Photodegradation of phenol red in the presence of oxyhydroxide of Fe(III) (Goethite) under artificial and a natural light

Abstract

The (α‐FeOOH) Goethite composite is a stable and an efficient catalyst in aqueous suspension under irradiation at 365 nm and by solar light. The photocatalytic activities of this composite were evaluated using Phenol Red (PR) dye (phenolsulfonphthalein class). In the dark, controlling factors, such as the pH and the adsorption of PR on Goethite surface were evaluated (before starting the photochemical experiments). It was found that the system PR‐Goethite present a small decrease in the main band of the dye (435 nm) which was explained by the low rate of adsorption of this dye on the Goethite. Also, we note that 40% of PR decolourisation was obtained after 200 min by the system PR‐Goethite‐hydrogen peroxide (H2O2) in dark due to the formation of •OH by thermal decomposition of H2O2 on the surface of Goethite. The effects of various experimental parameters, such as initial dye concentration, pH, photocatalyst amount, tert‐Butyl alcohol effect and H2O2 addition were investigated in the study of photodegradation of the dye. The results showed that the photodegradation of PR under UV‐A (365 nm) irradiation could be enhanced greatly in the presence of H2O2. Natural radiation tests (under sunlight) showed that degradation was faster comparing with that obtained using the artificial one at 365 nm. Studies of the mineralization using total organic carbon method under naturel light certify that this method, compatible with the environment, may be considered in the treatment of wastewater and generally in the process of removal of this kind of pollutant.

Photoreductive Dissolution of Iron (Hydr)oxides and Its Geochemical Significance

“…As mentioned above, photoreductive dissolution of iron (hydr)­oxides is accompanied by the generation of ROS, which can benefit the degradation of various organic contaminants. ,,, The formed •OH can oxidize dye, humic substances, phenolic compounds, and POPs, which has a significant influence on their persistence and ecotoxicity in the environment. − For example, goethite is able to degrade phenol red dye when exposed to light irradiation, and the authors believe that the main reason is the generation of •OH during the photolysis of Fe­(III)–OH . Pehkonen et al investigated the photooxidation of halogenated acetic acids during the photoreductive dissolution of different iron (hydr)­oxides, in which halogenated acetic acids serve as electron donors (similar to ligands in LMCT process) to reduce Fe­(III) in iron (hydr)­oxides.…”

“…121,213−215 As mentioned above, photoreductive dissolution of iron (hydr)oxides is accompanied by the generation of ROS, which can benefit the degradation of various organic contaminants. 101,169,216,217 The formed •OH can oxidize dye, humic substances, phenolic compounds, and POPs, which has a significant influence on their persistence and ecotoxicity in the environment. 218−220 For example, goethite is able to degrade phenol red dye when exposed to light irradiation, and the authors believe that the main reason is the generation of •OH during the photolysis of Fe(III)−OH.…”

“…218−220 For example, goethite is able to degrade phenol red dye when exposed to light irradiation, and the authors believe that the main reason is the generation of •OH during the photolysis of Fe(III)−OH. 216 Pehkonen et al 169 investigated the photooxidation of halogenated acetic acids during the photoreductive dissolution of different iron (hydr)oxides, in which halogenated acetic acids serve as electron donors (similar to ligands in LMCT process) to reduce Fe(III) in iron (hydr)oxides. The authors found that ferrihydrite has the highest reactivity toward the oxidation of halogenated acetic acid to yield the corresponding halo acids and CO 2 .…”

Photoluminescent and photocatalytic behaviour of zinc oxide nanostructures synthesized through the room temperature ultrasonication method

“…The chromophoric structure was responsible for the bands at 432 and 590 nm, whereas the benzoic ring was responsible for the band at 263 nm. [ 26–31 ] The formula used to compute the percentage of dye degradation in samples for the most strong absorption peak at 432 nm based on initial and final UV–visible absorption data is: where E represents the percentage deterioration, A 0 represents the initial absorbance, and A t represents the absorbance after various time intervals of irradiation. According to the absorbance readings, 59% of the dye was destroyed after 30 min and 93% after 75 min of UV light exposure.…”

“…The chromophoric structure was responsible for the bands at 432 and 590 nm, whereas the benzoic ring was responsible for the band at 263 nm. [26][27][28][29][30][31] The formula used to compute the percentage of dye degradation in samples for the most strong absorption peak at 432 nm based on initial and final UV-visible absorption data is:…”