UV-light assisted activation of persulfate by rGO-Cu3BiS3 for the degradation of diclofenac

Insight into the degradation of carbamazepine by electrochemical-pressure UV-activated peroxodisulphate process: kinetics, radicals, and degradation pathway

In this work, to improve the performance of peroxodisulphate-advanced oxidation, an electrochemical oxidation-assisted UV light-activated peroxodisulphate system (E/UV/PDS) was used to degrade carbamazepine. The degradation of carbamazepine by PDS, E/PDS, UV/PDS and E/UV/PDS systems was compared, and their synergistic effects were analysed. The influence of single factors, such as PDS addition, initial pH, DS voltage, target initial concentration, etc., on the degradation of the E/UV/PDS system was discussed, and the optimal degradation process parameters were given. The active substances were determined by free radical inhibition experiments, such as 1O2, SO 4 - ⋅ and ⋅ OH . It was proved that 1O2 contributes much more to the degradation of carbamazepine than SO 4 - ⋅ and ⋅ OH . The degradation pathway of carbamazepine was proposed. Finally, the degradation mechanism of carbamazepine in the E/UV/PDS system was speculated. The results indicate that the electrochemical combined with the E/UV/PDS system is of great potential application value in the removal of antibiotic drug pollution and environmental purification.

An insight into the role of experimental parameters in advanced oxidation process applied for pharmaceutical degradation

The advanced oxidation process (AOP) is an efficient method to treat recalcitrance pollutants such as pharmaceutical compounds. The essential physicochemical factors in AOP experiments significantly influence the efficiency, speed, cost, and safety of byproducts of the treatment process. In this review, we collected recent articles that investigated the elimination of pharmaceutical compounds by various AOP systems in a water medium, and then we provide an overview of AOP systems, the formation mechanisms of active radicals or reactive oxygen species (ROS), and their detection methods. Then, we discussed the role of the main physicochemical parameters (pH, chemical interference, temperature, catalyst, pollutant concentration, and oxidant concentration) in a critical way. We gained insight into the most frequent scenarios for the proper and improper physicochemical parameters for the degradation of pharmaceutical compounds. Also, we mentioned the main factors that restrict the application of AOP systems in a commercial way. We demonstrated that a proper adjustment of AOP experimental parameters resulted in promoting the treatment performance, decreasing the treatment cost and the treatment operation time, increasing the safeness of the system products, and improving the reaction stoichiometric efficiency. The outcomes of this review will be beneficial for future AOP applicants to improve the pharmaceutical compound treatment by providing a deeper understanding of the role of the parameters. In addition, the proper application of physicochemical parameters in AOP systems acts to track the sustainable development goals (SDGs).

Oxygen vacancy-rich CeO2 decorated with Cu3BiS3 nanoparticles: Outstanding visible-light photocatalytic performance towards tetracycline degradation

Recently, the degradation of antibiotics has attracted a lot of attention all over the world, because the accumulation of these recalcitrant compounds in the environment, and their entry into the food chain have severely affected on human health. Herein, oxygen vacancy-rich CeO2 was decorated with Cu3BiS3 nanoparticles to fabricate Z-scheme CeO2-x/Cu3BiS3 photocatalysts with a simple procedure. Intriguingly, photocatalytic ability of CeO2-x/Cu3BiS3 (30%) nanocomposite in the detoxification of tetracycline hydrochloride, cephalexin, azithromycin, and rhodamine B was elevated 31.3, 28.2, 45.2, and 10.1-folds as much as CeO2, and 5.19, 5.97, 32.2, and 4.69-folds compared with the CeO2-x photocatalyst, respectively. The admirable activity of CeO2-x/Cu3BiS3 (30%) nanocomposite was ascribed to the production of many charge carriers, efficacious segregation and transfer of charges, and improved textural features, which were confirmed by UV-vis DRS, EIS, photocurrent density, PL, and BET analyses. In addition, the TC degradation pathway was investigated with LC-MS analysis, and also the biocompatibility of the purified solution was displayed with wheat seed cultivation. Regarding outstanding activity and facile synthesis, the CeO2-x/Cu3BiS3 (30%) photocatalyst could be utilized for wastewater treatment.

