Volatile organic compounds adsorption/removal

Modification techniques for activated carhon were used to increase the removal capacity by surface adsorption and to improve the selectivity to volatile organic compounds (VOCs). Modified activated carbons (MACs) were prepared by modifying the purified activated carbon with various acids or bases. The effects of adsorption capacity and modified contents on the textural properties of the MACs were investigated. Furthermore, VOC adsorption and desorption experiments were carried out to determine the relationship between the adsorption capacity and the chemical properties of the adsorbents. High adsorption capacity for the selected VOCs was obtained over lwt%-H3P04/AC (lwt%-PA/AC). As a result, MAC was found to be very effective for VOC removal by adsorption with the potential for repeated use through desorption by simple heat treatment. 

Polyad [Polymer adsorbent] Also written POLYAD. A family of processes for removing volatile organic compounds from air streams by continuous adsorption on an adsorbent and desorption with hot air. Several adsorbents are used, depending on the sorbate, including a macroporous polymer ( Bonopore ). Used for control of emissions and for solvent recovery. COMBI-AD is a variant for simultaneously removing several solvents, using two different adsorbents. Developed and offered by Chematur Engineering, Sweden. Twelve units had been installed, in several countries, by 1995. 

Bisschops, M. A. T., van der Wielen, L. A. M. and Luyben, K. Ch. A. M. in Semel, J. (ed) Process Intensification in Practice, Applications and Opportunities (BHR Group, London, 1999) 229. Centrifugal adsorption technology for the removal of volatile organic compounds from water. 

There are six primary in-plant control methods for removal of priority pollutants and pesticides in pesticide manufacturing plants. These methods include steam-stripping, activated carbon adsorption, chemical oxidation, resin adsorption, hydrolysis, and heavy metals separation. Steam-stripping can remove volatile organic compounds (VOCs) activated carbon can remove semi volatile organic compounds and many pesticides and resin adsorption, chemical oxidation, and hydrolysis can treat selected pesticides [7]. Heavy metals separation can reduce toxicity to downstream biological treatment systems. Discussion of each of these methods follows. 

Ambersorb 600 is a carbonaceous adsorbent for removal of low levels of volatile organic compounds (VOCs) from vapor streams. The adsorbents are placed in a fluidized-bed adsorption system that can attain a high flow rate. Ambersorb 600 is a commercially available technology. 

Polyad [Polymer adsorbent] Also written POLYAD. A family of processes for removing volatile organic compounds from air streams by continuous adsorption on an adsorbent and desorption with hot air. Several adsorbents are used, depending on the sorbate, including a macroporous polymer... 

Steam regeneration is most commonly applied to activated carbon that has been used in the removal and/or recovery of solvents from gases. At volatile organic compound (VOC) concentration levels from 500 to 15,000 ppm, recovery of the VOC from the stream used for regeneration is economically justified. Below about 500 ppm, recovery is not economically justifiable, but environmental concerns often dictate adsorption followed by destruction. While activated carbon is also used to remove similar chemicals from water and wastewater, regeneration by steam is not usual. The reason is that the water-treatment carbon contains 1 to 5 kg of water per kg of adsorbent that must be removed by drying before regeneration or an excessive amount of superheated steam will be needed. In water treatment. 

Biofiltration can be used to remove volatile organic compounds, including odors, from waste air.295 Pseudomonas spp. can remove toluene, and Bacillus spp., ethanol. The process is suitable for use on food-processing plants, public treatment works, and others, to control odors. The cost can be quite a bit lower than that of incineration or adsorption on carbon. A biofilter with Nitrosomonas eu ropaea immobilized in calcium alginate removed 97.5% of ammonia from air.296... 

Zaitan H., Chafik T., FTIR Determination of Adsorption Characteristics for Volatile Organic Compounds Removal on Diatomite Mineral Compared to Commercial Silica (2005) C.R. Chimie 8,1701-1708. 

Ozturk, B. and Yilmaz, D. (2006) Absorptive removal of volatile organic compounds from flue gas streams. Process Safety and Environmental Protection, 84,391-398. Paethanom, A., Nakahara, S., Kobayashi, M. etal. (2012) Performance of tar removal by absorption and adsorption for biomass gasification. Fuel Processing Technology, 104, 144-154. 

More recently, a new technology for NO removal has been proposed as an alternative to SCR. This technology with the trade name SCONOx (8) allows the abatement of NO, CO, and volatile organic compounds (VOC) and is based on a cyclic operation NO are stored on a catalyst/sorber material during the adsorption phase, whereas during the subsequent regeneration phase the adsorbed NO species are reduced to nitrogen. 

Common poisons for the cathode include NO, SO2, and volatile organic compounds (e.g., benzene). Therefore, the air filter should not only remove particulates but also those poisoning species through chemical absorptions or physical adsorptions. The filter should be cleaned, regenerated, or replaced when saturated with any of those species. 

Rayon-based ACFs are used in the adsorption of many volatile organic compounds including formaldehyde (80), methyl ethyl ketones (81), and benzene (81). ACFs are also finding uses in natural gas storage (82), electrodes for batteries (83), catalyst supports (84), and NO removal (85). Stabilized rayon fibers are carbonized and then activated with air (80), steam (86), or carbon dioxide (87), much as in granular carbon activation. The extent of pyrolysis governs the pore structure, carbon yield, and surface area of the fiber, while activation impacts the presence of functional groups on the pore surface (12). Properties of some commercial ACFs are summarized in Table 6. 

Adsorption has been playing an increasingly important role in environmental control. The sorbents being nsed in common industrial adsorption systems for the removals of SO2 and volatile organic compounds (VOCs) are qnite weU-estabUshed. The VOC removal systems often use activated carbon, polymeric resins, and hydrophobic zeolites, for both gas and aqueous systems. Activated carbon (and alkalized forms) and hydrophobic zeolites are used for SO2 removal. Lime injection is used for SO2 removal from hot gases. For NO removal, on the contiary, no suitable sorbents have been established. For this reason, selective sorbents for NO remain an active research area, and will be discussed. The search for CO2 sorbents is also of interest. The subject of CO2 sorbents has been discussed recently in an excellent review by Yong et al. (2002) and will not be covered here. 

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