Microplastics pollution in China water ecosystems: a review of the abundance, characteristics, fate, risk and removal.

Microplastics pollution has been a focus for researchers in recent years worldwide, for the large quantities of plastics in production and the resistance to degradation. China's microplastics pollution attracts much attention because of its long coastline, large population and rapid economic development. This review addresses the widespread microplastics pollution in China's water ecosystems through available research results from recent years and analyses the abundance, characteristics, fate and risk of microplastics. This paper also discusses the current treatment technology of microplastics. The conclusions show that estuaries are severely affected by microplastics pollution; the accumulation of microplastics and adsorption of contaminants by microplastics could also lead to serious risks besides ingestion; there are few technologies that can efficiently remove microplastics pollution in sewage treatment plants. Finally, this review suggests directions for future research trends.

Study on the mechanism of degradation of tetracycline hydrochloride by microwave-activated sodium persulfate.

Among the different antibiotics, tetracycline hydrochloride (TCH) is one of the most commonly used. In this study, the activated sodium persulfate (SPS) process induced by microwave (MW) energy was used to treat TCH. The effect of different operational parameters of MW/SPS-treated TCH, such as SPS concentration, TCH concentration, initial pH, and MW power, was investigated. The concentration changes of TCH were determined using a spectrophotometer. The results of radical scavenger experiments indicated that the sulfate radical (SO4 ·-) was stronger than the hydroxyl radical (·OH). On the basis of high performance liquid chromatography-mass spectrometry (HPLC-MS) analysis, a possible degradation pathway of TCH was proposed. This research indicates that the MW/SPS system is a promising prospect for the treatment of TCH.

Characteristics and kinetics simulation of controlled-release KMnO4 for phenol remediation.

Controlled-release KMnO4 (CRP) technology has been recently developed as an improved, highly efficient technique in wastewater treatment. In this study, batch-style experiments were conducted to evaluate this technology. The release characteristics of CRP in distilled water and the reaction between CRP and phenol were studied and fitted using MATLAB software. Results indicated that in distilled water, temperature (T) and pH value had a larger effect than dissolved oxygen (DO) concentration on the release characteristics of KMnO4, and this relationship can be accurately described by the following kinetic equation: logQ = log[1.141T(0.152)(pH)(-1.0536)(DO)(0.4674)] + [0.0048T(0.3756)(pH)(1.8854)(DO)(-0.0509)]logt. KMnO4 released from CRP can effectively degrade phenol-contaminated water with different concentrations. A simulated equation (r = -dCA/dt = -15.1705 CA(0.6840)CP(-0.1406)) characterizing phenol degradation was developed using MATLAB software. Comparison between the theoretical phenol removal rates deduced by the above two equations and the initial phenol concentration as well as the CRP dosage with the experimental data indicates that the differences between them were less than 20%. The results indicate phenol can be effectively removed by CRP and smaller dosage of KMnO4 was required compared with literature values. The models can provide guidance for CRP application in real polluted sites, which can lower the cost for site remediation.

Factors influencing hydroquinone degradation in aqueous solution using a modified microelectrolysis method.

The discharge of hydroquinone (HQ), an important chemical raw material, to natural waters poses different ecological threats to aquatic organisms. In this study, we investigated the removal performance of traditional and modified microelectrolysis methods in aqueous solutions. The traditional microelectrolysis packing was modified by adding manganese (Mn), zinc (Zn), and copper (Cu) powder as additives. The factors affecting the removal performance of HQ, such as catalytic metal type, mass fraction of additive, reaction time, and initial pH, were examined. The results showed that the Mn modified packing exhibited the best performance compared to Zn and Cu powder. The removal rate of HQ using Mn modified packing can reach 94% after 4 h. In addition, 9% of Mn packing has a higher removal rate than other mass fractions. The acidic solution pH shows a more favorable degradation than a neutral and alkaline solution. The intermediates of HQ degradation by modified microelectrolysis were identified and then the pathway of HQ degradation was proposed. Our result indicates that Mn as catalytic metal holds promising potential to enhance HQ removal in water using the microelectrolysis method.

Pressure-driven membrane filtration technology for terminal control of organic DBPs: A review.

