Removal of phenolics from aqueous pyrolysis condensate by activated biochar

Aqueous pyrolysis condensate (APC) is rich in acetic acid and has been utilized as feedstock for anaerobic digestion to produce biogas. However, various phenolic compounds dissolved in the APC act as inhibitors, negatively affecting the anaerobic digestion. In this work, we have investigated the feasibility of employing pyrolytic biochar as an adsorbent for the selective removal of phenolics from APC. Biochars derived from the pyrolysis of soft wood, rice husks, and sewage sludge and their respective activated forms have been tested as potential adsorbents for the removal of pure phenol from water solutions. The experimental results showed that, among the adsorbents studied, activated soft wood (ASW) biochar has the highest adsorption efficiency and capacity for phenol removal from water. The kinetic and isotherm studies showed that the phenol adsorption data with ASW biochar may be well described by pseudo second-order equation and Freundlich model. Batch experiments were carried out to investigate the effects of pH, adsorbent loading, contact time, and temperature on phenolics adsorption onto ASW from APC. At optimal adsorption conditions (pH of 6.0, contact time of 30 min, adsorbent loading of 9.61 gadsorbent center dot gTotal phenolics-1, and temperature of 25 degrees C), an adsorption efficiency of 96.9% +/- 1.8% and a capacity of 100.78 +/- 2.7 mg center dot g(-1) were achieved. Finally, the adsorption efficiency and capacity of ASW for phenolics removal from APC was successfully compared with those of commercial activated carbon, showing comparable results, which indicated the suitability of ASW as an environmentally friendly adsorbent.

Automated summary

This study investigated the feasibility of using pyrolytic biochar as an adsorbent for the selective removal of phenolics from aqueous pyrolysis condensate (APC). The results showed that activated soft wood (ASW) biochar had the highest efficiency and capacity for removing phenol from water solutions. The adsorption data with ASW biochar were well described by pseudo second-order equation and Freundlich model, making it a promising environmentally friendly adsorbent for phenolics removal.