Simultaneous degradation of amoxicillin and norfloxacin by TiO2@nZVI composites coupling with persulfate: Synergistic effect, products and mechanism

PANI/GO and Sm co-modified Ti/PbO2 dimensionally stable anode for highly efficient amoxicillin degradation: Performance assessment, impact parameters and degradation mechanism

The abuse and uncontrolled discharge of antibiotics present a severe threat to environment and human health, necessitating the development of efficient and sustainable treatment technology. In this work, we employ a facile one-step electrodeposition method to prepare polyaniline/graphite oxide (PANI/GO) and samarium (Sm) co-modified Ti/PbO2 (Ti/PbO2-PANI/GO-Sm) electrode for the degradation of amoxicillin (AMX). Compared with traditional Ti/PbO2 electrode, Ti/PbO2-PANI/GO-Sm electrode exhibits more excellent oxygen evolution potential (2.63 V) and longer service life (56 h). In degradation experiment, under optimized conditions (50 mg L-1 AMX, 20 mA cm-2, pH 3, 0.050 M Na2SO4, 25 °C), Ti/PbO2-PANI/GO-Sm electrode achieves remarkable removal efficiencies of 88.76% for AMX and 79.92% for chemical oxygen demand at 90 min. In addition, trapping experiment confirms that ·OH plays a major role in the degradation process. Based on theoretical calculation and liquid chromatography-mass spectrometer results, the heterocyclic portion of AMX molecule is more susceptible to ·OH attacks. Thus, this novel electrode offers a sustainable and efficient solution to address environmental challenges posed by antibiotic-contaminated wastewater.

Light-driven photocatalysis as an effective tool for degradation of antibiotics

Antibiotic contamination has become a severe issue and a dangerous concern to the environment because of large release of antibiotic effluent into terrestrial and aquatic ecosystems. To try and solve these issues, a plethora of research on antibiotic withdrawal has been carried out. Recently photocatalysis has received tremendous attention due to its ability to remove antibiotics from aqueous solutions in a cost-effective and environmentally friendly manner with few drawbacks compared to traditional photocatalysts. Considerable attention has been focused on developing advanced visible light-driven photocatalysts in order to address these problems. This review provides an overview of recent developments in the field of photocatalytic degradation of antibiotics, including the doping of metals and non-metals into ultraviolet light-driven photocatalysts, the formation of new semiconductor photocatalysts, the advancement of heterojunction photocatalysts, and the building of surface plasmon resonance-enhanced photocatalytic systems.

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).

Enhanced photocatalytic reduction of Cr(VI) from aqueous solution using Fe0/TiO2-based polymeric nanocomposites

The combination of zerovalent iron (Fe0) and titanium dioxide (TiO2) has been investigated as a promising method for environmental remediation. However, it is a challenge to prepare conveniently desirable Fe0/TiO2 nanocomposites with excellent efficiency and reusability. Here, a novel nanocomposite material, Fe0/TiO2@D201, was synthesized to enhance the removal of Cr(VI) from an aqueous system by impregnating Fe0 and TiO2 inside a commercial anion exchanger (D201). The proposed structure and Cr(VI) removal mechanism of Fe0/TiO2@D201 were confirmed using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analysis. Compared to the monometallic samples (Fe0-D201 and TiO2-D201), Fe0/TiO2@D201 showed outstanding Cr(VI) removal and the removal ratio reached up to 97.30% after 120 min of UV light irradiation. The removal of Cr(VI) by Fe0/TiO2@D201 remained high (91.70%) even after four cycles, indicating the stability of the nanocomposites toward Cr(VI) removal and their strong potential for practical applications. The addition of ethylenediaminetetraacetic acid (EDTA) positively affected the Cr(VI) reduction process, whereas the addition of Na2S2O8 negatively affected the Cr(VI) process. The XPS results revealed that the photocatalytic reduction of Cr(VI) by Fe0/TiO2@D201 involved the capture of photoexcited electrons and Fe0 reduction. A path for the photogenerated electrons engaging in the reduction reaction to improve the utilization of Fe0 was proposed. These results demonstrate that Fe0/TiO2@D201 is a promising alternative composite catalyst for the efficient Cr(VI) removal from contaminated water.

