Paracetamol degradation via electrocatalysis with B and N co-doped reduced graphene oxide: Insight into the mechanism on catalyst surface and in solution

Boron-doped reduced graphene oxide as an efficient cathode in microbial fuel cells for biological toxicity detection

Electrodes with superior stability and sensitivity are highly desirable in advancing the toxicity detection efficiency of microbial fuel cells (MFCs). Herein, boron-doped reduced graphene oxide (B-rGO) was synthesized and utilized as an efficient cathode candidate in an MFCs system for sensitive sodium dodecylbenzene sulfonate (SDBS) detection. Boron doping introduces additional defects and improves the dispersibility and oxygen permeability, thereby enhancing the oxygen reduction reaction (ORR) efficiency. The B-rGO-based cathode has demonstrated significantly improved output voltage and power density, marking improvements of 75 % and 58 % over their undoped counterparts, respectively. Furthermore, it also exhibited remarkable linear sensitivity to SDBS concentrations across a broad range (0.2-15 mg/L). Notably, the cathode maintained excellent stability within the test range and showed significant reversibility for SDBS concentrations between 0.2 and 3 mg/L. The highly sensitive and stable B-rGO-based cathode is inspiring for developing more practical and cost-effective toxicant sensing devices.

Electrochemical filtration for drinking water purification: A review on membrane materials, mechanisms and roles

Electrochemical filtration can not only enrich low concentrations of pollutants but also produce reactive oxygen species to interact with toxic pollutants with the assistance of a power supply, making it an effective strategy for drinking water purification. In addition, the application of electrochemical filtration facilitates the reduction of pretreatment procedures and the use of chemicals, which has outstanding potential for maximizing process simplicity and reducing operating costs, enabling the production of safe drinking water in smaller installations. In recent years, the research on electrochemical filtration has gradually increased, but there has been a lack of attention on its application in the removal of low concentrations of pollutants from low conductivity water. In this review, membrane substrates and electrocatalysts used to improve the performance of electrochemical membranes are briefly summarized. Meanwhile, the application prospects of emerging single-atom catalysts in electrochemical filtration are also presented. Thereafter, several electrochemical advanced oxidation processes coupled with membrane filtration are described, and the related working mechanisms and their advantages and shortcomings used in drinking water purification are illustrated. Finally, the roles of electrochemical filtration in drinking water purification are presented, and the main problems and future perspectives of electrochemical filtration in the removal of low concentration pollutants are discussed.

Modulating Cu valence state in Cu and graphene oxide composites for electrocatalytic tetracycline hydrochloride degradation

Cu and graphene oxide composites (Cu-GO) were designed by anchoring Cu+ via oxygen groups in GO based on the heavy co-relationships of copper (Cu) anode electrocatalytic activity with Cu valence state. With the consumption of oxygen groups under various pyrolysis temperatures, the Cu valence state changed from Cu ions (as CuCl2 and CuCl) to Cu oxide (CuO and Cu2O) and the final metallic Cu. In which the Cu+ in CuCl was more favorable for electrocatalytic oxidation than other Cu valence states. Due to the dramatic contribution of 1O2 and active chlorine, 100% degradation efficiency was achieved using tetracycline hydrochloride (TCH) as the target pollutant. Cu+ showed a selective preference for 1O2 and active chlorine triggering, rather than metallic Cu. Under the attack of 1O2 and active chlorine, the degradation intermediates of TCH were then provided by LC-MS results. The final results not only prove the feasibility of the Cu-GO/electrocatalysis system for pollution control but also shed light on the anode design via Cu valence state modulation.

