The use of peat in fixed bed adsorption for removal of total oxygen demand in black liquor and alkyl benzene sulfonate in aqueous solution

Abstract

Peat moss was used as an adsorbent in a packed bed column to reduce TOD (Total Oxygen Demand) from black liquor of pulp and paper mills and ABS (Alkyl Benzene Sulfonate) from an aqueous solution. A peat moss column seemed to be capable of removing almost completely TOD and ABS from an initial TOD concentration of black liquor of approximately 50,000 ppm and an initial ABS concentration in aqueous solution of approximately 7 ppm. In the initial tests with black liquor, it was noticed that TOD was increased by the probable reaction between sulfite compounds of black liquor and peat moss compounds. Subsequent tests, performed with black liquor treated with calcium chloride to precipitate sulfite compounds, showed an increased adsorption. The tests indicated an adsorption capacity of approximately 36% and 0.03% by weight of peat moss in cases of TOD of initial concentration of 53,000 ppm and ABS of initial concentration of 7 ppm respectively. Comparing with the data on adsorption of ABS in aqueous solution by activated carbon (1), it was found that peat moss was approximately 0.20% as effective as activated carbon in adsorbing ABS. The conventional external mass transfer model was applied to describe the data of an experiment on adsorption of ABS and it was found that the model could describe the data up to point adsorbate compositions of approximately 0.125 mgm of ABS/gm of oven dry peat.