel on the fibre ferrules. Thulium-doped fibre was pumped using 1552 nm source in the ring cavity. The repetition rate for the pulses can be tuned from 13.33 kHz to 21.07 kHz by varying the pump power from 307.5 mW to 371.4 mW. At the maximum power, the pulse generated energy of 87.34 nJ with full-width at half maximum (FHWM) of 8.21 µs.Index Terms-Multi-walled carbon nanotubes, passive saturabe absorber, Q-switching.