Initial pH Range Research Articles

Continuous peroxymonosulfate activation by a novel CoFe2O4-functionalized carbon fiber electroactive filter towards ultrafast and cost-effective decontamination: Performance, mechanism and application

Constructing an integrated electrochemical filtration system for flow-through electrocatalytic peroxymonosulfate (PMS) activation presents an efficient strategy for treating wastewater containing organic micropollutants. However, there remains a deficiency of feasible and cost-effective flow-through systems for practical applications. Herein, we developed a novel electroactive CoFe2O4-functionalized carbon fiber filter (CoFe2O4/CFF) to activate PMS towards ultrafast and cost-effective degradation of sulfamethoxazole (SMX). CoFe2O4 nanoparticles were uniformly loaded onto the surface of carbon fiber by hydrothermal synthesis, resulting in a diameter of 110.6 ± 26.3 nm. Under optimal conditions, SMX was degraded 98.0 % in a single-pass through the CoFe2O4/CFF. The system exhibited robust performance across complicated matrices (e.g., tap water and lake water), a variety of micropollutants (75.4–98.0 %) and especially over a broad initial pH range (3 − 10). We identified the reaction pathways involving reactive oxygen species (1O2, SO4∙- and •OH) and high-valence metals, which collectively facilitated the efficient degradation of pollutants within the system. Theoretical calculations further confirmed that the Co-Fe bimetallic system in CoFe2O4 exhibited significant synergistic effects, consistent with experimental findings. The system’s superior catalytic performance can be attributed primarily to convection-enhanced mass transfer from the flow-through design and to the improved catalytic activity and robustness of CoFe2O4 catalysts, driven by accelerated redox cycles of Co3+/Co2+ and Fe3+/Fe2+ due to the applied cathode potential. Benefiting from the integration of electrochemistry, the proposed catalytic filtration system demonstrated strong anti-fouling properties. Detailed calculations and comparative analyses substantiated the cost-effectiveness of this system. Therefore, the electroactive CoFe2O4/CFF-based flow-through electrocatalytic PMS activation system offers a unique and economically viable approach for the efficient and ultrafast remediation of sulfamethoxazole.

Benzo(a)pyrene degradation by the interaction of Aspergillus brasilensis and Sphigobacterium spiritovorum in wastewater: optimisation and kinetic response

ABSTRACT Benzo(a)pyrene (BaP) is a well-known environmental contaminant that poses significant risks due to its carcinogenic nature and it is crucial to remove it from the environment, especially in wastewater. Thus, this study aims to enhance the degradation of BaP in wastewater through the optimised interaction of the fungus Aspergillus brasiliensis and the bacterium Sphingomonas spiritovorum. The ideal initial pH and temperature ranges for optimising BaP breakdown were determined using response surface methodology (RSM). For that, the range of initial pH chosen was pH 4–9 and the temperature was between 25℃ – 40℃. The first-order kinetic was used to determine the kinetic response for monoculture and co-culture. The co-culture of A. brasiliensis and S. spiritovorum successfully produced a BaP removal rate of over 50%, which was much higher than the removal rates observed in monoculture treatments under optimisation conditions. The kinetic response was obtained with 0.067 d− 1 (A. brasiliensis), 0.127 d− 1 (S.spriritovorum) and 0.144 d− 1 (co-culture) for the degradation rate constant, K. The degradation half-life time, t1/2 shows the decrement for the co-culture (4.83 days) compared to monoculture. The increased degradation has been attributed to the synergistic biochemical pathways, in which fungal ligninolytic enzymes initiate the breakdown of BaP, followed by bacterial degradation of the resulting compounds. The study's results, which have been validated by Analysis of Variance (ANOVA), offer insightful information for the enhancement of bioremediation strategies. This information is practicable for researchers, practitioners, and policymakers in the context of addressing carcinogenic pollutants in wastewater.

Highly Efficient Degradation of Emerging Contaminants with Sodium Bicarbonate-Enhanced Mn(II)/Peracetic Acid Process: Formation and Contribution of Mn(V).

