Synthesis of protonated chitosan flakes for the removal of vanadium(III, IV and V) oxyanions from aqueous solutions

Vanadium is included in the USEPA Contaminant Candidate List (CCL). Protonated chitosan flakes (PCF) were shown to effectively remove vanadium(III, IV, and V) oxyanions from aqueous solutions at high yields. It was also proven that the adsorption capacity of vanadium increases when using PCF instead of chitosan beads (CB). A 99-100% removal of vanadium oxyanions was achieved during the first 2 h of contact when using 5 g/L PCF adsorbent and the initial vanadium concentration of 0.500 mg/L, while CB only removed 4-18%. Adsorption experiments were performed by varying contact time, pH of the aqueous solution and adsorbent suspension solution, and analyzing the effect of common anions. Vanadium(III, IV and V) adsorption is favored in the Langmuir's model. These species of vanadium were removed efficiently without the need of pretreatment process, even when common anions were added, such as chloride, carbonate, sulfate and phosphate. The proposed mechanism for the removal of vanadium, when adding PCF, is by the process of electrostatic attraction.