Column bone char

In Tanzania where fluorosis is also endemic, a household bone char filter column defluoridator has been developed [4], This unit is slightly differently configured from those described above. It has two separate detached sections. The upper section holds water to be treated, while the lower section is column-like and contains the adsorption media. Water from the upper section is passed by gravity... 

Bone Char Decontamination of Mound Facility Waste Streams. Both bench and pilot plant scale studies have been performed to investigate the application and integration of bone char in schemes to remove alpha activity (238Pu, 239Pu, 233U) from various aqueous waste streams generated at the Mound Facility. These studies have culminated in installation and successful operation of a plant-size bone char column for tertiary treatment of the Mound Facility low-risk waste stream. Highlights of the Mound experience with bone char, based on results reported in part elsewhere, are briefly summarized in this paper. 

Two columns, each 0.6 m diameter and 1.1+ m high (Figure l) and each containing about 230 kg of bone char, are planned for further decontamination of the effluent from the sand filter. Figure 2 illustrates the flow diagram of the bone char tertiary... 

Figure 1. Bone char column used in tertiary treatment of mound facility low-risk...

The criteria used in designing the full-scale treatment system were based on data obtained from a pilot-plant study using a 0.38 m dia. by 0.6l m high bed of bone char operated at a rate of about bO Z/mln. Feed to the column contained an average 0.18 nCi/ alpha activity while the effluent contained about 0.09 nCi/ total alpha. This bed of bone char satisfactorily decontaminated 2.1 x 105 Z of feed before saturation. 

Figure 3. Pilot plant test of combined filtration-bone char decontamination of mound facility caustic waste fH) after filters, (A) after first bone char column, (O) after second bone char column, (%) after fourth bone char column. Conditions pH = 8 flow = 20 ml/min total bed height, 2.0 m of 275-fi bone char diameter of bed, 5.1 cm intial [Pu], 8 mg/L (3. X 1011 d/m/ml).

Ten different adsorbents were chosen for the present evaluation. They include four types of adsorbents (1) inorganic activated alumina and bone char adsorbents, (2) macroporous cation exchange resins, (3) macroporous anion exchange resins, and (4) chelating heavy metal removal agents. Equilibrium adsorption of Pu(IV) from actual PFP wastewater spiked with a Pu tracer was measured for each of the adsorbents. The plutonium tracer was required because the activity of plutonium in the wastewater was too low to be measured conveniently. Those adsorbents that adsorbed plutonium strongly were then tested in column flow-through experiments and the rate of plutonium adsorption was measured. 

Bone char appears to be the most effective adsorbent for removal of plutonium from the wastewaters because of high distribution coefficients for plutonium adsorption and rapid adsorption. The capacity of bone char for plutonium absorption can be calculated from a measured Kd value, assuming a reversible equilibrium adsorption reaction and a linear adsorption isotherm. If the capacity is defined as the point where the plutonium concentrations in the column feed and effluent are equal, the maximum volume of wastewater that can be treated (V ax) is (14)... 

The required size of the process bone char columns for PFP wastewater can be estimated from adsorption rate measurements. Values of C/Co are plotted in Figure 9 for the 26 mL bone char columns as a function of residence time. TTie required C/Co value is defined as follows ... 

Figure 9. Plutonium Adsorption on Bone Char for Various Column Residence Times...

Bone char, the forefather of activated carbon, has long been in the forefront of adsorbents for sugar refining. The granular char is placed in columns through which the hot syrups percolate until the char is exhausted, as evidenced by the appearance of color in the filtrate. The bone char is then regenerated by thermal means for re-use.3... 

The reactivation of bone char in sugar factories is a long established practice.3 The spent char is washed in the column to recover sugar syrup ( sweetening off ) and then heated to a dull red temperature in the almost complete absence of air. 

Technicians working with bone char have found that channelling is minimized by using granules of uniform particle size, and it has been recommended that a sample of char be screened into separate sizes, placing the largest size at the bottom of the laboratory column and the smallest size at the top.17 The carbon should be pre-soaked in the hot liquid to be treated, or in hot water to expel the air from the carbon. Some authorities recommend upward flow others prefer downward flow. 

The design of a suitable laboratory column presents difficulties. In order to provide time of contact and linear velocity of flow equal to that in a plant column, the laboratory column would need to be of equal length and that is not always practicable. Workers with bone char have devoted much study to tests with columns and have developed various procedures.17... 

FIGURE 15.29 Breakthrough curves for bone char column (500-710 /u.m) with 4 mmol/L cadmium ions in solution flowing at 50 mL/min. 

In a related study, a biomass material, bone char was investigated by Ma et al. (2008) for its feasibility as a cost-effective biosorbent for F removal from drinking water. The amorphous biosorbent powder, which is composed mainly of calcium phosphate and a small amount of carbon, was prepared by heating bone-biomass. The adsorption capacity of the hone char was shown to be better than that of activated aluminum and tourmaline (i.e., crystal horon sUicate mineral compounded with elements such as aluminum, iron, magnesium, sodium, hthium, or potassium). Removal of F was attributed to the processes of ion binding and ion exchange between bone char and F". The authors developed static and kinetic models which provided a satisfactory prediction of F concentration after adsorption. Experiments with fixed-bed columns... 

Bone char and granular carbon are generally used in fixed beds or in cylindrical columns 20 to 25 feet high and about 10 feet in diameter. Some recent systems percolate liquor upward or downward through a stationary bed of adsorbent or by counter-current flow of liquor and adsorbent (CAP or continuous adsorption process). (See below. Fig. 9.17.)... 

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