Posttreatment processes

Soils contaminated with high levels of organically bound sulfur compounds require the use of additional wet scrubbing. Soils contaminated with high levels of organically bound chlorine compounds require the use of additional wet or dry scrubbing equipment. Soils containing heavy metals may require additional posttreatment processes to stabilize or remove the metals. 

Posttreatment processes have been used to improve the quahty of the resulting membranes, such as ion exchange (to provide catalytic properties or change them between hydrophobic and hydrophilic surfaces), liquid or vapor sililation, coke deposition, CVD (chemical vapor deposition), and ALCVD (atomic layer chemical vapor deposition). These techniques are used to reduce the intercrystalline gaps and the pore-mouth size, modify the acid properties of the modified membranes, and remove amorphous material. Some of these modifications have demonstrated very high separation selectivities for the resulting membranes however, in many cases, they are of limited practical application due to the relatively low fluxes obtained. 

Kasper D.R. (1993), Pre- and posttreatment processes for membrane water treatment systems, Proc. of the AWWA Membrane Technology Conference, Aug 93, Baltimore, 105-137. 

The response behavior of the sensor could effectively be influenced by the choice of the posttreatment process. The presence of noncontinuous rising responses for some sensor types shows that there is not one single response mechanism. This is consistent with the results obtained with more conventional, electrodeposited chemoresistors [107b,109]. Possible interactions are interparticle interaction, swelling [107b,107c], and the modification of the particle resistance because of the partial charge transfer [110]. 

Du Pont, a leader in reverse osmosis technology built around a unique class of tailored aromatic polyamides, was also an early leader in the gas separation field. Molecuiariy engineered aromatic polyimides were found by Du Pont to provide extraordinarily good flux arxl selectivity properties for hydrogen separations. POsttreatment processes for these membranes were rmt reported. 

Figure 19.13 Posttreatment process (a) masking of copper zones (positive masking), and (b) Cn/Cu thermocouple junctions after local etching.

Arsenic found in lewisite is converted in the red and charcoal-L processes into chlorovinylarsonic acid (CVA) in quantities of up to 3 percent by weight in the neutralent waste stream (Table 2-2). The fate of CVA depends on the posttreatment processes. In a SCWO reactor and in the GPCR caustic scrubber brine, the CVA is expected to be converted to sodium arsenate salts (e.g., Na3As04 and Na4As207), which can then be treated with ferric chloride to produce ferric arsenic salts for disposal in a hazardous waste landfill. This treatment scheme, which was developed in Canada, is... 

Consideration is given to the different steps involved in rubber-to-metal bonding, including surface preparation of metal substrates, the application of primers and adhesives, and moulding, vulcanisation, curing and posttreatment processes. Factors which can lead to weak adhesion and bond failure are discussed, and approaches to the identification and correction of such problems are outlined. 

Pyrolysis oil consists of a complex mixture of aliphatic and aromatic oxygenates and particulates. Also known as cmde bio-oil, it is very viscous, acidic and unstable liquid with relatively low-energy density compared to conventional fossil oil. This nature of the bio-oil requires costly posttreatment processes that make the commercial pyrolysis economically less... 

Oxidation Most posttreatment processes arc used to alter the pore size distribution in the CMS membrane. The most common method used to increase the pore size in CMS membranes is low-temperature oxidation. Researchers have used several different techniques. Softer et al. (1987) treated hollow-fiber CMS membranes derived from cellulose precursors using 400°C air for 15 min to increase the permeance. Kusakabe et al. (1998) produced supported CMS membranes from BPDA-ODA polyimide. The membranes were then posttreated with oxygen at 300°C for 3 h. The posttreatment increased the permeance by an order of magiutude but had tittle effect on the selectivity. The authors attributed this to an increase in pore volume without broadening the pore size distribution. 

The results prove that the surface energy properties of plasma polymer films can be modified by using an appropriate thermal posttreatment process which appeared to be particularly useful for the production of strongly adherent protective coatings for metals. 

In most membrane modification processes, posttreatment processes remain one of the important steps for ensuring better, or even outstanding, membrane performance. However, a posttreatment process is not a compulsory step in the polyelectrolyte adsorption process (Shan et al. 2010). This can be an important advantage to compensate the drawbacks involved during the adsorption of the polyelectrolytes onto the polymeric membranes. In most cases, the polyelectrolyte-modified membranes can be used directly for membrane characterizations and applications. 

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