Adsorptive-Oxidative Removal of Sulfides from Water by MnO2-Loaded Carboxylic Cation Exchangers.

Łukasz J Wilk,Agnieszka Ciechanowska,Elżbieta Kociołek-Balawejder

doi:10.3390/ma13225124

Abstract

Hybrid ion exchangers (HIX) containing manganese(IV) oxide (MnO2) based on macroporous and gel-type carboxylic cation exchangers as supporting materials were obtained. The hybrid materials were characterized using scanning electron microscopy with energy dispersive spectrometry (SEM/EDS), Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD) and nitrogen adsorption isotherms at 77 K and mercury porosimetry. HIX with introduced MnO2 (20.0–32.8 wt% Mn) were tested for removal of dissolved sulfides from anoxic aqueous solutions with 100–500 mg S2−/dm3 concentrations. The process proceeded effortlessly at pH 10–13 despite unfavorable electrostatic interactions of the reactants. The highest exhibited sorption capacity was 144.3 ± 7.1 mg S2−/g. Approximately 65% of dissolved sulfides were oxidized to S2O32− ions and repelled from HIX structure. On average, 13% of sulfide removal products were adsorbed by the MnO2 surface. The impact of MnO2 load and the ionic form of HIX functional groups on removal of sulfides and resulting products was examined. The mechanism of the process is suggested.

Highlights

Sulfides (H2 S(aq), HS−, S2− ) are known as unwanted and troublesome constituents of natural waters and diverse aquatic environments
In one of our research papers [24], we reported that the drawbacks resulting from using powdered iron(III) oxide, in particular decrease in surface area due to aggregation, poor mechanical strength and separation of iron oxide from the solution, could be avoided by depositing the oxide in the inner structure of a cation exchanger
The method used for obtaining hybrid cation exchangers was described previously in the work of

Summary

Introduction

Sulfides (H2 S(aq) , HS− , S2− ) are known as unwanted and troublesome constituents of natural waters and diverse aquatic environments. Sulfides can originate from widespread, commonly occurring, natural anaerobic processes—for instance, the reduction of SO4 2− ions assisted by sulfate-reducing bacteria, and degradation of organic matter containing sulfur atoms in its structure. These processes take place in an uncontrolled manner in marine, lake and river sediments as well as during transportation and storage of domestic, municipal or agricultural wastes and wastewaters. In a wide pH range, emitted in the toxic form of

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