Organic ligands have been extensively used to enhance the catalytic performance of manganese ion (Mn(II)) for peracetic acid (PAA). In this study, sodium bicarbonate (NaHCO3), an economical and eco-friendly inorganic ligand, was introduced to enhance the degradation of emerging contaminants (ECs) in the Mn(II)/PAA process. NaHCO3 could significantly improve the oxidizing ability of the Mn(II)/PAA process over the initial pH range of 3.0-11.0. Mn(V) was identified as the primary reactive species for degrading naproxen in the NaHCO3/Mn(II)/PAA process. HCO3- could complex with Mn(II) to generate Mn(II)-HCO3-, which has a lower redox potential to enhance the catalytic activity of Mn(II). Mn(II)-HCO3- reacted with PAA to produce Mn(III)-HCO3- and CH3C(O)O•. Mn(V)-HCO3- was generated via two-electron transfer between Mn(III)-HCO3- and PAA. Although organic radicals were detected in the NaHCO3/Mn(II)/PAA process, naproxen was mainly degraded by Mn(V)-HCO3- via one-electron transfer along with the formation of MnO2. Notably, the coexisting hydrogen peroxide was vital in the reduction of MnO2 to Mn(II/III), thereby enhancing the continuous generation of Mn(V)-HCO3-. NaHCO3/Mn(II)/PAA process exhibited exceptional oxidation performance in actual water samples. This study proposed a strategy utilizing an eco-friendly inorganic ligand to address the inherent drawbacks of organic ligand-enhanced Mn(II)/PAA processes and highlighted its potential applications in the removal of ECs.

Bimetal-organic framework derived single-atom-like Co/Fe catalysts for peroxydisulfate activation: The dual amplification of radical and nonradical pathways

A novel single-atom-like Co/Fe catalyst (i.e., Co/Fe-N-C) was synthesized by pyrolysis of a Zn/Co/Fe zeolitic imidazolate framework, and applied in peroxydisulfate (PDS) activation for removal of organic contaminants from wastewater. The isolated diatomic metal-nitrogen sites were detected by X-ray adsorption fine-structure. The degradation of four contaminants (i.e., phenol, bisphenol A, 2,4-dichlorophenol, and N-methyl-2-pyrrolidone) with a concentration of 100 mg/L could be degraded separately within 20 min by the Co/Fe-N-C system with 10 mmol/L of PDS, 0.5 g/L of catalyst dosage, and initial pH of 3. Besides, 79.2 % of phenol could be mineralized in 120 min, and the turn-over frequency value of the catalyst was calculated to be 27.17 min−1, which was higher than the commonly reported homogeneous PS-AOPs. Moreover, the Co/Fe-N-C exhibited high stability (mineralization rate over 70 % after 5 cycles), a wide initial pH range (3−9), and high catalytic performance at 5–20 mmol/L of PDS concentrations. Based on the analysis of radical scavenging experiments and electron spin resonance spectra, the radical and non-radical pathways for PDS activation were proved in the system, and the contribution of phenol degradation by each pathway was clarified.

Caproiciproducens converts lactic acid into caproic acid during Chinese strong-flavor Baijiu brewing

Strong-flavor Baijiu, a type of Chinese liquor, is produced through anaerobic solid-state fermentation in a sealed mud pit. Ethyl caproate, the characteristic flavor compound of strong-flavor Baijiu, is influenced by caproic acid-producing bacteria in the pit mud. To better understand the formation of caproic acid, this study investigated the microbial composition and physicochemical parameters of pit mud from different layers (top, middle, and bottom) in Hubei and Sichuan provinces, China. The results revealed that Caproiciproducens plays a key role in caproic acid production by using lactic acid as a substrate, with its abundance increasing with the depth of the pit mud. A strain Caproiciproducens sp. R1, isolated from the pit mud, was shown to produce caproic acid from lactic acid within an initial pH range of 5.5–9.0 and lactic acid concentrations of 1 %–5 % (m/v). In addition, inoculation of strain R1 into Huangshui (a lactic acid-rich liquid from Baijiu production) resulted in 40.72 mM caproic acid production. This study demonstrates that Caproiciproducens plays a crucial role in caproic acid production from lactic acid during the fermentation process of strong-flavor Baijiu.

