Poly(3-hydroxybutyrate) (PHB) is a biodegradable, bio-based polymer with significant application potential. The development of efficient chemical recycling strategies for PHB is essential for advancing a circular bioeconomy. However, existing methods for depolymerizing PHB into crotonic acid (CA), a valuable platform chemical, often rely on harsh reaction conditions, suffer from low selectivity, or require high energy input. Herein, we report a novel catalytic system based on sodium crotonate (NaCA) and stearyl alcohol (StOH), which enables high-yield conversion of PHB to CA under mild conditions (150 degrees C, 3 Torr). Owing to the synergistic action of NaCA and StOH, rapid depolymerization of PHB is achieved, affording a CA yield of 80.8% with 99.6% purity. Further enhancement using the NaCA/StO-CA synergistic system increases the CA yield to 96.1% with 99.4% purity. Mechanistic investigations, supported by NMR, FTIR, and density functional theory (DFT) calculations, reveal that StOH serves dual roles: it acts as a transesterification agent to reduce the molecular weight of PHB and as a high-boiling solvent to promote continuous removal of CA. Meanwhile, NaCA catalyzes C-O bond cleavage and double bond formation, enabling sustained CA production. The catalytic system was successfully applied to post-consumer PHB waste and PHB in plastic blends, achieving CA yields exceeding 94%. Moreover, a sequential batch recycling strategy was developed for PLA/PHB mixed plastics, in which PLA is first depolymerized to lactide, followed by the selective conversion of PHB to CA, thereby avoiding cross-contamination. The catalytic system exhibits excellent recyclability, maintaining high efficiency over multiple cycles, and thus offers a promising and sustainable approach for closed-loop recycling of bio-based polyesters.

Microplastics (MPs) are pervasive vectors in soil, but their quantitative role in additive transport and transformation remains unclear. This study examines the release, transport, and transformation of TBBPA and BDE-209 from polystyrene MPs. Vertical MP migration forms an observed secondary emission front under hotspot-like conditions at 5-7 cm depth, which influences the spatial distribution of the strongly hydrophobic BDE-209, leading to a concentration plateau at this interface. We developed a mechanistic model based on Fick's second law, parameterized with the first-order release rate constant (krelease), colloidal diffusion coefficient (Dsc), and biodegradation rate constant (k) under our experimental conditions. This model successfully captured the distinct migration patterns of the two additives, supported by machine learning (XGB) validation within the scope. Depth and time were the primary experimental controls, while EC and pH were the key soil properties influencing additive fate. Beyond transport, MP-driven soil changes promoted extensive additive transformation into 59 byproducts. The majority of BDE-209 transformation products were predicted to exhibit significant oral toxicity and high persistence in the environment. Our findings propose a novel, comprehensive framework that advances beyond existing approaches by linking MP-mediated transport to hazardous product formation, providing essential insights for the risk assessment of plastic-contaminated soils.

Non-metallic photocatalysts represent a promising avenue for the green remediation of organic wastewater. In this study, O-doped g-C3N4 (OCN) was synthesized using a one-step calcination strategy and synergistically coupled with periodate (PI) under visible light to develop a novel non-radical OCN/PI/Vis photo-Fenton-like system for the efficient degradation of Acid Orange 7 (AO7). Systematic characterization techniques, including transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS) and photoluminescence (PL), along with density functional theory (DFT) calculations, were employed to elucidate the catalyst properties, oxidant adsorption, and reaction mechanisms. The OCN/PI/Vis system achieved a 93.9% removal of AO7 within 20 min and exhibited a reaction rate constant (k =1.48 & times; 10- 1 min- 1) that was 4.4 times higher than that of the OCN/ Vis system, significantly outperforming traditional oxidant-coupled systems (PMS/PDS/H2O2). DFT calculations indicated that OCN exhibited an ultra-strong PI adsorption affinity (Eads = -2.541 eV), leading to the elongation of the PI I-O bond and facilitating its activation. Quenching and electron paramagnetic resonance (EPR) experiments confirmed that singlet oxygen (1O2) is the dominant reactive species. Notably, the system demonstrated excellent anti-interference performance. This work establishes a high-efficiency, metal-free photo-Fentonlike system for dye wastewater treatment and provides a theoretical and experimental foundation for the rational design of g-C3N4-based PI activators, thereby opening new avenues for PI-based advanced oxidation processes (AOPs) in environmental remediation.

