[Show abstract][Hide abstract] ABSTRACT: Airborne hexavalent chromium has been classified as a human respiratory carcinogen and long term exposure has been known to cause ulceration and perforation of the nasal septum, bronchitis, asthma, and liver and kidney damage. Chromium electroplating plants are the major sources of atmospheric chromium and packed-bed scrubbers are the common control devices used to reduce emission of chromic acid mist from electroplating bathes. The feasibility of a new method to remove this pollutant using alginate beads as a biomass derivative was investigated by one factor at a time approach and Taguchi experimental design. Polluted air with different chromium mistconcentrations (10-5000 μg/m3) was contacted to alginate beads (3.3-20 g/L), floating in distilled water with adjusted pH (3-7), using an impinger at different temperatures (20 and 35oC), and various velocities (1.2 and 2.4 m/s). Although there were no statistical significant differences between factor levels, the higher ions removal efficiencies were achieved at lower levels of air velocities, pollution concentrations, higher levels of pHs, temperatures, and sorbent concentrations.
International journal of Environmental Science and Technology 03/2011; · 1.84 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A chromium electroplating bath with the ability to produce homogenous mist was used to evaluate parameters influencing hexavalent chromium (Cr +6) mist sampling methods. The results of 48 Cr +6 mist samples collected using the U.S. National Institute for Occupational Safety and Health method 7600 showed that Cr +6 concentration was higher: (1) For sampling by closed-face filter cassettes than for sampling by open-face filter cassettes (P <0.001); (2) for samples collected at 35 cm above the electroplating solution surface than for samples collected at 50 cm (P <0.001); (3) for sampling duration of 30 minutes than for sampling duration of 180 minutes (P <0.001); and, (4) for samples extracted immediately after sampling than for samples with delayed extraction (24 hours after sampling) (P <0.001). It is concluded that the accuracy of Cr +6 mist sampling in electroplating shops will be enhanced when: (1) closed-face filter cassette is used to prevent liquid splash contamination; (2) the recommended sampling height is 35 cm above the solution surface; (3) the sampling duration is short--approximately 30 minutes; and, (4) the extraction of the Cr +6 sample is performed as soon as the sampling is completed. INTRODUCTION Workers in many occupations are at risk due to exposure to hexavalent chromium (Cr 6+). Exposure to this chemical has been associated with cancer [1,2], ulceration, nasal septum perforation, contact dermatitis , occupational asthma , as well as kidney and liver damage . Chromium electroplating is a major source of atmospheric chromium pollution, and a majority of workers in electroplating facilities is exposed to Cr 6+ mist. While the actual number of non-registered electro-plating facilities is unknown, an estimated 2000 or more workers in approximately 400 registered electroplating workshops with the Iranian Electroplating Union in Tehran, Iran, are exposed to Cr 6+ . Thus, occupational health professionals have a strong interest in accurately determining Cr 6+ concentrations. Cr 6+ is relatively unstable and is likely to be reduced to its trivalent (Cr 3+) state [8,9]. Thus, hexavalent chromium sample as mentioned in MDHS 61, should proceed as soon as after sampling . Since the chemical stability and health effects of Cr 6+ differ signi-ficantly from those of Cr 3+ , the valence states of this chemical should be considered when evaluating potential risk to humans. Therefore, it appears that the sampling duration and sample-storage duration before analysis are two important parameters that should be considered when devising a Cr 6+ mist sampling method. Occupational exposure limits for most hazardous aerosols are based on some measure of "total suspended particulates" and samples are typically collected by using a sampling head, which is either a closed-face filter cassette or an open-face filter cassette. Current studies [11,12] have reported differences between the two types of sampling heads for a variety of aerosols and their sampling conditions. On the other hand, there are controversies among different methods and reports. For example, in MDHS 61 and US air force report stated open face and closed face samplers are suitable samplers, respectively [10, 13]. Therefore, choosing an appropriate type of sampling head (closed-face or open-face) seems to be an important Cr 6+ sampling method parameter. The height of the sampling location from the electroplating solution surface (sampling height) appears to be another important parameter and conflicting subject, affecting the Cr 6+ sampling method. In MDHS 52/3, Fig. 1: Set up of chromium mist generation system. A) Rectifier, B) Cathode, C) Anode, D) Electroplating bath, E) Anti acid pump, F&G) Valves, H) Plexiglas case, I) Hood.
[Show abstract][Hide abstract] ABSTRACT: Airborne hexavalent chromium is a known human respiratory carcinogen and allergen. Many workers are exposed to hexavalent chromium in various processes which chromium electroplating plants are the most common. In this study, the feasibility of a new control approach to remove this pollutant using chitosan beads as a biosorbent was investigated. Hexavalent chromium sorption was studied relative to pH, pollution concentration, sorbent concentration, temperature, and air velocity using one factor at a time approach and Taguchi experimental design. Polluted air with different chromium mist concentrations (10-5000 μg/m3) was contacted to chitosan beads (3.3-20 g/L), floating in distilled water with adjusted pH (3-7), using an impinger at different temperatures (20 and 35 °C), and various velocities (1.12 and 2.24 m/s). The ANOVA test result showed that, there were statistical significant differences between factor levels except optimized pH levels. The higher ions removal efficiencies were achieved at lower levels of air velocities, pollution concentrations, and higher levels of solution pH values, temperatures, and sorbent concentrations.
International journal of Environmental Science and Technology 06/2006; · 1.84 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Chromium mist generator is an essential tool for conducting researches and making science-based recommendations to evaluate air pollution and its control systems. The purpose of this research was to design and construct a homogenous chromium mist generator and the study of some effective factors including sampling height and distances between samplers in side-by-side sampling on chromium mist sampling method. A mist generator was constructed, using a chromium electroplating bath in pilot scale. Concentration of CrO3 and sulfuric acid in plating solution was 125 g L-1 and 1.25 g L-1, respectively. In order to create permanent air sampling locations, a Plexiglas cylindrical chamber (75 cm height, 55 cm i.d) was installed the bath overhead. Sixty holes were produced on the chamber in 3 rows (each 20). The distance between rows and holes was 15 and 7.5 cm, respectively. Homogeneity and effective factors were studied via side-by-side air sampling method. So, 48 clusters of samples were collected on polyvinyl chloride (PVC) filters housed in sampling cassettes. Cassettes were located in 35, 50, and 65 cm above the solution surface with less than 7.5 and/or 7.5-15 cm distance between heads. All samples were analyzed according to the NIOSH method 7600. According to the ANOVA test, no significant differences were observed between different sampling locations in side-by-side sampling (P=0.82) and between sampling heights and different samplers distances (P=0.86 and 0.86, respectively). However, there were notable differences between means of coefficient of variations (CV) in various heights and distances. It is concluded that the most chromium mist homogeneity could be obtained at height 50 cm from the bath solution surface and samplers distance of < 7.5 cm.
Journal of the Brazilian Chemical Society 01/2006; · 1.28 Impact Factor