Environmental protection, aqueous processing

Lloyd-Jones, P.J., Rangel-Mendez, J.R., and Streat, M., Mercury sorption from aqueous solution by chelating ion exchange resins, activated carbon and a biosorbent, Process Safety and Environmental Protection, 82 (4), 301-311, 2004. 

From a separation-process point of view, a fluid-fluid reaction is intended to enhance separation (e.g., preparation of feed for a subsequent process step, product purification, or effluent control for environmental protection). Examples include the use of ethanolamines for the removal of H2S and C02 (reactions (A) and (B) in Section 9.2), the removal of SO, by an aqueous stream of a hydroxide, and absorption of 02 by blood or desorption of C02 from blood. A solid catalyst may be involved as a third phase, as in hydrodesulfurization in a trickle-bed reactor. 

Environmental Protection Agency (22). Figure 1 is a plot of the sediment/aqueous concentration ratio versus time for this system. It is characterized by a rapid sorption process and a much slower sorption process which does not reach equilibrium until about 10 days after initial mixing of the sediment and chlorpyrifos solution. 

The method for the manufacture of polypropylene by the Ziegler-Natta process, which has been in widespread use for several decades, involved some years ago a polymerization in a relatively volatile solvent, for example a light petroleum fraction. That was the drawback of this process, since in the separation and subsequent drying of the polymer formed the solvent could not be completely recovered. Problems are thus experienced in fulfilling environmental protection requirements. An additional obstacle was the large volume of aqueous waste that is generated during workup of the polymer suspension. 

Aqueous processing is already being embraced for environmental protection, because of its numerous advantages. Moreover, it is highly likely that aqueous processing will truly dominate the menu of possible technological approaches... 

Process design the CER describes the role played by ESH in Clariant s Integrated Product Policy . Environmental protection aspects of new products and packaging are discussed, as is the use of chemical productivity indicators to assess environmental efficiency. By way of example, the development of a chromic acid aqueous oxidation is described and savings on energy and sulphuric acid are quoted. 

Consider the issue of designing a recycle reactor to accomplish the degradation of 99.99% of the phenol present at a concentration of 1.1 x 10 M in supercritical water at 380°C and 278 atm. This destruction level is selected on the basis of Environmental Protection Agency standards for thermal treatment of hazardous organic wastes. The corresponding inlet concentration of oxygen is 0.08 M. Prepare a plot of the reactor volume required to process 8 m /h of the supercritical aqueous solution versus the recycle ratio for values of this ratio between 0 and 20. Comment. 

---