PRODUCTION OF ACTIVATED CARBONS FROM THE WOODWORKING INDUSTRY WASTE

Abstract

Effective waste management is an urgent task of the woodworking industry. Thermochemical methods of wood biomass processing allow to secure comprehensive processing of untapped wood resources. This work considers the possibility of obtaining carbon adsorbents from the woodworking industry waste of hazard class V. Small waste from wood processing such as sawdust and chips of different breeds of softwood were used as raw materials. The paper shows the effect of introducing small amounts of inorganic additives (sulfuric acid, phosphoric acid, and a mixture of acids) on the porous structure and adsorption properties of the resulting activated carbons. The kinetics of carbonization of modified and unmodified carbon base as well as the kinetics of activation of carbonisates by water vapor are investigated. It is shown that the introduction of inorganic acids noticeably intensifies reactions of the synthesis of the organic mass of carbon, which leads to a decrease in the initial temperature of thermal decomposition, an increase in the temperature range of mass loss, and the yield of carbon residue during pyrolysis. The use of phosphoric acid and a mixture of inorganic acids as softwood waste modifiers slows the process of activation by water vapor, which results from the predominance of the polycondensation reaction. While modification with sulfuric acid does not significantly affect the activation rate, it contributes to a more uniform course of the process. The technological characteristics and parameters of the porous and microporous structures of activated carbons based on woodworking industry waste are evaluated. The influence of the degree of burn-off on activated carbons is determined. A significant change in the macroporous structure during the activation process is observed for chip samples, which is associated with the size and density of the material. The most intensive development of adsorbing porosity occurs due to an increase in the degree of burn-off from 30 to 45%. Modification with inorganic acids leads to an increase in the clarification capacity compared to commercially produced carbons. Based on the conducted research, a schematic diagram of obtaining clarified powdered carbons from softwood waste is proposed.