Degradation of Rhodamine B by contact glow discharge electrolysis with Fe3O4/BiPO4 nanocomposite as heterogeneous catalyst

Multi-catalysis of glow discharge plasma coupled with FeS2 for synergistic removal of antibiotic

Fe-based composites improved the energy utilization efficiency of plasma for removing contaminants through multi-catalysis have received much attention. However, the energy efficiency and catalytic activity are compromised by the slow transformation from Fe (Ⅲ) to Fe (Ⅱ). Here, given the electron-donating ability of reducing sulfur species, as well as the acidic environment generated by FeS₂, single FeS₂ was introduced into the glow discharge plasma (GDP) reactor for the removal of tylosin (TYL). The results showed that a significant synergistic effect between FeS₂ and GDP improved the energy efficiency of plasma and the removal efficiency of TYL (99.7%). FeS₂ boosted the generation of radicals (·OH, ·O₂^-) and nonradicals (h⁺, e^-) rather than H₂O₂ and O₃, which played an important role in TYL abatement. Moreover, the electrons donating sulfur and iron species from FeS₂ can accelerate the conversion of Fe(III) to Fe(II), which was conducive to the generation of radicals. Besides, acid solution self-adjustment resulted from the oxidation of FeS₂ improved heterogeneous Fenton reaction, the oxidation potential of ·OH and adsorption of positive charged TYL. The plausible degradation pathways of TYL were proposed in GDP/FeS₂ system. In summary, enhanced removal of TYL was mainly attributed to the catalytic pathway altered by FeS₂ through high-energy electrons, photocatalysis, heterogeneous Fenton and O₃ catalysis in the GDP system simultaneously. The strategy of integrating GDP with FeS₂ proposed in this work is expected to offer a feasible and potential technique for organic wastewater treatment.

Degradation mechanism of HCN by electrochemically coupled copper-loaded magnetic nanoparticles in a liquid phase pseudo-homogeneous system

Hydrogen cyanide (HCN) comes from a wide range of sources, but it is highly toxic and corrosive, harming the environment and human health. This experiment used magnetic nano-Fe₃O₄ particles loaded with Cu (Cu-Fe₃O₄ magnetic nanoparticles) for electrochemical catalytic purification of HCN in a liquid phase pseudo-homogeneous system. The results show that the purification efficiency of Cu-Fe₃O₄ magnetic nanoparticles on HCN is 70% without electricity. After a certain voltage is applied, the degradation efficiency of 2 h with iron-carbon particles is significantly improved, and the degradation efficiency can reach about 95%. And the degradation efficiency increases with the increase of voltage. The electrochemical synergistic degradation mechanism of Cu-Fe₃O₄ magnetic nanoparticles is complex, which can directly catalyze the degradation of HCN or form CNO^- intermediates to further degrade into CO₂, H₂O, and NH₃. Meanwhile, Fe²⁺, Cu⁺, and other transition metal ions in the liquid phase participate in the Fenton-like reaction to further degrade HCN. The results show that the synergistic electrochemical degradation of HCN by Cu-Fe₃O₄ magnetic nanoparticles has excellent potential to degrade highly toxic gases.

Superior dye degradation and adsorption capability of polydopamine modified Fe3O4-pillared bentonite composite

Owing to the increasing demand of environmentally benign materials for the degradation of hazardous dyes, herein we are reporting two different synthesis approaches for the fabrication of iron loaded bentonite composites by modifying and activating bentonite surface with polydopamine (PDA) followed by pillaring with Fe³⁺ (Fe-PDA-bentonite) and Fe₃O₄ (Fe₃O₄-PDA-bentonite). Both the composites were assessed for their adsorption and degradation performance using crystal violet (CV), Rhodamine B and Brilliant blue dyes following adopting advanced oxidation process type Fenton reaction under variable energy sources (Sunlight, UV light and Ultrasonication), concentration of H₂O₂ and catalyst dosage. Under UV light irradiation, the composites achieved complete degradation of the dyes within 60 min and showed degradation rate constant of 30.5E-3-81.8E-3. Textural characterizations of the composites were achieved via XRD, FTIR, TGA, XPS, SEM-EDX, TEM, N₂ adsorption, VSM and UV/Vis spectrophotometry. The adsorption data of CV over the two composites fitted well with Langmuir adsorption isotherm, exhibiting the maximum adsorption capacity of 862 mg/g and 1235 mg/g for Fe-PDA-bentonite and Fe₃O₄-PDA-bentonite composites respectively. LCMS analysis of the post degradation products revealed that both the composites followed different degradation pathways and Fe₃O₄-PDA-bentonite showed superior photocatalytic performance by accomplishing complete dye degradation without leaving any degradation products. FTIR analysis of the post-degradation composites confirmed their structural stability with negligible iron leaching. This study, accredited to its cost-effectiveness, ease of operation and high efficiency, provides useful reference information for the degradation of dyes on industrial level.

Contact Glow Discharge Electrolysis: Effect of Electrolyte Conductivity on Discharge Voltage

Contact glow discharge electrolysis (CGDE) can be exploited in environmental chemistry for the degradation of pollutants in wastewater. This study focuses on the employment of cheap materials (e.g., steel and tungsten) as electrodes for experiments of CGDE conducted in electrochemical cells with variable electrolytic composition. A clear correlation between breakdown voltage (VB)/discharge (or midpoint) voltage (VD) and the conductivity of the electrolyte is shown. Regardless of the chemical nature of the ionogenic species (acid, base or salt), the higher the conductivity of the solution, the lower the applied potential required for the onset of the glow discharge. Concerning practical application, these salts could be added to poorly conductive wastewaters to increase their conductivity and thus reduce the ignition potential necessary for the development of the CGDE. Such an effect could render the process of chemical waste disposal from wastewaters more economical. Moreover, it is evidenced that both VB and VD are practically independent on the ratio anode area to cathode area if highly conductive solutions are employed.