Fe(III)-citrate enhanced sunlight-driven photocatalysis of aqueous Carbamazepine

Effect of common low-molecular-weight organic acid on the photodegradation of sertraline by ferrihydrite

Sertraline is one of the most commonly used antidepressant pharmaceuticals with ubiquitous distribution in the aqueous environment. However, the environmental behavior of sertraline in the co-presence of low-molecular-weight organic acid (LMWOA) and iron oxide mineral is still poorly understood. In this study, the photodegradation of sertraline was systematically investigated in a common photosensitizing system (ferrihydrite (Fh)-LMWOA). Six LMWOAs, including citrate acid (CA), tartrate acid (TA), malate acid (MA), lactate acid (LA), succinate acid (SA) and malonic acid (MOA) were chosen as the representatives. Our results implied that the different Fe3+ dissolution rates would lead to rather different sertraline degradation patterns following the order of Fh-CA > Fh-TA > Fh-MA > Fh-LA > Fh-SA > Fh-MOA. The reaction was initiated by the interaction between LMWOA and Fh via ligand-promoted-dissolution mechanism. Furthermore, the Fe3+ dissolution rates also showed a strong correlation with the metal-organic complexation constants, indicating that the photodegradation process is strongly related to the complexation ability of LMWOA with Fe3+. •OH, O2•- and CO2•- were detected, indicating that they contributed to the photodegradation of sertraline. •OH was demonstrated to be the dominant Reactive oxygen species (ROS) for the degradation of sertraline, and the detailed transformation pathways were proposed based on the product analysis and theoretical calculation. According to the ecological structure activity relationship estimation, the photodegradation products of sertraline possessed lower toxicity compared to the parent compound. These findings contribute to a more comprehensive understanding of the environmental fate of sertraline and evaluate its potential ecotoxicity in natural systems.

Photochemistry of the Fe(III)-iminodiacetic acid complex under UVA and UV/Vis irradiation: synthesis and characterisation

The photochemistry of Fe(III)-Iminodiacetic acid complex (Fe(III)-IDA) was studied under UVA and UV/Vis irradiation. The synthesis was realised via molar ratio method modified by reaction of IDA as ligand with Fe(III) as metal. The interaction of Fe(III) with IDA was characterised using Fourier-transform infrared (FTIR) and spectroscopy UV-visible. The results confirmed the stability of the complex at pH > 5; with constant of stability (Log β = 10.02) and stoichiometry Fe(III): IDA = 1:1. In addition, the redox potential was calculated at 521 mV, which is significantly lower than E° for the Fe(III)/Fe(II) couple. The photolysis of this complex in the presence of UVA light and UV/Vis light at different pHs was carried out. This photolysis was followed by several assay Fe(II) and •OH. The results show that the Fe(III)-IDA complex present a photo-reactivities under either light source and the phenomenon is faster when the UV/Vis was used. The initial conversion rate (r0) decreased with increasing of initial pH. The formation of hydroxyl radicals via the Fenton reaction was improved at pH = 2.12 for both irradiation sources used. Reduction of total organic carbon was also studied using the total organic carbon (TOC). The feasibility of amino iron complexes to improve the Fenton process under irradiation was confirmed. Additionally, our research also evidenced the optimal conditions for the formation of hydroxyl radicals; which are the key factor in remove pharmaceuticals pollutants in aqueous media. Based on the results obtained, the Fe(III)-IDA complex could be efficiently photolysis under UV/Vis light.

New aspects of the photodegradation of iron(III) citrate: spectroscopic studies and plant-related factors

Iron (Fe) is an essential cofactor for all livings. Although Fe membrane transport mechanisms often utilize Fe^II, uncoordinated or deliberated ferrous ions can initiate Fenton reactions. Fe^III citrate complexes are among the most important complexed forms of Fe^III especially in plants that, indeed, can undergo photoreduction. Since leaves as photosynthetic organs of higher plants are generally exposed to illumination in daytime, photoreaction of ferric species may have biological relevance in iron metabolism, the relevance of which is poorly understood. In present work Fe^III citrate transformation during the photodegradation in solution and after foliar application on leaves was studied by Mössbauer analysis directly. To obtain irradiation time dependence of the speciation of iron in solutions, four model solutions of different pH values (1.5, 3.3, 5.5, and 7.0) with Fe to citrate molar ratio 1:1.1 were exposed to light. Highly acidic conditions led to a complete reduction of Fe together with the formation of Fe^II citrate and hexaaqua complexes in equal concentration. At higher pH, the only product of the photodegradation was Fe^II citrate, which was later reoxidized and polymerized, resulting in the formation of polynuclear stable ferric compound. To test biological relevance, leaves of cabbage were treated with Fe^III citrate solution. X-ray fluorescence imaging indicated the accumulation of Fe in the treated leaf parts. Mössbauer analysis revealed the presence of several ferric species incorporated into the biological structure. The Fe speciation observed should be considered in biological systems where Fe^III citrate has a ubiquitous role in Fe acquisition and homeostasis.

Fast and efficient degradation of water pollutant dyes and fungicide by novel sulfur-doped graphene oxide-modified Ag3PO4 nanocomposite

The sulfur-doped graphene oxide (sGO)-integrated Ag₃PO₄ composite displayed very high catalytic activity toward prominent water pollutants like textile dyes and fungicide under sunlight. The optimum amount of sGO doping was found as 5% for degradation. The novel composite degraded 99% of methylene blue (MB) in only 5 min of sunlight exposure, which is 16 and 8 times faster than Ag₃PO₄ and 5% GO-Ag₃PO₄. High mineralization was observed for MB with a total organic carbon (TOC) removal of 98% in 30 min. The composite mineralized rhodamine B, methyl orange, and acid red 18 dyes with a TOC removal above 95%. Moreover, a toxic dithiocarbamate fungicide thiram was degraded in 1 h with a TOC removal of 82% leaving less toxic thiourea. The formation of sGO-Ag₃PO₄ n-n heterojunction increases charge transport and photocatalytic activity of the composite to incredible extent along with hollow morphology and in situ formed Ag nanoparticles (AgNPs).

Insight Into the Formation Paths of Methyl Bromide From Syringic Acid in Aqueous Bromide Solutions Under Simulated Sunlight Irradiation

Methyl bromide (CH₃Br) is one of the largest natural sources of bromine in the stratosphere, where it leads to ozone depletion. This paper reported the photochemical production of CH₃Br from syringic acid (SA) that has been used as an environmentally relevant model compound for terrestrially-derived dissolved organic matter. The formation of CH₃Br increased with the increase of bromide ion concentration ranging from 0.8 to 80 mmol L⁻¹. Ferric ions (Fe(III)) enhanced CH₃Br production, while chloride inhibited it, with or without Fe(III). Meanwhile, methyl chloride (CH₃Cl) was generated in the presence of chloride and was inhibited by Fe(III). The different effects of Fe(III) on the formation of CH₃Cl and CH₃Br indicate their diverse formation paths. Based on the intermediates identified by liquid chromatography-mass spectrometry and the confirmation of the formation of Fe(III)-SA complexes, it was proposed that there were two formation paths of CH₃Br from SA in the bromide-enriched water under simulated sunlight irradiation. One path was via nucleophilic attack of Br⁻ on the excited state protonation of SA; the other was via the combination of methyl radical and bromine radical when Fe(III) was present. This work suggests that the photochemical formation of CH₃Br may act as a potential natural source of CH₃Br in the bromide-enriched environmental matrix, and helps in better understanding the formation mechanism of CH₃Br.