Strategy Removal mechanisms & efficiency INSIGHTS INTO NATURAL ORGANIC MATTER AND ITS REMOVAL BY ION EXCHANGE RESINS INDUSTRIAL CATALYSIS AND ADSORPTION TECHNOLOGY Elien Laforce, Emile R. Cornelissen, Pieter Vermeir and Jeriffa De Clercq Problem Statement Natural organic matter (NOM) • Originates from degradation and byproducts of living organisms and plants • Complex mixture (wide range of MW, hydrophobicity, functionalities) • Separation via Liquid Chromatograpy – Organic Carbon Detection (LC-OCD) into 5 fractions: • Biopolymers (1) – Humic substances (2) – Building blocks (3) – Low MW acids (4) – Low MW neutrals (5) Challenges • Complete removal not achieved by classical water treatment processes (e.g. demineralisation via ion exchange (IEX) → remaining NOM: biopolymers & low MW neutrals) • Increased risk on corrosion in steam cycle • Formation of disinfection by-products during drinking water production • Microbiological growth in water distribution systems Problem Statement pH effects Contact Jeriffa.DeClercq@ugent.be Elien.Laforce@ugent.be Conditioning procedure influences equilibrium pH and ionic strength, affecting removal efficiency and mechanisms – especially in batch mode experiments Selection of resin and conditioning procedure enables optimal removal of targeted NOM (fraction) Insight in removal mechanisms helps to optimize regeneration procedures Future work on (NOM fractions from) real surface water to investigate the effects of this more complex water matrix on NOM removal Conclusions Anion exchange resin (AER) conditioning Batch experiments: AER and NOM model compounds Weak Basic AER Strong Basic AER Set-up: 50 ppm model compound → BSA / dextran / alginate / HA / resorcinol 2 g resin OH- form (equivalent capacity Cl-form) 22h – 200 rpm – 25°C Analysis: pH – UV - TOC Resin Functionality MP62a WBA MP68a W/SBA (3.5/1) MP64a W/SBA (2.0/1) MP600a SBA (type II) MP500a SBA (type I) a Lewatit, Lanxess (NaOH) (HCl) (NaOH) (NaCl) Model compound SBA – OH- form NaOH conditioning pHeq. 9-10.5 SBA – Cl- form NaCl conditioning pHeq. 4.5-6 WBA – FB form NaOH conditioning pHeq. 6.5-8 WBA – Cl- form HCl conditioning pHeq. 3-3.5 Removal mechanism Removal a Removal mechanism Removal a Removal mechanism Removal a Removal mechanism Removal a BSA IEX - IEX + + + H-bond - n.a. - Dextran H-bond + + + n.a. - n.a. - n.a. - Alginate IEX, H-bond - / + IEX + IEX + H-bond, IEX + Humic acid IEX, H-bond, π- π + IEX + + H-bond, π- π + H-bond, π- π + Resorcinol H-bond, π- π, IEX + + + π- π + / + + π- π + + + π- π + + a removal efficiency (%) range coding: - : 0-20%; + : 20-60%; + + : 60-80%; + + + : 80-100%1 M solutionLow electrolyte Effluent Effluent • Aromatic NOM: π- π interactions (all counter ion forms) • Carboxyl groups: H-bonding with Cl- WBA & OH- SBA • Hydroxyl groups: H-bonding with OH- SBA • Charged (anionic) NOM: Ion exchange • W/SBA resins: behaviour depends on ratio weak versus strong basic functionalities • Release of ions in subsequent batch experimtent → ionic strength ↑; pH ↑or ↓ References: Laforce E, et al. Revealing the effect of anion exchange resin conditioning on the pH and natural organic matter model compounds removal mechanisms, Journal of Environmental Chemical Engineering, (2022)