Quantitative research on heavy metal removal of flue gas desulfurization-derived wastewater sludge by electrokinetic treatment.

Flue gas desulfurization-derived wastewater sludge (FGD-WWS) has been produced increasingly in China and India etc., and its content of heavy metals (HMs) including Cd, Cr, Cu, Hg, Ni and Zn seriously exceeds the limits allowed. Developing the suitable disposal of FGD-WWS is therefore significantly important and necessary. The novel process of electrokinetic treatment combined with chemical pretreatment of HMs in FGD-WWS were proposed here to improve the removal efficiency. Results indicate that the effects of different pretreatment agents (citric acid (CA), ammonia, tetrasodium of N, N-bis (carboxymethyl) glutamic acid (GLDA), and rhamnolipid) on the ET of HMs were different. To investigate the mechanism of combined process, the transformation potential (TP), exchange potential (EP) and removal potential (RP) were calculated. Correlation analysis shows the correlation between TP and RP was higher than that between EP and RP, indicating that the removal efficiency is mainly affected by the fraction transformation of HMs. Electric field, pH and pretreatment agents are main factors causing fraction transformation and affecting TP. Focusing on fraction transformation is an efficient way to improve further the removal efficiency. The work is promisingly valuable for developing the technology of treating FGD-WWS.

Single-/dual-pulse repetition rate variable supercontinuum light source with peak wavelength around 1.7 µm using a modulated pump.

A single-/dual-pulse repetition rate variable supercontinuum (SC) light source (SLS) with a peak wavelength of around 1.7 µm (SLS around 1.7 µm) is proposed and experimentally demonstrated. In our scheme, a 1.5 µm modulated pump source included a laser and an intensity modulator (IM). The pump source can generate pulse trains with different repetitions and pulse durations. A 1 km high nonlinear fiber (HNLF) was used as the nonlinear gain medium. A picosecond-pulsed SC signal was obtained by pumping the HNLF, and a wavelength division multiplexer was used for filtering residual pump. Additionally, a Sagnac loop was applied to create a multiwavelength pulse SC light source. The generated SC source covered from 1.59 to 1.96 µm, and its peak wavelength was around 1.7 µm. The single-/dual-pulse train can be produced and switched by adjusting the direct current bias and radio frequency driving voltages of the input signal to the IM. When the repetition rate of the generated pulse train was between 170 MHz and 2 GHz, the pulse duration of the dual-pulse train was between 60 ps and 180 ps. Additionally, the duty cycle of the dual-pulse operation was 40%. The single pulse SLS, around 1.7 µm, can be a choice to improve optical coherence tomography (OCT) performance, and the dual-pulse source will be a reference for laser drilling applications.

1.7 µm band narrow-linewidth tunable Raman fiber lasers pumped by spectrum-sliced amplified spontaneous emission.

A 1.7 µm band tunable narrow-linewidth Raman fiber laser based on spectrally sliced amplified spontaneous emission (SS-ASE) and multiple filter structures is proposed and experimentally demonstrated. In this scheme, an SS-ASE source is employed as a pump source in order to avoid stimulated Brillouin scattering. The ring configuration includes a 500 m long high nonlinear optical fiber and a 10 km long dispersion shifted fiber as the gain medium. A segment of un-pumped polarization-maintaining erbium-doped fiber is used to modify the shape of the spectrum. Furthermore, a nonlinear polarization rotation scheme is applied as the wavelength selector to generate lasers. A high-finesse ring filter and a ring filter are used to narrow the linewidth of the laser, respectively. We demonstrate tuning capabilities of a single laser over 28 nm between 1652 nm and 1680 nm by adjusting the polarization controller (PC) and tunable filter. The tunable laser has a 0.023 nm effective linewidth with the high-finesse ring filter. The stable multi-wavelength laser operation of up to four wavelengths can be obtained by adjusting the PC carefully when the pump power increases.

Optical characterization of Tm(3+) doped Bi2O3-GeO2-Ga2O3 glasses in absence and presence of BaF2.

In this paper, Two new Bi2O3-GeO2-Ga2O3 glasses (one presence of BaF2) doped with 1mol% Tm2O3 were prepared by melt-quenching technique. Differential thermal analysis (DTA), the absorption, Raman, IR spectra and fluorescence spectra were measured. The Judd-Ofelt intensity parameters, emission cross section, absorption cross section, and gain coefficient of Tm(3+) ions were comparatively investigated. After the BaF2 introduced, the glass showed a better thermal stability, lower phonon energy and weaker OH(-) absorption coefficient, meanwhile, a larger ~1.8 µm emission cross section σem (7.56 × 10(-21) cm(2)) and a longer fluorescence lifetime τmea (2.25 ms) corresponding to the Tm(3+): (4)F3 → (3)H6 transition were obtained, which is due to the addition of fluoride in glass could reduce the quenching rate of hydroxyls and raise the cross-relaxation ((3)H6 + (3)H4 → (3)F4 + (3)F4) rate. Our results suggest that the Tm(3+) doped Bi2O3-GeO2-Ga2O3 glass with BaF2 might be potential to the application in efficient ~1.8 µm lasers system.