Calcium silicate hydrate complex konjac glucomannan-based hydrogel selectively adsorbed phosphate in low alkalinity solution

The selective recovery of phosphate from wastewater can manage nutrients and realize the recycling of phosphorus resources. In this study, a novel konjac glucomannan/pectin/calcium silicate composite hydrogel (KP-CSH) was developed for efficient recovery of phosphate in aqueous solution. The amount of alkali released after the reaction of KP-CSH in a neutral solution was small (the pH of the solution after the reaction was < 9). In a wide initial pH range (3–10), the adsorption capacity of KP-CSH in 50 mg-P/L phosphate solution reached 39∼45 mg-P/g. Besides, even if the pH of the solution after the reaction was less than 8, it could still well adsorb phosphate. The kinetic and isothermal adsorption experiments indicated that the adsorption process of phosphate by KP-CSH was chemical adsorption, and the maximum adsorption capacity was 61.2 mg-P/g. KP-CSH preferentially adsorbed phosphate even in the presence of high concentrations of competitive ions. In the actual biogas slurry, KP-CSH also exhibited the strongest selectivity/affinity for phosphate, and its distribution coefficient (Kd) was significantly higher than that of other co-existing anions and cations. The adsorption mechanism analysis indicated that Ca was the main adsorption site of KP-CSH, and that the adsorption process of target pollutants mainly involved ligand exchange and the intra-sphere complexation. Further plant seed germination and seedling growth experiments suggested that KP-CSH after phosphate recovery did not exert a negative effect on the growth of plant seedlings, and increased the chlorophyll content of seedling leaves. These results demonstrate that KP-CSH is a potential adsorbent for efficient phosphate recovery, which can be used as a slow-release phosphate fertilizer after recovering phosphate.

In situ synthesized Ag nanoparticles encapsulated inside carbonized ZIF-8 for efficient Cr(VI) reduction

Effective reduction of carcinogenic contaminant Cr(VI) to low-toxic Cr(III) is of global importance for environmental and water source protection. Herein, a stable metal-organic framework (MOF), ZIF-8, was carbonized as a template to synthesize a novel nanocomposite involving Ag nanoparticles (NPs) inside (Ag@C-ZIF-8). Surprisingly, the Ag NPs synthesized in situ in the Ag+@C-ZIF-8/AB system exhibited outstanding reduction ability toward Cr(VI) and eliminated 100 % of Cr(VI) (20 mg/L) within 10 min in an initial pH range of 3–5. The Cr(VI) removal efficiency was much higher compared with these systems of AB (25.5 %), C-ZIF-8/AB (44.6 %), Ag+/AB (66.8 %), and Ag@C-ZIF-8/AB (39.3 %). Increasing the initial pH of the solution and the amount of C-ZIF-8 template accelerated Cr(VI) reduction. In four cycles of experiments, over 92 % of Cr(VI) was reduced without any treatment, demonstrating the excellent stability and reusability of Ag@C-ZIF-8. X-ray photoelectron spectroscopy (XPS) characterization and mechanism exploration experiments indicated that Ag NPs catalyzed AB dehydrogenation and efficiently reduced Cr(VI) together with the generated hydrogen. This is the first report on carbonized MOF-based Ag NPs synthesized in situ for Cr(VI) reduction by combining catalytic AB dehydrogenation with metal nanoparticle reducibility. This work provides new avenues for the utilization of heavy metal ions in water environments and the development of novel and efficient reductants/catalysts of Cr(VI) removal.

Efficient activation of molecular oxygen across a broad pH range (2.5 to 11) utilizing an aluminum-based solid-phase Fenton reagent

Zero-valent aluminum (Al0) is an excellent electron donor with extremely low redox potential (E0(Al3+/Al0) = − 1.667 V) that could directly activate the green oxidant O2, producing reactive oxygen radicals to effectively degrade pollutants in the Al0/O2 system. However, the surface of Al0 is covered with a dense oxide film and easily re-passivated under neutral or alkaline conditions after modification. This is why it is currently mostly used at a pH of less than 4 and an induction period is required. In this study, a novel composite material, Al0-FeSO4-EDTABM, was prepared using Al0 with surface modification using FeSO4·7H2O crystals and the common ligand ethylenediaminetetraacetic acid (EDTA) through environmentally friendly one-pot mechanical ball milling (BM) to destroy the oxide film of Al0 and stimulate its activity. The properties and mechanism of the activation of molecular oxygen by Al0-FeSO4-EDTABM composites were discussed in detail. At an initial pH range of 2.5 to 11.0, the model pollutant phenol could be efficiently removed by over 92 % through the activation of molecular oxygen, without requiring an induction period. During the BM process, FeSO4·7H2O and EDTA effectively disrupted the oxide film on the surface of Al0 and prevented secondary passivation. During the degradation reaction, Al0-FeSO4-EDTABM facilitated the generation of active oxygen radicals mainly through a heterogeneous Fenton-like process. In conclusion, the innovative Al0-based composite/O2 system presents a simple and potential new method for preparing solid Fenton reagents with promising practical applications.