Single-atom catalysts (SACs) are an effective strategy for maximizing the efficiency and reducing the costs of advanced oxidation processes (AOPs). Herein, a novel SAC with Fe-N3C sites was synthesized for emerging periodate (PI)-based AOPs. The optimized catalyst demonstrates superior performance, achieving 100 % removal of diclofenac (DCF) within 20 min via predominant singlet oxygen (1O2). Compared to the Fe-N4 configuration, the Fe-N3C site enables an unprecedented 152.9-fold increase in the pollutant degradation rate, surpassing most reported catalysts. Density functional theory (DFT) calculations reveal that the Fe-N3C sites reduce the oxophilicity of the Fe centers, thereby lowering the energy barrier for 1O2 desorption and promoting its preferential generation. The DCF degradation pathway was further elucidated by Fukui constants. Furthermore, the Fe-N3C/ PI system exhibits excellent stability with negligible leaching of Fe ions and strong resistance to common wastewater components. This work provides new insights into the design of efficient SACs and the construction of PI-based AOPs for water decontamination.

Chemical recycling of polyester waste presents a promising strategy for achieving a sustainable circular economy. However, the development of efficient, low-cost recycling methods that minimize energy consumption and carbon emissions remains challenging. Here, we report an approach for depolymerization polyester waste to bis (hydroxyethyl)terephthalate (BHET) using a reconstructed metal–organic framework ( r -Zn–MOF74–NT) catalyst under mild conditions. The r -Zn–MOF74–NT exhibited a space-time yield of 1035.8 g BHET g cat −1  h −1 at 190 °C. Importantly, this is an order of magnitude higher than that reported for similar MOF-based catalysts. In situ spectroscopy combined with theoretical calculations revealed that the depolymerization pathway involves the activation of oxygen and ethylene glycol adsorbed on r -Zn–MOF74–NT, forming nucleophilic intermediates. These intermediates then facilitate the cleavage of the polyester C─O bond through nucleophilic attack, thereby gradually generating the BHET product. Sustainability evaluation results validated the circular economy feasibility of the recycling approach, with a minimum sales price (MSP) of 498 $/ton, much lower than the MSP of the traditional petroleum-based production route (1000 $/ton). The approach also achieved a 61% reduction in energy use and a 52% decrease in greenhouse gas emissions. This work provides a sustainable solution for managing polyester waste accumulation.

The chemical recycling of waste poly(L-lactic acid) (PLLA) into its monomer, L-lactide, offers a promising strategy for establishing a circular economy for PLLA-based polymers. However, conventional approaches typically require high reaction temperatures and suffer from significant side reactions, thereby hindering the efficient recycling of waste PLLA. In this study, we present a low-temperature, continuous depolymerization process for waste PLLA, catalyzed by stearyl alcohol (StOH) and stannous octanoate (Sn(Oct)2) at a mild temperature of 165 degrees C. This system achieves an L-lactide yield of 99.31 % and purity of 98.02 % (ee = 99.73 %). Characterization of the reaction mechanism, supported by density functional theory (DFT) calculations, reveals that StOH displaces the octanoate ligands in Sn(Oct)2 to form tin(II) octadecyl alkoxide. This nucleophilic species interacts with the carbonyl groups of PLLA, promoting chain scission via ligand-assisted attack. The mechanism reduces the energy barrier for backbiting reactions, thereby enhancing the rate of L-lactide formation. This method exhibits strong practical viability, achieving a 97 % yield from real-world PLLA waste and selectively degrading PLLA in mixed plastic streams to enable efficient separation. Furthermore, a simplified continuous processing system was developed, demonstrating stable and sustained PLLA degradation. This work provides an innovative and scalable strategy for sustainable PLLA chemical recycling under mild conditions.

