Pine bark valorization by activated carbons production to be used as VOCs adsorbents

The exploitation of pine bark, a byproduct of timber industry, as biochar or activated carbons has been demonstrated. It can be successfully charred, and further activated, either by physical and chemical activation. The biochar yield and quality (amount of carbon) is mainly determined by the maximum temperature. Temperatures above 300 degrees C were required to convert pine bark into biochar (by means of cracking and volatiles release), and yield stabilized at 32% at the maximum temperature tested (850 degrees C). With uniform heating, the heating rate and the particle size did not affect significantly the biochar yield.The carbon loss in biochar activation was found to be dramatic with steam at 850 degrees C, while chemical activation significantly reduced it, preserving most of the biochar. The activated carbons obtained have been tested for adsorption of CO2 (at 90%) and toluene (a model VOC, between 500 ppm and 2.5%). Significant differences in VOC loading capacity have been measured and explained with the different microstructure of the activated carbons produced. BET specific surface up to 3342 m(2)/g has been measured, in carbons activated with H3PO4, and 1499 m(2)/g with K2CO3, and total pores volume up to 2.57 cm(3)/g.The chemically activated carbons were found very effective in VOC capture, up to 50% (5.5 mmol/g) of the original solid mass. Among them, the one activated by K2CO3 shows the highest loading capacity (32%, or 3.5 mmol/g) even at quite low toluene concentration (500 ppm), thanks to its largest share of micropores.