A Novel Nanogold Composite Fabrication, Its Characterization, and Its Application in the Removal of Methylene Blue Dye from an Aqueous Solution

A unique aspect of this research lies in the combination of polyethylene terephthalate (PET) nanofibers with Auo@PPh2-PIILP to create a nanogold composite (NGC). This NGC has proven to be highly efficient in removing methylene blue (MB) from wastewater. The prepared nanogold composite NGC was characterized by Fourier-transform infrared spectroscopy (FTIR), Field Emission Scanning Electron Microscopy (FE-SEM), transmission electron microscopy (TEM), Energy Dispersive X-ray Spectroscopy (EDAX), and Elements Distribution Mapping (EDM). Several factors were examined in batch adsorption experiments to determine their impact on dye adsorption. These factors included the initial pH range of four to eight, the dosage of NGC adsorbent ranging from 0.001 to 0.008 g, the initial concentration of MB dye ranging from 10 to 50 mg L−1, and the contact period ranging from 10 to 80 min. It has been observed that NGC is more efficient in removing MB from polluted water. The results of the pseudo-second-order model show good agreement between the calculated adsorption capacity (qe)cal. (4.3840 mg g−1) and the experimental adsorption capacity (qe)exp. (4.6838 mg g−1) values. Experimental findings suggest a monolayer capping of MB dye on the NGC surface with a maximum adsorption capacity Qm of 18.622 mg g−1 at 20 °C, indicating that it is well-fitted to the Langmuir isotherm.

Peracetic acid activation by natural magnetite for bisphenol A degradation: Performance and degradation mechanism

Advanced oxidation processes based on activated peracetic acid (PAA) have been widely used in water treatment. In this study, magnetite was first employed in PAA activation for Bisphenol A (BPA) degradation. The results showed that the magnetic/PAA system degraded 94.6 % BPA in 60 min at neutral pH (pH = 6.7), exhibiting a higher rate constant (kobs = 0.051 min−1) than PAA or magnetite alone. X-ray photoelectron spectroscopy (XPS) results proved that ≡Fe(II) and surface hydroxyl group (OOH) were the dominant active sites, which promoted the electron transfer between magnetite, PAA, and BPA. According to the scavenging experiments and electron paramagnetic resonance (EPR) spectrum, the main reactive oxygen species responsible for BPA degradation include organic radicals (CH3COOO), Hydroxyl radical (OH) and singlet oxygen (1O2). The BPA degradation pathway was determined by LC-MS analysis, and the toxicity of the intermediates was evaluated by ECOSAR and wheat seed growth inhibition experiment. In addition, the magnetite/PAA system presented a good adaptability under a wide initial pH range, demonstrating efficient degradation even in the presence of complex matrices such as Cl−, NO3− or humic acid in water bodies while HCO3− and H2PO4− inhibited BPA degradation. This study not only reveals the mechanism of magnetite activating PAA but also provides a new idea for applying magnetite in PAA-based AOPs to remove micropollutants in wastewater.

Catalytic Activity of CuO-bentonite Bead for the Removal of Methylene Blue by Fenton like Process

Non-biodegradable dyes, potentially contaminate the water and poses serious risk to the environment. So their removal requires alarming attention. The formation of CuO-bentonite bead and their dye removal application is the main focus of the current investigation. X-ray diffraction spectroscopy (XRD), Field emission scanning electron microscopy (FESEM), and Energy dispersive X-ray spectroscopy (EDS) analysis were implemented to evaluate the crystalline structure and morphology of the prepared sample. The catalytic activity of the CuO-bentonite bead was studied against the dye methylene blue (MB) by an advanced oxidation process like Fenton. The experimental data shows a maximum 94.08 % of the dye removal capacity of the beads in just 20 minutes. Further, for the detail dye removal study optimum environments such as initial MB concentration, pH range, and oxidant dosage were altered during the reaction. Additionally, the CuO-bentonite bead showed 89.03 % dye removal even after five reuse cycles; which exhibits the heightened stability and robustness of the CuO-bentonite bead as a catalyst. Therefore, this simply prepared CuO-bentonite bead revealed a new approach to wastewater treatment.