Disinfection by-products (DBPs), a series of undesired secondary contaminants formed during the disinfection processes, deteriorate water quality, threaten human health and endanger ecological safety. Membrane-filtration technologies are commonly used in the advanced water treatment and have shown a promising performance for removing trace contaminants. In order to gain a clearer understanding of the behavior of DBPs in membrane-filtration processes, this work dedicated to: (1) comprehensively reviewed the retention efficiency of microfiltration (MF), ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO) for DBPs. (2) summarized the mechanisms involved size exclusion, electrostatic repulsion and adsorption in the membrane retention of DBPs. (3) In conjunction with principal component analysis, discussed the influence of various factors (such as the characteristics of membrane and DBPs, feed solution composition and operating conditions) on the removal efficiency. In general, the characteristics of the membranes (salt rejection, molecular weight cut-off, zeta potential, etc.) and DBPs (molecular size, electrical property, hydrophobicity, polarity, etc.) fundamentally determine the membrane-filtration performance on retaining DBPs, and the actual operating environmental factors (such as solute concentration, coexisting ions/NOMs, pH and transmembrane pressure) exert a positive/negative impact on performance to some extent. Current researches indicate that NF and RO can be effective in removing DBPs, and looking forward, we recommend that multiple factors should be taken into account that optimize the existed membrane-filtration technologies, rationalize the selection of membrane products, and develop novel membrane materials targeting the removal of DBPs.

Performance of high temperature phase-stable high entropy oxide (MgCuMnCoFe)O x in catalytic wet air oxidation of chloroquine phosphate.

With the continuous spread of COVID-19, the water pollution problems caused by the abuse of chloroquine phosphate (CQP) as an antiviral drug have attracted wide attention. The cubic Fm-3m spinel high entropy oxide (HEO)-(MgCuMnCoFe)O x was prepared by coprecipitation method as the catalytic wet air oxidation (CWAO) catalyst to treat CQP simulated wastewater. Through electron spin resonance (ESR) analysis, HEO will stimulate the production of superoxide radical (·O2 -) and hydroxyl radical (·OH) in the wet air oxidation (WAO) process, which accelerates the degradation and mineralization of CQP. Through response surface method (RSM) optimization, the optimal degradation conditions of CQP in CWAO were proposed: initial oxygen pressure of 15 bar, catalyst dosage of 1.4 g/L and temperature of 230 °C. The advantages of HEO in CWAO were analyzed by principal component analysis (PCA). The degradation mechanism of CQP in CWAO by (MgCuMnCoFe)O x were explored. This work provides a new idea for the rapid development of HEO in the field of environmental catalysis. Supplementary Information: The online version contains supplementary material available at 10.1007/s10853-022-07271-z.

Degradation of nitrobenzene in simulated wastewater by iron-carbon micro-electrolysis packing.

The reductive degradation of nitrobenzene (NB) by iron-carbon micro-electrolysis packing was investigated. The influence of initial NB concentration, pH value and packing amount on the removal rate of NB were studied. The results showed that the reaction with packing followed the pseudo-first-order reaction. The optimum pH was 3.0 for the degradation of NB in the tested pH ranges of 3-9 and the optimum packing amount was 40 g/200 ml. The flow-through column packed with packing was designed to remove NB from simulated wastewater for approximately 68 days. The removal rate was over 90% within initial periods. It could be seen that after running for 68 days, the packing still had good performance after the long-term column experiment. In addition, the changes of the packing surfaces morphologies and matters before, during and after the column experiment were analysed by scanning electron microscopy in conjunction with energy-dispersion spectroscopy (EDS).

Characteristics and distribution of microplastics in the surface water of the Songhua River in China.

This paper studied on the microplastics (MPs) pollution in the surface water of the Songhua River in China. MPs were detected in all sampling sites of the river, the abundance of MPs ranged from 1.09 to 15.97 items/L, and the average abundance was 5.72 ± 4.02 items/L. Human interference had a significant impact on the abundance of MPs, and abundance in the downstream were higher than those in the upstream in the urban area along the Songhua River. In this study, MPs with size <0.5 mm and size [0.5,1) mm were the main sizes; fiber and debris were the most common types; yellow was the dominant color. MPs in the Songhua River might have similar sources and degradation experiences, because the size, type, and color had no significant difference (P>0.05) in different sampling sections. PE, PET, and PS were the most common polymers of MPs, accounting for 33.55%, 29.68%, and 18.71%, respectively.

Luminescent cellulose-based porous binary metal-organic gels in an adsorption bed for effective adsorption and sensitive detection of chlortetracycline hydrochloride.

Three novel (Fe-Eu) JLUE-MOGs were successfully fabricated through a solvothermal method and employed to construct the double-effect system for antibiotics adsorption and detection. The characterizations highlighted the properties of ample active sites, large surface areas and hierarchical porous structures, which did contribute to superb and rapid chlortetracycline hydrochloride (CTC) adsorption by JLUE-MOGs. Besides, the effects of initial pH values, JLUE-MOG dosages and co-existing inorganic ions on the CTC adsorption could be explained by pore filling, π-π EDA interaction, electrostatic interaction, water affinity as well as hydrogen bonding. Moreover, the optimized condition was cross-explored by response surface methodology (RSM) with tiny differences compared to actual experiments. In addition, fluorescent JLUE-MOG-7 was implemented for sensitive recognition of CTC and reflecting adsorption processes. Furthermore, shaping JLUE-MOG-7@cellulose aerogels were fabricated as filter materials for applying into an adsorption bed. The breakthrough process was fitted well by Bohart-Adams model and Thomas model, along with recognizable fluorescence changes of immobilized adsorbents. This work develops efficient and luminescent powder-like JLUE-MOGs for antibiotics adsorptive enrichment and sensitive detection. More importantly, immobilized JLUE-MOG@cellulose aerogels, as promising and alternative adsorbents with real-time fluorescence changes, can be utilized for continuously pollutants removal in real wastewater treatment.

