Transport behaviors of biochar particles in saturated porous media under DC electric field

The mobility of biochar in saturated quartz sand under a direct current (DC) electric field was investigated by column transport test. The effects of biochar preparation temperature (350 and 550 degrees C), solution chemistry (pH of 4, 7, and 10, and ion strength of 1, 10, 100 mM) and voltage gradient (0, 0.5 and 1.0 V cm(-1)) on the mobility of biochar were explored. It was found that DC electric field could significantly promote the migration of biochar, and the recovery rate of particles could be improved by 0.5-6.1 folds under 0.5 V cm(-1). Higher voltage potential, solution pH and ionic strength were more favorable for biochar migration. The transport of biochar could be well interpreted by deterministic nonequilibrium convection-dispersion equation model. The enhanced mobility caused by DC electric field was attributed to the following reasons: enhanced eleciromigration following electrostatic attraction from the anode; increasing surface negative charges and functional groups on biochar surface as a result of electrochemical oxidization; reducing size blocking of biochar particles by decreasing particle size. Moreover, the interaction between biochar particles and electrode could alter solution chemistry, in particular, increasing solution pH, which in turn facilitated the transport of biochar. 'Ibis study provided a perspective to modulate the transport behavior of biochar particle in the soil for the remediation of polluted sites.

Automated summary

The mobility of biochar in saturated quartz sand under a direct current (DC) electric field was investigated. It was found that the DC electric field significantly promoted the migration of biochar, with the recovery rate of particles being improved by 0.5-6.1 folds under 0.5 V cm(-1). Higher voltage potential, solution pH, and ionic strength were more favorable for biochar migration. The transport of biochar could be well explained by a deterministic nonequilibrium convection-dispersion equation model.