Removal of Manganese using Polymer gel composites

Manganese is the biggest concern in Bangladesh after Arsenic, as almost 50% area contains groundwater with Mn concentrations greater than the WHO drinking water guidelines. The previous studies suggested that γ-FeOOH could remove Mn effectively from water. However, those studies were conducted at higher pH levels and not in natural conditions. Additionally, the practical applicability of the Mn removal methods was not discussed. Moreover, additional separation processes required to separate the adsorbents and precipitations are not environmentally friendly. Therefore, to improve the Mn removal efficiency at natural pH levels and other natural water conditions, we examined Mn removal by adsorption technology using polymer gel composites. The gel composites were a cationic gel composite, N,N’-dimethylamino propylacrylamide, methyl chloride quaternary (DMAPAAQ), loaded with iron hydroxide (DMAPAAQ + FeOOH), and a non-ionic gel composite, N,N’-Dimethylacrylamide (DMAA), loaded with iron hydroxide (DMAA + FeOOH). DMAPAAQ + FeOOH gel contains 62.01 wt% of γ-FeOOH in its polymer structures because of the unique preparation method and this gel showed better As removal efficiency than the other adsorbents at natural conditions ensuring its environmental friendliness. Our results suggest that the cationic gel composite, DMAPAAQ + FeOOH, removed Mn more than that of DMAA + FeOOH because the content of γ-FeOOH particles was higher in the gel structure of DMAPAAQ + FeOOH. Besides the polymer component of DMAPAAQ + FeOOH contributing to the adsorption of Mn, it carried the higher amount of γ-FeOOH components, which helped to further increase Mn removal. Our results also suggested that the presence of As did not have any effect on the adsorption of Mn with DMAPAAQ + FeOOH gel composite because the polymeric component (DMAPAAQ) adsorbed As and the γ-FeOOH particles adsorbed Mn, which provides the basis for simultaneous adsorption of As and Mn. This research is a base for the simultaneous removal of harmful components such as As, Mn, Cr, Cd, and more.