Solar Photocatalysis Processes Research Articles

Amoxicillin Degradation by TiO2 P25 Solar Heterogeneous Photocatalysis: Influence of pH and Oxidizing Agent H2O2 Addition

Over the years, there has been an increase in the consumption of drugs, particularly antibiotics. Amoxicillin (AMX) is considered one of the most widely used antibiotics, causing resistance in microorganisms in the ecosystem where it is found. Additionally, it has been cataloged among the drugs under surveillance by the European Commission since 2020. The present work studies the efficiency of AMX degradation by photolysis and heterogeneous solar photocatalysis processes under different reaction pH levels (3.5, 4.15, 7 and 9) and observing the influence of different doses of H2O2 (nil and 4 mM), as an oxidizing agent. TiO2 P25 was used as photocatalyst, impregnated in glass supports of 0.1 and 1 m2 in flat plate reactors (FPR). A 2 × 2 × 4 statistical analysis carried out after repeated measurements to determine the relationship between the different parameters involved (process, H2O2 dose, and pH). The kinetics of the AMX degradation reaction showed the best rate constant (KphC = 0.10 min−1) under acidic medium conditions (pH 4.15), without addition of H2O2, and by heterogeneous photocatalysis when using a 1 m2 FPR to achieve 100% COD removal. ANCOVA showed significant differences (p < 0.05) in the use of H2O2 for the first minutes of the reaction and in the different FPR surfaces.

Construction of highly efficient separable p-n junction based light driven composite (NiFe2O4/MnWO4) for improved solar light utilisation

Magnetic separable p-NiFe2O4/n-MnWO4(NFMW) composites were synthesised by combined co-precipitation and hydrothermal process with varied stoichiometry ratio of p-NiFe2O4. The best composite having 20 mg of p-NiFe2O4(NFMW-2) demonstrated excellent band gap, work function, durability, photo stability, ferromagnetism properties etc. XRD shows wolframite MnWO4 and spinel structure of NiFe2O4. Elemental mapping confirms the uniform dispersion of composites. The optimized loading of p-NiFe2O4 results in enhanced Light-harvesting capability. Photoluminescence analysis shows the prolonged decay time of the composite (8.769 µs) with reduced recombination rate. Transient photocurrent and Nyquist plot reveals the excellent separation efficiency and mobility of the charge carriers. Although NFMW-2 has shown ~56% reduction in the coercivity but withstands its ferromagnetic nature. Further, its edge potentials were evaluated through MS plot suggests Z-scheme mode of electron transfer. The solar photocatalysis process was dominated by superoxide and hydroxyl radicals and thus resulted in complete removal of Congo red and 92% for phenol within 240 min and 360 min.

El uso sostenible del agua: Tributos medioambientales y nuevos procesos de descontaminación mediante energías renovables

La presencia de contaminación persistente y tóxica en las aguas ha impulsado el desarrollo de nuevas tecnologías de tratamiento, como es el caso, de la fotocatálisis solar homogénea, foto-Fenton solar, que aprovecha esa fuente de energía renovable para disminuir los costes del proceso. El fallo de mercado que supone la contaminación originada por el vertido de aguas residuales industriales, se corrige con el establecimiento de tributos medioambientales. La heterogeneidad en el diseño de estos tributos afecta tanto a los parámetros de contaminación considerados como a su peso específico en el cálculo de la cuota a pagar. En este trabajo se discute la posibilidad de los cánones de saneamiento como correctores de este fallo de mercado y como incentivos para invertir en tecnologías y procesos de depuración sostenibles.

Solar heterogeneous photocatalysis (ZnO/UV) for textile dyes removal

AbstractSolar photocatalytic studies were carried out using zinc oxide (ZnO) as a catalyst for the removal of the cationic methylene blue (MB) dye, and the anionic dye reactive red 198 (RR198), from simple and binary mixed solutions. The following parameters were experimentally investigated: catalyst concentrations (50–250 milliliters [ml]), initial pH of the solution (5, 7, and 9), and time of exposure (20–120 minutes [min]). The catalyst concentration has been found to be the variable with the greatest significance of the three, leading to degradation rates of up to 98% and 100%, for MB and RR198 dyes, respectively. When it comes to the RR198 dye, considerable decolorization rates (up to 75%) were achieved even at the shortest time interval (20 min). The results indicated that, especially for the RR198 dye, the majority of the color removal during the photocatalysis process was due to the adsorption of the dye onto the ZnO surface. Batch scale experiments were performed by mixing both MB and RR198 dyes in order to simulate a synthetic effluent. Color removal rates up to 98% were achieved after 90 min of sunlight exposure. Experiments in a pilot‐plant based on compound parabolic collectors were performed under the same conditions, and similar results were obtained. In addition, organic matter removal was investigated and rates up to 70% were achieved. The results showed the feasibility of the solar photocatalysis process with ZnO to achieve considerable rates of color removal from wastewater containing dyes from different classes.

