How hetero-single-atom dispersion reconstructed electronic structure of carbon materials and regulated Fenton-like oxidation pathways.

Single-atom catalysts (SACs) have emerged as competitive candidates for Fenton-like oxidation of micro-pollutants in water. However, the impact of metal insertion on the intrinsic catalytic activity of carrier materials has been commonly overlooked, and the environmental risk due to metal leaching still requires attention. In contrast to previous reports, where metal sites were conventionally considered as catalytic centers, our study investigates, for the first time, the crucial catalytic role of the carbon carrier modulated through hetero-single-atom dispersion and the regulation of Fenton-like oxidation pathways. The inherent differences in electronic properties between Fe and Co can effectively trigger long-range electron rearrangement in the sp2-carbon-conjugated structure, creating more electron-rich regions for peroxymonosulfate (PMS) complexation and initiating the electron transfer process (ETP) for pollutant degradation, which imparts the synthesized catalyst (FeCo-NCB) with exceptional catalytic efficiency despite its relatively low metal content. Moreover, the FeCo-NCB/PMS system exhibits enduring decontamination efficiency in complex water matrices, satisfactory catalytic stability, and low metal leaching, signifying promising practical applications. More impressively, the spatial relationship between metal sites and electron density clouds is revealed to determine whether high-valent metal-oxo species (HVMO) are involved during the decomposition of surface complexes. Unlike single-type single-atom dispersion, where metal sites are situated within electron-rich regions, hetero-single-atom dispersion can cause the deviation of electron density clouds from the metal sites, thus hindering the in-situ oxidation of metal within the complexes and minimizing the contribution of HVMO. These findings provide new insights into the development of carbon-based SACs and advance the understanding of nonradical mechanisms underpinning Fenton-like treatments.

Depth and contaminant-shaped bacterial community structure and assembly at an aged chlorinated aliphatic hydrocarbon-contaminated site.

Chlorinated aliphatic hydrocarbons (CAHs) are potentially toxic substances that have been detected in various contaminated environments. Biological elimination is the main technique of detoxifying CAHs in the contaminated sites, but the soil bacterial community at CAH-contaminated sites have been little investigated. Here, high-throughput sequencing analysis of soil samples from different depths (to 6 m depth) at an aged CAH-contaminated site has been conducted to investigate the community composition, function, and assembly of soil bacteria. The alpha diversity of the bacterial community significantly increased with increasing depth and bacterial community also became more convergent with increasing depth. Organohalide-respiring bacteria (OHRB) is considered keystone taxa to reduce the environmental stress of CAHs by reductive dechlorinate CAHs into nontoxic products, increases the alpha diversity of bacterial community and improves the stability of bacterial co-occurrence network. The high concentration of CAHs in deep soil and the stable anaerobic environment make deterministic processes dominate bacterial community assembly, while the topsoil is dominated by dispersal limitation. In general, CAHs at contaminated sites have a great impact on bacterial community, but the CAHs metabolic community acclimated in deep soil can reduce the environmental stress of CAHs, which provides foundation for the monitored natural attenuation technology in CAHs-contaminated sites.

Interaction Between Halotolerant Phosphate-Solubilizing Bacteria (Providencia rettgeri Strain TPM23) and Rock Phosphate Improves Soil Biochemical Properties and Peanut Growth in Saline Soil.

Soil salinity has adverse effects on soil microbial activity and nutrient cycles and therefore limits crop growth and yield. Amendments with halotolerant phosphate-solubilizing bacteria (PSB) and rock phosphate (RP) may improve properties of saline soil. In this study, we investigated the effects of RP either alone or in combination with PSB (Providencia rettgeri strain TPM23) on peanut growth and soil quality in a saline soil. With the combined application of RP and PSB, plant length and biomass (roots and shoots) and uptake of phosphorus (P), nitrogen (N), and potassium (K) increased significantly. Soil Na+ and Cl- contents decreased in the PR alone or PR combined with PSB treatment groups. There were strongly synergistic effects of RP and PSB on soil quality, including a decrease in pH. The soil available N, P, and K contents were significantly affected by the PSB treatments. In addition, the alkaline phosphomonoesterases, urease, and dehydrogenase activities increased significantly compared with the untreated group; highest alkaline phosphomonoesterases activity was observed in the RP and PSB treatment groups. The composition of rhizosphere soil bacterial communities was determined using 454-pyrosequencing of the 16S rRNA gene. In the PR alone or PR combined with PSB treatment groups, the structure of the soil bacterial community improved with increasing richness and diversity. With PSB inoculation, the relative abundance of Acidobacteria, Chloroflexi, and Planctomycetes increased. The three phyla were also positively correlated with soil available N and root dry weight. These results suggested microbiological mechanisms by which the combined use of RP and PSB improved saline soil and promoted plant growth. Overall, the study indicates the combined use of RP and PSB can be an economical and sustainable strategy to increase plant growth in P-deficient and salt-affected soils.

