Carbon dosage

To obtain a meaningful isotherm, as wide a range of carbon dosages as practical should be used. Recommended dosages are 0.05, 0.1, 0.2, 0.5, 1.0, 2.5, 5.0, and 10.0 g of carbon per 100 g of the test liquid. Prior to analysis of the treated liquid, the carbon must be removed from the liquid. Carbon can be removed by filtration. The filtration rate may be increased by using heat or pressure. If the liquid is so viscous that filtration is difficult, centrifugation can sometimes be used as a suitable separation. 

From an isotherm test it can be determined whether a particular organic material can be removed effectively. It will also show the approximate capacity of the carbon for the application and provide a rough estimate of the carbon dosage required. Isotherm tests also afford a convenient means of studying the effects of pH and temperature on adsorption. Isotherms put a large amount of data into concise form for ready evaluation and interpretation. Isotherms obtained under identical conditions using the same contaminated groundwater for two or more carbons can be quickly and conveniently compared to determine the relative merits of the carbons. 

Carbon dosage in pounds of pollutants removed per pound of carbon... 

Reactions of the hydronium ion with porous active carbon have been investigated in aqueous systems. Hydronium-ion activity, specific-anion concentration, and carbon dosage have been among the major variables studied. Rates of reaction have been found to be limited by pore diffusion, as partially verified by activation energies of —(2 to 3) kcal. per mole-deg. The results can be interpreted partly in terms of a reaction of the hydronium ion and dissolved oxygen with a surface benzpyran (chromene) group to produce hydrogen peroxide and a surface benzopyrylium (carbonium) ion with a sorbed anion, and partly in terms of physical sorption of the acid on the carbon surface. 

Salt Effects. The HCl-NaCl system has been studied further to determine the effect of NaCl concentration on the acid-carbon reaction. The carbon dosage was varied from 0.33 to 2.0 grams of 273-micron... 

Once filtrate normalities are set within the specified range, perform the following calculations for each carbon dosage ... 

Using logarithmic paper, plot XIM (as the ordinate) versus C (as the abscissa) for each of the three carbon dosages. Calculate the least squares fit for the three points, and plot. The iodine number is the XIM value at a residual iodine concentration (C) of 0.02 N. The regression coefficient for the least squares fit should be greater than 0.995. 

Carbon dosages may be estimated initially by using three values of C (usually 0.01, 0.02, and 0.03) as follows ... 

In the study of the adsorption phenomenon by means of adsorption isotlierms it must also be realized that the initial concentration of the adsorbate, the carbon dosage, and particle size all influence the results obtained [3 ]. Some of the observed effects are to be attributed to the complex nature of humic substances so that their adsorption is a multicomponent process. 

Set up at least five flasks and add a selected carbon dosage to each flask. 

If carbon dosages do not provide the desired range of results, repeat the test with different... 

T. C. Tan and W. K. Teo, Combined Effect of Carbon Dosage and Initial Adsorbate Concentration on the Adsorption Isotherm of Heavy Metals on Activated Carbon, Water Research, 21, 1183-1188 (1987). 

Among other factors that may influence the removal of metal ions by activated carbon, different surveys have pointed out the combined effect of initial metal concentration and activated carbon dosage with a decrease in adsorption as the metal/carbon ratio increases [24, 25], or of temperature [26]. 

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