Coupling electrocoagulation and solar photocatalysis for electro- and photo-catalytic removal of carmoisine by Ag/graphitic carbon nitride: Optimization by process modeling and kinetic studies

Kilogram-scale fabrication of TiO2 nanoparticles modified with carbon dots with enhanced visible-light photocatalytic activity

Incorrect discharge of dye wastewater will cause environment pollution and be very harmful to human health. Visible-light photocatalysis over large-scale synthesized semiconductor materials can become one of the feasible solutions for the practical application of purifying dye wastewater. As a new candidate, carbon dots (CDs) with unique fluorescence were fabricated on a tens of grams scale and then further applied to the kilogram-scale synthesis of a CDs/TiO₂ composite by one-step heat treatment. Compared with single TiO₂ nanoparticles (NPs), the CDs/TiO₂ composite with a large specific surface area exhibits enhanced photo-degradation performance for methyl orange (MO). This phenomenon can be attributed to the loading of CDs in the TiO₂ NPs, which is conducive to broadening the light absorption spectrum and improving absorption intensity, narrowing the band gap, charge carrier trapping, up-converting properties, and charge separation. The kilogram-scale synthesis of the CDs/TiO₂ photocatalyst does not affect the morphology, structure, optical properties and photocatalytic performance of the composite, which opens up a new avenue to construct elaborate heterostructures for enhanced photocatalytic performance using visible light as the light source.

g-C3N4/polyvinyl alcohol-sodium alginate aerogel for removal of typical heterocyclic drugs from water

Heterocyclic drugs (HCDs) detected at high frequencies in wastewater have raised great concerns and their advanced removal has been the hotspot for safe water reuse in recent years. Two-dimensional graphitic carbon nitride (g-C₃N₄) and its photocatalytic systems are increasingly emerging, however, there are inevitable drawbacks of stacking and difficulty in recycling, resulting in decreased pollutant removal and limited application. Herein, for the first time, this paper reported a three-dimensional g-C₃N₄/polyvinyl alcohol-sodium alginate aerogel (g-C₃N₄/PVA-SA aerogel) photocatalyst synthesized by ultrasonic exfoliation and in-situ polymerization for typical HCDs (sulfadiazine (SDZ), sulfamethoxazole (SMX), and carbamazepine (CBZ)) removal in water. The reduced stacking of g-C₃N₄ dispersed in PVA-SA aerogel was achieved as revealed by scanning electron microscopy (SEM) and X-ray diffractometer (XRD) analysis, and g-C₃N₄/PVA-SA aerogel was observed to possess encouraging degradation efficiencies and rates for SDZ (100%, 0.0249 min^-1), SMX (100%, 0.1762 min^-1) and CBZ (69.8%, 0.0056 min^-1), which were improved by 50%-60% and 133%-216% compared to those of g-C₃N₄, respectively. Meanwhile, environmental impact factors such as pH and coexisting ions had less impact on the degradation of SDZ and SMX by g-C₃N₄/PVA-SA aerogel. The novel aerogel also had a good recyclability, with less than 5% reduction in degradation efficiency after five cycles observed. The photodegradation of SDZ, SMX and CBZ was confirmed to be driven by ⋅O₂^- and h⁺ through scavenger-quenching experiments. The new low carbon and recyclable g-C₃N₄/PVA-SA aerogel reported in this study indicated a good potential for efficient removal of HCDs from water, which provides an alternative strategy for advanced purification and safe reuse of wastewater.

Removal of Azo Dye Carmoisine by Adsorption Process on Diatomite

This work aims to evaluate the adsorption capacity of an abundant natural diatomite (ND) to remove the azo dye carmoisine, known as a harmful emerging organic pollutant. Indeed, to the best of our knowledge, no results were reported on this subject. The ND was characterized by FTIR, XRD, and SEM/EDX analyses. The experimental study of adsorption was carried out in batch mode. Results showed that ND adsorbent is mainly composed of silica. A fraction of calcite and ankerite was also identified. It is a porous material with a specific surface of about 41 m2.g-1 and with a hydroxyl surface functional group -OH. Adsorption results showed that adsorption process on ND is found to be effective in removing the carmoisine colorant. The adsorption capacity is strongly affected by the adsorbent and adsorbate contents, the solution pH, the work temperature, and the water hardness and mineralization. At room temperature, optimal experimental conditions for the highest adsorption capacity (12 mg.g-1) were colorant concentration 50mg.L-1, pH 2, contact time 30min, and ND content 1 g.L-1. Modeling study has showed that experimental results are well modeled by the Freundlich isotherm in multilayer adsorption. The reaction kinetics are pseudo-second order, and the thermodynamic parameters indicated that the nature of the adsorption process is endothermic and spontaneous.

Electrocoagulation Process: An Approach to Continuous Processes, Reactors Design, Pharmaceuticals Removal, and Hybrid Systems—A Review

The electrocoagulation (EC) process has been widely studied in recent years to remove a wide range of contaminants present in different types of water: fluorides, arsenic, heavy metals, organic matter, colorants, oils, and recently, pharmaceutical compounds. However, most of the studies have been aimed at understanding the process factors that have the most significant effect on efficiency, and these studies have been mainly on a batch process. Therefore, this review is focused on elucidating the current state of development of this process and the challenges it involves transferring to continuous processes and the recent exploration of its potential use in the removal of pharmaceutical contaminants and its implementation with other technologies.