Cascaded nanozyme-based Fe3O4-GOx@ZIF-8/Ag Janus nanomotors with pH-responsive for photo-Fenton degradation of tetracycline hydrochloride.

Nano zero-valent iron (nZVI) has been considered as a promising material for groundwater remediation in the past few decades. The size distribution of nZVI is one of the main factors that influences its transport capability and remediation capacity. However, studies on the size distribution of nZVI under different environmental conditions are still limited. In this study, the influence of the pH (pH = 5, 7, 9) and ionic strength (IS = 0, 15, 30, 45 mM) on the size distribution of nZVI are investigated. The dynamic light scattering (DLS) method is used to study the variation of the size distribution of nZVI aggregate with time, and batch tests are performed to evaluate the efficiency of phosphate removal. Meanwhile, the phosphate removal capacity of nZVI with different size distribution was examined. Experimental results show that under low IS and high pH conditions, nZVI aggregate exhibited a stable, narrow and one-peak size distribution. By contrast, under high IS and low pH conditions, nZVI exhibited a wide and complicated size distribution with multiple peak values. This different pattern in size distribution was further explained by the Derjaguin–Landau–Verwey–Overbeek (DLVO) theory. The phosphate removal rate of nZVI under acidic and neutral conditions is higher than 98% but is only 68% under alkaline conditions. The phosphate removal capacity is insensitive to the variation of IS since the removal rate is higher than 97% for different IS conditions. Favorable environmental conditions for colloidal stability and removal capacity of nZVI can be different, which needs comprehensive consideration in the application.

The degradation of colorless tetracycline hydrochloride (TCH), a widely used antibiotic, is a significant environmental concern due to its persistence in aquatic systems. The zinc sulfide (ZnS) nanoparticle fabricated melamine-formaldehyde polymer (MFP)-based nanocomposite (ZnS-MFP) was prepared via a hydrothermal polymerization method, followed by surface modification through a simple precipitation route. The degradation of TCH through photocatalysis adheres to pseudo-first-order kinetics with a significantly faster rate under natural sunlight than under artificial bulb light. It is observed that a maximum 90% of 100 mg L-1 TCH is degraded within 120 min in the presence of ZnS-MFP, with more than two times higher degradation efficiency than under artificial bulb light. The comparative 1H NMR and UV-vis spectroscopic analysis of the TCH molecule and degraded products confirmed the degradation of TCH in the presence of the catalyst. Moreover, high-resolution mass spectrometry (HR-MS) was used to identify the intermediates that were formed during degradation. Radical scavenging experiments revealed the significant involvement of holes (h+), which further produce hydroxyl radicals (•OH) during photodegradation and are responsible for the degradation of TCH molecules. The efficacy of ZnS-MFP was further validated in real wastewater samples, where significant TCH removal was observed. Additionally, the composite retained considerable activity over five photocatalytic cycles. These results establish ZnS-MFP as a promising, recyclable photocatalyst for the sunlight-driven treatment of antibiotic-contaminated water.

The proper growth and development of tea plants requires moderately acidic soils and relatively low calcium levels, and excessive calcium at high pH can damage tea plant roots. To reveal the effects of calcium on the responses of tea plant to three pH levels (3.5, 5.0 and 6.5), a repeated test of two factors was designed. Root growth and elemental analysis indicated that excessive calcium improved the growth of tea roots at low pH conditions, whereas it did not harm the growth of tea roots under normal and high pH conditions, especially at pH6.5. Excessive calcium antagonized the absorption and utilization of magnesium by tea plants. Gas chromatography-mass spectrometry results showed that the addition of Ca2+ resulted in the primary metabolism in roots being more active at a low pH level. By contrast, it had obvious adverse effects on the accumulation of root metabolites with high calcium treatment at normal or high pH. Differential metabolites identified using ultra-performance liquid chromatography quadrupole time of flight mass spectrometry indicated that flavonoids demonstrated the largest number of changes, and their biosynthesis was partially enriched with excessive calcium at low and high pH conditions, whereas it was down-regulated under normal pH conditions. Kaempferol 3-(2'-rhamnosyl-6'-acetylgalactoside) 7-rhamnoside, quercetin 3-(6'-sinapoylsophorotrioside) and delphinidin 3-(3'-p-coumaroylglucoside) showed the greatest increase. The results of gene expression related to root growth and calcium regulation were consistent with root growth and root metabolism. The overall results demonstrated that high Ca concentrations further aggravate the detrimental effects of high pH to tea roots. However, it is interesting that excessive calcium reduced the harm of a low pH on tea root growth to some extent. © 2021 Society of Chemical Industry.