Exploration of DFT and TD-DFT computation to investigate the interaction between paracetamol and lithium or its compounds

Paracetamol is a commonly used antipyretic drug and its consumption drastically was increased during the COVID-19 times as fever was one of the symptoms. The excessive usage of paracetamol could harm humans, as the unused accumulated paracetamol can involve in the reaction with many small molecules as well as can interact with several biomolecules. Lithium chloride in its hydrated form is used as an antimanic drug and a geroprotector. It is needed in very small quantities by humans. Tetrahydrated form of lithium ion is the most stable hydrated form. Herein, the authors have investigated the interaction of paracetamol with tetrahydrated lithium chloride (1:1 and 1:2) using the DFT and TD-DFT calculations at 298 K and 310 K. The interaction of paracetamol with lithium chloride P1 (1:1), P2 (2:1), P3 (3:1) and P4 (4:1) are also studied by DFT calculations in default and CPCM model. The authors have calculated the free energy, optimization energy, dipole moment and other thermodynamic parameters of all the systems. Based on enthalpy and change in Gibbs free energy, the interaction was maximum between the paracetamol and tetrahydrated lithium chloride at 298 K as well as 310 K which indicates that the hydrated lithium chloride is being consumed by unused paracetamol. In P1 and P3, lithium showed interaction with oxygen of phenolic group and other atoms of all the paracetamol molecules present, while in P2 and P4, lithium showed these interactions with only one paracetamol molecule.

Closing the loop: Upcycling secondary waste materials into nanoarchitectured carbon composites for the electrochemical degradation of pharmaceuticals

In this study, we demonstrated the application of electrochemical oxidation as a safer and cleaner technology for minimizing the impact of pharmaceuticals in wastewaters, simultaneously mediated by upcycled secondary waste materials (SWMs)-derived electrodes, to further reduce their environmental impact. The modularity, scalability, ease of operation and reliability make electrochemical oxidation an ideal process for the destruction of emerging persistent pollutants; however, their full-scale application is hindered by energy efficiency and the potential release of toxic by-products. Thus, the answer to these issues can be found in the design of tailored multifunctional electrode material. For the first time, SWMs derived from combustion and industrial processes have been employed with the simultaneous dual function of functional fillers, in a polyacrylonitrile fibrous matrix, and as a catalyst for the growth of carbon nanofeatures over the fiber surface, to increase the surface area and charge transfer. Next, the tailored composites were employed as anodes for the electrochemical oxidation of acetaminophen, both in phosphate buffer and in a real wastewater sample. The results suggest that SWMs can substitute costly engineered fillers in carbon-based electrodes and that the absence of reaction by-products (monitored by UHPLC-ESI-MS/MS), together with the low energy consumption, make the tailored fibrous composite electrodes good candidates for the development of safer and cleaner technologies with reduced environmental impact.

Mechanism exploration of highly conductive Ni-metal organic frameworks/reduced graphene oxide heterostructure for electrocatalytic degradation of paracetamol: Functions of metal sites, organic ligands, and rGO basement

The highly conductive Ni-metal-organic framework/reduced graphene oxide (Ni-MOG/rGO) heterostructure shows an excellent catalytic activity through the modification of active sites, considerably enabling the electron transfer between rGO and Ni-MOF. However, the detailed mechanisms, i.e., the functions of separate metal sites and organic ligands and electron transfer orientation between Ni-MOFs and rGO, remain to be discussed. Here, the electrocatalytic mechanism of Ni-MOF/rGO was experimentally analyzed on the basis of the density functional theory. The dominant active sites of radical and nonradical generation were determined. Findings indicated that radicals (O2•- and •OH) and nonradicals (1O2 and active chlorine) contributed to paracetamol (APAP) degradation. Moreover, metal sites (Ni) were favorable to generate O2•- and partly •OH to initiate the reaction. By contrast, organic frameworks in Ni-MOF and rGO basement favored to generate •OH and nonradicals (1O2 and active chlorine). In this case, N sites (in Ni-MOF), which seized electrons from Ni sites, acted as the primary bonding bridge to accelerate the electron transfer from rGO to Ni-MOF. This study provided essential information to decipher the mechanism of Ni-MOF/rGO heterostructure applicable to the electrocatalytic system.