Peroxymonosulfate activation by tin(IV) phosphate supported cobalt composite for acetaminophen degradation: Performance and mechanism

Tin(IV) phosphate-supported cobalt composite (Co-SnP) was prepared and employed as a heterogeneous activator of peroxymonosulfate (PMS) for acetaminophen (APAP) degradation. The results indicated that almost all APAP (5 mg L−1) was eliminated by PMS (0.5 mM) assisted with Co-SnP (0.2 g L−1) in an initial pH range of 7–9 within 15 min, mainly owing to the role of OH and SO4−, with contributions of 59.7 % and 39.6 %, respectively. The rate constant (k) value increased gradually with the increase in catalyst dosage and PMS concentration. APAP degradation was suppressed by Cl−, HCO3− and humic acid but promoted by NO3−. The Co-SnP/PMS system exhibited strong oxidation ability toward APAP in real water matrices and toward other organic pollutants (rhodamine B, phenacetin, bisphenol A, and sulfisoxazole), indicating the outstanding catalytic performance of Co-SnP for PMS activation. Furthermore, the superior stability and reusability of the Co-SnP catalyst were confirmed through four consecutive uses. Finally, the intermediates of APAP degradation were identified and the APAP degradation pathways were proposed. This work demonstrates the potential application of the Co-SnP/PMS system in the elimination of organic pollutants from water and provides a novel avenue for the recovery and utilization of phosphorus and cobalt ions in wastewater.

Adsorption of phosphate over a novel magnesium-loaded sludge-based biochar.

The production of sludge-based biochar to recover phosphorus (P) from wastewater and reuse the recovered phosphorus as agricultural fertilizer is a preferred process. This article mainly studied the removal of phosphate (PO4-P) from aqueous solution by synthesizing sludge-based biochar (MgSBC-0.1) from anaerobic fermentation sludge treated with magnesium (Mg)-loading-modification, and compared it with unmodified sludge-based biochar (SBC). The physicochemical properties, adsorption efficiency, and adsorption mechanism of MgSBC-0.1 were studied. The results showed that the surface area of MgSBC-0.1 synthesized increased by 5.57 times. The material surface contained MgO, Mg(OH)2, and CaO nanoparticles. MgSBC-0.1 can effectively remove phosphate in the initial solution pH range of 3.00-7.00, with a fitted maximum phosphorus adsorption capacity of 379.52 mg·g-1. The adsorption conforms to the pseudo second-order kinetics model and Langmuir isotherm adsorption curve. The characterization of the adsorbed composite material revealed the contribution of phosphorus crystal deposition and electrostatic attraction to phosphorus absorption.

Efficient removal of Cr(VI) by mechanochemically modified pyrites: Self-regulated neutralization behaviors

The pH of the aqueous environment commonly occurs during the application of natural/modified pyrite in water/soil remediation. In this study, mechanochemical modification of natural pyrite (M−pyrite) was employed to remove Cr(VI) over a wide pH range. Self-regulated neutralization was observed during Cr(VI) removal by M−pyrite in the initial pH range of 2.0–12.3. The reductive immobilization of total Cr occurred effectively when the solution self-regulated to a circumneutral pH (pH 5.0–9.0), but only efficient Cr(VI) reduction occurred under strongly acidic or alkaline conditions. Three pathways, i.e., Fe(II) removal, surface sulfide reduction and both combinations, could be revealed for Cr(VI) removal by M−pyrite at circumneutral pH and under strongly alkaline and acidic conditions. As Cr(VI) is reduced by ferrous and sulfide species, the protons generated from pyrite oxidation by O2 are consumed, causing neutral restoration to resist the initial sharp decrease in pH. Effective immobilization of the reduced Cr(VI) was confirmed at an initial pH of 5.0–9.0, but this immobilization did not occur at more acidic and alkaline pH values due to strong Fe(II) dissolution or surface precipitation. The M−pyrite was successfully applied in treating four types of saline industrial Cr(VI) wastewaters, demonstrating the advantage of self-regulated neutralization resistance in complex wastewater matrices.

