Modeling Manganese Removal in a Pilot‐Scale Postfiltration Contactor

Abstract

A model of manganese (Mn) adsorption and subsequent oxidation by chlorine was applied to experimental data from two pilot‐scale postfiltration Mn contactors to estimate the oxidation rate constant. Experiments showed the ability of the contactors to adequately remove soluble Mn under varying operating conditions. A pseudo first‐order rate expression was found to be more appropriate than a second‐order rate expression. The fitted, pseudo first‐order rate constant ranged from 2.8 × 10–4 to 5.2 × 10–4/s and from 1.1 × 10–4 to 1.8 × 10–4/s in the two pilot‐scale postfiltration contactors. A sensitivity analysis showed the model was most sensitive to the adsorption isotherm constants and the oxidation rate constant, suggesting that these two processes controlled the removal of soluble Mn in the contactor. Combined with bench‐scale experiments, the model described in this article could be used to predict the performance of a postfiltration contactor across a range of influent Mn concentrations and chlorine dosages that might be encountered in a water treatment facility.

Oxidative removal of soluble divalent manganese ion by chlorine in the presence of superfine powdered activated carbon

“…Thus, we conclude that the dependence of kC on chlorine concentration was small, confirming our prediction that k and kC would be independent of chlorine concentration when equation ( 5) was derived from equations ( 2) to (4). Bierlein et al (2015) and Knocke et al (2010) have reported similar results for the effect of free chlorine concentration on the removal of Mn(II) by MnOx. Li et al (2019a) have also reported no change in the Mn(II) removal rate at chlorine doses of 1 to 4 mg/L.…”

“…Li et al (2019a) have interpreted the pseudo-first-order reaction kinetics of Mn(II) removal from the perspective of chemical oxidation. However, we applied an external-film mass transfer model because this model has been widely used to describe Mn(II) removal by MnOx-coated filter media in the presence of chlorine in previous studies (Bierlein et al, 2015;Dashtban Kenari et al, 2019;Merkle et al, 1997). These studies present the model equations in the form of removal kinetics using filter media, but the basic form of the reaction kinetics can be written as follows:…”

Removal of soluble divalent manganese by superfine powdered activated carbon and free chlorine: Development and application of a simple kinetic model of mass transfer–catalytic surface oxidation

“…The two-resistance model incorporating mass-transfer and oxidation rates has been applied in previous studies analyzing Mn 2+ removal with a granular MnO X catalyst ( Bierlein et al., 2015 ; Kenari et al., 2019 ; Merkle et al., 1997 ). MnO X would have a higher adsorption capacity for Mn 2+ than activated carbon, which reduces the rate resistance of adsorption, and the particle size of MnO X , which is much larger than SPAC/PAC, increases the mass-transfer resistance.…”

“…They assumed the local equilibrium of the Freundlich adsorption isotherm in the Mn 2+ adsorption process. The basics of the Merkle model have been followed in later studies ( Bierlein et al., 2015 ; Kenari et al., 2019 ). …”

The Impact of Microstructure of Filtration Materials on Its Auto-Activation for Manganese Removal from Groundwater

“…In traditional groundwater treatment systems based on aeration followed by rapid filtration with no chemical dosage, manganese removal is possible due to the presence of manganese dioxide catalyst on the grains of the filtration material [3][4][5]. The chemically non-active filtration material, such as silica sand, has to be activated first by covering the grains with manganese dioxide during the filtration of natural groundwater [6]. After activation of filtration material, manganese removal becomes an autocatalytic and heterogenic process [2,5].…”