Precipitation processes early work

Since the discovery of the Loeb-Sourirajan technique in the 1960s, development of the technology has proceeded on two fronts. Industrial users of the technology have generally taken an empirical approach, making improvements in the technique based on trial and error experience. Concurrently, theories of membrane formation based on fundamental studies of the precipitation process have been developed. These theories originated with the early industrial developers of membranes at Amicon [19,22,24] and were then taken up at a number of academic centers. Unfortunately, much of the recent academic work is so complex that many industrial producers of phase separation membranes no longer follow this literature. 

Most investigators agree on the necessity of avoiding the development of an alkaline front from the cathode compartment into the soil since most heavy metals precipitate/adsorb to the soil in the alkaline environment, and the result is that the remediation process ceases, as shown in many of the early works on EK soil remediation (Kim and Kim, 2001). Most commonly, pH control maintains acidic conditions in the cathode compartment, and thus efficiently prevents the alkaline front from developing into the soil (Hicks and Tondorf, 1994 Wieczorek et al, 2005). Implementation of ion exchange membranes as mentioned above is another way to prevent the alkaline front (Hansen et ai, 1999). In laboratory experiments, the soil is commonly homogenized and the water is saturated. In full-scale experiments, the situation is different Here the electrode compartments are placed directly into the inhomogeneous soil, whose humidity is decided by the natural precipitation, as these systems are open and most often in situ. This could be one major reason why the scale up from laboratory cell experiments to full-scale remediation is so difficult (Hansen et al, 1997 Ottosen et al, 1997). 

The genesis of the LO-CAT process is found in the early work by Humphreys and Glasgow in London. The initial British process, named the C.I.P. (Chelated Iron Process), used Ethylene Diamine Tetra Acetic Acid (EDTA) to keep the iron in solution. The first application of the process in an oil refinery in Landarcy, Wales, in 1964, was unsuccessful because of the instability of the chelated iron solution. The instability problem was due to a combination of two factors The precipitation of hydrated iron oxides at elevated pH, and the degradation of the chelating agent over time (Meuly and Ruff, 1972 Meuly. 1973). 

Blumenfeld An early version of the Sulfate process for making titanium dioxide pigment, in which the nucleation of the precipitation of titania hydrate is accomplished by dilution under controlled conditions. Invented by J. Blumenfeld, a Russian working in London in the... 

Plutonium peroxide was investigated by Hamaker and Koch, (0 Hopkins, (2) and Koshland, et al. (3) in the 19 0 s and Leary (h) in the early 1950 s. This work showed that the composition of the precipitate varied and often incorporated anions from the solution from which it was precipitated. These investigations, as well as other work (5), also showed that the peroxide precipitate exists in both hexagonal and cubic crystalline forms. Although both forms are compounds of Pu(lV), they have slightly different O /Pu ratios (6). The cubic form can be colloidal and therefore is less suitable for process application than the hexagonal form. The acidity of the solution has an effect on the... 

---