Advanced Reduction Methods Research Articles

Reductive removal of As(V) and As(III) from aqueous solution by the UV/sulfite process: Recovery of elemental arsenic

The removal of arsenic (As(V) and As(III)) from contaminated water has attracted great attention. However, the generation of arsenic-containing hazardous waste by traditional methods has become an inevitable environmental problem. Herein, a UV/sulfite advanced reduction method was proposed to remove As(V) and As(III) from aqueous solution in the form of valuable elemental arsenic (As(0)), thus avoiding the generation of arsenic-containing hazardous waste. The results showed that greater than 99.9% of As(V) and As(III) were reduced to the high purity As(0) (> 99.5 wt%) with the residual arsenic concentration below 10 μg L−1. The hydrated electrons (eaq−), H• and SO3•− radicals are generated by the UV/sulfite process, of which eaq− and H• serve as reductants of As(V) and As(III) while the SO3•− radicals inhibit arsenic reduction by oxidizing arsenic. The effective quantum efficiency (Φ) for the formation of As(0) in the As(V) and As(III) removal process is approximately 0.0078 and 0.0055 mol/Einstein, respectively. The reduction of arsenic is favorable under alkaline conditions (pH > 9.0) due to the higher photolysis efficiency of SO32− than HSO3− (pKa = 7.2) and higher stability of eaq−/H• under alkaline conditions. The presence of dissolved oxygen (O2), NO2−, NO3−, CO32−, PO43− and humic acid (HA) inhibited arsenic reduction through light blocking or eaq−/H• scavenging effects while Cl−, SO42−, Ca2+ and Mg2+ had negligible effects on arsenic reduction. The proposed method can effectively remove and recover arsenic from contaminated water at a low cost, demonstrating feasibility for practical application. This study provides a novel technology for the reductive removal and recovery of arsenic from contaminated water.

TRAO 13CO Outer Galaxy Survey

AbstractWe have observed the parts of the second quadrant of the Galactic Plane in 13CO(1-0) using the multibeam receiver system installed on the 14 m telescope at Taeduk Radio Astronomy Observatory (TRAO). The first target region A (L=108° to 112°.5) is the part of the 12CO Outer Galactic Plane Survey (OGS; Heyer et al. 1998), and it is for the exact Galactic plane with the latitude range of +1 and -1 degree. A total of 48,000 spectra (about 9 square degrees) were obtained on 50″ grid. Two following regions were also observed; Region B: L = 120° ∼ 121°.7, B = −1° ∼ +1° (38,000 spectra) Region C: L = 130° 132°, B = −1° ∼ +1° (42,000 spectra). Eventually all the regions of the OGS will be covered. The selected velocity resolution is 0.63 km s−1 and the covered velocity is 320 km s−1, from −210 to 110 km s−1. The typical system temperature is ranging from 400 to 800 K, and average sensitivity per channel is 0.17 K.We developed a new reduction method, which effectively deals with a relatively noisy 3-dimensional database. After using simple linear baseline subtraction, we mainly used the IRAF twod.longslit.background task in 3D within some scripts, as well as IRAF tasks dealing with statistics, and a revised FCRAO reduction package, which is working within IRAF as external user's tasks. The collected 13CO database will be manipulated with pre-existing 12CO data to get several physical parameters. As it is located in the second quadrant, the kinematic distances of the individual clouds, which will be identified, can be estimated straightforwardly without any distance ambiguity. In this meeting we present the reduction method, integrated intensity maps, and spatial-velocity maps. We intend to clarify any difference of their characteristics between the clouds in the Outer Galaxy and Inner Galaxy using our data base.The present TRAO receiver system has aged, and thus its performance level degraded. However, we have a plan to renovate our receiver system to a brand new one within the next two years. This will speed up the TOGS project. At present, it costs substantial amount of time to homogeneously reduce the spectra obtained with our present receiver system. To compensate this, we invested more integration time, and developed more advanced reduction methods (see above). A future multibeam array receiver system at the TRAO would be at least 16 beams with most recent mixers (Tsys ∼ 150 K at 110GHz), hopefully.

Phase-differential NIR integral field spectroscopy of transiting Hot Jupiters

AbstractTransiting exoplanets provide a unique opportunity for follow up exploration through phase-differential observation of their emission and transmission spectra. From such spectra immediate clues about the atmospheric composition and the planets chemistry can be drawn. Such information is of imminent importance for the theory of the formation of planets in general as well as for their particular evolution. Ground-based spectroscopy of exoplanet transits is a needful extension of results already obtained through space-based observations. We present results of an exploratory study to use near-infrared integral field spectroscopy to observe extrasolar planets. We demonstrate how adaptive optics-assisted integral field spectroscopy compares with other spectroscopic techniques currently applied. An advanced reduction method using elements of a spectral-differential decorrelation method is also discussed. We have tested our concept with a K-Band time series observations of HD209458b and HD189733b obtained with SINFONI at the VLT and OSIRIS at Keck during secondary transits at a spectral resolution of R=3000.