Osmoregulation and systemic acid-base balance in decapod crustaceans are largely controlled by a set of transport-related enzymes including carbonic anhydrase (CA), Na + /K + -ATPase (NKA) and V-type- H + -ATPase (HAT). Variable pH levels and changes in osmotic pressure can have a significant impact on the physiology and behaviour of crustaceans. Therefore, it is crucial to understand the mechanisms via which an animal can maintain its internal pH balance and regulate the movement of ions into and out of its cells. Here, we examined expression patterns of the cytoplasmic (CAc) and membrane-associated form (CAg) of CA, NKA α subunit and HAT subunit a in gills of the freshwater crayfish Cherax quadricarinatus. Expression levels of the genes were measured at three pH levels, pH 6.2, 7.2 (control) and 8.2 over a 24 hour period. All genes showed significant differences in expression levels, either among pH treatments or over time. Expression levels of CAc were significantly increased at low pH and decreased at high pH conditions 24 h after transfer to these treatments. Expression increased in low pH after 12 h, and reached their maximum level by 24 h. The membrane-associated form CAg showed changes in expression levels more quickly than CAc. Expression increased for CAg at 6 h post transfer at both low and high pH conditions, but expression remained elevated only at low pH (6.2) at the end of the experiment. Expression of CqNKA significantly increased at 6 h after transfer to pH 6.2 and remained elevated up to 24 h. Expression for HAT and NKA showed similar patterns, where expression significantly increased 6 h post transfer to the low pH conditions and remained significantly elevated throughout the experiment. The only difference in expression between the two genes was that HAT expression decreased significantly 24 h post transfer to high pH conditions. Overall, our data suggest that CAc, CAg, NKA and HAT gene expression is induced at low pH conditions in freshwater crayfish. Further research should examine the physiological underpinnings of these changes in expression to better understand systemic acid/base balance in freshwater crayfish.

An electron transfer tuning strategy for the efficient degradation of tetracycline hydrochloride by Fe-N co-doped carbon materials activated with peroxymonosulfate

Tetracycline hydrochloride (TCH) degradation by cobalt modified silicate ore (CoSO) catalytic ozonation in aqueous solution was investigated. CoSO catalyst was synthesized by an impregnation method using Co(NO3)2 as the precursor and natural silicon ore (SO) as the support. The key catalyst preparation conditions (i.e., impregnation concentration, calcination temperature and time) were optimized. The activity and stability of CoSO catalyst and its catalytic ozonation mechanism for TCH degradation were studied. The results showed that Co3O4 was successfully coated on the silicon ore and the CoSO catalyst was highly efficient in catalytic ozonation for TCH degradation. The TCH removal by CoSO/O3 could reach 93.2%, while only 69.3% by SO/O3 and only 46.0% by O3 alone at 25 min. The reaction of TCH degradation followed pseudo-first order kinetics. TOC removal rate by CoSO/O3 was 2.0 times higher than that by SO/O3, and 3.5 times higher than that by O3 alone. The reaction conditions (TCH initial concentration, catalyst concentration, pH and temperature) for catalytic ozonation were systematically investigated. The possible mechanism for the CoSO catalytic ozonation process was proposed, where hydroxyl radical oxidation mainly accounted for the substantial TCH degradation. Furthermore, CoSO showed great durability and stability after seven reaction cycles.

