Application of hollow fibre membrane reactor for biological removal of H2S

<p>Hydrogen sulfide (H<sub>2</sub>S) is a toxic pollutant and harmful to human health. Industries such as pulp and paper manufacturing, rayon production, natural gas extraction and refining, and crude petroleum refineries generate waste gas streams with high H<sub>2</sub>S concentrations. Both physico-chemical and biological methods are used for H<sub>2</sub>S removal from the gas stream. Biological methods offer several advantages such as environmental friendly, less expensive and require simple operation and maintenance compared to physico-chemical methods. In this study, a hydrophilic hollow fibre membrane (HFM) based bioreactor configuration has been tested for biological H<sub>2</sub>S removal. Three reactors were fabricated and operated for ~ 3 months where two reactors were used for biological conversion process and the third reactor was used for abiotic process. The effective membrane area of a HFM module used in each reactor was 0.0138 m<sup>2</sup>. The bioreactors demonstrated efficient gas-liquid mass transfer through the HFM module and achieved ~ 99% removal efficiency with an elimination capacity of ~ 17.0 g m<sup>-3</sup> h<sup>-1</sup>. The H<sub>2</sub>S flux of the bioreactor was ~ 0.20 g m<sup>-2</sup> day<sup>-1</sup> which was ~ 9 times higher than the abiotic reactor for an inlet H<sub>2</sub>S concentration of ~ 0.90 g m<sup>-3</sup>. The overall mass transfer coefficient value for the biotic process was 17.2 µm s<sup>-1</sup> which was ~ 25 times higher than the abiotic process. The bioreactors demonstrated both microbial attached growth on the membrane surface and suspended growth in the liquid phase. Microbial community analysis confirmed the presence of diverse sulfur-oxidizing bacteria at genus level including <em>Acinetobacter</em>, <em>Dechloromonas</em>, <em>Hydrogenophaga</em>, <em>Rhodopseudomonas</em> and <em>Sulfurospirillum</em>. Moreover, the enrichment of other bacterial genera such as ammonia-oxidizing (e.g. <em>Nitrosospira</em>), organic matter degrading (e.g. <em>Trichococcus</em>) and methanogenic (e.g. <em>Methanosaeta</em>) microorganisms demonstrate the diverse microbial ecology of the sludge growing in the bioreactor.</p>

Prehydrolysis kraft pulping of jute cutting and caddis mixture for rayon production

Jute cutting, jute caddis, and cutting-caddis mixtures were prehydrolyzed by varying time and temperature to get about 90% prehydrolyzed yield. At the conditions of 170°C for 60 min of prehydrolysis, the yield for 100% jute cutting was 76.3%, while the same for jute caddis was only 67.9%. But with prehydrolysis at 150°C for 60 min, the yield was 90% for jute cutting, where 49.94% of original pentosan was dissolved and prehydrolysis of jute caddis at 140°C in 60 min yielded 86.4% solid residue. Jute cutting-caddis mixed prehydrolysis was done at 140°C for 30 min and yielded 92% solid residue for 50:50 cutting-caddis mixtures, where pentosan dissolution was only 29%. Prehydrolyzed jute cutting, jute caddis, and cutting-caddis mixtures were subsequently kraft cooked. Pulp yield was only 40.9% for 100% jute cutting prehydrolyzed at 170°C for 60 min, which was 10.9% lower than the prehydrolysis at 140°C. For jute cutting-caddis mixed prehydrolysis at 140°C for 45 min followed by kraft cooking, pulp yield decreased by 3.3% from the 100% cutting to 50% caddis in the mixture, but 75% caddis in the mixture decreased pulp yield by 6.7%. The kappa number 50:50 cutting-caddis mixture was only 11.3. Pulp bleachability improved with increasing jute cutting proportion in the cutting-caddis mixture pulp.

Rayon Goes to War

This chapter examines the use of viscose rayon as a strategic maté by both sides during World War II. Viscose may have been coming into its own in World War II, but the military roots of the viscose rayon industry go much farther back than that. In fact, in the 1920s a recurring critique of the rapidly expanding artificial silk industry was rayon's potential use as a platform for rapid conversion to munitions manufacturing. This concern was driven in large part by the close chemical and manufacturing links between artificial silk made through the nitrocellulose process and the production of explosives. The United States entered the war after the initial European epidemic of toxic jaundice from tetrachlorethane. For Germany and Italy, rayon meant textile independence. In Japan, silk played this role. In the United States, the rayon production boom of the World War II era was only one small part of a far larger mobilization effort. Unfortunately, there was no parallel war time expansion in experimental research into the dangers of carbon disulfide.

Dissolving pulp from white press cuttings

Upgrading of white press cuttings into dissolving pulp was carried out by acidification followed by alkaline extraction. Acid treatment decreased ash content of white press cutting pulp from 11.25% to 0.33% at pH 2. The yield after acidification and screening was 87%. Alkaline extraction removed hemicelluloses and increased α-cellulose content to 92% with viscosity value of 4.3 mPa.s. The overall pulp yield after alkaline extraction was 76.6%. Alkaline extracted liquor contains 9.2% total organics, mostly pentose sugars in the oligomeric form. The produced dissolving pulp can be used for rayon production.