Equilibrium adsorption isotherms and rates of thermal decomposition were measured for sodium dodecyl-benzene sulfonate (DBS) adsorbed on powdered activation carbon. The rate data were obtained in a thermal gravimetric apparatus operated both at constant temperature (522 to 666 K) and with a constant rate of temperature increase from 298 to 1023 K.About 50% of the adsorbed material could be removed at temperatures up to 748 K and only a small amount of the remaining 50% could be eliminated by further heating to 1,023 K. The residual adsorbate at 1,023 K was considerably greater than could be accounted for by inorganic materials such as NaeSOr.The kinetics of the decomposition up to 748 K could be explained by a two-reaction sequence, either parallel or consecutive reactions. Rates of decomposition were slower than found in earlier studies (Chihara et al., 1981) SCOPERegeneration of activated carbon normally requires drying of the spent carbon at temperatures up to 378 K, followed by heating and gasification at temperatures up to 1,073 K. The gasification process with an oxidizing gas is usually necessary to retain most of the original adsorption capacity. A large fraction of the deposited material can be removed by thermal decomposition prior to gasification (oxidation). For an adsorbate such as sucrose with no inorganic residue, nearly all of the adsorbed material is volatilized by heating alone. With more refractory materials such as DBS, heating to 1,073 K leaves significant carbonaceous material in addition to the inorganic residue.For design of regenerators, rate equations are necessary for both thermal decomposition and gasification. In a prior study (Chihara et al., 1981), kinetics were measured for these two processes with carbon containing adsorbed sucrose. For this easily decomposed adsorbate, the overall thermal decomposition process could be explained by separate, single, rate-controlling steps, the first for 298 K < T < 428 K and the second occuring at 428 < T < 773 K. The objective of the current work was to measure rates of thermal decomposition and gasification for a refractory adsorbate, and DBS was considered to be r e p resentative of such components found in wastewaters.First, equilibrium isotherms were measured at 303 and 308 K. Then thermal decomposition data were obtained in a TGA apparatus operated at constant temperatures up to 666 K and with a constant rate of temperature rise up to 1,023 K, all at atmospheric pressure in a stream of helium. These results are reported in Part I. In Part I1 rates of gasification of residual adsorbed material are reported and analyzed. CONCLUSIONS AND SIGNIFICANCEEquilibrium isotherms for DBS on BPL activated carbon (bituminous coal base) indicate capacities of 0.28 to 0.60 kg adsorbed per kg of activated carbon over a range of solution concentrations (aqueous) from 20 to 9, OOO ppm. These capacities are more than twice those for sucrose on the same carbon.No thermal decomposition was observed below about 490 K for DBS, while for sucrose more than 30% of...

The kinetics of the reaction between steam and thermally‐regenerated activated carbon containing DBS residue was studied at 973 to 1,062 K and atmospheric pressure. The results fit a Langmuir‐Hinshelwood rate equation originally developed for the oxidation of other types of carbon with steam. The rates of reaction were relatively high. Auxiliary experiments with added Na2SO4 indicated that the non‐volatile inorganic residue from DBS has a catalytic effect.Readsorption measurements on regenerated samples demonstrated that thermal regeneration alone resulted in considerable loss (35%) in adsorption capacity but that thermal regeneration followed by steam gasification could completely restore the adsorption capacity for DBS on the remaining virgin carbon.

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