Screening of catalytic activity of natural iron-bearing materials towards Fenton-like degradation of a model contaminant

INCHAURRONDO N.; PINTAR A.; MAESTRE A; RAMOS C; ZERJAV G; HAURE P.

Praga

Conferencia; 5th European Conference Environmental Applications of Advanced Oxidation Processes; 2017

The development of an active, selective, stable and low-cost catalyst constitutes one of the main targets towards the industrial implementation of Advanced Oxidation Processes, such as the Fenton-like reaction. In this context, different natural materials, i.e. sand, pumice, volcanic ash and bentonite will be evaluated in the Fenton-like oxidation of an azo-compound, Orange II (OII).The volcanic ash was originated from the eruption of the Puyehue volcano (year 2012) and collected in Bariloche, Argentina. The black sand was obtained from the Praia Preta in Ilha Grande (Brazil). The bentonite Montanit300® was provided by a collaborative Slovenian group (purchased from Montana ?alec). Pumice was purchased from a local supplier (Argentina). All of these samples were washed several times with distilled water, dried and then tested free of diffusional restrictions. Fresh and used samples were characterized by XRF, XRD, SEM-EDX, Mossbauer spectroscopy, TGA and the surface area was determined by the BET method.The volcanic ash, black sand and pumice exhibit a BET surface area in the range of 0.5-1.2 m2/g, while the bentonite exibits a higher value (36 m2/g). According to XRD, FRX and SEM/EDX results all samples show Fe in their composition. The volcanic ash presents abundant volcanic glass and also quartz crystals, cristobalite, and paglioclasa, iron oxide and manganosite. The black sand is mostly composed of goethite and some anatase. The bentonite shows abundant phases of heulandite, clinoptilolite and quartz. Pumice presents abundant amorphous SiO2 and paglioclasa, quartz crystals, cristobalite, aluminosilicate and CaCO3.The samples were used in the Fenton-like oxidation of OII (100 mg/L) with the stoichiometric requirement of H2O2, in a batch reactor at 70°C, with initial pH=3, reaction time of 4 hours and a catalyst loading equivalent to 200 mg/L of Fe in the reaction media. OII adsorption assays presented negligible OII and TOC conversions (5 %). OII was also treated in the absence of a catalyst using the stoichiometric amount of H2O2, at 70ºC. OII and TOC conversions of 100 and 20 % were obtained, respectively. Reaction outcomes are summarized in Table 1.Table 1. Reaction outcomes of OII oxidation at t=240 min.Volcanic ashBlack sandPumiceMontanit300®%XOII100100100100%XTOC48292470%XH2O262397598ppm Feleached2.10.6-3.3These inexpensive natural materials presented good mineralization levels with low Fe leaching. Their performance is comparable to more expensive and sophisticated synthetic catalysts.