Mechanochemical and chemical activation of lignocellulosic material to prepare powdered activated carbons for adsorption applications

• Mechanochemical activation method for preparing activated carbons was introduced.
• Mechanochemical activation is superior to the chemical activation with K2CO3.
• The effects of milling time on the properties of activated carbons were investigated.
• Horse chestnut shell is a suitable precursor for preparation of activated carbon.
• Activated carbons were mesoporous with a maximum surface area of 1040 m2/g.

This work presents a solvent-free mechanochemical approach toward controlled preparation of powdered activated carbons from lignocellulosic residue (horse chestnut shell, CS). The physicochemical changes of the biomass during mechanochemical and chemical activation with K2CO3 and the properties of the final materials obtained after pyrolysis at 700 °C have been investigated by means of thermogravimetric analysis (TG–DTG), scanning electron microscopy (SEM), X-ray diffraction (XRD), N2 adsorption–desorption, infrared and micro-Raman spectroscopy. The results indicated that the mechanochemical activation is superior to the traditional chemical activation in terms of specific surface area, pore development and the degree of structural order of the activated carbons. Furthermore, it has been observed that the later parameters depend on the milling time and the maximal BET surface area (1040 m2/g) and total pore volume (1.01 cm3/g) of the resulting mesoporous material can be obtained after 3 h milling of the raw material/K2CO3 mixture. In addition, malachite green oxalate (MGO) adsorption capacities of the carbons were also examined and adsorption uptake up to 250 mg/g is observed. This study demonstrates the potential use of CS as a precursor in the preparation of activated carbon for adsorption applications and opens up new ways for activation of lignocellulosic materials under ball-milling conditions.

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