[Decomposion of carbon disulfide by pulse corona under oxidizing and reducing atmosphere].

The removal of CS2 by a wire-in-tube pulsed corona reactor was experimentally investigated. The effects of O2 and H2 in Ar gas on the removal of CS2 were examined. It was shown that the removal of CS2 increased with the increase of input pulse voltage. The decomposition of CS2 was improved in the presence of O2 in gas stream and the maximal removal was over 97%. The main gaseous products of CS2 decomposition with the addition of O2 in Ar gas were CO, CO2 COS and SO2, while, with the presence of H2 in Ar gas, the main products of CS2 decomposition were H2S and CH4. It was found that with the co-existence of sorbent Ca(OH)2 in the reactor, the gaseous products of CS2 decomposition (SO2 and H2S) were not detected, showing that the products were absorbed by the sorbent Ca(OH)2. It was also found that the removal of CS2 decreased when there was water vapor in gas stream.

Reverse-flow strategy in biofilters treating CS2 emissions.

The bacteriostatic properties of carbon disulphide (CS2) hamper its biodegradation in conventional biofilters. The response of four biofilters operating in downflow mode and reverse-flow mode was compared in a laboratory-scale plant treating CS2 under sudden short-term changes in operating conditions. A process shutdown for 24 h, an inlet concentration increase and an interruption of the inlet air humidification for 48 h at an empty bed residence time (EBRT) of 240 s did not impact significantly on biodegradation performance, regardless of flow mode. Nevertheless, a reduction in the EBRT to 60 s resulted in a significant decrease in removal efficiency in all the biofilters. The CS2 degradation profile showed that the reverse-flow mode strategy rendered a more homogenous distribution of biomass along the bed height. The benefits of the reverse-flow mode were demonstrated even when the unidirectional flow mode was re-established.

Coupling catalytic hydrolysis and oxidation for CS2 removal.

CS2 removal was obtained by coupling catalytic hyidation on bi-functional catalyst. On the hydrolysis active sites, CS2 is hydrolyzed to H2S, while on the oxidation active sites, H2S is oxidized to elemental S or sulfuric acid deposited on the porous support. The above process can be expressed as follows: CS2 -->(H2O)COS -->(H2O) -->H2S -->(O2)--> S/SO4(2-). H2S oxidation eliminates its prohibition on CS2 hydrolysis so that the rate of coupling removal CS2 is 5 times higher than that of CS2 hydrolysis. The same active energy of hydrolysis and coupling reaction also indicates that H2S oxidation does not change the reaction mechanism of CS2 hydrolysis. Temperature has obvious effect on the process while the mole ratio of O2 concentration to CS2 concentration (O/S) does not, especially in excess of 2.5. The formation of sulfuric acid on the catalyst surface poisons hydrolysis active sites and causes the decrease of left OH(-1) concentration on the catalysts surface. Lower temperature is suggested for this bi-functional catalyst owing to the low yield ratio of S/SO4(2-).

Carbon disulfide removal by zero valent iron.

The use of zero valent iron (Fe0) for the remediation of water contaminated with carbon disulfide (CS2), a common groundwater contaminant, has been evaluated in this study. Mineralogical analysis of Fe0 filings and polished Fe0 cross-sections indicates that iron sulfide is formed due to the removal of carbon disulfide from solution by Fe0. The kinetics of CS2 removal by Fe0 was examined through both batch and column testing, and it is demonstrated that CS2 is removed rapidly from solution. A linear relationship was observed, through batch testing, between the pseudo-first-order rate constant (k(obs)) and the surface area concentration of Fe0 (rho(a)). Data obtained from kinetic batch tests performed at four temperature levels conformed to the Arrhenius equation, and the calculated apparent activation energy (E(a)) was 37 +/- 2.3 kJ mol(-1), indicating that the kinetics of CS2 removal by Fe0 is controlled by a chemical surface reaction. The temperature correction factors for CS2 from a reference of 25 degrees C were x 1.4 for 18 degrees C, x 1.7 for 15 degrees C, x 2.0 for 12 degrees C, and x 2.3 for 9 degrees C. Surface area normalization of k(obs) obtained through batch and column testing gives specific reaction rate constants (k(SA)) within 1 order of magnitude, indicating that k(SA) values are useful as a general descriptor of CS2-Fe0 reaction kinetics and that these values provide a clear starting point for design calculations prior to commencing site-specific treatability studies for permeable reactive barrier design.

Efficacy of a novel biofilter in hatchery sanitation: II. Removal of odorogenous pollutants.

The present research assessed the treatment efficiency of odorogenous pollutants in air from a hatchery hall vented on organic and organic-mineral beds of an enclosed-container biofilter. In this study, the following media were used: organic medium containing compost and peat (OM); organic-mineral medium containing bentonite, compost and peat (BM); organic-mineral medium containing halloysite, compost and peat (HM). The concentration of odorogenous gaseous pollutants (sulfur compounds and amines) in the hatching room air and in the air after biotreatment were determined by gas chromatography. In the hatchery hall among the typical odorogenous pollutants, there were determined 2 amines: 2-butanamine and 2-pentanamine, hydrogen sulfide, sulfur dioxide, carbon disulfide, sulfides and mercaptans. Ethyl mercaptan showed the highest levels as its mean concentration in the hatchery hall air exceeded 60 microg/m3 and in single samples even 800 microg/m3. A mean concentration of 2-butanamine and sulfur dioxide in the examined air also appeared to be relatively high--21.405 microg/m3 and 15.279 microg/m3, respectively. In each filter material, the air treatment process ran in a different mode. As the comparison reveals, the mean reduction of odorogenous contaminants recorded in the hall and subjected to biotreatment was satisfying as it surpassed 60% for most established pollutants. These high removal values were confirmed statistically only for single compounds. However, a low removal level was reported for hydrogen sulfide and sulfur dioxide. No reduction was recorded in the bentonite supplemented medium (BM) for sulfur dioxide and methyl mercaptan. In the organic medium (OM) no concentration fall was noted for dipropyl sulfide either. In all the media investigated, the highest removal rate (100%), not confirmed statistically, was observed for carbon disulfide. Very good results were obtained in the medium with a bentonite additive (BM) for both identified amines, whose mean elimination rate exceeded 60% (p

[Purification feasibility of malodorous waste gas contained H2S and CS2 by DBD technique].

Dielectric barrier discharge(DBD) technique was applied to remove H2S and CS2 in industrial waste gas. In the research of laboratory, when the voltage between two electrodes was 12 kV, 4 x 10(3) Pa H2S was discharged in air for 5 seconds, about 100% of H2S was transformed into H2O and SO2; 1.33 x 10(3) Pa CS2 was discharged in air for 15 seconds, about 80% of CS2 was transformed into CO2, CO and SO2. When the concentration of H2S and CS2 increased, the decomposition of them decreased. Based on the results, a DBD purification apparatus which can dispose 420 m3/h, 10 m/s waste gas was designed and manufactured, the removal rate of H2S can reach 89% and the energy consumption was 5.2 W.h/m3. It was concluded that the DBD technique is worth disposing malodorous industrial waste gases contained H2S and CS2.