Recent Advances in Nanoscale Zero-Valent Iron (nZVI)-Based Advanced Oxidation Processes (AOPs): Applications, Mechanisms, and Future Prospects

The fast rise of organic pollution has posed severe health risks to human beings and toxic issues to ecosystems. Proper disposal toward these organic contaminants is significant to maintain a green and sustainable development. Among various techniques for environmental remediation, advanced oxidation processes (AOPs) can non-selectively oxidize and mineralize organic contaminants into CO2, H2O, and inorganic salts using free radicals that are generated from the activation of oxidants, such as persulfate, H2O2, O2, peracetic acid, periodate, percarbonate, etc., while the activation of oxidants using catalysts via Fenton-type reactions is crucial for the production of reactive oxygen species (ROS), i.e., •OH, •SO4-, •O2-, •O3CCH3, •O2CCH3, •IO3, •CO3-, and 1O2. Nanoscale zero-valent iron (nZVI), with a core of Fe0 that performs a sustained activation effect in AOPs by gradually releasing ferrous ions, has been demonstrated as a cost-effective, high reactivity, easy recovery, easy recycling, and environmentally friendly heterogeneous catalyst of AOPs. The combination of nZVI and AOPs, providing an appropriate way for the complete degradation of organic pollutants via indiscriminate oxidation of ROS, is emerging as an important technique for environmental remediation and has received considerable attention in the last decade. The following review comprises a short survey of the most recent reports in the applications of nZVI participating AOPs, their mechanisms, and future prospects. It contains six sections, an introduction into the theme, applications of persulfate, hydrogen peroxide, oxygen, and other oxidants-based AOPs catalyzed with nZVI, and conclusions about the reported research with perspectives for future developments. Elucidation of the applications and mechanisms of nZVI-based AOPs with various oxidants may not only pave the way to more affordable AOP protocols, but may also promote exploration and fabrication of more effective and sustainable nZVI materials applicable in practical applications.

Efficient photoelectrocatalytic degradation of amoxicillin using nano-TiO2 photoanode thin films: A comparative study with photocatalytic and electrocatalytic methods

Excessive utilization of antibiotics in human, animal, and aquaculture poses a substantial threat to human health and the environment. Photoelectrochemical processes are increasingly applied for water remediation because they generate oxidizing species and mineralize organic pollutants, making even small water quantities more amenable for utilization. Thus, this study presents the fabrication of an efficient nano-TiO2 photoanode thin film (PATF) specifically designed for the photoelectrocatalytic (PEC) degradation of amoxicillin (AMX). The TiO2 PATFs were deposited on fluorine-doped tin oxide (FTO) substrate using an ultrasonic spray pyrolysis process with various titanium isopropoxide (TTIP) acetylacetone (AcacH) molar ratios (1:1 to 1:10). The PEC oxidation of AMX was investigated using various molar ratios of TTIP:AcacH TiO2 PATF/FTO by linear sweep voltammetry, and a 1:8 M ratio of PATF exhibited superior PEC oxidation activity than other TiO2 PATFs. Subsequently, the PEC degradation efficiency of AMX was compared with that of photocatalytic (PC) and electrocatalytic (EC) methods. The results demonstrated that the PEC process effectively eliminated 76.2% of AMX within 120 min at 0.8 V, outperforming the removal rates attained by the EC (32.3%) and PC (52.6%). Notably, increasing the voltage to 1.0 V accelerated the PEC degradation of AMX, attaining a removal efficiency of 91.2% within 90 min and exceeding 95% within 120 min.