An Update on Graphene Oxide: Applications and Toxicity

Graphene oxide (GO) has attracted much attention in the past few years because of its interesting and promising electrical, thermal, mechanical, and structural properties. These properties can be altered, as GO can be readily functionalized. Brodie synthesized the GO in 1859 by reacting graphite with KClO3 in the presence of fuming HNO3; the reaction took 3-4 days to complete at 333 K. Since then, various schemes have been developed to reduce the reaction time, increase the yield, and minimize the release of toxic byproducts (NO2 and N2O4). The modified Hummers method has been widely accepted to produce GO in bulk. Due to its versatile characteristics, GO has a wide range of applications in different fields like tissue engineering, photocatalysis, catalysis, and biomedical applications. Its porous structure is considered appropriate for tissue and organ regeneration. Various branches of tissue engineering are being extensively explored, such as bone, neural, dentistry, cartilage, and skin tissue engineering. The band gap of GO can be easily tuned, and therefore it has a wide range of photocatalytic applications as well: the degradation of organic contaminants, hydrogen generation, and CO2 reduction, etc. GO could be a potential nanocarrier in drug delivery systems, gene delivery, biological sensing, and antibacterial nanocomposites due to its large surface area and high density, as it is highly functionalized with oxygen-containing functional groups. GO or its composites are found to be toxic to various biological species and as also discussed in this review. It has been observed that superoxide dismutase (SOD) and reactive oxygen species (ROS) levels gradually increase over a period after GO is introduced in the biological systems. Hence, GO at specific concentrations is toxic for various species like earthworms, Chironomus riparius, Zebrafish, etc.

Hierarchical Nanoflowers of MgFe2O4, Bentonite and B-,P- Co-Doped Graphene Oxide as Adsorbent and Photocatalyst: Optimization of Parameters by Box–Behnken Methodology

In the present study, nanocomposites having hierarchical nanoflowers (HNFs) -like morphology were synthesized by ultra-sonication approach. HNFs were ternary composite of MgFe₂O₄ and bentonite with boron-, phosphorous- co-doped graphene oxide (BPGO). The HNFs were fully characterized using different analytical tools viz. X-ray photoelectron spectroscopy, scanning electron microscopy, energy dispersion spectroscopy, transmission electron microscopy, X-ray diffraction, vibrating sample magnetometry and Mössbauer analysis. Transmission electron micrographs showed that chiffon-like BPGO nanosheets were wrapped on the MgFe₂O₄-bentonite surface, resulting in a porous flower-like morphology. The red-shift in XPS binding energies of HNFs as compared to MgFe₂O₄-bentoniteand BPGO revealed the presence of strong interactions between the two materials. Box–Behnken statistical methodology was employed to optimize adsorptive and photocatalytic parameters using Pb(II) and malathion as model pollutants, respectively. HNFs exhibited excellent adsorption ability for Pb(II) ions, with the Langmuir adsorption capacity of 654 mg g⁻¹ at optimized pH 6.0 and 96% photocatalytic degradation of malathion at pH 9.0 as compared to MgFe₂O₄-bentonite and BPGO. Results obtained in this study clearly indicate that HNFs are promising nanocomposite for the removal of inorganic and organic contaminants from the aqueous solutions.

Recent advances in electrocatalytic membrane for the removal of micropollutants from water and wastewater

The increasing occurrence of micropollutants in water and wastewater threatens human health and ecological security. Electrocatalytic membrane (EM), a new hybrid water treatment platform that integrates membrane separation with electrochemical technologies, has attracted extensive attention in the removal of micropollutants from water and wastewater in the past decade. Here, we systematically review the recent advances of EM for micropollutant removal from water and wastewater. The mechanisms of the EM for micropollutant removal are first introduced. Afterwards, the related membrane materials and operating conditions of the EM are summarized and analyzed. Lastly, the challenges and future prospects of the EM in research and applications are also discussed, aiming at a more efficient removal of micropollutants from water and wastewater.