Guanidine-modified cellulose enhances capturing and recovery of phosphates from wastewater†

The recovery of dwindling materials from wastewater could be helpful in resolving the rising need for resources in society. Phosphate is a nutrient that all living organisms require, but a reduction in global phosphate rock deposits could severely impact human food security in the near future. To mitigate this problem, we developed a Zn(II) coordinated 1-aminoguanidine (ag) functionalized cellulose-based biopolymer. The chemical structure of the synthesized biopolymer was characterized using several analytical techniques, including Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), FESEM-energy dispersive X-ray spectroscopy (FESEM-EDX), and X-ray photoelectron spectroscopy (XPS). The phosphate binding to the polymer was investigated by FT-IR, FESEM–EDX, XPS and ion chromatography (IC) analyses. The IC analysis revealed strong and fast phosphate removal efficacy of the polymer, with a maximum adsorption capacity of 310 mg g⁻¹ (pH 7.0). Interestingly, the sequestered phosphate could be readily retrieved, and the biopolymer could be easily recycled by changing the pH (∼13) of the aqueous solution. Further studies revealed that the presence of guanidinium moieties was essential for its exfoliation in aqueous media and antibacterial activity against both Gram-negative and Gram-positive bacteria. The present work will assist in improving the design of water-insoluble biopolymers that could efficiently extract and recover phosphate from wastewater, thus reducing the detrimental effect of water eutrophication.