Metal-doped g-C3N4 materials have been extensively investigated and utilized as catalysts in the domain of wastewater treatment. In this study, additional O was introduced in Mn-doped g-C3N4 (MCN) to synthesize Mn/O co-doped material (MOCN), and a new non-radical oxidation system of periodate (PI) activation with MOCN was established for degradation of pollutants. The results indicated that additional O doping can enhance the cata-lytic performance of MOCN. This was primarily demonstrated by the 3.5-fold increase in the degradation rate (k) of sulfadiazine (SDZ) by MOCN/PI system compared to MCN/PI one. Simultaneously, density functional theory (DFT) calculations have revealed that MOCN material exhibit a higher affinity for adsorbing PI (adsorption energy Eads =-4.992 eV), resulting in an elongation of the I-O bond length (lI-O = 1.874 angstrom) and facilitating bond cleavage of PI to generate reactive active species (ROS). The reaction process was confirmed to be primarily driven by non-radical singlet oxygen (1O2), as demonstrated by electron paramagnetic resonance (EPR) and free radical quenching experiments. In addition, possible degradation pathways of SDZ were proposed based on the identified intermediate products and the calculated Fukui constants. The MOCN/PI catalytic system was highly efficient and environmentally friendly, with great potential for development in sewage treatment.

Plastic films typically receive the addition of plastic additives, such as 2-(2 H-benzotriazol-2-yl)- 4,6-di-tertpentylphenol (UV-328), to improve their service life. However, plastic films can release some additives into the environment due to their non-chemical binding with plastics, causing some adverse effects on environmental health. This study focused on the transfer of the typical polyethylene plastic additive UV-328 from plastic films to soil, as well as the migration and transformation process in soil. The results showed that increasing simulated rainfall would reduce the concentration of UV-328 released into soil. When the soil depth exceeded 7 cm, the residual concentration of UV-328 in the soil was significantly reduced, which may be attributed to high logKow and logKoc values of UV-328. The pH value and excess organic matter of soil were negatively affecting the migration of UV-328 from plastic films to soil, while fine soil particle size facilitated the soil sorption. The migration of UV-328 in soil was negatively correlated with the soil adsorption capacity. About thirteen transformation products of UV-328 on the surface of plastic mulches and topsoil were identified. Three transformation pathways were proposed, which mainly involved hydrolysis, aliphatic chain cleavage and hydroxylation. The migration of phototransformation products in soil was also observed. This study is of great significance to explore the migration and transformation of plastic film additives in the environment.

The agricultural greenhouse plastics have resulted in significant greenhouse gas (GHG) emissions and primary energy demand (PED), hindering the achievement of agricultural plastics sustainability and energy conservation and emission reduction policies. Starting from three sustainability measures, this paper quantified the impacts of raw material selection, management measures, and green energy use on GHG emissions and PED for 6 petroleum-based plastics and 17 biobased plastics used in plastic greenhouse systems and analyzed their uncertainties using Monte Carlo simulation. The results demonstrated that any of the three measures could effectively reduce the environmental impact of agricultural greenhouse plastics, but the combination of the three measures changed the optimal choice of waste plastic management measures. Specifically, waste biobased plastics with negative GHG emissions in the production process could be treated in landfills to achieve optimal carbon reduction effects. Moreover, the utilization of low-carbon electricity significantly reduces the environmental benefits associated with incineration power generation.

