There are scarce data about the accumulation pattern and risk assessment of potentially toxic elements (PTEs) in soil and associated potential ecological risks, especially in less-developed countries. This study aims to assess the pollution levels and potential ecological risks of PTEs (As, Cr, Cd, Cu, Ni, Mn, Pb and Zn) in wastewater-irrigated arable soils and different edible-grown plants in selected areas of Vehari, Pakistan. The results revealed that the values of PTEs in soil samples were higher than their respective limit values by 20% for As, 87% for Cd, 15% for Cu, 2% for Cr, 83% for Mn, 98% for Fe, and 7% for Zn. The values of soil risk indices such as the potential ecological risk (PERI >380 for all samples), pollution load index (PLI >4 for 94% of studied samples), and degree of contamination (Dc > 24 for all samples) showed severe soil contamination in the study area. Some vegetables exhibited a high metal accumulation index (e.g., 8.1 for onion), signifying potential associated health hazards. Thus, long-term wastewater irrigation has led to severe soil contamination, which can pose potential ecological risks via PTE accumulation in crops, particularly Cd. Therefore, to ensure food safety, frequent wastewater irrigation practices need to be minimized and managed in the study area. 

Accumulation pattern and risk assessment of potentially toxic elements in selected wastewater-irrigated soils and plants in Vehari, Pakistan.

Highly efficient photodegradation of ciprofloxacin by dual Z-scheme Bi2MoO6/GQDs/TiO2 heterojunction photocatalysts: mechanism analysis and pathway exploration

Enhancing photocatalytic efficiency of mixed-pollutant degradation is a critical issue for the application in wastewater purification, especially under natural-sunlight illumination. CuBi 2 O 4 rods decorated with Fe 2 O 3 nanoparticles were synthesized by the hydrothermal method. The Fe 2 O 3 /CuBi 2 O 4 composites exhibited significantly enhanced photocatalytic activity for Fenton oxidation of Rhodamine B (RhB) and 4-nitrophenol (4-NP) in the near-neutral catalytic system, and the degradation efficiency of the above two pollutants reached above 90% after 50 min of visible-light irradiation. Meanwhile, the good catalytic performance and stability were maintained in the seventh cycling test. Notably, the efficient synchronous degradation of the above mixed pollutants was accomplished under natural-sunlight over the optimal 7%Fe 2 O 3 /CuBi 2 O 4 catalyst. The staggered band structure in the heterojunction was determined by DRS and UPS results, and the S-scheme electron transfer mode was verified by the in situ-XPS measurement under dark and light conditions. The study is expected to be beneficial to explore step-scheme (S-scheme) semiconductor photocatalysts for natural-sunlight-driven Fenton oxidation of mixed pollutants. • Fe 2 O 3 nanoparticles decorated CuBi 2 O 4 rods was synthesized. • The photocatalysis for mixed degradation was accomplished under natural light. • The 4-NP and RhB degradation performance was promoted by the heterojunction. • S-scheme charge transfer was proven by the in situ-XPS measurement. 

Natural-sunlight-driven synchronous degradation of 4-nitrphenol and rhodamine B over S-scheme heterojunction of α-Fe2O3 nanoparticles decorated CuBi2O4 rods

Tuning of graphitic carbon nitride (g-C3N4) for photocatalysis: A critical review

Binary visible-light-triggered ZnO/Bi4O5Br2 photocatalysts with n-n heterojunction: Simple fabrication and impressively activation of peroxodisulfate ions for degradation of tetracycline

With the tremendous development of the economy and industry, the pollution of water is becoming more serious due to the excessive chemical wastes that need to remove thru reduction or oxidation reactions. Simultaneous removal of dual pollutants via photocatalytic redox reaction has been tremendously explored in the last five years due to effective decontamination of pollutants compared to a single pollutants system. In a photocatalysis mechanism, the holes in the valence band can remarkably promote the oxidation of a pollutant. At the same time, photoexcited electrons are also consumed for the reduction reaction. The synergistic between the reduction and oxidation inhibits the recombination of electron-hole pairs extending their lifetime. In this review, the binary pollutants that selectively removed via photocatalysis reduction or oxidation are classified according to heavy metal-organic pollutant (HM/OP), heavy metal-heavy metal (HM/HM) and organic-organic pollutants (OP/OP). The intrinsic between the pollutants was explained in three different mechanisms including inhibition of electron-hole recombination, ligand to metal charge transfer and electrostatic attraction. Several strategies for the enhancement of this treatment method which are designation of catalysts, pH of mixed pollutants and addition of additive were discussed. This review offers a recent perspective on the development of photocatalysis system for industrial applications. 