A gold nanoparticle-based colorimetric mercury(II) biosensor using a DNA probe with phosphorothioate RNA modification and exonuclease III-assisted signal amplification.

Herein, we report a rapid and sensitive colorimetric detection of Hg2+ by designing a specific DNA probe with phosphorothioate RNA modification (PS-probe) for Hg2+ recognition and utilizing DNA-modified gold nanoparticles (DNA-AuNPs) as the transducer. The distance between two DNA-AuNPs is controlled by a linker DNA, providing the linker DNA-regulated aggregation or dispersion status of AuNPs in solution. Exonuclease III (Exo III) can trigger the recycled digestion of linker DNA strands, inhibiting the reformation of aggregated nanoparticles and hence leading to a color shift from purple to red. However, the Hg2+-induced cleavage of the PS-probe can efficiently prevent the digestion of linker DNA strands by Exo III and hence reassemble the modified AuNPs to form aggregates in purple color. Thus, a positive correlation between the linker DNA strands left and the addition of Hg2+ provides a quantitative basis for Hg2+ sensing. A linear range of A520/A700 versus Hg2+ concentration is achieved in the range 2-100 nM associated with a detection limit as low as 1.30 ± 0.04 nM. Moreover, the biosensor exhibits excellent selectivity for Hg2+. The strong selectivity behavior was confirmed by recoveries ranging from 96 to 114% in real water samples. Graphical abstractSchematic representation of sensing mechanism of Hg2+ using a DNA probe with phosphorothioate RNA modification (PS-probe) and Exo III-assisted signal amplification.

Erratum: Author Correction: Isolation and characterization of halotolerant phosphate-solubilizing microorganisms from saline soils.

[This corrects the article DOI: 10.1007/s13205-018-1485-7.].

Isolation and characterization of halotolerant phosphate-solubilizing microorganisms from saline soils.

Halotolerant phosphate-solubilizing microorganisms (PSMs) capable of producing plant-growth-promoting traits were grown on salt medium containing Ca3(PO4)2 or egg yolk. The number of colonies on plates with Ca3(PO4)2 was higher than that on plates with egg yolk. Further, a total of 42 PSM isolates were purified. The majority were Bacillus spp., while one Providencia rettgeri strain was confirmed, for the first time, as a PSM. All PSMs had a phosphate-solubilizing index (PSI) between 1.1 and 2.58 and a strong capacity for dissolving calcium phosphate between 2.25 and 442 mg·L-1. In contrast, these PSMs were less effective when dissolving aluminum phosphate, ferric phosphate and lecithin. Isolates were also tested for growth-promoting substances. The results showed that all isolates were able to secrete indole-3-acetic acid in amounts ranging from 2.7 to 31.8 mg·L-1 and exopolysaccharide within the range 74.3 and 225.7 mg·L-1. Only 12 siderophore-producing strains with siderophore units of 1.9-42.1% were detected. Among them, ten isolates with solubilization rates greater than 200 mg·L-1 and relatively high NaCl tolerance (1.5 M) were classified as candidate PSMs. Eight different organic acids with different contents were detected in the culture filtrates, and propionic and oxalic acids have been proposed as the main mechanisms for solubilization. The ten isolates have the potential for use as bioinoculants to protect plants in saline environments.

The characteristic evolution of soluble microbial product and its effects on membrane fouling during the development of sponge membrane bioreactor coupled with fiber bundle anoxic bio-filter for treating saline wastewater.

Membrane fouling mitigation was observed during the development of novel sponge membrane bioreactor coupled with fiber bundle anoxic bio-filter (AF-MBMBR). Soluble microbial product (SMP) was found to be positively correlated with membrane fouling. To further clarify the mechanism of fouling mitigation, the effects of bio-carriers (sponge and fiber bundles) on characteristics and fouling potential of SMP were investigated. Characterization of SMP implied that as a consequence of employing bio-carriers, tyrosine and tryptophan in SMP significantly decreased, instead relative proportions of humic and fulvic acids increased. Meanwhile, batch filtration tests demonstrated that fouling potential of SMP was significantly alleviated, flux decline caused by filtrating SMP decreased from 84.5% to 60.1%. Further analysis on foulants and filtrate revealed that proteins performed high adhesion propensity on membrane while humic and fulvic acids mainly can pass through the membrane; this finding could well explain the mitigation of SMP fouling potential induced by bio-carriers.