CFD-Assisted Process Optimization of an Integrated Photocatalytic Membrane System for Water Treatment

An integrated photocatalytic membrane system (IPMS) was developed for potential use in the remediation of naproxen using real water samples from a drinking water treatment plant. Key parameters such as time, pH, water matrix, mixing speeds, flow rate, and light intensity undeniably affected photocatalytic and membrane separation processes. The system optimization was based on improving irradiation to generate a more reactive species and mass transfer to increase the reaction rate. Upon optimization, IPMS achieved 99% naproxen removal efficiency. Computational fluid dynamics (CFD) simulated the flow patterns and radiation distribution inside the photocatalytic membrane reactor to improve irradiation and mass transfer during operation. The simulated flow field revealed the presence of dead zones with different velocities in the photocatalytic membrane reactor; this limited the mass transfer of reactive species in the reactor, resulting in uneven distribution of reactive radicals. The dead zones were mitigated by increasing the mixing speed, and as a result, convective mass flow improved process performance. The governing parameters (flow patterns and radiation distribution) of the simulated and experimental data were in agreement. The absorption of irradiation by the active site of the membranes improved with light intensity; at higher light intensities, the light irradiated deeper into the membrane. As such, the CoFe2O4 nanoparticles incorporated inside the membrane pores became highly activated, thus enhancing degradation. The obtained space-time yield (STY) (1.23 × 1011 mol/cm2.s) and photocatalytic space-time yield (PSTY) (4.39 × 1011 mol/W.s) showed that the developed IPMS was efficient regarding energy intensiveness and throughput for treatment of pollutants in water.

Effective degradation of atrazine by spinach-derived biochar via persulfate activation system: Process optimization, mechanism, degradation pathway and application in real wastewater

Herein, biochar derived from spinach remnants was prepared for the first-time for the utilization in persulfate (PS) activation to effectively degrade atrazine. Characteristics of the prepared biochar were explored using advanced analyses. Control experiments implied the efficient activation of PS in the presence of the synthesized biochar. The highest degradation of atrazine (99.8%) could be attained at atrazine concentration of 7.2 mg/L, PS concentration of 7.7 mM, biochar dose of 1.88 g/L and reaction time of 120 min. The prepared biochar displayed a high recyclability performance attaining degradation ratios of 98.2, 96.53, 96.4, 92.8 and 88% in five sequential cycles under the optimum conditions. The degradation mechanism was explored showing that sulfate radicals were the prime reactive species in the degradation system. The degradation intermediates were specified, and the degradation pathways were propositioned. The highest REs in agrochemical industrial wastewater reached 80.21 and 83.43% of atrazine and TOC after 2 h. NH₃ (348.4 mg/L) was reduced to 168.3 mg/L (RE: 51.7%) while level of NO₃ (94.7 mg/L) was increased by 98.8% (188.3 mg/L) in the treated effluent due to oxidation of NH₃ to nitrite and then nitrate. Extension of reaction time could contribute to achieving full mineralization of the real wastewater due to the residual PS after 120 min. The effectiveness and low-cost of biochar@PS system as well as its high performance in degrading real wastewater support the efficiency of the prepared biochar to be applied on an industrial scale.

Photocatalytic Reduction of Hexavalent Chromium Using Cu3.21Bi4.79S9/g-C3N4 Nanocomposite

