Abstract
A series of activated carbons (ACs) were produced by chemical activation of hemp stem with phosphoric acid in nitrogen and steam atmospheres. The potential of hemp-derived waste for the manufacture of porous carbons with a wide spectrum of porosity, ranging from microporous to mesoporous, has been demonstrated. The influence of the variables, such as the H3PO4/hemp stem impregnation ratio, the soaking time and the gaseous atmosphere, on the porosity development was studied. Depending on the processing conditions, the H3PO4 activation produces ACs with a wide range of textural parameters, reaching surface areas >2,500 m2/g, micropore pore volumes up to 0.89 cm3/g and mesopore volumes up to 1.80 cm3/g. The amount of H3PO4 used in the impregnation step affects the porous texture of the resultant ACs to a greater extent than the soaking time. At low and medium impregnation ratios, a steam atmosphere favors the formation of mesopores during H3PO4 activation.
Highlights
Hemp (Cannabis sativa L.) is an annual and highly productive herbaceous plant
The evolution of the porous structure with an increasing impregnation ratio was studied for activated carbons (ACs) obtained at 480 °C in a steam atmosphere with a soaking time of 30 min
The isotherm of the hemp stem impregnated at XP = 0.16 represents a typical Type I isotherm according to the IUPAC classification [31]
Summary
Hemp (Cannabis sativa L.) is an annual and highly productive herbaceous plant. It has been widely cultivated in China, mainly for its bast fiber and seed oil [1]. The world cultivation of hemp occupies over 40,000 ha. Hemp has many industrial applications, including the production of paper, textiles, building materials, food, medicine, paint, detergents, oil and fuel. A huge amount of waste and by-products such as hemp seed, hemp bast and hemp stem are generated during hemp processing. The production of hemp-derived waste was estimated to be approximately 54,000 tons in 2012. The preparation of activated carbons (ACs) from hemp stem waste as a precursor can be considered an attractive alternative to its disposal
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