The combined influence of hydrophobicity, charge and molecular weight on natural organic matter removal by ion exchange and coagulation

Abstract

Three different source waters were investigated using virgin and pre-used anion exchange resins, coagulation, and ion exchange combined with coagulation (IEX&Coagulation). The hydrophobicity, size distribution and charge of natural organic matter (NOM) were used to evaluate its removal. Dissolved organic carbon (DOC) removal by pre-used IEX resin was 67-79%. A consistent ratio of different hydrophobicity fractions was found in the removed DOC, while the proportion and quantity of the molecular weight fraction around 1 kDa was important in understanding the treatability of water. For pre-used resin, organic compounds were hypothesised to be restricted to easily accessible exchange sites. Comparatively, virgin resin achieved higher DOC removals (86-89%) as resin fouling was absent. Charge density and the proportion of the hydrophobic fraction were found to be important indicators for the specific disinfection byproduct formation potential (DBP-FP). Treatment of raw water with pre-used resin decreased the specific DBP-FP by between 2-43%, while the use of virgin resin resulted in a reduction of between 31-63%. The highest water quality was achieved when the combination of IEX and coagulation was used, reducing DOC and the specific DBP-FP well below that seen for either process alone.

Sorptive removal of disinfection by-product precursors from UK lowland surface waters: Impact of molecular weight and bromide

“…This can be attributed to the fact that the > 10,000 g/mol fraction blinds the adsorption sites for the < 350 g/mol MW compounds. This is consistent with that seen for SIX treatment of DOC from an upland source [37] and for GAC [3] such that these organic compounds are less readily removed compared to the same size fraction in the Riv source.…”

Anion Exchange Resin and Inorganic Anion Parameter Determination for Model Validation and Evaluation of Unintended Consequences during PFAS Treatment

“…SUVA breakthrough peaked at ∼250 BVs (Figure S8) and then stabilized at 1.2–1.3 C / C 0 for column 1 and 1.3–1.4 C / C 0 for columns 1 + 2. The differences in the removal of UVA 254 vs. TOC as well as in rates of removal over the course of treatment could be attributed to the heterogeneous nature of NOM, with different fractions exhibiting distinct properties (e.g., hydrophobicity, charge density, and molecular weight) affecting removal by AEX resin. ,− The UVA 254 -absorbing NOM fraction is attributed to acidic, aromatic substances and is associated with disinfection byproduct (DBP) formation. , The relatively greater UVA 254 breakthrough observed indicates that this fraction was poorly removed compared to overall TOC, corresponding with increased SUVA.…”

Organic matter removal with bicarbonate-form ion exchange: water quality, kinetics and mass transfer mechanisms

“…The overall mass transfer resistance is the sum of the resistances caused by the film, particle and the exchange of ions itself (SenGupta, 2017). The resin age and previous organic matter saturation can influence these factors, in turn affecting the uptake rate of organic matter (Finkbeiner et al, 2020). It was hypothesised that pore blockage caused by continuous use could hinder the uptake of organic matter using resins of increasing age, despite frequent regeneration.…”