Evaluating the Quality of Reports About Randomized Controlled Trials of Acupuncture for Low Back Pain.

OBJECTIVE: This study aims to improve the reporting quality of randomized controlled trials (RCTs) by evaluating RCTs of acupuncture for low back pain (LBP) based on the CONSORT and STRICTA statements. METHODS: Literature from the Cochrane Library, Medline, Embase, Ovid, China National Knowledge Infrastructure (CNKI), WanFang database, and Chongqing Weipu (VIP) was systematically searched from 2010 to 2020. The general characteristics and the overall quality score (OQS) of the literature were evaluated by two investigators. The agreement between investigators was calculated using Cohen's kappa statistics. RESULTS: A total of 31 RCTs were extracted in the final analysis. Based on the CONSORT statement, the items "title and abstract", "background and objectives", "intervention", "outcomes", "statistical methods", "baseline data", "outcomes and estimation" and "interpretation" have a positive rate of greater than 80%. The items "implementation", "generalizability" and "protocol" have a positive rate of less than 30%. Based on the STRICTA statement, the items "style of acupuncture", "needle retention time", "number of treatment sessions", "frequency and duration of treatment" and "precise description of the control or comparator" have a positive rate of greater than 80%. The item "extent to which the treatment was varied" has a positive rate of less than 30%. The agreements among most items are determined to be moderate or good. CONCLUSION: The reporting quality of RCTs of acupuncture for LBP is moderate. Researchers should rigidly follow the CONSORT and STRICTA statements to enhance the quality of their studies.

Removal of chlortetracycline by nano- micro-electrolysis materials: Application and mechanism.

Nano micro-electrolysis materials (nMETs) have been used to degrade refractory pollutants in batch experiments. The reasonable formation mechanism of nMETs was given through DMXY digital biomicroscopy. Based on the kinetic data of Chlortetracycline (CTC) removal by nMETs in batch experiments, combined with the binomial distribution equation of CTC reduction by nano materials an experimental-scale fluidized bed (ESFB) was designed. The effects of CTC removal performance, pH and iron ion concentration were investigated. Under pure CTC solution environment, the experimental data showed that the average removal rates of CTC by nMET and nano micro-electrolysis material with loading copper (Cu-nMET) are 90.0% and 95.7% in ESFB, respectively. In the presence of nitrate, although the consumption of two kinds of nano-materials increased, their removal efficiencies of pollutants have 2.2%, 0.2% increase compared with the nitrate-free ESFB. At the same time, the CTC degradation pathway and the enhanced removal mechanism by Cu-nMET was proposed. Through microelectrolysis reaction, complexation reaction and the active substances produced, the intermediate products can be degraded completely to NH4+, CO2, H2O and so on. This study aims to provide a theoretical basis for the environmental application of nMETs.

One-Step Synthesis of Metal-Modified Nanomagnetic Materials and Their Application in the Removal of Chlortetracycline.

Magnetic nanomaterials are promising heterogeneous catalysts for environmental applications. According to X-ray diffraction, Brunauer-Emmett-Teller method, scanning electron microscopy, high-resolution transmission electron microscopy, and vibrating-sample magnetometer, a kind of copper-modified nanomagnetic material (Cu-nFe3O4) was successfully prepared by a one-step synthesis method. Among them, compared with the two-step synthesis method of Cu/Fe3O4 and Cu/nFe3O4, Cu-nFe3O4 has the best effect on chlortetracycline (CTC) removal. The batch study results indicate that the maximum removal of chlortetracycline is 99.0% at a dosage = 2.0 g L-1, copper loading = 0.8 mM, and C 0 = 100 mg L-1 at the optimum conditions within 90 min. The effects of humic acids (HA), NO3 -, Cl-, CO3 2-, and PO4 3- on the CTC removal by Cu-nFe3O4 are also investigated. Repeated experiments were performed on the prepared Cu-nFe3O4, indicating that Cu-nFe3O4 has good recyclability. The kinetics of the Cu-nFe3O4 removal of CTC was investigated, indicating that the reaction conformed to the double constant model and the reaction is mainly dominated by a chemical reaction with physical adsorption. Finally, the mechanism of the CTC removal by Cu-nFe3O4 in a heterogeneous environment was clarified. This study aims to provide an experimental basis for the environmental application of Cu-nFe3O4.

