Phosphate Adsorption Removals by Five Synthesized Isomeric α-, β-, γ-FeOOH

摘要

The FeOOH polymers commonly existing in nature are potential adsorbent materials for phosphate ions (P). In this work, five synthesized isomeric α-, β-, γ-FeOOH (goethite, akaganeite and lepidocrocite samples of Gth1 and Gth2, Akal and Aka2, and Lep, respectively) were used to investigate their P adsorption characteristics and mechanisms, under various times, the levels of phosphate and FeOOH, solution pH, temperatures, and coexisting anions. Under 1.0 g/L of dosage and 20 mg/L of P, Lagergren second order rate model could describe well kinetic behaviors of P adsorptions for FeOOH (R~2 being 0.999) at pH 7. Phosphate adsorption behaviors could be described well by both Langmuir (R2 being 0.968-0.999) and Freundlich (R2 being 0.945 - 0.988). The maximum adsorption capacities (mg/g) were 8.09(Gthl), 6.5(Gth2), 5.49(Akal), 12.9(Aka2), and 7.36(Lep). In addition, P adsorptions presented the better capacities in a pH range of 3 - 8. The SO_4~(2-) had the stronger effects on P adsorptions, while the other anions (Cl~-, NO_3~- and CO_3~(2-)) had little effects. The possible P adsorption mechanisms by FTIR and XPS results for FeOOH mainly were electrostatic attractions and ion exchanges. It is obvious that isomeric FeOOH are the promising adsorbents for P removal.