Bone char

Fig. XVII-29. Nitrogen isotherms the volume adsorbed is plotted on an arbitrary scale. The upper scale shows pore radii corresponding to various relative pressures. Samples A, Oulton catalyst B, bone char number 452 C, activated charcoal F, Alumina catalyst F12 G, porous glass S, silica aerogel. (From Ref. 196).

DecoloriZation. Filtration, often a refinery botdeneck, especially with poor-quaHty raw sugar, is foUowed by decolorization with bone char (traditional), granular activated carbon (now most common), ion-exchange resias, or any combination of these. Comparative merits and regeneration of these decolorizing systems are a frequent topic ia the Hterature (r6—r8,rll). 

Loss on carbon (equivalent decolorization use to bone char) 0.08%... 

BONE CHAR A decolorizing and de-ashing filtration material made from dried cattle bones that have been crushed and retorted (at >550°C) to activate their alkaline calcium phosphate crystalline structure and carbonaceous residue. 

The refining effect of ion exchange treatment is of sufficient magnitude to permit the elimination of a substantial portion of activated carbon, or bone char requirement. At least a portion of the cost of operation of the ion exchange unit is thus paid for by the savings in requirement of color adsorbent. 

In addition to removing colored impurities and other colloids, ion exchange resins effectively remove the uncolored precursor of these colored substances. It has long been recognized that a small amount of 5-hydroxymethylfurfural (HMF), formed from dextrose by the action of acid catalysts, decomposes to form organic acids as well as pigments which polymerize to form highly colored bodies.23 Normal bone char... 

Pb(ll) 3.900-533,000 (Florida. North Carolina, HAP. Bone Char, Apatite 11) Kaplan et ttl. 2002 Knox et al. 2003 Wright etal. 1995 This work... 

IIAP (Cas(POj),OH). FAP (Ca (P04hF). Carbonate FAP iCa,0uP04isCOjlOH.Fj. Florida is a mined naiural apatile mixiure of FAP and HAP (IMC Agrico. Mulberry. FL). North Carolina is mined natural Carbonate FAP (Aurora Phosphate Mine. Lee. NC). Bone char is apaiile made from bone char. Apuliic II is an FAP and HAP mixture made from fish bones. 

Bostick, W. D., Stevenson, R. J., Jarabek, R. J. Conca, J. L. 2000. Use of apatite and bone char for the removal of soluble radionuclides in authentic and simulated DOE groundwater. Advances in Environmental Research, 3, 488-498. 

Choy and McKay (2005) studied the removal of Cu2+ from aqueous phase using bone char in a batch reactor. The volume of the liquid was 1.7 L, the volume of the tank 2 L, and its diameter 0.13 m. A six-bladed flat impeller with a diameter of 0.065 m and a blade height of 0.013 m was used. Absorbent particles of 605- pm diameter were used for the adsorption experiments. 

The Thomas model has been used for the sorption of heavy metals using fungal biomass, bone char, chitin, and goethite (Kapoor and Viraraghavan, 1998 Lehmann et al.,... 

The dependence of q0 on residence time has been noticed and modeled elsewhere, in the case of zinc and acid dyes adsorption by bone char and activated carbon, respectively (Ko et al., 2002). The following equations were successfully applied ... 

Entrapment in alginate gel Adsorption on modified cellulose Cross-link with glutaraldehyde Adsorption on bone char... 

Figure 15.1. Processes for making adsorbents, (a) Flowsketch of a process for making molecular sieve adsorbents, (b) Process for reactivation of bone char, (c) Silica gel by the BASF process. The gel is formed and solidifies in air from sodium silicate and sulfuric acid, then is washed.free of sodium sulfate with water (Ullmann, Encyclopedia of Chemical Technology, Verlag Cliemie, Weinheim, Germany).

After activated carbon has become saturated with a vapor or an adsorbed color, either the vapor can be steamed out, condensed, and recovered (Fig. 2), or the coloration can be destroyed and the carbon made ready for reuse. The oldest example of this process uses the decolorizing carbon long known as bone char, or bone black. This consists of about 10% carbon deposited on a skeleton of calcium phosphate [Ca3(P04)2] and is made by the carbonization of fat-free bones in closed retorts at 750 to 950°C. 

Adsorption in water treatment is a robust technique for removing water-soluble ions, especially when these ions exist in water at low concentrations. Coincidentally, fluoride ions exist in some groundwaters at low concentrations, which are above the permissible limits. The principle behind this technique is that a component (fluoride in our case) is transported by diffusion from the bulk phase to the solid surface where it is bound at the surface or interface between two phases by either chemical or physical forces [35], Numerous investigations have focused on surface adsorption as a means of removing fluoride from water. As a result of these studies various water treatment plants using treatment media such as activated alumina or bone char have been constructed and are in use in several countries. One example is a water purification plant in Kansas that utilizes activated alumina [36], Several other smaller fluoride treatment facilities are scattered all over India, Kenya and Tanzania, among other nations. 

In a laboratory study, Abdel-Raouf and Daifullah [53] reported that the bone char derived by heating animal bone to 500-600°C could be used to remove fluoride from drinking water. Table 3 summarizes some of the capacities of bone char reported in literature. 

Table 3. Summary of adsorption capacities of various grades of bone char...

---