Bone char material for Volatile Organic Compounds (VOCs) adsorption: Effect of the activation on surface characteristics and performance

Air pollution is a problem of great concern, with increasing atmospheric concentrations of toxic Volatile Organic Compounds (VOCs) such as BTEX (benzene, toluene, ethylbenzene and o-xylene). We report the development of adsorbant materials derived from tuna fish bones. Tuna Bone Char (TBC) was obtained with a pyrolysis process; and activated with K2CO3 treatment (indicated as KTBC, due to the potassium carbonate activation). Characterisation showed that the activation protocol led to a significant increase in the surface area – from 97.45 to 1826.59 m2/g for TBC and KTBC; furthermore, the activated material also showed higher porosity (total pore volume of 2.22 cm3/g, micropore volume of 0.38 cm3/g). BTEX dynamic adsorption tests showed KTBC excellent adsorption properties, particularly with o-xylene (adsorption capacity q of 147 mg/g). The higher adsorption of o-xylene was explained considering its kinetic diameter matching KTBC pore size dimension. KTBC also showed to be very efficient in humid conditions (q = 61.2 mg/g). Repeated tests with the same powder indicated a 20 % decrease after the first cycle, with no further decrease in additional cycles. Empirical regression models for q0 and kTh (Thomas model), and τ and KYN (Yoon-Nelson model) were developed for BTEX breakthrough curves and showed agreement with experimental breakcurve data (R2 > 0.905). These results show that bone char can be used for gaseous pollutants with the activation playing a key role in surface modification and performance enhancement. This research offers a sustainable and effective route to convert marine biowaste into advanced adsorbents for VOC and air pollution control.