(2024) Environmental Research_Optimizing bone and biomass co-torrefaction parameters: High-performance arsenic removal from wastewater via co-torrefied bone char

Chen W.-H.; Biswas P.P.; Kwon E.E.; Lin K.-Y.A.; Rajendran S.; Chang J.-S.

(Academic Press Inc.) Environmental Research ISSN: 139351 Vol.252 Issue. Article No.118990 DOI: 10.1016/j.envres.2024.118990

This study aimed to investigate bone char's physicochemical transformations through co-torrefaction and co-pyrolysis processes with biomass. Additionally, it aimed to analyze the carbon sequestration process during co-torrefaction of bone and biomass and optimize the process parameters of co-torrefaction. Finally, the study sought to evaluate the arsenic sorption capacity of both torrefied and co-torrefied bone char. Bone and biomass co-torrefaction was conducted at 175 °C–300 °C. An orthogonal array of Taguchi techniques and artificial neural networks (ANN) were employed to investigate the influence of various torrefaction parameters on carbon dioxide sequestration within torrefied bone char. A co-torrefied bone char, torrefied at a reaction temperature of 300 °C, a heating rate of 15 °C·min⁻¹, and mixed with 5 g m of biomass (wood dust), was selected for the arsenic (III) sorption experiment due to its elevated carbonate content. The results revealed a higher carbonate fraction (21%) in co-torrefied bone char at 300 °C compared to co-pyrolyzed bone char (500–700 °C). Taguchi and artificial neural network (ANN) analyses indicated that the relative impact of process factors on carbonate substitution in bone char followed the order of co-torrefaction temperature (38.8%) > heating rate (31.06%) > addition of wood biomass (30.1%). Co-torrefied bone chars at 300 °C exhibited a sorption capacity of approximately 3 mg g^−1, surpassing values observed for pyrolyzed bone chars at 900 °C in the literature. The findings suggest that co-torrefied bone char could serve effectively as a sorbent in filters for wastewater treatment and potentially fulfill roles such as a remediation agent, pH stabilizer, or valuable source of biofertilizer in agricultural applications. © 2024 Elsevier Inc.

The authors gratefully acknowledge the financial support from the National Science and Technology Council, Taiwan, R.O.C, under the contracts NSTC 113-2222-E-029-001-, NSTC 112-2218-E-006-025-, and NSTC 112-2218-E-002-052- for this study.