Photo-Fenton degradation of methylene blue using hematite-enriched slag under visible light

Enhanced Fenton catalytic degradation of methylene blue by the synergistic effect of Fe and Ce in chitosan-supported mixed-metal MOFs (Fe/Ce-BDC@CS)

Methylene blue (MB) is a refractory organic pollutant that poses a potential threat to the aquatic environment. Fenton reaction is considered a primrose strategy to treat MB. However, the traditional Fenton process is plagued by narrow pH application range, poor stability, and secondary pollution. To solve these problems, many Fenton-like catalysts including metal-organic frameworks (MOFs) have been prepared. Herein, a novel bimetallic MOF (Fe/Ce-BDC@CS) was prepared through simple adsorption for the effective removal of MB, where chitosan (CS) was used as the carrier. The degradation performance of Fe/Ce-BDC@CS (100 % within 20 min) was better than that of most reported monometallic MOFs. Moreover, Fe/Ce-BDC@CS exhibited good repeatability and its anti-interference performance of some inorganic ions was also remarkable. Column loading experiments showed that the removal efficiency of MB was still about 50 % over 155 h with a flowing speed of 0.30 L/h. Comparative analysis indicated that such excellent performances could be attributed to the synergistic effect between Fe and Ce. Furthermore, the results of quenching tests indicate that OH, O2-, and 1O2 contributed to MB degradation. In brief, Fe/Ce-BDC@CS has promising prospects in MB treatment, which can provide scientific references for the design and application of bimetallic MOFs.

Application of Deep Eutectic Solvents (DES) for the Synthesis of Iron Heterogeneous Catalyst: Application to Sulfamethoxazole Degradation by Advanced Oxidation Processes

The development of novel approaches to the remotion of pharmaceuticals in wastewater is a subject of concern due to their effect on living beings and the environment. Advanced oxidation processes and the use of relevant catalysts are feasible treatment alternatives that require further development. The development of suitable heterogeneous catalysts is a necessity. This work proposes the synthesis of an iron catalyst in a deep eutectic solvent (Fe-DES) composed of choline chloride and citric acid, which was physically and chemically characterized using SEM-EDS and TEM, FTIR, RAMAN, XRD and XPS. The characterisation confirmed the presence of iron in the form of hematite. Fe-DES was shown to be a multipurpose catalyst that can be applied in the removal of sulfamethoxazole as a reagent in the Fenton and electro-Fenton processes and as an activator of peroxymonosulfate (PMS) processes. After testing the catalyst with the aforementioned techniques, the best result was achieved by combining these processes in an electro-PMS, with great efficiency achieved by dual activation of the PMS with the catalyst and electric field, attaining total elimination at natural pH in 90 min. Furthermore, the degradation was confirmed by the detection of short-chain carboxylic acids (oxalic, succinic, and acetic) and reduction in toxicity values. These results confirm the suitability of Fe-DES to degrade high-priority pharmaceutical compounds.

Humic acid coupled with coal gasification slag for enhancing the remediation of Cd-contaminated soil under alternated light/dark cycle

In this study, the synthesis of a coal gasification slag-humic acid (SA) hybrid was purposed for the remediation of cadmium (Cd)-contaminated soil. In order to investigate the effect of SA on the Cd-contaminated soil and plant growth, a series of experiments were carried out under different illumination condition. The results showed that the SA has some the photocatalytic activity, and adding 10 wt% of SA to the soil could obviously improve the soil fertility and decrease the mobility of Cd in the soil under alternated light/dark cycle (12L/12D); the content of the residual fraction in the SA-amended soil reached 69.5%, and the Cd decreasing rates for the leaf, stem, and root of Artemisia ordosica were near 100%, 91.3%, and 75.3%, respectively. Characterizations of amendments suggested that the synergistic effect of precipitation and surface complexation played a major role in the remediation of Cd-contaminated soil.

Fe-Immobilised Catechol-Based Hypercrosslinked Polymer as Heterogeneous Fenton Catalyst for Degradation of Methylene Blue in Water

Clean water is one of the sustainable development goals. Organic dye is one of the water pollutants affecting water quality. Hence, the conversion of dyes to safer species is crucial for water treatment. The Fenton reaction using Fe as a catalyst is a promising process. However, homogeneous catalysts are normally sensitive, difficult to separate, and burdensome to reuse. Therefore, a catechol-based hypercrosslinked polymer (catechol-HCP) was developed as an inexpensive solid support for Fe (catechol-HCP-Fe) and applied as a heterogenous Fenton catalyst. The good interaction of the catechol moiety with Fe, as well as the porous structure, simple preparation, low cost, and high stability of catechol-HCP, make it beneficial for Fe-loading in the polymer and Fenton reaction utilisation. The catechol-HCP-Fe demonstrated good catalytic activity for methylene blue (MB) degradation in a neutral pH. Complete decolouration of 100 ppm MB could be observed within 25 min. The rate of reaction was influenced by H₂O₂ concentration, polymer dose, MB concentration, pH, and temperature. The catechol-HCP-Fe could be reused for at least four cycles. The dominant reactive species of the reaction was considered to be singlet oxygen (¹O₂), and the plausible mechanism of the reaction was proposed.

Effect of heat treatment on the photocatalytic activity of α-Fe2O3 nanoparticles: towards diclofenac elimination

α-Fe₂O₃ nanoparticles were synthesized via a straightforward method. XRD, FTIR, SEM, ESR, and DRS techniques investigated the influence of various calcination temperatures on the crystal structure, optical, and photocatalytic properties of the samples. The obtained results demonstrated that the average crystallite size increased with the increase in the calcination temperature. Measured and computed optical properties were in accordance and the bandgap energy decreased with the increase in the calcination temperature. The highest photocatalytic degradation efficiency for diclofenac (DCF) was obtained with the sample calcinated at 300 °C (96%). The photocatalytic process occurs because of the presence of OH• radicals. The addition of H₂O₂ led to the inhibition of OH• radicals that H₂O₂ scavenged.

Photocatalytic degradation of organic dyes and phenol by iron-silicate glass prepared by the sol–gel method

A highly efficient photo-Fenton catalyst iron silicate glass was successfully prepared by a simple sol–gel method.