Removal of antibiotic resistant microbes by Fe(II)-activated persulfate oxidation

Molecular level removal of antibiotic resistant bacteria and genes: A review of interfacial chemical in advanced oxidation processes

As a kind of novel and persistent environmental pollutants, antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) have been frequently detected in different aquatic environment, posing potential risks to public health and ecosystems, resulting in a biosecurity issue that cannot be ignored. Therefore, in order to control the spread of antibiotic resistance in the environment, advanced oxidation technology (such as Fenton-like, photocatalysis, electrocatalysis) has become an effective weapon for inactivating and eliminating ARB and ARGs. However, in the process of advanced oxidation technology, studying and regulating catalytic active sites at the molecular level and studying the adsorption and surface oxidation reactions between catalysts and ARGs can achieve in-depth exploration of the mechanism of ARGs removal. This review systematically reveals the catalytic sites and related mechanisms of catalytic antagonistic genes in different advanced oxidation processes (AOPs) systems. We also summarize the removal mechanism of ARGs and how to reduce the spread of ARGs in the environment through combining a variety of characterization methods. Importantly, the potential of various catalysts for removing ARGs in practical applications has also been recognized, providing a promising approach for the deep purification of wastewater treatment plants.

Solar photo-Fenton and persulphate-based processes for landfill leachate treatment: A critical review

Landfilling is the most usual solid waste management strategy for solid residues disposal. However, it entails several drawbacks such as the generation of landfill leachate that seriously threaten human life and the environment due to their toxicity and carcinogenic character. Among various technologies, solar photo-Fenton and sulphate-based processes have proven to be suitable for the treatment of these polluted streams. This review critically summarises the last three decades of studies in this field. It is found that the solar homogeneous photo-Fenton process should be preferably used as a pre- and post-treatment of biological technologies and as a standalone treatment for young, medium, and mature leachates, respectively. Studies on heterogeneous solar photo-Fenton process are lacking so that this technology may be scaled-up for industrial applications. Sulphate radicals are attractive for removing both COD and ammonia. However, no study has been reported on solar sulphate activation for landfill leachate treatment. This review discusses the main advances and challenges on treating landfill leachate through solar AOPs, it compares solar photo-Fenton and solar persulphate-based treatments, indicates the future research directions and contributes for a better understanding of these technologies towards sustainable treatment of landfill leachate in sunny and not-so-sunny regions.

Effects of aging methods on the adsorption of antibiotics in wastewater by soybean straw biochar

BACKGROUND

The environmental pollution and ecological risks caused by the widespread use of antibiotics have attracted attention in recent years. Biochar materials have a rich pore diameter and can effectively adsorb pollutants from wastewater. However, biochar will experience high temperatures, freezing and thawing in nature, affecting its physicochemical properties and adsorption capacity. Three types of aged biochar were prepared by artificial simulated aging using soybean straw as raw material. The aged biochar's elemental composition and functional group species were investigated by characterization analysis, and their adsorption kinetics and adsorption isotherms were studied.

RESULTS

The specific surface area and pore size of the three aged biochars were lower than those of fresh biochars. The increased number of oxygen-containing functional groups of the aged biochars formed a water cluster interaction with norfloxacin (NOR), which was unfavorable to the adsorption of NOR. The adsorption mechanism of biochar on NOR comprises pore filling, electrostatic interaction, ion exchange and complexation.

CONCLUSION

The adsorption of NOR on biochar before and after aging was spontaneous and was described by quasi-second kinetics and the Langmuir equation. Different aging methods influenced the physicochemical properties and adsorption performance of biochar, and the adsorption capacity of biochar was significantly reduced after aging. Therefore, the influence of climatic factors needs to be considered when using biochar to remove target pollutants. © 2023 Society of Chemical Industry.

