Vanadium, modified biochar, metal adsorption, biosorbant
Adsorption studies were carried out on a red mud modified sawdust biochar material to assess its capacity in the removal of vanadium (V) from aqueous solution. In this study, a number of parameters which can potentially influence V(V) adsorption were investigated including equilibrium V(V) solution concentration, contact time for effective V(V) removal, temperature of the adsorption process, solution pH and ionic strength. The uptake of V(V) was shown to be heavily influenced by solution pH with maximum uptake (16.45 mg g−1) achieved in the pH range of 3.5 - 5.5. The adsorption process was best described by the Langmuir model. The kinetics of the adsorption process indicated that V(V) uptake occurred within 60 min of contact and that pseudo-second order kinetics best described the kinetics of the overall adsorption process. There was a clear increase in V(V) uptake with increasing temperature (range 293–343 K) indicating an endothermic adsorption process and the level of uptake remained largely unchanged at solution salt concentrations of up to 0.1 M NaCl and competing cation concentrations of up to 2000 mg L-1 of sodium and 200 mg L-1 aluminium. The relatively weak interaction between V(V) and the modified biochar surface may indicate a possibility of recovery of the bound V(V) and subsequent regeneration of the adsorbent.