A green synthesized medicine residue carbon-based iron composite for the removal of chromium (VI) and cadmium (II): Performance, kinetics and mechanism

Nowadays, clean-up of heavy metals from wastewaters using waste residue carbon-based material has received increasing attention. In this work, a novel Chinese medicine residue carbon-based nano zero-valent iron composite (CM-nZVI) had been successfully prepared using the combined Chinese medicine residue, FeCl3 and green tea extract. Cr(VI) and/ or Cd(II) removal in water by the CM-nZVI were systematacially investigated with a series of batch experiments. The most relevant findings indicated the adsorption efficiecy and capacity of Cr(VI) by CM-nZVI were respecitvely nearly 98% and 26 mg/g under optimized reaction conditions. The negative influences of the cations on the Cr(VI) removal followed the order of Al3+ > Ca2+ > Mg2+ Na+ > K+, but the anions followed the order of HCO3- > PO43- > NO3- > Cl- > SO42-. Humic acid (HA) and ionic strength with high concentrations severely inhibited Cr(VI) removal. The Cr(VI) adsorption on CM-nZVI fitted well by the pseudo-second-order kinetic and Langmuir models. A monolayer endothermic chemisorption occurred on Cr(VI) adsorption over CM-nZVI, and Cr(VI) removal by CM-nZVI primarily involved in the absorption, reduction, precipitation and complexation processes. Both Cr(VI) and Cd(II) removals had been achieved by CM-nZVI at their low concentrations. This CM-nZVI showed a better reusability proprity for Cr(VI) and Cd(II) removal with the regeneration of CM-nZVI through simple pickling. The outcomes of this work show that CM-nZVI could be used an effective material for heavy metals removal from water.

Degradation of ciprofloxacin by persulfate activated with pyrite: mechanism, acidification and tailwater reuse

Residues of ciprofloxacin (CIP) in the environment pose a threat to human health and ecosystems. This study investigated the degradation of CIP by persulfate (PS) activated with pyrite (FeS₂). Results showed that when [CIP] = 30 μM, [FeS₂] = 2.0 g L^-1, and [PS] = 1 mM, the CIP removal rate could reach 94.4% after 60 min, and CIP mineralization rate reached 34.9%. The main free radicals that degrade CIP were SO₄˙^- and HO˙, with contributions of 34.4% and 35.7%, respectively. Additionally, compared to the control (ultrapure water), CIP in both tap water and river water was not degraded. However, acidification could eliminate the inhibition of CIP degradation in tap water and river water. Furthermore, acidic tailwater from CIP degradation could be utilized to adjust the pH of untreated CIP, which could greatly promote the degradation of CIP and further reduce disposal costs. The reaction solution was not significantly biotoxic and three degradation pathways of CIP were investigated. Based on the above results and the characterization of FeS₂, the mechanism of CIP degradation in the FeS₂/PS system was that FeS₂ activated PS to generate Fe(iii) and SO₄˙^-. The sulfide in FeS₂ reduced Fe(iii) to Fe(ii), thus achieving an Fe(iii)/Fe(ii) cycle for CIP degradation.

Broad Spectral Response Z-Scheme Three-Dimensional Ordered Macroporous Carbon Quantum Dots/TiO2/g-C3N4 Composite for Boosting Photocatalysis

Photocatalytic degradation technology is one of the effective protocols to solve environmental problems. TiO₂ has always been favored for its photostability and low cost. However, the insufficient photocatalytic activity of TiO₂ limits its application due to the severe recombination of photogenerated electrons and holes and a narrow light response range. Therefore, 3DTCN, a TiO₂/g-C₃N₄ composite with a three-dimensional ordered macroporous structure was prepared by a colloidal crystal template technique to form a heterojunction for inhibiting the photogenerated electron-hole recombination. On 3DTCN, carbon quantum dots (CQDs) were loaded by impregnation to obtain x % CQDs/3DTCN with a broad spectral response to light. The physical and chemical properties of samples were investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy (TEM), high-resolution-TEM, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, Brunauer-Emmett-Teller analysis, photoluminescence spectroscopy, and ultraviolet-visible diffuse reflectance spectroscopy. The photocatalytic activity was evaluated via degrading the rhodamine B (RhB) dye, and the degradation efficiency of 1% CQDs/3DTCN (98%) was found to be much higher than that of 3DTCN (42%) in 80 min under simulated sunlight irradiation. Furthermore, it also possessed excellent durability. Meanwhile, the sample also showed an outstanding photoelectric property. Finally, the proposed mechanism of the composites had been mainly analyzed by density functional theory calculations. This work thus provides an idea to form a 3D structure heterojunction and further improve the photocatalytic activity.