UV and solar photocatalytic disinfection of municipal wastewater: inactivation, reactivation and regrowth of bacterial pathogens

Pollution of water sources by pathogens is a major concern worldwide. This study investigated critical disinfection aspects such as bacterial regrowth or decay and evaluation of metal-ion leaching during photocatalytic disinfection. The inactivation of waterborne bacterial pathogens (Escherichia coli, Salmonella species, Shigella species and Vibrio cholerae) using ultraviolet and solar photocatalysis was evaluated. Bare and metal-ion (silver, copper and iron)-doped titanium dioxide photocatalysts were used to explore comparative performance. The influence of photocatalyst concentration (0.1–1.0 g/L), source of radiation (ultraviolet or solar light) and water type (synthetic and municipal wastewater) was examined. The disinfection data were fitted to the pseudo-first-order model. The disinfection efficiency was higher in saline deionized water (99.9998–100%) that was spiked with the target pathogens (106 colony forming units/mL), compared to actual wastewater samples. Within 180 min of treatment under solar irradiation, disinfection efficacy of 86.8–100% was achieved, while 99.4–100% disinfection efficacy was attained under ultraviolet irradiation within 60 min. A significant difference (p < 0.05) between ultraviolet and solar photocatalysis was observed, and silver-doped titanium dioxide displayed the best performance under all conditions tested. Nevertheless, after a contact time of 180 min, there was no bacterial regrowth observed even for the solar photocatalysis processes; in fact, bacterial decay occurred. The elution of doping metals into the treated wastewater was insignificant. Therefore, the metal-ion-doped photocatalysts were effective under solar radiation, thus overcoming the limitation of bare titanium dioxide which is only effective under ultraviolet light and preventing bacterial regrowth.

Disinfection of dairy wastewater effluent through solar photocatalysis processes

Due to the strict regulations and reuse policies that govern wastewater's use as an irrigation water resource for agricultural purposes, especially in dry climates, optimization of the disinfection process is of the utmost importance. The effects of solar radiation along with Titanium dioxide (TiO2) nanoparticles applied to optimization of the photolysis and photocatalysis processes for inactivating heterotrophic bacteria were investigated. Temperature, pH, and dissolved oxygen fluctuations in the dairy wastewater effluent treated by activated sludge were examined. In addition, different dosages of TiO2 were tested in the solar photocatalysis (ph-C S) and concentrated solar photocatalysis (ph-C CS) processes. The results show that the disinfection efficiencies of the solar photolysis (ph-L S) and concentrated solar photolysis (ph-L CS) processes after 30 min were about 10.5% and 68.9%, respectively, and that the ph-C S and ph-C CS processes inactivated 41% and 97% of the heterotrophic bacteria after 30 min, respectively. The pH variation in these processes was negligible. Using the ph-L CS and ph-C CS processes, the synergistic effect between the optical and thermal inactivation caused complete disinfection after three hours. However, disinfection was faster in the ph-C CS process than in the ph-L CS process. Significant correlations were found between the disinfection efficiency and the variation of the dissolved oxygen concentration in the ph-C S and ph-C CS processes, while the correlations between the disinfection efficiency and temperature variation were not significant in the ph-L S and ph-C S processes. Moreover, the oxygen consumption rate was greatest (3.2 mg·L−1) in the ph-C CS process. Hence, it could be concluded that the ph-C CS process is an efficient photocatalysis process for disinfection of dairy wastewater effluent.

Efficiency evaluation of solar photolysis and solar photocatalysis processes used for the wastewater disinfection

ABSTRACTThe wastewater reuse, especially for irrigation, requires a safer microbial quality. However, the tertiary treatment is often nonexistent, especially in developing countries where, unfortunately, wastewater treatment needs to be more systematic. Solar water disinfection processes could be appropriate treatments for improving the microbial quality of the wastewater reuse. This study evaluates the effectiveness of both solar photolysis and solar photocatalysis processes in disinfecting secondary-treated wastewater recovered from an activated sludge wastewater treatment plant where the disinfection treatment is not applied. The best parameters of the solar disinfection processes were determined. The experiments were conducted in a bench test composed of 4 flat-bottom flasks with a volume of 2 L each. Then, the disinfection efficiency of both processes was evaluated by a comparative study where 250 Wh/m2 of UV radiation was cumulated. The disinfection efficiency of studied pathogenic (1) total colifor...

Abatement of ibuprofen by solar photocatalysis process: Enhancement and scale up

The aim of this work is to evaluate the degradation of the emerging pharmaceutical contaminant ibuprofen (IBP) in water by heterogeneous photocatalysis in three different solar pilot plants. IBP and TOC removal increase directly proportional to concentration of catalyst (TiO 2). The addition of H 2O 2 increases the removal efficiency. The complete IBP removal and decrease of TOC to sufficient extent was stated in optimal experimental conditions and biodegradability and average oxidation state (AOS) results conducted suggest a post-biological treatment of solution. Surface responses obtained from the experimental results, for different initial IBP and TiO 2 concentrations used, can allow to predict time needed for a sufficient TOC removal to reach sufficient biodegradability.

Degradation of recalcitrant organic contaminants by solar photocatalysis

Biological pre-treated landfill leachates of Djebel Chakir contains some macromolecular organic substances that are resistant to biological degradation. The aim of the present work is to assess the feasibility of removing refractory organic pollutants in biological pre-treated landfill leachate by solar photocatalyse process. Leachate pollutant contents are studied to assess their contribution to leachate pollution and their treatability by solar photocatalyse process. Phenol is chosen as model of pollutants, to evaluate its removal and the efficiency of the photocatalytic system. The experiments were carried out in suspended photocatalytic reactor, using TiO2 Degussa P25, under sunlight illumination (UV-A: 15-31 W/cm2). Under optimum operational conditions, applied to single reactant (phenol), the system presents a TOC removal of 90% (the degradation follows a first-order kinetic). Based on the TOC removal, the results shows that the degradation of biological pre-treated leachate follows a zero-order kinetic. After 5 h of sunlight exposure, 74% of COT is removed. The TOC removal is the best without any correction of the pH and at the TiO2 concentration of 2.5 g/L. The photocatalytic degradation of organic contaminants as well as the formation and disappearance of the by-products were followed by GC/MS. The solar photocatalysis processes induce several modifications of the matrix leading to more biodegradable forms: all the remaining and new compounds generated after the biological pre-treatment of leachate are degraded and other types of organics appear, mainly carboxylic acid, aliphatic hydrocarbons and phtalic acids.