Removal of antibiotic resistant bacteria and genes by nanoscale zero-valent iron activated persulfate: Implication for the contribution of pH decrease

The mechanism of removing antibiotic resistant bacteria (ARB) and antibiotic resistant genes (ARGs) by persulfate was attributed to the generation of reactive oxygen species (ROS). However, the potential contribution of decreased pH in persulfate system to ARB and ARGs removal has rarely been reported. Here, the efficiency and mechanism of removing ARB and ARGs by nanoscale zero-valent iron activated persulfate (nZVI/PS) were investigated. Results showed that the ARB (2 × 10⁸ CFU/mL) could be completely inactivated within 5 min, and the removal efficiencies of sul1 and intI1 were 98.95% and 99.64% by nZVI/20 mM PS, respectively. Investigation of mechanism revealed that hydroxyl radicals was the dominant ROS of nZVI/PS in removing ARB and ARGs. Importantly, the pH of nZVI/PS system was greatly decreased, even to 2.9 in nZVI/20 mM PS system. Impressively, when the pH of the bacterial suspension was adjusted to 2.9, the removal efficiency of ARB, sul1 and intI1 were 60.33%, 73.76% and 71.51% within 30 min, respectively. Further excitation-emission-matrix analysis confirmed that decreased pH contributed to ARB damage. The above results on the effect of pH indicated that the decreased pH of nZVI/PS system also made an important contribution for the removal of ARB and ARGs.

Adsorption of norfloxacin from wastewater by biochar with different substrates

The type of feedstock and pyrolysis temperature are the main reasons affecting the properties of the resulting biochar. Therefore, this paper investigates the effects of different feedstocks (peanut shell, corn straw and soybean straw) and different pyrolysis temperatures (300, 450 and 600 ℃) on the structural morphology and elemental composition of the resulting biochar. The optimum pyrolysis temperature of 600 ℃ was selected based on the comparison of the adsorption of NFX (norfloxacin) by the biochar prepared at different temperatures. Characterization of biochar materials using x-ray diffractometer, fourier transform infrared spectrometer and scanning electron microscope to study the changes in the physicochemical and structural properties of biochar. The results showed that the pH, surface area and ash content of biochar are increased with increasing temperature. The results of isothermal adsorption and adsorption kinetics experiments showed that the adsorption processes of the three biochar species on NFX were consistent with the Langmuir model and Pseudo-second order kinetic model. The adsorption process occurred in the surface layer of the biochar and was dominated by chemisorption. The inhibition of the adsorption of NFX was more obvious with the higher valence state of cations and the higher ion concentration. The adsorption mechanism of biochar on NFX includes pore filling, hydrogen bonding and electrostatic interactions.

Modern knowledge-scape possess petite influence on the factual persistence of resistance determinants (ARGs/MGEs): A map and assessment of discharged wastewater and water bodies

Antibiotic resistance genes (ARGs) and Mobile genetic elements (MGEs) are major global emerging pollutants of the environment and water nexus which various investigators of related studies have reported. Observing ARGs and MGEs in water bodies, wastewater treatment systems, and estuaries is indicative of relevant risk, resistant bacteria/ARGs spread or potential health concern and may result environmental pathogen bloom if appropriate research-based strategies are not implemented to remove these lethal genetic materials. Despite reports and knowledge-based strategies for removal, the challenge yet persists. This study aims to appraise the impact/contribution of related studies and emphasize the necessity for applying combined research-based/practitioners approach in addressing the expanding challenge of ARGs/MGEs in wastewater/waterbodies. The study describes a bibliometric assessment of antibiotic resistance determinants annual scientific publications on the Web of Science, an annual growth rate of related articles, top articles per citations with search topics and content-review analysis to evaluate the methods of removal of ARGs/MGEs. A total of 1301 articles of wastewater treatment systems were retrieved with date range of 1997-2019. A description of the study Annual Growth Rate of 37.82% at R² of 0.7863 was observed with an increasing article publication and a decreasing total citation rate indicating persistent reports of dispersion on ARGs/MGEs studies in the water bodies and environment. Although there abound extensive studies and reports of ARGs and MGEs in water nexus and wastewater release with research based removal strategies, the impact of such reports have not been fully actualized amongst wastewater system practitioners. A lucid drive towards implementing ARGs/MGEs removal strategies from the environment by applying affirmed research-based methods are suggestive.

Sulfate radical based advanced oxidation processes for agro-industrial effluents treatment: A comparative review with Fenton's peroxidation

Agro-industrial wastewater management becomes a major task while environmental regulations are becoming stricter worldwide. Agro-industrial wastewaters are known by high content of organic pollutants that cause an adverse effect on the water bodies. Industries are looking for efficient, easy-to-use and affordable treatment processes. Sulfate radical based advanced oxidation processes (S-AOPs) are arising as suitable alternatives for agro-industrial effluents treatment. In this review, the major findings regarding the application of this technology for real agro-industrial wastewater depuration are discussed. Moreover, these technologies are compared as an alternative to Fenton's process, which is a widely studied advanced oxidation process and with high efficiency in the treatment of agro-industrial effluents. The studies already carried out are promising, but there is still a great lack of studies in this area and using this technique.

