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Kinetics and fate of natural organic matter under different water matrices using strong basic ion exchange resins Bazri, Mohammad Mahdi

Abstract

This research has investigated the factors influencing the kinetics and efficacy of natural organic matter (NOM) removal during the anionic ion exchange process (IEX). A holistic approach was undertaken to evaluate various IEX resins in terms of their NOM removal kinetics and regeneration efficiency under batch and consecutive multiple loading cycles. Initial screenings indicated the strongly basic resin as a better candidate for NOM removal, and hence it was employed for subsequent experiments. Different treatment parameters (resin dose, contact time, NOM source) were tested and detailed kinetic evaluations were conducted to determine the affinity and removal rate of NOM as well as nitrate, and sulfate that are generally present in natural waters. Results obtained showed a substantial removal of NOM (up to 80 %) and nitrate (up to 80 %), and a superior removal for sulfate (up to 98 %). Charge density and molecular weight were found to play a major role in the removal process. Different mathematical and physical models were employed to predict the experimental data and the rate-limiting step was found to be pore diffusion which was affected by the resin dose/solute concentrations ratio. Moreover, the impact of IEX resins on NOM fractions and subsequent water quality parameters was investigated in this study. Humic (-like) substances were mainly targeted by IEX, and more hydrophilic and/or non-ionic fractions were slightly removed. Application of IEX reduced the formation potential of carbonaceous and nitrogenous disinfection by-products by 13-20 % and 3-50 %, respectively. Also, the practice of IEX treatment reduced the assimilable organic carbon levels by 30-40 %. Additionally, a positive effect of IEX, as a pretreatment to UV/H₂O₂, at reducing the ⦁OH scavenging characteristics of the water was observed. Electrical energy per order for removing a probe compound (i.e., pCBA) showed 20-40 % reduction indicating the improvement in the efficacy of UV/H₂O₂ treatment. Findings of this study display the robustness of IEX process for drinking water applications and lay down a quantitative approach for evaluating the kinetics of this process under various treatment conditions.

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Attribution-NonCommercial-NoDerivatives 4.0 International

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