Exothermic laws applicable to the degradation of o-phenylenediamine in wastewater via a Fe3+/H2O2 homogeneous quasi-Fenton system

Preparation of Fe3O4@CSAC catalyst and its degradation performance and heat release mechanisms in sewage degradation

To investigate the exothermic characteristics of a heterogeneous Fenton system during the degradation of organic sewage and provide technical support for energy recovery in sewage treatment, the catalyst Fe3O4@CSAC (coconut shell-activated carbon) was prepared. Subsequently, both the degradation performance and exothermic behaviour of the (Fe3O4@CSAC)-H2O2 heterogeneous Fenton-like system in the degradation of sewage were studied. The results demonstrated that the (Fe3O4@CSAC)-H2O2 heterogeneous Fenton-like system exhibited a high degradation rate for sewage and released a significant amount of heat during the degradation process, making it suitable for energy recovery through a sewage-source heat pump. These findings showed that the concentration of added Fe3O4@CSAC and H2O2 significantly influenced the heat release in the reaction system, underscoring its potential for sustainable and adaptable applications in sewage treatment processes.

Monoclonal antibody based immunoassay: An alternative way for aquatic environmental selenium detection

Environmental concerns about human health encouraged increasing methodological interest in selenium (Se), which is an essential non-metal trace element and varies within a narrow concentration range between essential and toxic. In this study, two types of long-armed Se haptens (Se-hapten-lc-NHS) were synthesized for the first time using active ester formalization. In producing monoclonal antibodies (mAbs), the derivatization of haptenized Se at para- (meta-) and ortho-sites showed different properties. Finally, a mAb derived from hybridoma 5A5² was confirmed to be capable of establishing an indirect competitive enzyme-linked immunosorbent assay (ic-ELISA). There was a successful quantitative determination of Se⁴⁺ with a detection range of 17 to 207 pmol mL^-1 and a limit of detection of approximately 3.9 pmol mL^-1. The mAb was found to be remarkably sensitive and specific, with no evidence of cross-reactivity with other ions. The assay was validated for four kinds of Se forms in water samples and showed satisfactory recoveries between 80 % and 108 %, with coefficients of variation of 2.1 %-11 %. The method proposed in our study offers a useful protocol for the rapid screening of Se and provides an alternative solution for the analysis of Se in aquatic environments.

Heterogeneous Fenton Degradation of Organic Pollutants in Water Enhanced by Combining Iron-type Layered Double Hydroxide and Sulfate

Water pollution derived from organic pollutants is one of the global environmental problems. The Fenton reaction using Fe²⁺ as a homogeneous catalyst has been known as one of clean methods for oxidative degradation of organic pollutants. Here, a layered double hydroxide (Fe²⁺ Al³⁺ -LDH) containing Fe²⁺ and Al³⁺ in the structure was used to develop a "heterogeneous" Fenton catalyst capable of mineralizing organic pollutants. We found that sulfate ion (SO₄ ^2- ) immobilized on the Fe²⁺ Al³⁺ -LDH significantly facilitated oxidative degradation (mineralization) of phenol as a model compound of water pollutants to carbon dioxide (CO₂ ) in a heterogeneous Fenton process. The phenol conversion and mineralization efficiency to CO₂ reached >99% and ca. 50%, respectively, even with a reaction time of only 60 min.

The CdS/g-C3N4 nano-photocatalyst: Brief characterization and kinetic study of photodegradation and mineralization of methyl orange

The CdS/g-C₃N₄ hybrid was prepared mechanically and characterized by different techniques including XRD, SEM, DRS, FTIR, and cyclic voltammetry (CV). The SEM study showed that CdS nanoparticles (NPs) have been randomly dispersed on the surface of graphitic carbon nitride (g-C₃N₄). The CV results showed better charge carriers' transfer for the modified carbon paste electrode (CPE) by the CdS/g-C₃N₄ system concerning the modified CPE by single CdS or g-C₃N₄ modifier. The band gap (Bg) energies of 1.7, 2.7, and 1.9 eV were obtained from DRS results for CdS, g-C₃N₄, and CdS/g-C₃N₄ systems, respectively. The photocatalytic activity of the single and hybrid systems was tested towards methyl orange (MO). The degradation extents of 16%, 22%, and 34% were respectively obtained for CdS NPs, g-C₃N₄, and CdS/g-C₃N₄ systems at initial steps. To enhance the degradation efficiency, the mole ratio of the component was changed in the second step. The work was then focused on the kinetic study of both photodegradation and mineralization processes. For this goal, the degradation extents of the photodegraded MO solutions were calculated based on the recorded absorbance of the solutions in the visible-light and the results were then subjected to the Hinshelwood equation. Then the solutions were subjected to COD experiment to follow the mineralization extent of MO. Form the slopes of the Hinshelwood plots, the rate constants of 0.024 and 0.025 min^-1 were obtained for the degradation and mineralization of MO molecules, respectively. TOC results confirmed the mineralization of 187.5 μmoles of MO molecules in a 50 ppm MO solution.