Recovery of Phosphate(V) Ions from Water and Wastewater Using Chitosan-Based Sorbents Modified-A Literature Review

Over the past two decades, there has been increasing interest in the use of low-cost and effective sorbents in water treatment. Hybrid chitosan sorbents are potential materials for the adsorptive removal of phosphorus, which occurs in natural waters mainly in the form of orthophosphate(V). Even though there are numerous publications on this topic, the use of such sorbents in industrial water treatment and purification is limited and controversial. However, due to the explosive human population growth, the ever-increasing global demand for food has contributed to the consumption of phosphorus compounds and other biogenic elements (such as nitrogen, potassium, or sodium) in plant cultivation and animal husbandry. Therefore, the recovery and reuse of phosphorus compounds is an important issue to investigate for the development and maintenance of a circular economy. This paper characterizes the problem of the presence of excess phosphorus in water reservoirs and presents methods for the adsorptive removal of phosphate(V) from water matrices using chitosan composites. Additionally, we compare the impact of modifications, structure, and form of chitosan composites on the efficiency of phosphate ion removal and adsorption capacity. The state of knowledge regarding the mechanism of adsorption is detailed, and the results of research on the desorption of phosphates are described.

Convenient Confinement: Interplay of Solution Conditions and Graphene Oxide Film Structure on Rare Earth Separations

Graphene oxide (GO) membranes are excellent candidates for a range of separation applications, including rare earth segregation and radionuclide decontamination. Understanding nanoscale water and ion behavior near interfacial GO is critical for groundbreaking membrane advances, including improved selectivity and permeability. We experimentally examine the impact of solution conditions on water and lanthanide interactions with interfacial GO films and connect these results to GO membrane performance. The investigation of the confined films at the air-water interface with a combination of surface-specific spectroscopy and X-ray scattering techniques allows us to understand water and ion behaviors separately. Sum frequency generation spectroscopy reveals a dramatic change in interfacial water organization because of graphene oxide film deprotonation. Interfacial X-ray fluorescence measurements show a 17× increase in adsorbed lanthanide to the GO film from subphase pH 3 to pH 9. Liquid surface X-ray reflectivity data show an additional 2.7 e^- per Ų for GO films at pH 9 versus pH 3 as well. These results are connected to GO membrane performance, which show increased selectivity and decreased flux for membranes filtering pH 9 solutions. We posit insoluble lanthanide hydroxides form at higher pHs. Taken together, these results highlight the importance of interfacial experiments on model GO systems.

PVA/PEI crosslinked electrospun nanofibers with embedded La(OH)3 nanorod for selective adsorption of high flux low concentration phosphorus

Phosphorus (P) is a limiting element causing eutrophication, and thus, its removal has elicited significant attention in recent years. In this study, a La(OH)₃ embedded nanorod loaded PVA/PEI crosslinked nanofiber membrane (LNPPM) was synthesized for phosphorus removal at a low concentration and under high flux conditions. Comparative tests demonstrated that an LNPPM exhibited a high phosphate adsorption capacity (165.9 mg P/g La) and performed well even under interference with the pH and coexisting ions (Cl^-, SO₄^2-, NO₃^-, and F^-). Through a continuous adsorption test, LNPPM also showed a fast adsorption efficiency with a 73.7% capacity used for C/C₀ = 0.5 under a low concentration and high flux phosphate solution. Fourier transform infrared, X-ray diffraction, X-ray photoelectron spectroscopy, SEM-EDS, and high-resolution transmission electron microscopy analyses indicated that the La(OH)₃ nanorod intensively and uniformly embedded into the nanofibers, providing an ideal condition for phosphate adsorption. A mechanistic analysis showed that the ligand exchange played a vital role in the phosphate adsorption of LNPPM. A cost index (capacity/synthesis cost) comparison with typical super phosphate adsorbents also indicated that LNPPM (795 mg P/USD) could be a viable option owing to its simple synthesis procedure, low synthesis cost, and considerable capacity. This technique shows promise for use in most dephosphorization applications.