Industrial production and human activities have resulted in significant oil pollution issues. The utilization of electrospinning nanofibrous membranes for the separation of oil-water mixtures and emulsions has been widely adopted. However, these membranes face challenges due to their low flux and membrane fouling. In this study, we conducted a chemical modification on a novel cross-electrospinning material, amidoximated polyacrylonitrile-regenerated cellulose acetate (AOPAN-RC), through deacetylation and ammoximation conversions. This modification led to the development of a superhydrophilic and antifouling composite membrane with excellent properties. The modified composite nanofibrous membranes exhibited remarkable hydrophilicity and strong underwater superoleophobicity, indicated by an underwater oil contact angle of 157.5 degrees +/- 1.24 degrees, as well as a high water flux value exceeding 6000 LMH. The AOPAN-RC membranes demonstrated exceptional performance in separating highly emulsified surfactant -free and surfactant -stabilized oil -in -water emulsions, achieving separation efficiencies of over 94 +/- 0.8 % and 90 +/- 1.1 %, respectively. Furthermore, we discovered that higher water flux and improved emulsion separation efficiency can be achieved under low pH and ionic strength conditions with minimal addition of surfactants. Moreover, due to its superior antifouling property, the membrane enables long-term separation of high -viscosity oil -in -water emulsions and actual oily wastewater under various solution conditions. Notably, the flux of the AOPAN-RC membrane did not decrease significantly, making it significantly better than the PAN -CA and PAN -RC membranes. Additionally, the separation efficiency of the AOPAN-RC membrane also surpassed that of the other two. While the presence of surfactant -surrounded oil droplets may cause irreversible fouling over time, this innovative nanofibrous membrane exhibits great potential for practical applications in the treatment of a wider range of oil -contaminated wastewater sources.

The utilization of wasted Poly(lactic acid) (PLA) as low-cost carbon sources in solid-phase denitrification is hindered by its low biodegradability, which can be attributed to its high molecular weight. This study presents a new approach by blending high-molecular-weight PLA with a small amount of L-lactide (PLA/LAx) to treat nitrate-contaminated wastewater. The addition of L-lactide enhanced the release of carbon from high-molecular-weight PLA. An impressive denitrification efficiency of 96.7% was achieved, accompanied by extremely low levels of accumulated NO- 2-N (0.1 mg/L) and NH+4-N (0.4 mg/L). The quantity of L-lactide used significantly impacted the bacterial community structure. A high abundance of the phyla Bacteroidota and Chloroflexi asso-ciated with polymer degradation was observed. The most dominant denitrifier was the genus unclassi-fied_f__Rhodocyclaceae belonged to the phylum Proteobacteria. This study demonstrates that blending PLA with just 5 wt% lactide can transform it into a highly effective solid-phase carbon source to eliminate nitrates.

This paper proposed a new system, electrochemically activated periodate (E/PI) with a Ti/RuO2-IrO2 anode, for the efficient degradation of endocrine disrupting chemical bisphenol S (BPS). The results suggested that the degradation efficiency reached 100 % after 30 min at the conditions of PI 0.25 mM, current density 2 mA/cm2 and pH 7.2. In comparison to other activators of PI (e.g., ultrasonic or visible light) and electrochemically activated different oxidants (e.g., persulfates or H2O2), the E/PI system was found to be more effective in degrading BPS. The system showed a faster degradation rate with increasing current density or PI dose, and demonstrated a strong anti-interference capability against the humic acid and inorganic anions present in water. The system also demonstrated excellent stability, and can still remove 100 % of BPS even after 40 intermittent semi-continuous operations (20 h). The singlet oxygen (1O2) was identified as the primary reactive oxygen species (ROS) for the BPS degradation, as revealed by the free radical quenching and the electron paramagnetic resonance (EPR) experiment. In addition, the intermediates of BPS during its degradation process and main degradation pathways were proposed. The E/PI system can be used as a new AOPs and has practical application potential in water treatment.

Heavy metal contamination in the surface sediments of large shallow lakes in China is becoming increasingly serious. However, more attention has been paid to the human health risk of heavy metals in the past, while little consideration has been given to aquatic organisms. Taking Taihu Lake as an example, we explored the spatial and temporal heterogeneity of the potential ecological risks of seven heavy metals (Cd, As, Cu, Pb, Cr, Ni, and Zn) to species at different taxonomic scales using an improved species sensitivity distribution (SSD) method. The results showed that all six heavy metals, except Cr, were exceeded to some extent compared to background levels, with Cd being the most severe exceedance. Based on the hazardous concentration for 5% of the species (HC5), Cd had the lowest HC5 value, implying the highest ecological risk of toxicity. Ni and Pb had the highest HC5 values and the lowest risk. Cu, Cr, As and Zn were at a relatively moderate levels. For the different groups of aquatic organisms, the ecological risk of most heavy metals was generally lower for vertebrates than for the whole species. The risk for invertebrates and algae was higher than that for all species. Zn and Cu had the highest potentially affected fractions (PAFs) for all classification cases, with mean PAFs of 30.25% and 47.2%, respectively. Spatially, the high ecological risk of sediment heavy metals was significantly related to the spatial characteristics of the type and intensity of human activities in the catchment. Administratively, the environmental quality standards for freshwater sediments proposed by America and Canada are insufficient to protected against the ecological risks of heavy metals in Taihu Lake. In the absence of such standards, China urgently needs to establish an approptiate system of environmental quality standards for heavy metals in lake sediments.

