Effect of structural properties of green rusts on phosphate fixation and implication for eutrophication remediation

As mixed-valent iron(hydr)oxides green rusts (GRs) are widely found in natural and anthropic phosphate removal processes. Effect of structural properties of GRs on phosphate adsorption is rarely studied. It is found that a Fe(II)/Fe(III) ratio of 5/1 resulted in the maximum phosphate adsorption by GRs interlayered with chloride or sulfate anions. Phosphate anions exchange with chloride or sulfate anions in GRs and then get fixed on the basal plane and lateral surface of GRs. The interlayered chloride or sulfate anions have little influence on the phosphate adsorption by GRs. The phosphate adsorption efficiency by GRs was almost constant when pH increasing from 5.5 to 7.5, but decreased when pH further increased to 9.5. Revealing the relationship between the structural properties of GRs and their phosphate adsorption performance deepen our understanding of the fate and transformation of iron (hydr)oxides and phosphate in both natural and engineered environments.