Effective removal of ammonia nitrogen from waste seawater using crystal seed enhanced struvite precipitation technology with response surface methodology for process optimization.

Traditional biological treatment was not effective for removing nitrogen from saline wastewater due to the inhibition of high salinity on biomass activity. In this context, a method of removing ammonia nitrogen from waste seawater was proposed by struvite precipitation which was enhanced by seeding technique. The abundant magnesium contained in waste seawater was used as the key component of struvite crystallization without additional magnesium. The effects of pH and P:N molar ratio on ammonia nitrogen removal efficiency were studied. The results showed that optimum pH value was in range of 8.5-10 and the P:N molar ratio should be controlled within 2:1-3:1. XRD and SEM-EDS analyses of the precipitates proved that Ca2+ and excess Mg2+ contained in waste seawater inhibited the struvite crystallization by competing PO43- to form by-products. Then, seeding technique for enhancing the struvite crystallization was investigated, and the results indicated that using preformed struvite as crystal seed significantly improved the ammonia nitrogen removal efficiency, especially when initial ammonia nitrogen concentration was relatively low. Moreover, response surface optimization experiment following a Box-Behnken design was conducted. A response surface model was established, based on which optimum process conditions were determined and interactions between various factors were clarified. At last, economic evaluation demonstrated this proposed method was economic feasible.

Membrane fouling mitigation in a moving bed membrane bioreactor combined with anoxic biofilter for treatment of saline wastewater from mariculture.

Membrane fouling mitigation in a novel AF-MBMBR system (moving bed membrane bioreactor (10L) coupled with anoxic biofilter (4L)) under high salinity condition (35‰) was systematically investigated. Pre-positioned AF served as a pretreatment induced significant decrease of suspended biomass by 85% and dissolved organic matters by 51.7% in subsequent MBR, which resulted in a reduction of cake layer formation. Based on this, sponge bio-carriers in MBMBR further alleviated the fouling propensity by modifying extracellular polymeric substances (EPS) properties. The protein component in EPS decreased from 181.4 to 116.5mg/g MLSS, with a decline of protein/carbohydrate ratio from 4.6 to 3.4. In particular, elimination of hydrophobic groups like aromatic protein-like substance in EPS was detected. These caused the less biomass deposition on membrane surface, thereby alleviating membrane fouling. In summary, mitigation of membrane fouling in AF-MBMBR should be attributed to contributions from both pre-positioned AF and sponge bio-carriers.

[Qualitative-Quantitative Analysis of Rice Bran Oil Adulteration Based on Laser Near Infrared Spectroscopy].

The purpose of this study is mainly to have qualitative-quantitative analysis on the adulteration in rice bran oil by near-infrared spectroscopy analytical technology combined with chemo metrics methods. The author configured 189 adulterated oil samples according to the different mass ratios by selecting rice bran oil as base oil and choosing soybean oil, corn oil, colza oil, and waste oil of catering industry as adulterated oil. Then, the spectral data of samples was collected by using near-infrared spectrometer, and it was pre-processed through the following methods, including without processing, Multiplicative Scatter Correction(MSC), Orthogonal Signal Correction(OSC), Standard Normal Variate and Standard Normal Variate transformation DeTrending(SNV_DT). Furthermore, this article extracted characteristic wavelengths of the spectral datum from the pre-processed date by Successive Projections Algorithm(SPA), established qualitatively classified calibration methods of adulterated oil through classification method of Support Vector Machine(SVM), optimized model parameters(C, g) by Mesh Search Algorithm and determined the optimal process condition. In extracting characteristic wavelengths of the spectral datum from pretreatment by Backward interval Partial Least Squares(BiPLS) and SPA, quantitatively classified calibration models of adulterated oil through Partial Least Squares(PLS) and Support Vector Machine Regression(SVR) was established respectively. In the end, the author optimized the combination of model parameters(C, g) by Mesh Search Algorithm and determined the optimal parameter model. According to the analysis, the accuracy of prediction set and calibration set for SVC model reached 95% and 100% respectively. Compared with the prediction of the adulteration oil content of rice bran oil which was established by the PLS model, the SVR model is the better one, although both of them could implement the content prediction. Furthermore, the correlation coefficient R is above 0.99 and the Root Mean Square Error (MSE) is below 5.55 x 10(-4). The results show that the near-infrared spectroscopy technology is effective in qualitative-quantitative analysis on the adulteration of rice bran oil. And the method is applicable to analyze adulteration in other oils.