Polychlorinated biphenyls (PCBs) in soil are difficult to remove by biodegradation, photodegradation and other conventional oxidation methods. This work tried to use FeS-activated persulfate (PS) combined with permanganate (KMnO4) to treat PCBs contaminated soil using 3,3',4,4'-tetrachlorobiphenyl (PCB77) as a model pollutant. Compared with Fe-0/PS and KMnO4/PS systems, the FeS/PS system showed a stronger degradation effect on PCB77. After reacting for 4 h in FeS/PS system, the addition of KMnO4 could increase the degradation efficiency of PCB77 from 50.27% to 79.20% in a total reaction time of 8 h. In FeS/PS/KMnO4 system, the degradation efficiency of PCB77 was directly proportional to the concentration of FeS, and greater amount of PCB77 was removed when more spiked soils were treated. Based on electron paramagnetic resonance (EPR) analysis and radical quenching experiments, circle OH, SO4 circle-, O-1(2) and O-2(circle-) were determined to play an important role in the oxidation of PCB77. Combined with identified intermediates and theoretical calculations, six main possible reaction pathways were proposed, including dechlorination, hydroxyl substitution, hydroxyl addition, sulfate substitution, sulfate addition, and C-C bridge bond cleavage. Acute toxicity and bioconcentration factors of intermediate products were predicted by T.E.S.T software, and the results showed that the ecotoxicity of PCB77 in soil was effectively reduced during the FeS/PS/KMnO4 treatment process. This work demonstrated that FeS/PS/ KMnO4 system is applicable to treat PCB77 contaminated soil and has a great potential for soil remediation.

The carbon nanotubes (CNT) were modified with graphitic carbon nitride (g-C3N4) for the first time to prepare new metal-free composites for peroxymonosulfate activation. The results showed that the modification of CNT with g-C3N4 significantly enhanced the catalytic performance in activating PMS for the degradation of p-hydroxybenzoic acid (HBA)than the traditional N doping. Moreover, the oxidation system was not affected by the water quality factors (e.g., Cl−, NO3−, HCO3−, and humic acid) as it had a high pollutant mineralization rate with the removal of total organic carbon (TOC) was ≈72%, and could effectively remove other pollutants (e.g., ferulic acid, methylparaben, phenol, and paracetamol). The singlet oxygen was the main active species involved in the reaction, indicating that HBA degradation mainly depended on non-free radical oxidation mechanisms.

As the utilization of degradable polymer coatings increased, the accompanying trade-off between good degradability and high-efficiency antidiatom adhesion due to their hydrophobic nature remains unresolved. The study presents a new hydrophobic surface-fragmenting coating consisting of degradable hyperbranched polymers (hereafter denoted as h-LLAx) synthesized by reversible complexation-mediated copolymerization with isobornyl acrylate (IBOA) and divinyl-functional oligomeric poly(l-lactide) (OLLA-V2), both derived from biomass, that exhibited superior resistance (∼0 cell mm-2) to marine diatom Navicula incerta (N. incerta) attachment with higher OLLA content. The combined impact of the microscale hollow semisphere micelles that self-assembled degradable hyperbranched copolymers and hydrolysis-driven self-renewable surfaces following immersion in seawater may account for the remarkable resistance of h-LLAx coatings against N. incerta. Detailed investigations were conducted across multiple perspectives, from hydrolytic degradation to broad-spectrum antibacterial attachment to ecotoxicity assessment. The excellent features of high resistance to marine diatoms and bacterial attachment, degradability, and environmental friendliness make the as-prepared h-LLAx coatings widely sought after for antifouling coating applications.

