Molasses, adsorption

Molasses adsorption based on color units adsorption of dyes expressed as g/g carbon at an equilibrium solution concentration of 0.10 g/liter. 

Anthracite pre-roasted with alkali, then washed and steam-activated at 750° C. b Iodine adsorption expressed as g todtne/g carbon, molasses adsorption as color units adsorbed/g carbon. 

By fermentation with Streptomyces griseus, S. olivaceus, S. aureofaciens. Bacillus megatherium or Propionobacterium freudenreichii. Molasses is used generally as fermentation medium, C0CI2 and 5,6-dimethylbenzimidazole are added. Various adsorption and extraction methods are used for isolation from the fermentation liquors. 

Membrane fouling due to adsorption of polyelectrolytes (such as humic acids, surfactants, and proteins) may severely reduce ion permeability, especially in the anion-exchange membranes. However, exhausted anion-exchange membranes used in the ED of molasses, whey, citric acid, or sodium dodecyl-benzenesulfonate can be reactivated by circulating simultaneously an acidic solution in one compartment and an alkaline solution in the other one, both solutions at titres greater than 0.1 kmol/m3 (Tokuyama Soda Co., 1983). 

This work intends to show the complexity of the dynamic adsorption process and to evaluate capacity of some granular carbons of various firms to remove pollutants from water. Adsorbents have been tested by various methods, and static and dynamic adsorption have been compared. Characteristics of carbons has been evaluated by the determination of porous structure, specific surface, content of ashes (mineral substances) and crushing strength and abrasion resistance. Adsorption capacity of activated carbon has been determined by means of phenol, iodide, methylene blue, sodium lauryl sulphate and molasses indicators for static conditions, and surfactant has been used for dynamic conditions. Analysis of some factors influencing adsorption has been accomplished and directions of further studies have been shown. 

Values of adsorption capacity of granular carbons (Tab. 3) were determined in static conditions by means of FIBDM — indicator [11] (F — phenol, molecule size - 5 A, I - iodine - 10 A, B - methylene blue - 15 X, D - sodium laurylosulphate - 19 A, and M - molasses — 28 A). These values may be used for evaluation of powdered carbons and for determination of portions of adsorbents for phenol and surfactant adsorption for practical application. 

Quantitative measure of decolorizing capacity based on the change in color of molasses relates to adsorption of large molecules from a liquid. 

Six common isotherm shapes are shown in Figure 14.4. In fact, those are the classic isotherm types suggested by Brunauer et al. (1940). Each can be represented by numerous empirical equations, some of which are discussed later. The inherent shapes or types arise from the pore structure of the adsorbent, the nature of the forces between the adsorbent surface and adsorbate, and the dependence on concentration. Besides isotherms, other properties are related to adsorption capacity, especially surface area and pore size distribution. Some other properties are application oriented, such as CTC (carbon tetrachloride) index, iodine number, methylene blue factor, and molasses number, all defined in Table 14.1. They are frequently employed to describe activated carbons. 

The liquid-phase materinls are usually characterized by sorption tests using phenol, indina. or "molasses namber." The vapor-phase activated carbons are usually characterized by carbon tetrachloride or benzene ndsorplion tests. The adsorption capacity and the bulk density define the volumetric (mating capability of the material. 

In evaluating the effect of pH, it is always well to examine for possible indicator action which could be misinterpreted as an adsorption effect. Many colors in agricultural and industrial products behave as acid-base indicators, in which case a change in pH may alter the hue or change the intensity of the color, e.g., the color of a molasses solution diminished by one-third in going from pH 9 to 4. When it is desired to compare decolorizations conducted at different pH levels, all filtrates should be adjusted to an identical pH when reading the residual color intensities. 

The first step in refining is known as affination. This consists of washing the raw crystals in a centrifuge to remove any adhering film of molasses. A saturated sugar syrup is used because this will wash away the molasses film without eroding the sugar crystals. The washed crystals—now about 99° purity—are dissolved (melted) to form a 50-60% syrup and this is defecated. Lime is used for this— often in conjunction with phosphoric acid. The combined action of lime and phosphoric acid causes a co-precipitation of many residual impurities, and the filtered syrup is now ready for the adsorption station. 

The molasses test, M-RE, is perhaps one of the most widely used tests, and in some earlier days was the only control test used in the manufacture of many brands of decolorizing carbons. At that time many assumed that when a batch of carbon attained a desired M-RE all adsorptive powers would be uniformly developed and based on a general absence of customer complaints such a conclusion seemed to be justified. Incidents in more recent years have led to a modification of that earlier view. It is now recognized that the M-RE does not mirror every mutation and deviation in the activation environment and some deviations that do not affect the M-RE can and do alter other adsorptive powers. Consequently, a carbon may have a satisfactory M-RE and still be deficient in certain other affinities that can be essential for the purification of a particular product. 

Some mention should be made of a pseudo-activated carbon prepared by treating wood, peat, molasses, and similar materials with concentrated sulfuric or phosphoric acid, and heating to 120° to 300° C.69,70 The pseudo-carbon residue, after being washed with water, has adsorptive and ionic-exchange properties. These pseudocarbons should be used in their original wet state because drying causes a loss of adsorptive power. 

A similar relationship is shown in Table 9 3 between the adsorption of iodine and molasses color.30... 

Although similar methods of activation give similar isothermal slopes, the converse does not necessarily follow, and one should not conclude that two carbons were produced by the same method because the isothermal slopes are found to be parallel under a single set of conditions. Thus, the isotherms for molasses color with carbons L and M were found to be almost identical at 25° C, but were dissimilar when the adsorption was conducted at 95° C (Table 9 5). Here, although two carbons have a similar slope at 25° C, the same type of surface is not present on both carbons, as is revealed by the different response to temperature. From a practical point of view, the different response to temperature emphasizes the fact that industrial studies of adsorptive power should be conducted at the temperature to be employed in the process. 

ADSORPTION OF MOLASSES COLOR BY CARBON (Influence of Temperature on Adsorption Exponent)... 

Fig. 14 3. Adsorption of molasses color Carbon dosage expressed as g/SO ml solution...

Pore volumes of carbons are typically of the order of 0.3 cm /g. Porosities are commonly quoted on the basis of adsorption with species such as iodine, methylene blue, benzene, carbon tetrachloride, phenol or molasses. The quantities of these substances adsorbed under different conditions give rise to parameters such as the Iodine Number, etc. Iodine, methylene blue and molasses numbers are correlated with pores in excess of 1.0,1.S and 2.8 nm, respectively. Other relevant properties of activated carbons include the kindling point (which should be over STO C to prevent excessive oxidation in the gas phase during regeneration), the ash content, the ash composition, and the pH when the carbon is in contact with water. Some typical properties of activated carbons are shown in Table 2.2. 

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