[Low carbon number fatty acid content prediction based on near-infrared spectroscopy].

The rapid prediction of the low-carbon fatty acids (C < or = 14) content in grease samples was achieved by a mathematical model established by near infrared spectroscopy combined with support vector machine regression (SVR). In the present project, near-infrared spectrometer SupNIR-5700 was used to collect near-infrared spectra of 58 samples; partial least square (PLS) was applied to remove the strange samples, and principal component analysis (PCA) was conducted on the measurements; radial basis function (RBF) kernel function was selected to establish a regression model supporting vector machine, and then detailed analysis and discussions were conducted concerning their spectral preprocessing and parameters optimization methods. Experimental results showed that by applying particle swarm optimization (PSO) the model demonstrated improved performance, stronger generalization ability, better prediction accuracy and robustness. In the second pretreatment method after PSO, when the optimization parameters are: C = 2.085, gamma = 22.20, the prediction set and calibration set correlation coefficient (gamma) reached 0.998 0 and 0.925 8, respectively; and root mean square errors (MSE) were 0.000 4 and 0.014 3, respectively. Research results proved that the method based on near infrared spectroscopy and PSO-SVR for accurate and fast prediction of the low-carbon fatty acid content in vegetable oil is feasible.

[Study of ammonium-nitrogen removal in suspended carrier biofilm reactor].

In order to improve the ammonium-nitrogen (NH4+ -N) biodegradation rate, a suspended carrier was exploited and biofilm was cultivated in three different phases in a sequencing batch reactor (SBR). A flimsy honeycomb-shape biofilm was formed between the endocentric columns on the suspended carrier,which increased the cling amount of nitrobacteria and provided the better condition for nitrobacteria. The bioreactor was operated at the temperature ranges of 24-29 degrees C and pH between 7.8 and 8.2. When the influent COD and NH4+-N concentrations varied in a range of 140-300 mg x L(-1) and 40- 78 mg x L(-1) , respectively, under 90 min aeration, the effluent concentrations were less than 40 mg x L(-1) and 2 mg x L(-1) , respectively. Under 180 min aeration, the influent COD concentration varied from 150 to 350 mg x L(-1) and NH4+-N concentration in the range of 80 - 130 mg x L (-1), the effluent concentration below 45 mg x L(-1) and 3.5 mg x L(-1), respectively. The results indicated that the ammonium-nitrogen biodegradation rate is much greater than that of the conventional activated sludge process. The active fraction of the biofilm is affected by the concentration of substrates in the bulk liquid, the actual metabolic rates within the biofilm, and the thickness of the biofilm. The suspended carrier configuration used in this investigation and the method of cultivating biofilm are beneficial for decreasing biofilm thickness, for increasing the activated biomass of nitrobacteria, and for increasing surface area of the biofilm relative to the volume of the reactors, which insulting in a high rate of nitrification.

[Treating high strength antibiotic wastewater by micro-aerobic hydrolysis and acidification process].

The effect of micro-aerobic hydrolysis and acidification to high strength antibiotic wastewater treatment is studied. The results demonstrate that micro oxygen enhanced the physiological metabolizability of facultative hydrolytic and acidogenic bacteria, and aerating stirring improved the hydraulic condition. Degree of acidification (AD) and volatile fatty acid (VFA) in the effluent reached 58.64% and 4825 mg/L with the shortest HRT 10 h and the maximal OLR 20 kg/(m3 x d), respectively. Wastewater biodegradability was improved greatly and rising BOD5/COD was about 17%, which offered good substrate for post aerobic treatment. The effluent quality was relative stable with the fluctuant influent, and COD and SS were 7000-8000 mg/L and 150-300 mg/L, respectively, while the removal efficiencies of COD and SS were 15%-30% and 90%-95%. The changement of VFA lagged behind that of AD in the effluent, and AD would represent the effect of hydrolysis and acidification process more properly. The sludge bed in the bottom of the reactor was the main reaction field for VFA production, and the height of the reactor for stable VFA production increased with the increase of OLR. The filling field mainly aimed to entrap SS in the effluent and benefited little to VFA production. Sludge in the reactor was mainly little sludge particles with the size of 0.5-1.0 mm and flocculent sludge.