Uridine diphosphate glycosyltransferases (UGTs) as fine catalysts of glycosylation are increasingly used in the synthesis of natural products. Sucrose synthase (SuSy) is recognized as a powerful tool for in situ regenerating sugar donors for the UGT-catalyzed reaction. It is crucial to select the appropriate SuSy for cooperation with UGT in a suitable way. In the present study, eukaryotic SuSy from Arabidopsisthaliana (AtSUS1) helped stevia glycosyltransferase UGT76G1 achieve the complete conversion of stevioside (30 g/L) into rebaudioside A (RebA). Position of the individual transcription units containing the genes encoding AtSUS1 and UGT76G1 in the expression plasmid has an effect, but less than that of the fusion order of these genes on RebA yield. Fusion of the C-terminal of AtSUS1 and the N-terminal of UGT76G1 with rigid linkers are conducive to maintaining enzyme activities. When the same fusion strategy was applied to a L637M-T640V double mutant of prokaryotic SuSy from Acidithiobacillus caldus (AcSuSym), 18.8 ± 0.6 g/L RebA (a yield of 78.2%) was accumulated in the reaction mixture catalyzed by the fusion protein Acm-R3-76G1 (the C-terminal of AcSuSym and the N-terminal of UGT76G1 were linked with (EAAAK)3). This work would hopefully reveal the potential of UGT-SuSy fusion in improving the cascade enzymatic glycosylation.

This work demonstrates the potential utility of ferrate(VI)-based advanced oxidation processes for the degradation of a representative UV filter, BP-4. The operational parameters of oxidant dose and temperature were determined with kinetic experiments. In addition, the effects of water constituents including anions (Cl−, HCO3−, NO3−, SO42−), cations (Na+, K+, Ca2+, Mg2+, Cu2+, Fe3+), and humic acid (HA) were investigated. Results suggested that the removal rate of BP-4 (5 mg/L) could reach 95% in 60 min, when [Fe(VI)]:[BP-4] = 100:1, T = 25 °C and pH = 7.0, The presence of K+, Cu2+ and Fe3+ could promote the removal of BP-4, but Cl−, SO42−, NO3−, HA and Na+ could significantly inhibit the removal of BP-4. Furthermore, this Fe(VI) oxidation processes has good feasibility in real water samples. These results may provide useful information for the environmental elimination of benzophenone-type UV filters by Fe(VI).

Understanding the sensitivity of the response of chlorophyll (Chla) to nutrients (e.g., nitrogen and phosphorus) concentrations is important for predicting cyanobacterial bloom risk. However, the processes by which nutrients in lake that affect cyanobacterial growth and outbreaks are nonlinear, gradual and spatially and temporally heterogeneous, and the single response thresholds of concentrations between nutrients and the Chla proposed in current studies maybe hardly reflect these characteristics. Due to three decades of rapid regional socio-economic development, the eutrophication in Taihu Lake of China is serious and there are cyanobacterial blooms every year. In this study, we quantified the interaction effects of different forms of nitrogen and phosphorus on Chla concentrations in lake water and sediment pore water. And a refined response threshold range with continuous variation was proposed to characterize the relationship between the Chla concentration and the NH4-N, total nitrogen (TN) and total phosphorus (TP) concentrations. The results showed that TP was the dominant factor influencing the spatial variation of cyanobacteria blooms in most areas of Taihu Lake, followed by TN. TP should therefore be the highest priority for future pollution load reduction in Taihu Lake. The effects of the interactions between the pollution factors were greater than the sum of them individually. NH4-N and dissolved inorganic phosphorus (DIP) are likely to be preferentially consumed by algae for growth and should be the focus of nutrient control efforts in Taihu Lake. For cyanobacterial risk prediction, prevention and control, NH4-N, TN and TP concentrations of 0.06 mg/L, 2.89 mg/L and 0.06 mg/L, respectively, can be used to indicate the beginning of cyanobacterial blooms in Taihu Lake, and concentrations of 0.34 mg/L, 4.67 mg/L and 0.11 mg/L, respectively, can be used as reference thresholds to indicate serious cyanobacterial blooms.