Regeneration of activated carbon. Part I: Thermal decomposition of adsorbed sodium dodecylbenzene sulfonate

Abstract

AbstractEquilibrium 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 Na2SO4.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) with adsorbed sucrose, and the kinetic steps were different. With sucrose, considerable decomposition occurred between 298 and 428 K. While with DBS, no decomposition was observed in this temperature range. Above 400 K, it was possible to explain the kinetics of decomposition in the case of sucrose by a single step forming residual carbon and volatile products, while with DBS, a two‐reaction sequence was required.