Posttreatment oxidation

Most gas blacks are oxidatively posttreated to increase the concentration of acid groups on the surface even further (see Section 5.7.6.2.4). Due to their good dispersion properties, gas black is mainly used as pigment black in the paint and printing ink industries. 

In many cases it is desirable to augment the content of volatile components. This is accomplished by oxidative posttreatment in which acidic surface groups are formed. This oxidation can be carried out at high temperatures both in the liquid phase and in the gas phase with e.g. ... 

Oxidative posttreatment can increase the surface-content of acid groups and thereby make the carbon black more hydrophilic... 

The entire non-stockpile inventory of binary CWM components is stored in canisters and drnms at Pine Bluff Arsenal, a stockpile site. Options for treatment include destruction in the Pine Bluff Chemical Disposal Facility, direct destruction in a plasma arc system, or chemical neutralization followed by oxidative posttreatment of the neutralents. The high concentration of fluorine in the binary component DF raises concerns about corrosion in some treatment systems. 

Recommendation Ideally, the binary precursors methyl-phosphonic difluoride (DF) and ethyl-2-diisopropylamino-ethyl methylphosphonite (QL) stored at Pine Bluff Arsenal should be destroyed directly, either by burning in the Pine Bluff Chemical Destruction Facility incinerator or by plasma arc treatment. If these facilities cannot handle the fluorine-rich DF destruction products, the committee recommends that on-site neutralization followed by oxidative posttreatment of the neutralents be developed. The easiest posttreatment may be shipment to a commercial incinerator capable of dealing with high levels of fluorine (Recommendation 3-2). 

Neutralization on-site is an attractive alternative for destruction of this materiel if direct destruction by a high-tem-perature process is not feasible. As described in Chapter 2, neutralization of DF and QL by water hydrolysis was demonstrated in a campaign at APG in 1997. However, this procedure produces neutralents that contain large amounts of CWC Schedule 2 precursor compounds. Therefore, it may be necessary to incinerate the neutralents or to develop an oxidative posttreatment system to destroy these compounds prior to final disposal. The DF neutralent will also contain fluoride, which may limit the number of commercial TSDFs capable of destroying it. However, one TSDF operator has indicated that his facility frequently burns high-fluoride solutions. Alternatively, the fluoride content of oxidized neutralent could be immobilized by treatment with calcium hydroxide (slaked lime) in preparation for final disposal. 

Fuertes and Menendez (2002) and Centeno and Fuertes (1999, 2001) have published a series of studies using this precursor. Centeno and Fuertes (1999) have spin coated a small amount of a novolak-type phenolic resin on the surface of carbon supports. The membranes were then carbonized in a tubular furnace from 500 to 1000°C in vacuum. The resulting membranes had O2/N2 selectivity of around 10 and CO2/CH4 selectivity of 160. This work was later extended and in that case (Centeno and Fuertes, 2001 Fuertes and Menendez, 2002) a novalak-type phenolic resin was deposited on the inner face of a ceramic tubular membrane used for ultrafiltration. The membrane was subsequently pyro-lyzed to 700°C. In some cases an oxidative pretreatment was used before pyrolysis or an oxidative posttreatment after pyrolysis. The resulting membranes had O2 permeabilities around 100 Barrers and O2/N2 selectivities around 12 at 25°C. Films dip coated with resin three times had lower permeability and only slightly higher selectivities than those dipped only once. For hydrocarbon mixtures, the separation performance was increased by several treatments air oxidation of the resin, air oxidation of the carbon, or chemical vapor deposition (CVD) posttreatment of the carbon. 

Chemical Oxidation. Chemical oxidation can be appHed ia iadustrial wastewater pretreatment for reduction of toxicity, to oxidize metal complexes to enhance heavy metals removal from wastewaters, or as a posttreatment for toxicity reduction or priority pollutant removal. 

Materials obtained from the LDH show a reduction in SSA with the temperature as reported in the literature. This reduction can be attributed to the crystallisation of the material [15,17]. However, post-treatment with mineral acid was an increase in the SSA for all temperatures. It is possible to attribute this increase to two combined effects, which can both increase the porosity of the materials, as well as yield more active adsorption sites (i) the elimination of ZnO and (ii) the elimination Zn(II) cations occupying octahedral sites in the spinel oxide structure. Even though the SSA had varied sensibly, the average pore size (APS) remained fairly constant with temperature. Acid treatment increases the APS value for all temperature tested, although the effect was very small (Figure 5b). Comparison of the materials obtained by the different synthesis methods showed that spinel oxides obtained from the LDH presented greater SSA values than those obtained by other methods, principally after the posttreatment with mineral acid. On other hand, the treatment with acid had little influence on the textural properties of the spinel oxides obtained by the other methods. 

Non-oxide ceramic nanomaterials, such as carbides, nitrides, borides, phosphides and silicides, have received considerable attention due to their potential applications in electronics, optics, catalysis, and magnetic storage. In contrast with the traditional processes, such as solid state reactions, CVD, MOCVD and PVD, which involve using high temperatures, toxic organometallic precursors, or complicated reactions and posttreatments, solvothermal method is a low temperature route to these materials with controlled shapes and sizes. 

The composition of macro PS is largely pure silicon micro PS can have considerable amounts of hydrides, oxides, and other compounds depending on the conditions of anodization and posttreatment. 

Posttreatment is necessary, because ammonium nitrate is highly hygroscopic. In view of its strong oxidizing power, only inorganic substances such as attapulgite, kieselguhr or clay can be used. 

This posttreatment is mainly carried out on gas blacks for pigment manufacture. Strongly oxidized gas blacks can contain more than 20% by weight of volatile components. 

The third strategy for minimizing NOx, known as posttreatment, involves removing NOx from the exhaust gases after the NOx has already been formed in the combustion chamber. Two of the most common methods of posttreatment are selective catalytic reduction (SCR) and selective noncatalytic reduction (SNCR).7 Wet techniques for posttreatment include oxidation/absorption, oxidation/absorption/reduc-tion, absorption/oxidation, and absorption/reduction. Dry techniques for posttreatment, besides SCR and SNCR, include activated carbon beds, electron beam radiation, and reaction with hydrocarbons. 

In water and wastewater treatment ozone is used for the following purposes 1) disinfection 2) oxidation of organic compounds, including removal of taste, odor, and color and 3) oxidation of inorganic com-pounds.f Ozone is usually used as pre-, intermediate-, or posttreatment with other processes such as sedimentation, adsorption, filtration, etc. 

Electrochemical oxidation with Ag(ll) is dropped from the second track because it seems a poor choice for posttreating the chloride-rich neutralents derived from HD, CG, and L agents, which are likely to be involved in most... 

---