Study on the enhancement of Fenton-like degradation of methylene blue by foam glass-supported α-Fe2O3/S in a wide initial pH range

BackgroundMethylene blue (MB) is a refractory organic dye that can pose a great threat to the aquatic environment. Fenton oxidation technique is considered as a primrose strategy to treat MB. However, the traditional Fenton reaction has the problems of a narrow pH application range, poor reusability, and lame stability. MethodsHerein, S-doped α-Fe2O3 was supported on foam glass (FG) by one-step hydrothermal method, and a novel Fenton-like catalyst (FG@α-Fe2O3/S) was successfully prepared for excellent degradation of MB. Significant findingsThe removal efficiency of 30 mg/L MB by FG@α-Fe2O3/S was 100 % within 15 min. The universality and reusability of the catalyst were also excellent. Notably, the degradation performance of the catalyst is almost unaffected by the change in pH values from 3 to 11. Furthermore, the application scope of FG@α-Fe2O3/S was explored by an anti-interference experiment. The results of the quenching test indicate that ·OH and 1O2 contributed to MB degradation. Comparative analysis shows that such excellent performances are primarily attributed to the stable acid oxide SiO2 in FG. In summary, this study successfully prepared a novel Fenton-like catalyst to solve the problems faced by the traditional Fenton reaction from various aspects, which can provide scientific references for subsequent relevant studies.

Biochar from waste green coffee extracted bioactive compounds as materials for ammonium adsorption

This study investigates the adsorption potential of AC-GCB biochar, obtained by pyrolyzing green coffee extracted bioactive compounds at 400 ºC, for ammonium removal from groundwater. The biochar's microstructure was characterized using scanning electron microscope (SEM), Fourier-transform infrared spectroscopy (FTIR), and Energy dispersive spectrometry (EDS) Mapping. Optimal adsorption conditions were observed at an initial pH range of 4 to 8, an initial NH4+ concentration of ≤ 25 mg.L-1, and a biochar dose of 10 g.L-1. The ammonium adsorption of AC-GCB was consistent with both Langmuir and Freundlich's adsorption theories (R2 &gt; 0.92). The AC-GCB biochar obtained the maximum adsorption capacity Qm was 14,48 mg.g-1, higher than the control BC-GCB biochar that pyrolysised without bioactive compound extracted with Qm was only 5.41 mg.g-1.

Porous hydrochar loaded nZVI as an efficient catalyst to activate persulfate for phenol degradation: Performance and mechanism

Persulfate (PS) activation by nano zerovalent iron (nZVI) is promising for water purification, which is restricted due to its easy agglomeration and oxidation. Herein, porous hydrochar loaded nZVI (nZVI@PHC) was successfully synthesized by one-step process. nZVI@PHC not only had excellent adsorption capacity (178.6 mg/g) and abundant functional groups, but also possessed highly dispersed nZVI for PS activation to produce reactive oxygen species. Impressively, 0.2 g/L of nZVI@PHC (PHC/nZVI = 5:3) and 0.4 g/L of PS could achieve 99.7 % of phenol removal within 10 min. Moreover, nZVI@PHC/PS system showed superior applicability among wide range of initial pH (3.0–9.0) and temperatures (25–55 °C). Phenol removal mechanisms were elaborated by dissolved iron ions, scavenging experiments, and electronic paramagnetic spectrometer. As a result, both non-free radical pathway mediated by O21 and free radical pathway (SO4•−, HO•, and O2•−) participated in phenol degradation. Additionally, nZVI@PHC/PS system had favorable reusability and high tolerance to co-existing substance and different water bodies. This study provides a promising strategy to tailor highly active nZVI for PS activation to organic contaminants degradation.