Removal of chloramphenicol in aqueous solutions by modified humic acid loaded with nanoscale zero-valent iron particles.

As a natural organic carbon skeleton, humic acid (HA) was loaded with nanoscale zero-valent iron (nZVI) Particles to remove chloramphenicol (CAP) from aqueous solution. The pore morphology and structure, the type, the distribution and valence state of element, and the class of functional groups on the surface of the material were shown by SEM/EDS, XPS, BET and FTIR. When the load ratio of nZVI on HA was 1:30, the iron content in the material was minimized, the specific gravity of the economic material-HA was increased, and the removal efficiency of CAP was 80.0% or higher. In addition, the mass ratio of nZVI on HA, the dosage of nZVI/HA-30, the initial pH and CAP concentration of the solution, these four general factors, played an important role in the efficiency and equilibrium time of the CAP removal. The removal efficiency of CAP by nZVI/HA-30 was 84.2% when the dosage was 1.0 g (100 mL)-1, the initial concentration of CAP was 30 mg L-1 and the pH was 3. The reaction pathway and removal mechanism of ZVI/HA-30 were studied by the concentration of total and ferrous iron ions in the solution, UV-Vis and MS. The CAP was continuously denitrified and dechlorinated, decomposed into easily degradable substances by nZVI particles supported on HA, which was consistent with the first-order kinetic model within 5 min. This newly synthesized material was economical and efficient, easy to store, effectively prevented agglomeration and passivation of nZVI, and had a good application prospect for removing contaminants from water.

High efficiency biotransformation of bisphenol A in a fluidized bed reactor using stabilized laccase in porous silica.

We developed a high efficiency bisphenol A (BPA) treating system in a fluidized bed reactor (FBR) using stabilized laccase (Lac) in mesoporous silica (SER/Lac). The SER/Lac, prepared by cross linking of each enzymes inside the porous silica using glutaraldehyde, presented improved stability than the free Lac over various pH and temperatures with shaking. When the SER/Lac was used for BPA biotransformation in a batch reaction, higher efficiency was achieved than the free or adsorbed Lac (ADS/Lac). Also, the SER/Lac presented better reusability compared to ADS/Lac, and it could be reused for three times without decrease of biotransformation efficiency, and half of it was remained after ten times use. Due to great stability and robustness property, SER/Lac was successfully applied for high efficiency and continuous BPA treatment in FBR with better performance than the batch reaction.

Multi-Functional Laccase Immobilized Hydrogel Microparticles for Efficient Removal of Bisphenol A.

Hghly stable, reusable, and multi-functional biocatalytic microparticles with Laccase (Lac) enzyme (Lac/particles) were synthesized for bisphenol A (BPA) removal from aqueous solution. The Lac/particles were prepared by encapsulating Lac enzymes into poly ethylene glycol (PEG) hydrogel via the UV assisted emulsion polymerization method followed by cross linking with glutaraldehyde (GA). The obtained Lac/particles were spherical and micron sized (137⁻535 µm), presenting high enzyme entrapment efficiency of 100%, high activity recovery of 18.9%, and great stability at various pHs (3⁻7) than the free Lac. The Lac/particles could adsorb the BPA into the catalytic particles in a short time, promoting contact between BPA and enzyme, and further enzymatically degrade them without the shaking process and independent surrounding buffer solution. The Lac/particles could be reused for another round BPA adsorption and biotranformation by maintaining over 90% of BPA removal efficiency after seven times reuse. The synergistic effects of adsorption and biocatalytical reaction of Lac/particles have significant values in high efficient and cost-effective BPA removal.

Study of catalytic ozonation for tetracycline hydrochloride degradation in water by silicate ore supported Co3O4.

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.

Heterogeneous catalytic ozonation of ciprofloxacin in aqueous solution using a manganese-modified silicate ore.

Manganese modified silicate ore (MnSO) prepared using an impregnation method was used as a heterogeneous ozonation catalyst, and the catalytic activity was evaluated by the degradation of ciprofloxacin (CIP). The results showed that the manganese oxide was successfully loaded onto natural silicate ore (SO). The degradation and mineralization efficiencies of CIP were considerably improved in the presence of MnSO. Under optimal conditions, the CIP removal process followed the pseudo-first-order reaction model well. The degradation rate constant of MnSO/O3 was 1.7 times and 3.3 times higher than those of SO/O3 and only O3, respectively. During the ozonation of the CIP aqueous solution in the presence of MnSO, the TOC removal rate reached 61.2% at 60 min, but was only 30.8% using ozonation alone. The addition of tert-butanol (TBA) significantly inhibited the degradation efficiency of CIP, which indicated that catalytic ozonation of MnSO followed a hydroxyl radical (·OH) reaction mechanism. Furthermore, MnSO showed great stability and durability over several reaction cycles.