On the suitability of agricultural by-products for the manufacture of granular activated carbon

An investigation of several agricultural by-products revealed that their suitability for activated carbon production is not determined by general material-specific features (elemental composition) but by type-specific features. A coarse-cellular structure (as in wood), which is indicated by porosities of the raw materials higher than ∼35% is disadvantageous. A specific change in the properties of cokes (porosity, density, hardness) is possible by varying the conditions of pyrolysis. By rapid heating in the pyrolysis step, for instance, macroporous residues are produced. Temperature and burnoff have the greatest influence on the quality of the activated carbon during the activation step. Of the investigated materials, coconut shells yield granular activated carbon of the highest quality. The following order of suitability of raw materials for activated carbon production was established: coconut shells > peach stones > plum stones > hazelnut shells > walnut shells > cherry stones.