The photocatalytic reduction of hexavalent chromium, Cr(VI), to the trivalent species, Cr(III), has continued to inspire the synthesis of novel photocatalysts that are capable of achieving the task of converting Cr(VI) to the less toxic and more useful species. In this study, a novel functionalized graphitic carbon nitride (Cu3.21Bi4.79S9/gC3N4) was synthesized and characterized by using X-ray diffraction (XRD), thermogravimetry analysis (TGA), energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), transmission electron microscope (TEM), and scanning electron microscope (SEM). The composite was used for the photocatalytic reduction of hexavalent chromium, Cr(VI), under visible light irradiation. A 92.77% efficiency of the reduction was achieved at pH 2, using about 10 mg of the photocatalyst and 10 mg/L of the Cr(VI) solution. A pseudo-first-order kinetic study indicated 0.0076 min−1, 0.0286 min−1, and 0.0393 min−1 rate constants for the nanoparticles, pristine gC3N4, and the nanocomposite, respectively. This indicated an enhancement in the rate of reduction by the functionalized gC3N4 by 1.37- and 5.17-fold compared to the pristine gC3N4 and Cu3.21Bi4.79S9, respectively. A study of how the presence of other contaminants including dye (bisphenol A) and heavy-metal ions (Ag(I) and Pb(II)) in the system affects the photocatalytic process showed a reduction in the rate from 0.0393 min−1 to 0.0019 min−1 and 0.0039 min−1, respectively. Finally, the radical scavenging experiments showed that the main active species for the photocatalytic reduction of Cr(VI) are electrons (e−), hydroxyl radicals (·OH−), and superoxide (·O2−). This study shows the potential of functionalized gC3N4 as sustainable materials in the removal of hexavalent Cr from an aqueous solution.

Interdependence of Kinetics and Fluid Dynamics in the Design of Photocatalytic Membrane Reactors

Photocatalytic membrane reactors (PMRs) are a promising technology for wastewater reclamation. The principles of PMRs are based on photocatalytic degradation and membrane rejection, the different processes occurring simultaneously. Coupled photocatalysis and membrane filtration has made PMRs suitable for application in the removal of emerging contaminants (ECs), such as diclofenac, carbamazepine, ibuprofen, lincomycin, diphenhydramine, rhodamine, and tamoxifen, from wastewater, while reducing the likelihood of byproducts being present in the permeate stream. The viability of PMRs depends on the hypotheses used during design and the kinetic properties of the systems. The choice of design models and the assumptions made in their application can have an impact on reactor design outcomes. A design’s resilience is due to the development of a mathematical model that links material and mass balances to various sub-models, including the fluid dynamic model, the radiation emission model, the radiation absorption model, and the kinetic model. Hence, this review addresses the discrepancies with traditional kinetic models, fluid flow dynamics, and radiation emission and absorption, all of which have an impact on upscaling and reactor design. Computational and analytical descriptions of how to develop a PMR system with high throughput, performance, and energy efficiency are provided. The potential solutions are classified according to the catalyst, fluid dynamics, thickness, geometry, and light source used. Two main PMR types are comprehensively described, and a discussion of various influential factors relating to PMRs was used as a premise for developing an ideal reactor. The aim of this work was to resolve potential divergences that occur during PMRs design as most real reactors do not conform to the idealized fluid dynamics. Lastly, the application of PMRs is evaluated, not only in relation to the removal of endocrine-disrupting compounds (EDCs) from wastewater, but also in dye, oil, heavy metals, and pesticide removal.

Novel gamma-irradiated chitosan-doped reduced graphene-CuInS2 composites as counter electrodes for dye-sensitized solar cells

To address the issues associated with traditional counter electrodes, a novel gamma-irradiated chitosan-doped reduced graphene-CuInS₂ composite (Chi@RGO-CIS) was used as the counter electrode (CE). The system was fabricated following a simple hydrothermal method. The prepared Chi@RGO-CIS was characterized by various spectroscopic and microscopic techniques. The synergistic effect between chitosan, CuInS₂, and reduced graphene oxide can help in producing a large surface area. It can also help in the generation of catalytic sites toward I-/I₃-redox electrolytes. We used a composite (based on electrical considerations) to study the effect of the amount of graphene on the characteristics and photovoltaic efficiency of the Chi@RGO-CIS composites. The solar cell assembled with 1.5% Chi@RGO-CIS exhibited an efficiency of 12.21%. The efficiency was higher than that of a Pt-based device (9.96%) fabricated under the same conditions. Hence, Chi@RGO-CIS can be potentially used as the CE of dye-sensitized solar cells (DSSCs). It can be used as a substitute for Pt in DSSCs.

To address the issues associated with traditional counter electrodes, a novel gamma-irradiated chitosan-doped reduced graphene-CuInS₂ composite (Chi@RGO-CIS) was used as the counter electrode (CE).