Characterization and Mechanisms of a New Carbonaceous Adsorbent Based on Black Liquor Loaded with Iron Oxide for Removal of Tripolyphosphate Ions

The impregnation process has successfully prepared a novel composite of iron oxide/carbon from black liquor (CA-BL/Fe) as an adsorbent for the removal of tripolyphosphate ions. Black liquor is a secondary product of the bioethanol pre-treatment process. X-ray diffraction results showed that the main iron oxide species present in the CA-BL/Fe was goethite (α-FeOOH). Interestingly, the specific surface area of CA-BL/Fe was 504 m 2 /g higher than that of commercial activated carbon of 356 m 2 /g. The adsorption performance showed that tripolyphosphate ion removal efficiency increased by increasing the adsorbent dosage, pH, and contact time. At the same time, it decreased with an increase in the initial concentration of tripolyphosphate. By controlling the environment pH value, the optimum removal efficiency of tripolyphosphate ions with CA-BL/Fe was 96.87%, with the adsorption capacity of 1.5922 mg/g for 1 h measurement. In this study, the dominant mechanisms of tripolyphosphate adsorption are electrostatic attraction and ion exchange. The result of this study is expected to be the basis for further promising adsorbent material for tripolyphosphate ion.