Solvent adsorption technology

Not all sites view the adsorption unit as a positive addition to the value of an enterprise. Some sites view it as a distinct drawback to the use of solvent cleaning technology. They ascribe the need for it to the advent of more stringent safety, exposure, and pollution (SHE) regulations. 

An alternative carbon adsorption technology uses the cam rotary valve method, which, unlike conventional adsorption technology that employs duplex systems, uses only a single unit that is divided into multiple compartments. On a rotary basis, a central valve in the unit distributes contaminated air to an individual compartment. While each compartment in turn undergoes regeneration, the rest are purifying the solvent-laden air. This device provides continuous, uninterrupted adsorption and uses less activated carbon. 

A wide range and a number of purification steps are required to make available hydrogen/synthesis gas having the desired purity that depends on use. Technology is available in many forms and combinations for specific hydrogen purification requirements. Methods include physical and chemical treatments (solvent scmbbing) low temperature (cryogenic) systems adsorption on soHds, such as active carbon, metal oxides, and molecular sieves, and various membrane systems. Composition of the raw gas and the amount of impurities that can be tolerated in the product determine the selection of the most suitable process. 

Soil samples have been found to contain 500 ppm of TCE and 750 ppm of benzene. Two technologies are being considered to remediate the soil. One is based on vapor extraction combined with carbon adsorption. The other technique is simply to inject steam into the ground, vaporize the solvents and then withdraw them as a vapor extraction technique, discharging the... 

In ODS, sulfur compounds present in fuels are oxidized to more polar sulfones / sulfoxides to facilitate their removal by solvent extraction or adsorption. Various oxidation systems have been reported in the literature for this transformation. Among these oxidants like hydrogen peroxide (H2O2) and carboxylic acid as catalyst3"5. For the chemical industry, it becomes more and more important to develop cleaner technologies. Solvent extraction processes are used to separate sulfones / sulfoxides from oxidized fuels. These processes required suitable and selective solvents for separation of oxidized sulfur compounds from petroleum feedstocks. 

Membrane extraction offers attractive alternatives to conventional solvent extraction through the use of dialysis or ultrafiltration procedures (41). The choice of the right membrane depends on a number of parameters such as tlie degree of retention of the analyte, flow rate, some environmental characteristics, and tlie analyte recovery. Many early methods used flat, supported membranes, but recent membrane technology has focused on the use of hollow fibers (42-45). Although most membranes are made of inert polymers, undesired adsorption of analytes onto the membrane surface may be observed, especially in dilute solutions and when certain buffer systems are applied. 

Research continues on this technology. It is hoped that a carbon impregnated cofoam will eventually demonstrate the required carbon adsorption and solvent extraction effects. 

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