I suggest removing the KOH-treated biochar from the filter before it fully dries. Once removed, you can either dry it and use a ball mill to reduce it to powder or proceed with heat treatment of the unground biochar. Heat-treated biochar becomes brittle, making it much easier to grind afterward.

Activated carbon encompasses a broad range of amorphous carbon-based materials having high degrees of porosity and extensive surface areas. The properties of each finished activated carbon are influenced by the starting materials used and by the conditions of activation. The result is a myriad of activated carbons, each having a specific utility. The method most frequently used for preparation of activated carbon involves carbonization of the precursors at high temperature in an inert atmosphere followed by activation. There are mainly two different methods for activation, namely physical and chemical. Physical activation process comprises treatment of the char obtained from carbonization with some oxidizing gases, generally steam or carbon dioxide at high temperature. The porous structure is created due to the elimination of volatile matter during pyrolysis and the carbon on the char is removed during activation. The main function of gasification is to widen the pores, creating large mesoporosity. In chemical activation, a chemical agent is impregnated to the precursors prior to heat treatment in an inert atmosphere. The pores are developed by dehydration and oxidation reactions of the chemicals.

Activated carbons find wide applications as adsorbents, catalyst or catalyst supports. Activated carbon is one of the most important adsorbents from an industrial point of view. The main application of this adsorbent is for separation and purification of gaseous and liquid phase mixtures. In general, activated carbons can be divided into gas-adsorbing and liquid-phase carbons. The main distinction between gas-adsorbing and liquid-phase carbons lies in the pore size distribution. Basically, the structure of activated carbons containing pores are classified according to the International Union of Pure and Applied Chemistry [17] classification into three groups, micropores (pore size  50 nm). Gas-adsorbing carbons usually have the most pore volume in the micropore and macropore ranges, whereas liquid-phase carbons have significant pore volume in the mesopore or transitional pore range, permitting ready access of liquids to the micropore structure which results in rapid attainment of adsorption equilibrium for smaller adsorbates.

Activated carbons concern many industries as diverse as food processing, pharmaceuticals, chemical, petroleum, nuclear and automobile, because of their adsorptive properties due to high available surface area which is presented in their extensive internal pore structure. The high porosity of activated carbons is a function of both the precursor as well as the scheme of activation. Activated carbons are now frequently used in environmental processes for removing toxic gases and in wastewater as well as potable water treatments.

Dear A. P. Soares Dias ,

thank you for your suggestions.