Bryophytes growing on siliceous boulders were studied in two forests in east-central Sweden to investigate the influence of different overstorey tree species on bryophyte species composition. Granite boulders, 0.5–2.0 m across, lying below the crowns of Ulmus glabra, Fraxinus excelsior, Acer platanoides, Quercus robur, Betula pendula, and Picea abies were studied in mixed stands. The presence, abundance and sporophyte frequency of all bryophyte species were noted. Tree species was the factor explaining most of the variation in bryophyte species composition. Boulders below tree species with a high bark pH (Ulmus, Fraxinus and Acer) had a similar species composition, with many bryophytes present indicating high pH conditions such as Brachythecium populeum, Homomallium incurvatum and Pseudoleskeella nervosa. On boulders below Picea the bryophyte composition was very different, with species indicating low pH conditions such as Ptilidium pulcherrimum, Dicranum montanum and Platygyrium repens. Below Quercus and Betula the bryophyte composition was intermediate between these two groups, with species indicating both high and low pH conditions such as Brachythecium reflexum and Hedwigia ciliata. The amount of litter on the boulders was another important factor explaining much of the variation. Species like H. incurvatum and Orthotrichum urnigerum were more common on boulders with much litter, while P. pulcherrimum was more common on boulders without litter. The size of the boulder was also important for bryophyte species composition, primarily because of the larger number of species on large boulders. Trunk diameter, canopy cover and distance from the tree had little or no influence on the bryophytes. The conclusion is that throughfall chemistry and chemical composition of leaf litter are the two most important factors explaining bryophyte species composition on boulders in these forests.

A novel oil/brine surface complexation model: Capturing the dynamic nature of the interface using IFT

Heterogeneous Fenton-like degradation of tetracyclines using porous magnetic chitosan microspheres as an efficient catalyst compared with two preparation methods

Influence of humic acids on oil sand processing. Part II: Relationship between bitumen extraction, humic acids concentration and power draw measurements on oil sand slurries

Ocean warming and acidification can induce oxidative stress in marine species, resulting in cellular damage and apoptosis. However, the effects of pH and water temperature conditions on oxidative stress and apoptosis in disk abalone are poorly understood. This study investigated, for the first time, the effects of different water temperatures (15, 20, and 25 °C) and pH levels (7.5 and 8.1) on oxidative stress and apoptosis in disk abalone by estimating levels of H2O2, malondialdehyde (MDA), dismutase (SOD), catalase (CAT), and the apoptosis-related gene caspase-3. We also visually confirmed apoptotic effects of different water temperatures and pH levels via in situ hybridization and terminal deoxynucleotidyl transferase dUTP nick end labeling assays. The levels of H2O2, MDA, SOD, CAT, and caspase-3 increased under low/high water temperature and/or low pH conditions. Expression of the genes was high under high temperature and low pH conditions. Additionally, the apoptotic rate was high under high temperatures and low pH conditions. These results indicate that changes in water temperature and pH conditions individually and in combination trigger oxidative stress in abalone, which can induce cell death. Specifically, high temperatures induce apoptosis by increasing the expression of the apoptosis-related gene caspase-3.

An artificial organic-inorganic Z-scheme photocatalyst WO3@Cu@PDI supramolecular with excellent visible light absorption and photocatalytic activity

Heterogeneous catalytic oxidation of tetracycline hydrochloride based on persulfate activated by Fe3O4/MC composite

Tetracycline hydrochloride degradation by activation of peroxymonosulfate with lanthanum copper Ruddlesden-Popper perovskite oxide: Performance and mechanism

TiO2(P25) has been widely used to treat wastewater; however, the elimination of TiO2(P25) suspended in the treated water causes running costs and induces secondary pollution, which greatly restricts its practical applications. Consequently, several methods have been implemented to immobilize TiO2(P25) on various substrates. This work deals with the immobilization of TiO2(P25) in chitosan film by using the cross-linking method. The prepared catalyst was characterized using X-ray diffraction (XRD), Fourier transform infrared spectrometry (FTIR), UV-Vis diffuse reflectance spectra (DRS) and scanning electron microscopy (SEM), and its catalytic activity in tetracycline hydrochloride (TC) degradation under UV light was explored. XRD, FTIR, DRS and SEM characterization indicated that TiO2(P25) was successfully immobilized on chitosan film, the chemical structure of TiO2(P25) did not change after the immobilization and the TiO2(P25) was uniformly dispersed in the composite. Chitosan/TiO2(P25) was used for the removal of TC by photocatalysis under UV irradiation. The effects of operational parameters such as amount of TiO2(P25), agitation speed and the initial TC concentration were investigated. An 87% removal efficiency of TC was obtained with 0.12 g of TiO2(P25) and TC removal was significantly enhanced by the agitation of the solution. The TC removal efficiency decreased from 72 to 44% when TC concentration increased from 30 to 40 mg/L after 60 min reaction time, the photocatalytic reactions followed the pseudo-second-order kinetic.