Activated carbons volatile organic compounds removal using

The removal of volatile organic compounds (VOC) from air is most often accompHshed by TSA. Air streams needing treatment can be found in most chemical and manufacturing plants, especially those using solvents. At concentrations from 500 to 15,000 ppm, recovery of the VOC from steam used to regenerate activated carbon adsorbent thermally is economically justified. Concentrations above 15,000 ppm ate typically in the explosive range and... 

Potable Water Treatment. Treatment of drinking water accounts for about 24% of the total activated carbon used in Hquid-phase apphcations (74). Rivers, lakes, and groundwater from weUs, the most common drinking water sources, are often contaminated with bacteria, vimses, natural vegetation decay products, halogenated materials, and volatile organic compounds. Normal water disinfection and filtration treatment steps remove or destroy the bulk of these materials (75). However, treatment by activated carbon is an important additional step in many plants to remove toxic and other organic materials (76—78) for safety and palatability. 

Removal of hydrocarbons, volatile organic compounds (VOCs), and odors using activated carbon. 

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. 

When granular activated carbons (GAC) are used as the filter media, the GAC filter can also remove dissolved organics (such as TTO, total toxic organics or VOC, volatile organic compounds).1011... 

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. 

Activated carbon columns are frequently used to remove trace or dilute organic impurities from an inert nonadsorbing gas. These impurities may consist of toxic compounds, odor-forming compounds, solvent vapors, volatile organic compounds, etc. A TSA process is generally used for these applications. However, both TSA and PSA processes are used for the particular application of solvent vapor removal and recovery which are described in Section 22.4.1.1... 

The feasibility of using adsorbents, particularly activated carbon, as an alternative to steam stripping or chemicals injection techniques, for the removal of volatile organic compounds from an SBR latex is demonstrated using batch... 

Rey et al. ° removed chlorinated aromatic hydrocarbon from a pharmaceutical plant by stripping the chlorinated hydrocarbons with air and then adsorbing in activated carbon beds. The removal of chlorinated volatile organic compounds such as trichloroethane, cis, and trans dichloroethane from ground water contaminated with these nonaqueous liquids was carried out by Yu et al." using activated carbon fibers. All the halogenated compounds were adsorbed rapidly by the activated carbon... 

Home Filtration Systems. The same filtration and purification methods used in large water treatment plants have been downscaled for home use. Faucet-mount filters use carbon filtration, ion-exchange filtration, and submicron filtration to reduce sediment, chlorine, lead, mercury, iron, herbicides, pesticides, insecticides, industrial solvents, volatile organic compounds, synthetic organic compounds, and tri-halomethanes (THMs, chlorine and its by-products). These apparatuses rapidly provide filtered water that tastes and smells better with less cloudiness. Shower filters typically use copper-zinc oxidation media and carbon filtration to remove chlorine for softer skin and hair. Whole-house-use water filters are plumbed into the main water line and commonly include a sediment pre-filter, then copper-zinc oxidation media and crushed mineral stone or natural pumice to reduce chlorine, then activated carbon to remove other chemicals. 

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. 

Another popular method which gives a high-quality water is reverse osmosis (RO), often called ultrafiltration or hyperfiltration. Though often considered too expensive for industrial use, RO has found extensive applications in domestic water supplies. The production of highly efficient osmotic membranes has made RO competitive with distillation for the production of salt-free water. RO does not, however, remove volatile organic compounds (VOC) from the water supply. Treatment with granulated activated carbon (GAC) can be very effective for this purpose (see Chap. 16 and Appendix C). 

Activated carbon cloth (ACC) is used for the removal of volatile organic compounds fix)m effluent gas streams [1], Specific micropore structures in ACCs make them real candidates for use in adsorption processes where a high rate of adsorption is accompanied with short contact time between adsorbent and adsorbate. It is very important for manufacturers to produce ACC with desirable pore size distributions, and be able to control the development of various pores from primary micropores to mesopores during activation processes. Adsorption selectivity towards various gases is another very important property, which can be achieved by introducing oxygen complexes onto the surface during activation [2-4]. 

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