Adsorptive removal of arsenate from aqueous solutions by biochar supported zero-valent iron nanocomposite: Batch and continuous flow tests

[Display omitted] •Biochar supported nZVI (nZVI/BC) was synthesized.•nZVI/BC showed excellent As(V) removal efficiency in batch and CMR experiments.•100% removal efficiency was achieved in CMRs.•Surface adsorption was the dominant removal mechanism. Arsenate (As(V)) removal ability by nanoscale zero-valent iron (nZVI) is compromised by aggregation of nZVI particles. In this work, pine derived biochar (PB) was used as a supporting material to stabilize nZVI for As(V) removal. The biochar supported nZVI (nZVI/BC) was synthesized by precipitating the nanoparticles on carbon surfaces. Experiments using batch and continuous flow, completely mixed reactors (CMRs) were carried out to investigate the removal of As(V) by the nZVI/BC from aqueous solutions. Batch experiments showed that nZVI/BC had high As(V) removal capacity in a wide range of pH (3–8). Kinetic data revealed that equilibrium was reached within 1h and the isotherm data showed that the Langmuir maximum adsorption capacity of the nZVI/BC for As(V) at pH 4.1 was 124.5gkg−1. As(V) (100mgL−1) adsorption in anoxic condition was about 8% more than in oxic conditions, where As(V) reduction was observed in anoxic condition. The performance of the nZVI/BC in flowing condition was evaluated in CMRs at influent As(V) concentrations of 2.1 and 5.5mgL−1 and the adsorbent removed 100% and 90% of the As(V), respectively. Furthermore, the nZVI/BC composite is magnetic which facilitates collection from aqueous solutions.