Synthesis of a ferric hydroxide-coated cellulose nanofiber hybrid for effective removal of phosphate from wastewater

• The Fe(OH)3@CNFs were used in the removal of phosphate for the first time.
• The maximum sorption capacity of Fe(OH)3@CNFs for phosphate was 142.86 mg/g.
• It achieved a superior adsorption capacity over a wide range of pH conditions.
• An increased solution ionic strength would remarkably enhance the adsorption.

Ferric hydroxide-coated cellulose nanofibers (Fe(OH)3@CNFs) were synthesized for the removal of phosphate from wastewater. The maximum sorption capacity of Fe(OH)3@CNFs for phosphate was estimated to be 142.86 mg/g, demonstrating a superior adsorption capacity compared with many adsorbents reported in the literature. Batch experiments were performed to investigate various adsorption conditions on the adsorption performance. It was discovered that an increased solution ionic strength would remarkably enhance the adsorption. Additionally, Fe(OH)3@CNFs achieved a favorable adsorption performance over a wide range of pH conditions, which could result in operation cost savings. The adsorption of phosphate can be described by both the Langmuir isotherm and pseudo-second-order models. The phosphate adsorbed by Fe(OH)3@CNFs was characterized using XPS, SEM, SBET and EDS. The data obtained revealed that the electrostatic attraction and ligand exchange constituted the major forces in phosphate adsorption. This work suggested that Fe(OH)3@CNFs are a promising adsorbent for phosphate removal.