Optimization of PNP Degradation by UV-Activated Granular Activated Carbon Supported Nano-Zero-Valent-Iron-Cobalt Activated Persulfate by Response Surface Method

Nitrophenols are toxic substances that present humans and animals with the risk of deformities, mutations, or cancer when ingested or inhaled. Traditional water treatment technologies have high costs and low p-nitrophenol (PNP) removal efficiency. Therefore, an ultraviolet (UV)-activated granular activated carbon supported nano-zero-valent-iron-cobalt (Co-nZVI/GAC) activated persulfate (PS) system was constructed to efficiently degrade PNP with Co-nZVI/GAC dosage, PS concentration, UV power, and pH as dependent variables and PNP removal rate as response values. A mathematical model between the factors and response values was developed using a central composite design (CCD) model. The model-fitting results showed that the PNP degradation rate was 96.7%, close to the predicted value of 98.05 when validation tests were performed under Co-nZVI/GAC injection conditions of 0.827 g/L, PS concentration of 3.811 mmol/L, UV power of 39.496 W, and pH of 2.838. This study demonstrates the feasibility of the response surface methodology for optimizing the UV-activated Co-nZVI/GAC-activated PS degradation of PNP.

Adsorption of norfloxacin from aqueous solution on biochar derived from spent coffee ground: Master variables and response surface method optimized adsorption process

In this study, biochar derived from spent coffee grounds (SCGB) was used to adsorb norfloxacin (NOR) in water. The biochar properties were interpreted by analysis of the specific surface area, morphology, structure, thermal stability, and functional groups. The impacts of pH, NOR, and ion's present on SCGB performance were examined. The NOR adsorption mode of SCGB is best suited to the Langmuir model (R² = 0.974) with maximum absorption capacity (69.8 mg g^-1). By using a Response Surface Method (RSM), optimal adsorption was also found at pH of 6.26, NOR of 24.69 mg L^-1, and SCGB of 1.32 g L^-1. Compared with biochars derived from agriculture such as corn stalks, willow branches, potato stem, reed stalks, cauliflower roots, wheat straw, the NOR adsorption capacity of SCGB was 2-30 times higher, but less than 3-4 times for biochars made from Salix mongolica, luffa sponge and polydopamine microspheres. These findings reveal that spent coffee grounds biochar could effectively remove NOR from aqueous solutions. Approaching biochar derived from coffee grounds would be a promising eco-friendly solution because it utilizes solid waste, saves costs, and creates adsorbents to deal with emerging pollutants like antibiotics.

Insights into enhanced peroxydisulfate activation with S doped Fe@C catalyst for the rapid degradation of organic pollutants

In this study, the S modified iron-based catalyst (S-Fe@C) for activating peroxydisulfate (PDS) was fabricated by heating the S-MIL-101 (Fe) precursor at 800 °C. The resulted S-Fe@C composite mainly consisted of carbon, Fe⁰, FeS, FeS₂, and Fe₃O₄, and showed strong magnetism. Compared with Fe@C obtained from MIL-101 (Fe), the S-Fe@C exhibited much higher performance (1.5 times larger) on PDS activation and the S-Fe@C/PDS could rapidly degrade various organic pollutants in 5 min under the attack of the species of SO₄^-·, ¹O₂, electro-transfer and Fe(IV). The S element in enhancing the PDS activation mainly involved two mechanisms. Firstly, the doped S could speed up the electron transfer efficiency, resulting in a promotion on PDS decomposition; secondly, the S^2- S₂^2- or S⁰ could achieve the circulation of Fe²⁺ and Fe³⁺, leading to the formation of non-radicals Fe(IV) and ¹O₂.

Fe(II) Redox Chemistry in the Environment

Iron (Fe) is the fourth most abundant element in the earth's crust and plays important roles in both biological and chemical processes. The redox reactivity of various Fe(II) forms has gained increasing attention over recent decades in the areas of (bio) geochemistry, environmental chemistry and engineering, and material sciences. The goal of this paper is to review these recent advances and the current state of knowledge of Fe(II) redox chemistry in the environment. Specifically, this comprehensive review focuses on the redox reactivity of four types of Fe(II) species including aqueous Fe(II), Fe(II) complexed with ligands, minerals bearing structural Fe(II), and sorbed Fe(II) on mineral oxide surfaces. The formation pathways, factors governing the reactivity, insights into potential mechanisms, reactivity comparison, and characterization techniques are discussed with reference to the most recent breakthroughs in this field where possible. We also cover the roles of these Fe(II) species in environmental applications of zerovalent iron, microbial processes, biogeochemical cycling of carbon and nutrients, and their abiotic oxidation related processes in natural and engineered systems.

