Edward Apraku

All Publications

• Probing the Mechanism of Selective Phosphate Adsorption from Wastewater Using Aqueous and Synchrotron X-ray Characterization. Journal of the American Chemical Society Sharma, N., Apraku, E., Holmes, H. E., Gong, M., Bustamante, D., Martinez, A. N., Weker, J. N., Bone, S., Tarpeh, W. A. 2025

  Abstract

  Ion exchange shows promise for recovering phosphate from wastewater as value-added products but requires high phosphate selectivity to compete with conventional treatment. Hybrid anion exchange (HAIX) resins, which contain nonselective basic functional groups and selective iron oxide nanoparticles (FeOnp), can remove phosphate from wastewater. However, knowledge gaps remain regarding the mechanisms of phosphate selectivity and influence of competing ions, hindering efforts to model adsorption dynamics and design adsorption processes for varying wastewaters. To address these gaps, we integrated aqueous-phase adsorption analysis with solid-phase, synchrotron-based X-ray characterization; this integration facilitated elucidation of the distribution and speciation of iron, phosphate, and competing anions on HAIX resins. We compared a quaternary ammonium-functionalized HAIX resin (strong base anion exchange, SBA) to a tertiary amine version (weak base anion exchange, WBA) to determine the role of functional groups. X-ray radiography revealed differences in FeOnp speciation (goethite vs ferrihydrite) and distribution (peripheral vs homogeneous) between the resins, resulting in varied phosphate affinity and intraparticle diffusion resistance. Using micro-X-ray fluorescence (μ-XRF) and micro-X-ray absorption near-edge structure (μ-XANES) spectroscopy, we identified differences in where and how phosphate binds across resin types and wastewaters. Across wastewater compositions, FeOnp sites in WBA contribute more to phosphate adsorption than in SBA, possibly due to variations in Fe distribution and speciation. Phosphate adsorption densities calculated from quantitative μ-XRF maps matched those from aqueous analysis, demonstrating the effectiveness of this integrated approach. Overall, results demonstrate the use of synchrotron-based X-ray characterization for investigating adsorption mechanisms and advance HAIX as a phosphate recovery technology from wastewaters.

  View details for DOI 10.1021/jacs.5c10899

  View details for PubMedID 40789021

• Integrating adsorbents and electrochemistry to advance selective wastewater phosphate separations CURRENT OPINION IN CHEMICAL ENGINEERING Sharma, N., Apraku, E., Gong, M., Tarpeh, W. A. 2025; 47

  View details for DOI 10.1016/j.coche.2024.101080

  View details for Web of Science ID 001392010000001

• Toward a circular nitrogen bioeconomy: integrating nitrogen bioconcentration, separations, and high-value products for nitrogen recovery. Current opinion in biotechnology Apraku, E., Farmer, M., Lavallais, C., Soriano, D. A., Notestein, J., Tyo, K., Dunn, J., Tarpeh, W. A., Wells, G. F. 2024; 91: 103225

  Abstract

  Recovering nitrogen (N) from wastewater is a potential avenue to reduce reliance on energy-intensive synthetic nitrogen fixation via Haber-Bosch and subsequent treatment of N-laden wastewaters through nitrification-denitrification. However, many technical and economic factors hinder widespread application of N recovery, particularly low N concentrations in municipal wastewater, paucity of high-efficiency separations technologies compatible with biological treatment, and suitable products and markets for recovered N. In this perspective, we contextualize the challenges of N recovery today, propose integrated biological and physicochemical technologies to improve selective and tunable N recovery, and propose an expanded product portfolio for recovered N products beyond fertilizers. We highlight cyanophycin, an N-rich biopolymer produced by a diverse range of bacteria, as a potential target for N bioconcentration and downstream recovery from municipal wastewater. This perspective emphasizes the equal importance of integrated biological systems, physicochemical separations, and market assessment in advancing nitrogen recovery from wastewater.

  View details for DOI 10.1016/j.copbio.2024.103225

  View details for PubMedID 39602850

• Enhancing Resource Recovery through Electro-Assisted Regeneration of an Ammonia-Selective Cation Exchange Resin ACS ES&T WATER Apraku, E., Laguna, C. M., Wood, R. M., Sharma, N., Dong, H., Tarpeh, W. A. 2024

  View details for DOI 10.1021/acsestwater.4c00543

  View details for Web of Science ID 001313793100001

• Ligand Exchange Adsorbents for Selective Phosphate and Total Ammonia Nitrogen Recovery from Wastewaters ACCOUNTS OF MATERIALS RESEARCH Clark, B., Sharma, N., Apraku, E., Dong, H., Tarpeh, W. A. 2024

  View details for DOI 10.1021/accountsmr.3c00290

  View details for Web of Science ID 001184781200001