the spent liquors of thermomechanical (tmp) and neutral sulfite semichemical (nssc) pulping processes contain some lignocelluloses that are recently treated in the waste water of the processes, and thus wasted. in this dissertation, the adsorption concept was considered to separate lignocelluloses from the spent liquors (sl)s of tmp and nssc processes. various adsorbents such as activated carbon, fly ash, bentonite, kaolin, kaolinite, calcium carbonate, talc and aluminium silicate were used in order to adsorb lignocelluloses. the operating conditions of adsorption were optimized by adjusting ph, temperature and time of treatment. moreover, various alternatives, such as ph adjustment, polymer addition and multi-stage adsorption processes were considered to improve the overall extraction of lignocelluloses from sls. the properties of adsorbents, e.g. charge density and surface area, were related to the adsorption performance and the properties, e.g. turbidity and chemical oxygen demand (cod), of sls after adsorption. the high removals in turbidity and cod showed that the suggested processes were not only effective in extracting lignocelluloses but also efficient in decreasing the load of wastewater treatment of the plant. generally, the results showed that fly ash and precipitated calcium carbonate (pcc) were the best adsorbents for lignin removal, and the products could be used as fillers in composites.