Enhancing manganese sorption: Batch and fixed-bed column studies on activated zeolite

Abstract

Dissolved Mn2+ in groundwater is dangerous for human health since it may act as a neurotoxin. To address this issue, sorption has emerged as an environmentally-friendly technology for Mn2+ removal. This study aimed to assess the effect of activation of Chilean natural zeolite, by modification of its compensating cations with NaCl, on its capacity for Mn2+ removal using batch and fixed-bed column studies. The natural and activated zeolites were characterized by SEM-EDS, TXRF, XRD, and N2 adsorption assays. The results of batch studies demonstrate that Na+ enhances the Mn2+ removal capacity of these zeolites from 4.55 to 5.9−1, with negligible changes in the pore structure. The experimental data fitted well with the pseudo-second-order kinetic and Langmuir adsorption models. Furthermore, MnOx(s) formed during the Mn2+ removal was identified on the surface of the zeolite by XRD and SEM-EDS analysis. The fixed-bed column studies were conducted at two bed heights: H1 (5 cm) and H2 (10 cm). The breakthrough curves adjusted to models of Thomas and Dose-response. The dose-response model adequately described both experimental data with an R2 > 0.90. The Mn2+ adsorption capacity of the system (qmdr) was 2.38 and 5.13 mg g−1, for H1 and H2, respectively. The regeneration of the activated zeolite was achieved using NaCl solution improving the efficiency of Mn2+ removal after reuse. This work highlights natural zeolite potential as an effective material for Mn2+ removal and as a viable technology to improve the water quality affected by geogenic contamination.