A review on synergistic coexisting of pollutants for efficient photocatalytic reaction in wastewater remediation.

A novel Z-scheme titania loaded on fibrous silica ceria (Ti-FSC) was triumphantly fabricated via hydrothermal followed by electrolysis method and evaluated for the visible-light degradation of ciprofloxacin (CIP). Noticeably, Ti-FSC exhibits as an efficient photocatalyst for CIP photodegradation with 95% as followed by titania loaded on fibrous silica (Ti-FS) (68%), Ti-CeO2 (35%), FSC (47%), FS (22%), and CeO2 (17%). The combination of the inherent merits of Ti loaded on FSC is able to realize the crucial role of Ce in harnessing the high dispersion of Ti, which could beneficial for improving the performance proven by XRD, FESEM, TEM and FTIR. Consequently, high dispersion of Ti on FSC has worthwhile towards the interaction of the Si-O-Ti, Ce-O-Ti, and Si-O-Ti, which could enhance the CIP photodegradation by providing more surface defects, narrowing the band gap, improving electron-hole separation and suppressing electron-hole recombination that revealed by XPS, UV-vis/DRS, Nyquist plots and PL studies, respectively. The scavenger study revealed that the controlling species in the system was hydroxyl radical and holes. A potential Z-scheme heterojunction mechanism for Ti-FSC was deduced from the band structure analysis. The possible photodegradation pathway was proposed based on GCMS analysis. Besides, the acceptable reusability, which exceeded 90% of degradation indicated the great application potential of Z-scheme Ti-FSC in wastewater treatment and others application. 

An intriguing Z-scheme titania loaded on fibrous silica ceria for accelerated visible-light-driven photocatalytic degradation of ciprofloxacin.

In this work, titania-supported fibrous silica (TiO2-KCC1) and Fibrous Silica-Titania (FST) were prepared via microemulsion technique with a different sequence of titania incorporation method. The catalysts were characterized by x-ray diffraction (XRD), N2 adsorption-desorption, field emission scanning electron microscopy (FESEM), transmission electron microscopes (TEM), and fourier-transform infrared spectroscopy (FTIR). The results discovered that the FST catalyst had high crystallinity, higher specific surface area, and large pore volume. The alternate arrangement of TiO2 and silica in the framework of fibrous silica on FST catalyst had an excellent dispersion and it triggered stronger TiO2–SiO2 interactions. It was observed that in the absence of triethylamine (TEA), formic acid (HCOOH) was much favourable produced by both catalysts, with the highest HCOOH product was obtained using TiO2/KCC-1 (2933 µmol/gcat.h). In the presence of TEA as a sacrificial agent, superior methanol production was perceived using FST (3487 µmol/gcat.h) as compared to TiO2/KCC-1 (2773 µmol/gcat.h). It was proposed that the unique structure of the FST catalyst absorbed many photons and was able to absorb more carbon dioxide (CO2) molecules onto the active site of the catalyst to produce carbonic acid (H2CO3) active radicals. With the assist of TEA, methanol production drastically boosts up almost three times higher than the absence of TEA, probably due to an excess of electrons leading to the formation of more active radicals, thus enhancing the methanol production. The response surface methodology (RSM) result indicated that the utmost yield could be obtained at catalyst dosage 0.619 g/L, TEA volume 157.24 µL, and CO2 flow rate 9.47 mL/min. The experimental validation of the predicted optimum condition revealed that the methanol yield is 3062.966 mol g−1 h−1, compared to the predicted value of 3026.95 mol g−1 h−1, with only a 1.18% difference. 

F. Aziz

Papers

A review on synergistic coexisting of pollutants for efficient photocatalytic reaction in wastewater remediation.

An intriguing Z-scheme titania loaded on fibrous silica ceria for accelerated visible-light-driven photocatalytic degradation of ciprofloxacin.

Influence of TiO2 dispersion on silica support toward enhanced amine assisted CO2 photoconversion to methanol

Enriching the methanol generation via CO2 photoconversion over the cockscomb-like fibrous silica copper

Si-Ti interaction in unique morphology of fibrous silica titania photoanode for enhanced photoelectrochemical water splitting