UV and Solar Light Induced Natural Iron Oxide Activation: Characterization and Photocatalytic Degradation of Organic Compounds

Abstract

In this study we demonstrate the efficiency of a natural mineral as a photocalyst. This natural mineral was provided from the iron ore deposit from Chaabet-El-Ballout which is located in North-East of Algeria. The characterization analysis of the mineral by the Energy-dispersive X-ray spectroscopy (EDX) revealed that the natural powder has a mixed elemental composition and consist mainly of iron oxide with 50 % of iron. In order to determine the crystal phase composition of the natural iron oxide (NIO), X-ray diffraction (DRX) measurement and infrared absorption spectroscopy (FTIR) were carried out. The results showed that the NIO has a mixed crystal structure composed mainly of hematite and lesser extent of goethite. The specific surface area and the total pore volume of the NIO were 79.015 m2g−1 and 0.0892 cm3g−1 respectively, measured by the Brunauer Emmett–Teller method (BET). The Raman spectrum of the NIO confirmed that the sample has seven characteristic peaks attributable to hematite. The optical properties of soil powder were examined by UV-vis diffuse reflectance spectroscopy (DRS). The pH of point of zero charge (pHpzc) of the adsorbent was determined, a value of 8.3 was found. The photocatalytic activity of the NIO particles was tested by the decomposition of aqueous solution of different class of compounds; phenolic compounds, pesticides and dyes due to their presence in many types of wastewaters. The sorption on the surface of the NIO with photocatalytic oxidation using oxalic acid and hydrogen peroxide would be an effective oxidation process for the removal of contaminants under UV and solar irradiation. High percentages of degradation of 1- Naphtol (1-NP) and Linuron were found about, 94.6 %, 97.2 % respectively, in presence of NIO and H2O2 under UV irradiation. The presence of oxalic acid with NIO enhanced the photodegradation of 2,6-dimethylphenol (2,6-DMP), 2-chlorophenol (2-CP) and Methylene blue (MB) with 72 %, 92 % and 100 % percentages of degradation respectively.

Laser-Induced Photoreduction of Iron(III) Oxide Nanoparticles Enhanced by the Presence of Organic Chromophores

“…This mode of light sensitization can enhance the photoreductive dissolution of hematite to aqueous Fe(II) and lead to degradation of the bound organics (advantageous in the case of pollutant organics). From the standpoint of the iron redox behavior, this process can be written in its generalized form as Fe 2 O 3 + 2e - + 6H + → 2Fe 2+ + 3H 2 O Fe 2 O 3 + 2 e − + 6 H + → 2 Fe 2 + + 3 H 2 O which entails (i) interfacial transfer of electrons from bound organic donors to surface Fe 3+ sites; (ii) transport of injected electrons within the iron oxide; and (iii) hydration and release of soluble Fe 2+ into solution. − In the photic zone of natural aquatic environments, common organic acids tend to bind to and catalyze this reaction at hematite surfaces. − Indeed, this sensitization by natural organic matter plays a major role in regulating the bioavailability of metal nutrients such as iron, manganese, and copper …”

Photocatalyzed electron exchange between organic chromophores and hematite nanoparticles and the role of solid-state charge transport

“…The efficiency of this photoreductive dissolution process is typically enhanced by common organic acids that sorb to and act as photosensitizers on hematite surfaces. 15–18 By driving Fe( ii )/Fe( iii ) redox cycling, such processes not only affect iron bioavailability 19–22 but also contribute to carbon cycling by transforming sorbed organic matter, either by direct photolysis 23,24 or by reaction with intermediate reactive oxygen species. 25–32…”

“…The efficiency of this photoreductive dissolution process is typically enhanced by common organic acids that sorb to and act as photosensitizers on hematite surfaces. [15][16][17][18] By driving Fe(II)/Fe(III) redox cycling, such processes not only Environ. Sci.…”