Growth kinetics and patulin production by Penicillium setosum in pineapple juice under different temperatures and initial pH values

Penicillium setosum, a member of the Penicillium section Lanata-divaricata, is known for its ability to produce high levels of patulin. However, there is a notable lack of information regarding the influence of environmental factors on the growth and patulin production in fruit juice of this species. In this study, we investigated the impacts of temperature (25, 30, 35, or 40 °C), initial pH value (3, 5, or 7), and incubation time (2, 4, or 6 days) on the growth and patulin production in pineapple juice of the selected P. setosum strain HR9-5. The modified Gompertz model was applied to estimate the maximum growth rate and lag time prior to growth. This strain had the highest growth rate with the shortest lag time within the temperature range 30–35 °C, with an initial pH range of 3–5. Furthermore, it had the greatest biomass dry weight and patulin production at 35 °C with an initial pH of 3, and at 25 °C with an initial pH of 7, respectively. The growth rate and lag time prior to growth of P. setosum HR9-5 were significantly influenced by the initial pH, whereas the biomass dry weight was strongly affected by temperature and incubation time. Additionally, all factors and their interactions had a significant impact on patulin production. This study provided the first report on the effect of environmental factors on growth and patulin production by P. setosum in pineapple juice. These findings can contribute to formulating effective prevention strategies to control the growth of P. setosum and subsequent patulin production in pineapple and other fruit juices.

Microbial activity of lactic acid bacteria and hydrogen producers mediated by pH and total solids during the consolidated bioprocessing of agave bagasse

Lactic acid bacteria (LAB) coexist with Clostridium spp. in hydrogen production processes from complex substrates; however, the role of LAB is still unclear. This study analyzed the fermentation products in a wide range of initial pH (pHi, 5.5–6.9) and total solids (TS%, 8–22%) to determine the activity of these two microbial groups over time (from 24 to 120 h). Agave bagasse served as the feedstock for hydrogen production via consolidated bioprocess (CBP), while the inoculum source was the indigenous mature microbiota. In the early stage of the CBP, hydrogen production from lactic acid occurred only at pHi ≥ 6.0 (ρ = 0.0004) with no effect of TS%; lactic acid accumulated below this pHi value. In this stage, lactic acid production positively correlated with a first cluster of LAB represented by Paucilactobacillus (r = 0.64) and Bacillus (r = 0.81). After 72 h, hydrogen production positively correlated with a second group of LAB led by Enterococcus (r = 0.71) together with the hydrogen producer Clostridium sensu stricto 1 (r = 0.8) and the acetogen Syntrophococcus (r = 0.52) with the influence of TS% (ρ < 0.0001). A further experiment showed that buffering the pH to 6.5 increased and lengthened the lactic acid production, doubling the hydrogen production from 20 to 41 mL H2/gTSadded. This study confirmed the prevalence of distinct groups of LAB over time, whose microbial activity promoted different routes of hydrogen production.

Mechanistic investigation of the electricity and gallic acid synergistically accelerated Fe(III)/Fe(II) cycle for the degradation of carbamazepine

This study investigated the application of a natural plant polyphenol, gallic acid (GA) to form complex with iron to promote the redox cycle of Fe(III)/Fe(II) under neutral initial pH conditions in the electrochemical (EC) system for activation of peroxymonosulfate (PMS) to efficiently degrade carbamazepine (CBZ). Results demonstrated that the synergistic effects of GA and EC significantly improved the removal efficiency, and the EC/GA/Fe(III)/PMS system effectively removed 100% of CBZ within a wide initial pH range of 3.0–7.0. The optimum stoichiometric ratio of GA to Fe(III) was found as 2:1. Investigations including quenching experiment, chemical probe analysis, and electron paramagnetic resonance (EPR) analysis were conducted to identify the primary reaction radicals as •OH, SO4•−, along with the 1O2 and Fe(IV). In the EC/GA/Fe(III)/PMS system, the synergistic effect of GA and electrochemistry led to a remarkable enhancement in the generation of •OH. Furthermore, the complexation reduction mechanism of GA and Fe(III) was proposed based on experimental and instrumental analyses, which demonstrated that the semi-quinone products of GA were the main substances promoting the Fe(III)/Fe(II) cycle. Mass spectrometry results showed that CBZ generated 27 byproducts during degradation, with formic acid as the main product of GA. The degradation efficiency of the EC/GA/Fe(III)/PMS system remained stable and excellent, exhibiting remarkable performance in the presence of various inorganic anions, including Cl− and NO3−, as well as naturally occurring organic compounds such as fulvic acid (FA). Overall results indicated that the EC/GA/Fe(III)/PMS system can be applied to effectively treat practical wastewater treatment without requirement of pH adjustment.