Technologies towards antibiotic resistance genes (ARGs) removal from aquatic environment: A critical review

Antibiotic resistance genes (ARGs) have been recognized as emerging pollutants that are widely distributed and accumulated in most of aquatic environment. Although many ARGs-removal technologies are employed, a corresponding discussion of merits and limitations of known technologies is still currently lacking. More importantly, the removal mechanisms of ARGs remain unclear, hindering their ecological feasibility. Thus, further in-depth studies are highly required. In this review, the occurrence and risk of ARGs in aquatic environment are introduced, and the main routes and potential impacts of ARGs dissemination are enumerated. In addition, several novel ARGs detection methods are critically reviewed. Notably, to ensure greater applicability of these technologies, systematic information on how recent technologies impact the ARGs removal and control are comprehensively compared and summarized. Finally, future research directions to alleviate the risk of ARGs in aquatic environment are briefly introduced. Taken together, this review provides useful information to facilitate the development of innovative and feasible ARGs removal technologies and increase their economic viability and ecological sustainability.

Cysteine enhanced degradation of monochlorobenzene in groundwater by ferrous iron/persulfate process: Impacts of matrix species and toxicity evaluation in ISCO

Monochlorobenzene (MCB), a solvent and synthetic intermediate, has been widely detected in groundwater at industrial contaminated sites. Cysteine (Cys) enhanced Fe²⁺/persulfate (Fe²⁺/Cys/PS) process with high degradation efficiency of organic pollutants has the potential for in-situ chemical oxidation of MCB. In this study, we systematically explored the impacts of common anions (CO₃^2-, HCO₃^-, SO₄^2-, NO₃^-, NO₂^-, PO₄^3-, HPO₄^2-, H₂PO₄^-, Cl^-, Br^-), cations (NH₄⁺, Mg²⁺, Al³⁺, Mn²⁺, Cu²⁺) and natural organic matter (NOM) on the degradation kinetics of MCB by the novel Fe²⁺/Cys/PS process and evaluated the ecotoxicity. The results showed that the removal of MCB in absence of matrices was enhanced by Cys due to its reduction and complexation ability. All of the anions inhibited the MCB degradation through the scavenging of SO₄^•- and HO^•, though the inhibition degree of SO₄^2-and NO₃^- was slight. Cations such as NH₄⁺, Mg²⁺ and Al³⁺ hardly interfered with the reaction. Low concentrations of Cu²⁺ and NOM promoted the MCB oxidation, but the promotion strength weakened and turned into inhibition with the increased concentration of Cu²⁺ and NOM. The toxicity assessment of the transformation products (TPs) in the presence of Cl^- and Br^- based on the quantitative structure-activity relationships model showed the potentially higher toxicity of some TPs than their parent MCB. These results indicate that groundwater matrices may interfere with the MCB oxidation process. To accurately evaluate the effects of groundwater matrices on Fe²⁺/Cys/PS process for MCB oxidation and its potential toxicity, the field tests should be carried out in the future.

Activation of peroxymonosulfate by biochar and biochar-based materials for degrading refractory organics in water: a review

Water pollution caused by refractory organics has attracted widespread concern in recent years. At this time peroxymonofulfate (PMS) has been widely used to generate sulfate radicals with high reactivity and potential. The direct reaction rate between PMS and organics is very low. However, the activated PMS has a strong oxidizing ability on organics due to its conversion into sulfate radicals. Recently, the free radicals generated by oxidant PMS and catalyst biochar have proven to be an effective species in dealing with refractory organics. In order to enable researchers to better understand the current research status of PMS/biochar, and to promote the development and application of PMS/biochar system, we have written this review. This review in detail described the mechanism of PMS activated by biochar materials, and summarized the influencing factors of refractory organics degradation in the PMS/biochar system. In addition, the active sites of PMS/biochar, the degradation mechanism of refractory organics, and the reusability of biochar catalysts were also discussed. Finally, the concluding remarks and perspectives were made for future research on the PMS/biochar system in the degradation of refractory organics.