Phosphorus recovery from wastewater using pyridine‐based ion‐exchange resins: Role of impregnated iron oxide nanoparticles and preloaded Lewis acid (Cu²⁺)

Abstract

Inputs of P into receiving water bodies are attracting increasing attention due to the negative effects of eutrophication. Presently available P treatment technologies are unable to achieve strict P discharge limits from wastewater treatment plants (WWTPs) that may be as low as 10 µg/L as P. Moreover, P is a nonrenewable resource and needs to be recycled in a closed‐loop process for environmental sustainability. This article provides details of a process where a pyridine‐based polymeric ion exchanger is modified with a combination of impregnated hydrated ferric oxide (HFO) nanoparticles and a preloaded Lewis acid (Cu2+) to effectuate selective P removal from wastewater and its recovery as a solid‐phase fertilizer. Three such ion exchangers were studied: DOW‐HFO, DOW‐Cu, and DOW‐HFO‐Cu. Each of these materials displays selective phosphate affinity over competing anions chloride and sulfate, and also has the ability to be regenerated upon exhaustion to strip off the P in a concentrated solution. The P in concentrated regenerant can be recovered as struvite, MgNH4PO4, a slow‐release fertilizer, after addition of MgCl2 and NH4Cl. Results of equilibrium and kinetic studies and column experiments with synthetic solutions and a real WWTP effluent are discussed. Practitioner points Fixed‐bed columns with DOW‐HFO, DOW‐Cu, or DOW‐HFO‐Cu—can selectively remove phosphorus over competing anions. Fixed‐bed columns of above‐listed ion exchangers can produce an effluent P < 6 μg/L. DOW‐Cu fixed‐bed column ran for ≈500 Bed Volumes before breakthrough when fed Dartmouth WWTP secondary effluent. Regeneration of the exhausted DOW‐Cu column resulted in ≈90% recovery of the phosphorus. Regenerant solution was used to generate high‐purity crystals of magnesium ammonium phosphate, MgNH4PO4 (struvite), a slow‐release fertilizer.

Evaluating Sustainable Development Pathways for Protein- and Peptide-Based Bioadsorbents for Phosphorus Recovery from Wastewater

“…Given P limitations in receiving waterbodies, 26% of POTWs have ultralow permits in the μg L –1 range, with 17% of the facilities at ≤500 μg L –1 and 2% at ≤100 μg L –1 . Conventional P treatment strategies, such as biological nutrient removal, adsorption, crystallization, and precipitation, are typically unable to reduce P below approximately 100 μg L –1 due to thermodynamic and kinetic limitations. − Thus, advanced strategies are needed to satisfy increasingly stringent P regulations . Moreover, P recovery is an increasingly important consideration, given the potential of capturing 3.7 Mt P year –1 from municipal wastewater (which is approximately 20% of agricultural demands) .…”

Editorial: Let's talk about P(ee)

“…A range of technologies exist for P removal and recovery (e.g., as reviewed by Batstone et al, 2014; Mayer et al, 2013; Morse et al, 1998). Yet, advancements capable of achieving P removal to the ultra‐low levels (e.g., low µg/L) targeted in P‐sensitive areas are needed given that current technologies often struggle to achieve stringent discharge limits (Beaudry & Sengupta, 2021). Additionally, the circular P economy demands technologies capable of recovering the P in a pure, concentrated form suitable for agricultural reuse.…”

“…Reversible sorption‐based processes offer one promising approach (Beaudry and Sengupta, 2021), which is further buoyed by the potential for fundamental materials research to develop new technologies and systems that allow us to better remove, recover, and reuse P (Jones et al, 2020). Sensitive P‐selective adsorbents such as inorganic ion exchangers (e.g., Blaney et al, 2007; Mullen et al, 2019; Sengupta & Pandit, 2011; Williams et al, 2015; Zhao & Sengupta, 1998) and bioadsorbents (e.g., Hussein et al, 2020; Venkiteshwaran et al, 2018, 2020a, 2020b; Yang et al, 2016) have been developed and tested for this purpose.…”

“…Sensitive P‐selective adsorbents such as inorganic ion exchangers (e.g., Blaney et al, 2007; Mullen et al, 2019; Sengupta & Pandit, 2011; Williams et al, 2015; Zhao & Sengupta, 1998) and bioadsorbents (e.g., Hussein et al, 2020; Venkiteshwaran et al, 2018, 2020a, 2020b; Yang et al, 2016) have been developed and tested for this purpose. The May 2021 Editor's Choice article Phosphorus recovery from wastewater using pyridine‐based ion‐exchange resins: Role of impregnated iron oxide nanoparticles and preloaded Lewis acid (Cu 2+ ) by Beaudry and Sengupta (2021) further advances development, understanding, and implementation of P removal and recovery from wastewater using P‐selective ion‐exchange resins.…”

“…Beaudry and Sengupta (2021) studied the performance of three different hybrid ion exchangers consisting of a pyridine‐based polymeric base material modified with varying combinations of impregnated hydrated ferric oxide (HFO) nanoparticles and preloaded Cu 2+ serving as a Lewis acid. They explored the thermodynamics and kinetics of the ion‐exchange materials, including evaluating binary separation factors, multiple kinetic models, and the intraparticle diffusivity of P uptake.…”